Occurrence
Assessment
for
the
Stage
2
DBPR
July
2003
Proposal
i
Contents
Exhibits
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Acronyms
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viii
1.
Introduction
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1­
1
1.1
Purpose
of
the
Occurrence
Document
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1­
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1.2
Regulatory
Background
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1­
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1.2.1
Total
Trihalomethane
Rule
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1­
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1.2.2
Surface
Water
Treatment
Rule
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1­
4
1.2.3
Total
Coliform
Rule
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1­
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1.2.4
Regulatory
Negotiation
Process
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1­
5
1.2.5
Information
Collection
Rule
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1­
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1.2.6
Safe
Drinking
Water
Act
Reauthorization
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1­
5
1.2.7
M­
DBP
Advisory
Committee
(
Stage
1
DBPR)
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1­
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1.2.8
Stage
1
Disinfectants
and
Disinfection
Byproducts
Rule
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1­
6
1.2.9
Interim
Enhanced
Surface
Water
Treatment
Rule
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1­
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1.2.10
Proposed
Ground
Water
Rule
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1­
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1.2.11
Filter
Backwash
Recycling
Rule
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1­
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1.2.12
Long
Term
1
Enhanced
Surface
Water
Treatment
Rule
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1­
10
1.2.13
M­
DBP
Advisory
Committee
(
Stage
2
DBPR)
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1­
10
1.3
Factors
Affecting
DBP
Formation
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1­
12
1.3.1
Impact
of
Disinfection
Method
on
Organic
DBP
Formation
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1­
12
1.3.2
Disinfectant
Dose
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1­
13
1.3.3
Time
Dependency
of
DBP
Formation
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1­
14
1.3.4
Concentration
and
Characteristics
of
Precursors
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1­
14
1.3.5
Water
Temperature
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1­
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1.3.6
Water
pH
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1­
15
1.4
The
Primary
Data
Source:
Information
Collection
Rule
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1­
15
1.4.1
Description
of
the
ICR
Data
Set
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1­
15
1.4.2
ICR
Implementation
Activities
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1­
21
1.4.3
ICR
Sampling
Plans
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1­
21
1.4.4
Data
Management
Activities
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1­
21
1.4.5
Quality
Assurance
Activities
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1­
21
1.4.6
Development
of
Auxiliary
Databases
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1­
23
1.4.7
Representativeness
of
ICR
Data
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1­
23
1.4.8
Methods
and
Assumptions
for
Analyzing
ICR
Results
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1­
25
1.4.9
Documentation
of
ICR
Data
Analyses
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1­
27
1.5
Other
Data
Sources
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1­
27
1.5.1
ICR
Supplemental
Survey
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1­
29
1.5.5
State
Data
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1­
31
1.6
Document
Organization
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1­
32
Occurrence
Assessment
for
the
Stage
2
DBPR
July
2003
Proposal
ii
2.
Use
of
Disinfectants
in
the
United
States
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2­
1
2.1
Overview
of
Disinfection
Processes
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2­
1
2.2
Disinfection
Byproducts
(
DBPs)
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2­
2
2.3
Inventory
of
Disinfecting
Water
Systems
and
Population
Served
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2­
3
2.4
Disinfection
Types
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2­
5
2.5
Chlorine
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2­
7
2.5.1
Description
of
Chemistry
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2­
8
2.5.2
Use
and
Distribution
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2­
9
2.5.3
Advantages
and
Disadvantages
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2­
9
2.5.4
Dose
Ranges
and
Points
of
Application
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2­
10
2.5.5
Byproducts
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2­
14
2.6
Chloramines
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2­
14
2.6.1
Description
of
Chemistry
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2­
14
2.6.2
Use
and
Distribution
.
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2­
15
2.6.3
Advantages
and
Disadvantages
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2­
15
2.6.4
Dose
Ranges
and
Points
of
Application
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2­
16
2.6.5
Byproducts
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2­
17
2.7
Chlorine
Dioxide
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2­
17
2.7.1
Description
of
Chemistry
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2­
17
2.7.2
Use
and
Distribution
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2­
18
2.7.3
Advantages
and
Disadvantages
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2­
19
2.7.4
Dose
Ranges
.
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2­
19
2.7.5
Byproducts
.
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2­
20
2.8
Ozonation
.
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.
2­
21
2.8.1
Description
of
Chemistry
.
.
.
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2­
21
2.8.2
Use
and
Distribution
.
.
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.
2­
22
2.8.3
Advantages
and
Disadvantages
.
.
.
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.
2­
22
2.8.4
Dose
Ranges
.
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2­
23
2.8.5
Byproducts
.
.
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.
2­
24
3.
National
Occurrence
Data
.
.
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.
3­
1
3.1
ICR
Data
.
.
.
.
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.
.
3­
1
3.1.1
DBP
Precursors
.
.
.
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.
3­
2
3.1.2
Disinfectant
Residuals
.
.
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.
3­
10
3.1.3
DBPs
.
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.
3­
11
3.2
Medium
and
Small
Systems
.
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.
.
3­
25
3.2.1
Overview
of
Available
Data
for
Medium
and
Small
Systems
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
25
3.2.2
Surface
Water
Systems
.
.
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.
3­
27
3.2.2.1
Medium
Surface
Water
Systems
.
.
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.
3­
29
3.2.2.2
Small
Surface
Water
Systems
.
.
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.
3­
35
3.2.3
Ground
Water
Systems
.
.
.
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.
3­
48
3.2.3.1
Medium
Ground
Water
Systems
.
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.
3­
48
3.2.3.2
Small
Ground
Water
Systems
.
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.
.
3­
50
3.3
Analysis
of
Co­
Occurrence
.
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.
.
3­
53
3.3.1
Total
Organic
Carbon
Concentration
and
Alkalinity
.
.
.
.
.
.
.
.
.
.
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.
.
.
.
.
.
.
3­
53
Occurrence
Assessment
for
the
Stage
2
DBPR
July
2003
Proposal
iii
3.3.2
TOC,
Bromide,
and
TTHM
.
.
.
.
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.
.
3­
54
3.3.3
TTHM
and
HAA5
.
.
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.
.
3­
60
3.4
Analysis
of
Regional
Trends
.
.
.
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.
3­
66
3.4.1
Occurrence
of
TOC
.
.
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.
3­
66
3.4.2
Occurrence
of
Bromide
.
.
.
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.
3­
68
4.
Predicted
Post­
Stage
1
DBP
Occurrence
.
.
.
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.
.
4­
1
4.1
Methodology
for
Predicting
Post­
Stage
1
DBP
Occurrence
.
.
.
.
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.
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.
.
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.
.
.
4­
1
4.2
Summary
of
Post­
Stage
1
Occurrence,
Plant­
Mean
Data
.
.
.
.
.
.
.
.
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.
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.
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.
.
.
.
.
4­
2
4.3
Spatial
and
Temporal
Variability
of
TTHM
and
HAA5
Occurrence,
Post
Stage
1
Conditions
.
.
.
.
.
.
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.
.
4­
4
4.3.1
Occurrence
of
Individual
DBP
Observations
Above
the
MCL
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4­
5
4.3.2
Occurrence
of
Yearly
Averages
Above
the
MCL
at
Specific
Locations
.
.
.
.
.
.
.
.
.
4­
10
4.3.3
Occurrence
of
Peak
DBPs
at
Locations
Other
Than
the
DS
Maximum
.
.
.
.
.
.
.
.
4­
15
Occurrence
Assessment
for
the
Stage
2
DBPR
July
2003
Proposal
iv
Exhibits
Exhibit
1.1
Chronology
of
EPA's
Drinking
Water
M­
DBP
Rulemaking
Efforts
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1­
3
Exhibit
1.2
Stage
1
DBPR
Standards
.
.
.
.
.
.
.
.
.
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.
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.
.
.
.
.
.
.
.
1­
7
Exhibit
1.3
TOC
Percent
Reduction
Requirements
for
Systems
Employing
Enhanced
Coagulation
and
Enhanced
Softening
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1­
8
Exhibit
1.4
ICR
Plant
Monitoring
Requirements
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
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.
.
.
.
.
.
.
.
1­
18
Exhibit
1.5a
Percentage
of
Surface
Water
Systems
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
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.
.
.
.
.
.
.
.
1­
24
Exhibit
1.5b
Percentage
of
Ground
Water
Systems
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
.
.
.
.
.
.
1­
25
Exhibit
1.6
Summary
of
Non­
ICR
Occurrence
Survey
Data
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1­
28
Exhibit
2.1
List
of
Disinfection
Byproducts
(
DBPs)
Measured
During
the
ICR
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2­
3
Exhibit
2.2
Number
(
and
Percent)
of
Disinfecting
CWSs
and
NTNCWSs
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2­
4
Exhibit
2.3
Population
Total
(
and
Percent)
Served
by
Disinfecting
CWSs
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2­
4
Exhibit
2.4
Percentage
of
Surface
Water
Plants
Applying
Specific
Disinfection
Types
for
Combined
Plant/
Distribution
System
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
.
.
.
.
.
.
.
.
.
.
.
.
.
2­
6
Exhibit
2.5
Percentage
of
Ground
Water
Plants
Applying
Specific
Disinfection
Types
for
Individual
and
Combined
Plant/
Distribution
System
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2­
7
Exhibit
2.6
Chlorine
Dose
Ranges
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
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.
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.
.
.
.
.
.
.
.
.
.
.
.
2­
10
Exhibit
2.7
Cumulative
Distributions
of
Mean
Total
Chlorine
Dose
for
Surface
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2­
12
Exhibit
2.8
Cumulative
Distributions
of
Mean
TotalChlorine
Dose
for
Ground
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2­
13
Exhibit
2.9
Cl
2:
NH
3­
N
Weight
Ratios
in
Surface
Water
CL2_
CLM
and
CLM
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2­
16
Exhibit
2.10
Chlorine
Dioxide
Doses
(
Plant
Minimum,
Mean,
and
Maximum)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2­
20
Exhibit
2.11
Ozone
Doses
(
Plant
Minimum,
Mean,
and
Maximum)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
2­
24
Exhibit
3.1
Summary
of
Influent
Water
Quality
Parameter
ICR
Data
for
All
Large
Plants
.
.
.
.
.
.
.
.
.
.
.
3­
3
Exhibit
3.2
Cumulative
Distribution
of
Plant­
Mean
TOC
Concentrations
of
Influent
Samples
Based
on
ICR
Data
for
Large
Surface
and
Ground
Water
Plants
(
mg/
L
as
C)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
4
Exhibit
3.3
Cumulative
Distribution
of
Plant­
Mean
Water
Temperature
of
Influent
Samples
Based
on
ICR
Data
for
Large
Surface
and
Ground
Water
Plants
(
degrees
Celsius)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
5
Exhibit
3.4
Cumulative
Distribution
of
Plant­
Mean
Bromide
Concentrations
of
Influent
Samples
Based
on
ICR
Data
for
Large
Surface
and
Ground
Water
Plants
(
mg/
L)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
6
Exhibit
3.5
Cumulative
Distribution
of
Plant­
Mean
UV­
254
Concentrations
of
Influent
Samples
Based
on
ICR
Data
for
Large
Surface
and
Ground
Water
Plants
(
mg/
L)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
7
Exhibit
3.6
Cumulative
Distribution
of
Differences
Between
Highest
and
Lowest
Monthly
Parameter
Values
for
Influent
Water
Sample
Location
Based
on
ICR
Data
for
All
Large
Plants
.
.
.
.
.
.
.
3­
9
Exhibit
3.7
Summary
of
Disinfectant
Residual
ICR
Data
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
10
Exhibit
3.8
Summary
of
Halogenated
DBP
Data
Measured
During
the
ICR,
DS
Average
(
Parameter
Occurrence
Values
in
µ
g/
L)
for
All
Large
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
13
Exhibit
3.9
Summary
of
TTHM
(
:
g/
L)
ICR
Data
for
All
Large
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
14
Exhibit
3.10
Cumulative
Distribution
of
Plant­
Mean
DS
Average
(
RAA)
for
ICR
TTHM
Occurrence
Data
for
All
Large
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
15
Exhibit
3.11
Cumulative
Distribution
of
Single
Highest
ICR
TTHM
Occurrence
Data
for
All
Large
Surface
and
Ground
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
16
Occurrence
Assessment
for
the
Stage
2
DBPR
July
2003
Proposal
v
Exhibit
3.12
Cumulative
Distribution
of
Highest
LRAA
for
ICR
TTHM
Occurrence
Data
for
Large
Surface
and
Ground
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
17
Exhibit
3.13
Summary
of
HAA5
ICR
Data
for
All
Large
Plants
(
:
g/
L)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
19
Exhibit
3.14
Cumulative
Distribution
of
Plant­
Mean
DS
Average
(
RAA)
for
ICR
HAA5
Occurrence
Data
for
Large
Surface
and
Ground
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
20
Exhibit
3.15
Cumulative
Distribution
of
Single
Highest
ICR
HAA5
Occurrence
Data
for
Large
Surface
and
Ground
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
21
Exhibit
3.16
Cumulative
Distribution
of
Highest
LRAA
ICR
HAA5
Occurrence
Data
for
Large
Surface
and
Ground
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
22
Exhibit
3.17
Summary
of
Bromate
in
Finished
Water,
Plant­
Mean
ICR
Data
for
All
Large
Plants
(
:
g/
L)
3­
24
Exhibit
3.18
Summary
of
Chlorite
ICR
Data
(
µ
g/
L)
for
Large
Surface
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
25
Exhibit
3.19
Summary
of
Non­
ICR
DBP
Precursor
ICR
Data
for
Large
Surface
and
Ground
Water
Plants,
Plant­
Means
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
28
Exhibit
3.20
Summary
of
Non­
ICR
DBP
Precursor
ICR
Data
for
Large
Surface
Water
Plants,
Individual
Observations
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
28
Exhibit
3.21
Percentages
of
Medium
and
Large
Surface
Water
Systems
Using
Different
Source
Water
Types
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
30
Exhibit
3.22
Comparison
of
Source
Water
TOC
for
Medium
and
Large
Surface
Water
Systems
.
.
.
.
.
3­
30
Exhibit
3.23
Comparison
of
Source
Water
TOC
for
Small,
Medium
and
Large
Surface
Water
Systems
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
31
Exhibit
3.24
Comparison
of
Source
Water
Turbidity
For
Medium
and
Large
Surface
Water
Systems
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
31
Exhibit
3.25
Comparison
of
Source
Water
Alkalinity
for
Medium
and
Large
Surface
Water
Systems
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
32
Exhibit
3.26
Comparison
of
Treatment­
In­
Place
for
Medium
and
Large
Surface
Water
Systems
.
.
.
.
.
3­
32
Exhibit
3.27
Comparison
of
Physical
Unit
Processes
for
Medium
and
Large
Surface
Water
Systems
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
33
Exhibit
3.28
Comparison
of
Disinfectant
Type
for
Medium
and
Large
Surface
Water
Systems
Using
Conventional
Filtration
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
33
Exhibit
3.29
Comparison
of
Finished
Water
Annual
Average
TTHM
for
Medium
and
Large
Surface
Water
Systems
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
34
Exhibit
3.30
Comparison
of
Distribution
System
TTHM
Data
for
Medium
and
Large
Surface
Water
Systems
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
34
Exhibit
3.31
Plant
Influent
TOC
Data
for
Small
Surface
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
36
Exhibit
3.32
Plant
Influent
Bromide
Data
for
Small
Surface
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
36
Exhibit
3.33
Plant
Influent
Alkalinity
for
Small
Surface
Water
Systems
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
37
Exhibit
3.34
Plant
Influent
Temperature
for
Small
Surface
Water
Systems
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
37
Exhibit
3.35
Distribution
of
Time
Operated
per
Day
Among
Small
Surface
Water
Plants
.
.
.
.
.
.
.
.
.
.
3­
38
Exhibit
3.36
Treatment
Objectives
Among
Small
Surface
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
38
Exhibit
3.37
Comparison
of
Disinfectants
Used
by
Small
and
Large
Surface
Water
Plants
.
.
.
.
.
.
.
.
.
3­
39
Exhibit
3.38
Comparison
of
Total
Chlorine
Doses
in
Large
and
Small
Surface
Water
Plants
Using
Only
Chlorination
(
Cl
2/
Cl
2)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
39
Exhibit
3.40
Summary
of
NRWA
DBP
Individual
Observations
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
40
Exhibit
3.41
Distribution
of
TTHM
Occurrence
in
Plant
Finished
Water
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
41
Exhibit
3.42
Distribution
of
TTHM
Occurrence
at
the
Point
of
Average
Residence
Time
in
the
Occurrence
Assessment
for
the
Stage
2
DBPR
July
2003
Proposal
vi
Distribution
System
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
41
Exhibit
3.43
Distribution
of
TTHM
Occurrence
at
the
Point
of
Maximum
Residence
Time
in
the
Distribution
System
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
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.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
42
Exhibit
3.44
Distribution
of
HAA5
Occurrence
in
Plant
Finished
Water
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
42
Exhibit
3.45
Distribution
of
HAA5
Occurrence
at
the
Point
of
Average
Residence
Time
in
the
Distribution
System
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
43
Exhibit
3.46
Distribution
of
HAA5
Occurrence
at
the
Point
of
Maximum
Residence
Time
in
the
Distribution
System
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
43
Exhibit
3.47
Cumulative
Distribution
of
Mean
TTHM
Occurrence
in
Distribution
Systems
for
Small
and
Large
Surface
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
45
Exhibit
3.48
RAA
TTHM
vs.
RAA
HAA5
for
Small
Surface
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
46
Exhibit
3.49
Percentage
of
DS
Maximum
Observations
for
TTHM
and
HAA5
by
Sampling
Location
.
3­
47
Exhibit
3.51
Annual
Average
TOC
in
Influent
Water
TOC
for
Ground
Water
Systems
.
.
.
.
.
.
.
.
.
.
.
.
3­
49
Exhibit
3.52
Treatment
Summary
for
Ground
Water
Systems
(
Chlorinating
and
Non­
Chlorinating)
.
.
.
3­
49
Exhibit
3.53
Annual
Average
Finished
Water
TTHM
for
Ground
Water
Systems
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
50
Exhibit
3.54
Comparison
of
Effluent
TOC
for
Chlorinating
Small,
Medium,
and
Large
Ground
Water
Systems
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
52
Exhibit
3.55
Cumulative
Distribution
of
TTHM
Occurrence
as
Distribution
System
Average
for
Small
and
Large
Ground
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
52
Exhibit
3.56
Percent
TOC
Removal
Requirements
for
Systems
Employing
Enhanced
Coagulation
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
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.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
53
Exhibit
3.57
Distribution
of
Monthly
TOC
(
mg/
L)
and
Monthly
Alkalinity
(
mg/
L)
Samples
Based
on
ICR
Data
for
All
Large
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
54
Exhibit
3.58
Finished
Water
TTHM
Concentrations
(
Mean
of
Plant­
Means)
by
Influent
TOC
and
Bromide
Concentrations
Based
on
ICR
Data
for
All
Large
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
56
Exhibit
3.59
Finished
Water
TTHM
Concentrations
(
90th
Percentile
of
Plant­
Means)
by
Influent
TOC
and
Bromide
Concentrations
Based
on
ICR
Data
for
All
Large
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
57
Exhibit
3.60
Finished
Water
HAA5
Concentrations
(
Mean
of
Plant­
Means)
by
Influent
TOC
and
Bromide
Concentrations
Based
on
ICR
Data
for
All
Large
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
58
Exhibit
3.61
Finished
Water
HAA5
Concentrations
(
90th
Percentile
of
Plant­
Means)
by
Influent
TOC
and
Bromide
Concentrations
Based
on
ICR
Data
for
All
Large
Plants
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
59
Exhibit
3.62
RAA
of
TTHM
Occurrence
versus
RAA
of
HAA5
Occurrence
for
Large
Surface
Water
Plants
Based
on
ICR
Data
(
N
=
213)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
60
Exhibit
3.63
RAA
of
TTHM
Occurrence
versus
RAA
of
HAA5
Occurrence
for
Large
Ground
Water
Plants
Based
on
ICR
Data
(
N
=
82)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
61
Exhibit
3.64
Highest
LRAA
TTHM
versus
Highest
LRAA
HAA5
for
Large
Surface
Water
Plants
Based
on
ICR
Data
(
N
=
213)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
62
Exhibit
3.65
Highest
LRAA
TTHM
versus
Highest
LRAA
HAA5
for
Large
Ground
Water
Plants
Based
on
ICR
Data
(
N
=
82)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
63
Exhibit
3.66
Single
Highest
TTHM
versus
Single
Highest
HAA5
for
Large
Surface
Water
Plants
Based
on
ICR
Data
(
N
=
213)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
64
Exhibit
3.67
Single
Highest
TTHM
versus
Single
Highest
HAA5
Based
on
ICR
Data
for
Large
Ground
Water
Plants
(
N
=
82)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
3­
65
Exhibit
3.68a
Influent
Water
TOC
Occurrence
Distribution
for
Large
ICR
Surface
Water
Systems
.
.
.
3­
66
Exhibit
3.69
Mean
Influent
Bromide
Concentrations,
Large
ICR
Surface
Water
Plants
.
.
.
.
.
.
.
.
.
.
.
3­
68
Occurrence
Assessment
for
the
Stage
2
DBPR
July
2003
Proposal
vii
Exhibit
4.1
Summary
of
Post­
Stage
1
TTHM
Occurrence
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4­
3
Exhibit
4.2
Summary
of
Post­
Stage
1
HAA5
Occurrence
for
ICR
Plants
in
Compliance
with
Stage
1
MCLs
with
or
without
a
Safety
Factor
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4­
4
Exhibit
4.3a
Single
Highest
vs.
RAA
for
TTHM,
All
Plants
in
Compliance
with
Stage
1
MCLs
of
80/
60
RAA
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4­
6
Exhibit
4.3b
Single
Highest
vs.
RAA
for
TTHM,
All
Plants
in
Compliance
with
Stage
1
MCLs
with
Safety
Factor
(
64/
48
RAA)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4­
7
Exhibit
4.4a
Single
Highest
vs.
RAA
for
HAA5,
All
Plants
in
Compliance
with
Stage
1
MCLs
of
80/
60
RAA
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4­
8
Exhibit
4.4b
Single
Highest
vs.
RAA
for
HAA5,
All
Plants
in
Compliance
with
Stage
1
MCLS
with
Safety
Factor
(
64/
48
RAA)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4­
9
Exhibit
4.5a
Cumulative
Percentage
of
TTHM
LRAAs,
All
Plants
in
Compliance
with
80/
60
RAA
(
Stage
1
MCL)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4­
11
Exhibit
4.5b
Cumulative
Percentage
of
TTHM
LRAAs,
All
Plants
in
Compliance
with
64/
48
RAA
(
Stage
1
MCL
with
SF)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4­
12
Exhibit
4.6a
Cumulative
Percentage
of
HAA5
LRAAs,
All
Plants
in
Compliance
with
80/
60
RAA
(
Stage
1
MCL)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4­
13
Exhibit
4.6b
Cumulative
Percentage
of
HAA5
LRAAs,
All
Plants
in
Compliance
with
64/
48
RAA
(
Stage
1
MCL
with
SF)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4­
14
Exhibit
4.7
Frequency
at
Which
Highest
TTHM
or
HAA5
LRAAs
Occurred
at
Each
Sample
Location
for
All
ICR
Plants
in
Compliance
with
80/
60
RAA
(
Stage
1
MCL)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4­
16
Exhibit
4.8
Frequency
at
Which
Highest
TTHM
or
HAA5
LRAAs
Occurred
at
the
Same
Location
for
All
ICR
Plants
in
Compliance
with
80/
60
RAA
(
Stage
1
MCL)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4­
17
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
viii
Acronyms
80/
60
RAA
TTHM
and
HAA5
levels
of
80
µ
g/
L
and
60
µ
g/
L
calculated
as
a
running
annual
average
64/
48
RAA
TTHM
and
HAA5
levels
of
64
µ
g/
L
and
48
µ
g/
L
calculated
as
a
running
annual
average
AUX1
Auxiliary
Database
1
AUX2
Auxiliary
Database
2
AUX3
Auxiliary
Database
3
AUX4
Auxiliary
Database
4
AUX5
Auxiliary
Database
5
AUX6
Auxiliary
Database
6
AUX8
Auxiliary
Database
8
AVG1
Average
1
Distribution
System
Sampling
Location
AVG2
Average
2
Distribution
System
Sampling
Location
BAT
Best
Available
Technology
BCAA
Bromochloracetic
Acid
BCAN
Bromochloroacetonitrile
BDCAA
Bromodichloroacetic
Acid
BDCM
Bromodichloromethane
BDL
Below
Detection
Limit
C
Carbon
CaCO
3
Calcium
Carbonate
CDBAA
Chlorodibromoacetic
Acid
CH
Chloral
Hydrate
CHBr
3
Bromoform
CHCl
3
Chloroform
Cl
!
Chloride
Cl
2
Chlorine
Cl
2:
NH
3­
N
Chlorine
to
Ammonia
Nitrogen
ratio
Cl
3
Trichloride
ClO
2
Chlorine
Dioxide
ClO
2
!
Chlorite
ClO
3
!
Chlorate
CNCl
Cyanogen
Chloride
CP
Chloropicrin
CT
Concentration
(
Time
CWS
Community
Water
System
CWSS
Community
Water
System
Survey
DBAA
Dibromoacetic
Acid
DBAN
Dibromoacetonitrile
DBCM
Dibromochloormethane
DBP
Disinfection
Byproducts
DBPR
Disinfectants/
Disinfection
Byproducts
Rule
DCAA
Dichloroacetic
Acid
DCAN
Dichloroacetonitrile
DCP
Dichloropropanone
DS
Distribution
System
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
ix
DSE
Distribution
System
Equivalent
EPA
U.
S.
Environmental
Protection
Agency
ESWTR
Enhanced
Surface
Water
Treatment
Rule
FACA
Federal
Advisory
Committee
Act
FBRR
Filter
Backwash
Recycling
Rule
FR
Federal
Register
GWSS
Groundwater
Supply
Survey
GWUDI
Groundwater
Under
the
Direct
Influence
of
Surface
Water
HAA
Haloacetic
Acid
HAA5
Haloacetic
Acid­
Five
HAA6
Haloacetic
Acid­
Six
HAA9
Haloacetic
Acid­
Nine
HAN
Haloacetonitrile
HAN4
Haloacetonitriles­
Four
HCl
Hydrochloric
Acid
HOCl
Hypochlorous
Acid
ICR
Information
Collection
Rule
ICRFED
Information
Collection
Rule
Federal
Database
System
ICRSS
Information
Collection
Rule
Supplemental
Surveys
IDSE
Initial
Distribution
System
Evaluation
IESWTR
Interim
Enhanced
Surface
Water
Treatment
Rule
kg
Kilogram
L
Liter
LRAA
Locational
Running
Annual
Average
LT1ESWTR
Long
Term
1
Enhanced
Surface
Water
Treatment
Rule
LT2ESWTR
Long
Term
2
Enhanced
Surface
Water
Treatment
Rule
M­
DBP
Microbial
and
Disinfection
Byproduct
MBAA
Monobromoacetic
Acid
MCAA
Monochloroacetic
Acid
MCLG
Maximum
Contaminant
Level
Goal
MCL
Maximum
Contaminant
Level
MDL
Method
Detection
Limit
mg
Milligram
µ
g
Microgram
MRDL
Maximum
Residual
Disinfectant
Level
MRDLG
Maximum
Residual
Disinfectant
Level
Goal
MRL
Minimum
Reporting
Level
N
Nitrogen
Na
Sodium
NH
3
Ammonia
NODA
Notice
of
Data
Availability
NOM
Natural
Organic
Matter
NPDWR
National
Primary
Drinking
Water
Regulation
NRWA
National
Rural
Water
Association
NTNCWS
Nontransient
Noncommunity
Water
System
NTU
Nephelometric
Turbidity
Units
O
2
Oxygen
O
3(
aq)
Aqueous
Ozone
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
x
OCl­
Hypochlorite
Ion
OGWDW
Office
of
Ground
Water
and
Drinking
Water
PAC
Powdered
Activated
Carbon
ppb
parts
per
billion
ppm
parts
per
million
PWS
Public
Water
System
RPD
Relative
Percent
Difference
QA/
QC
Quality
Assurance
and
Quality
Control
RAA
Running
Annual
Average
SDS
Simulated
Distribution
System
SDWA
Safe
Drinking
Water
Act
SQL
Structured
Query
Language
SUVA
Specific
UV
Absorbance
SWAT
Surface
Water
Analytical
Tool
SWTR
Surface
Water
Treatment
Rule
TBAA
Tribromoacetic
Acid
TCAA
Trichloroacetic
Acid
TCAN
Trichloroacetonitrile
TCR
Total
Coliform
Rule
TCP
Trichloropropanone
THM
Trihalomethanes
TNCWS
Transient
Noncommunity
Water
System
TOC
Total
Organic
Carbon
TOX
Total
Organic
Halides
TTHM
Total
Trihalomethanes
TWG
Technical
Working
Group
UV
Ultraviolet
Radiation
VOC
Volatile
Organic
Compound
WTP
Water
Treatment
Plant
1For
the
purposes
of
this
document,
"
States"
are
defined
as
States
or
territories
with
primacy
or
other
primacy
agencies.

2PWSs
are
systems
that
provide
water
for
human
consumption
through
pipes
or
other
constructed
conveyances
and
that
have
at
least
15
service
connections
or
regularly
serve
an
average
of
at
least
25
individuals
per
day
for
at
least
60
days
per
year.

Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
1
1.
Introduction
The
United
States
Environmental
Protection
Agency
(
EPA)
Office
of
Ground
Water
and
Drinking
Water
(
OGWDW)
is
developing
interrelated
drinking
water
regulations
to
control
microbial
pathogens
and
disinfectants/
disinfection
byproducts
in
drinking
water.
These
rules
are
required
by
the
Safe
Drinking
Water
Act
(
SDWA)
Amendments
of
1996
and
are
collectively
known
as
the
microbial
and
disinfection
byproducts
(
M­
DBP)
rules.

The
Stage
1
Disinfectants
and
Disinfection
Byproducts
Rule
(
Stage
1
DBPR)
and
the
Interim
Enhanced
Surface
Water
Treatment
Rule
(
IESWTR),
the
first
set
of
M­
DBP
rules
under
the
SDWA
Amendments,
were
promulgated
in
December
1998.
The
Stage
1
DBPR
and
the
IESWTR
were
the
culmination
of
a
6­
year
rule
development
process
that
included
regulatory
negotiations
with
representatives
of
the
water
industry,
environmental
and
public
health
groups,
and
local,
State1,
and
Federal
government
agencies.

To
support
rule
development,
EPA
expanded
its
microbial
and
disinfection
byproduct
(
DBP)
research
program
and
entered
into
collaborative
efforts
with
other
agencies
and
the
water
industry
to
collect
data.
This
data
collection
effort
included
the
Information
Collection
Rule
(
ICR)
and
the
ICR
Supplemental
Survey
(
ICRSS).
In
addition,
under
a
joint
effort
between
EPA
and
the
National
Rural
Water
Association
(
NRWA),
NRWA
State
chapters
conducted
a
survey
of
disinfection
byproduct
and
treatment
information
at
small
public
water
systems
(
PWSs)
2.

EPA
has
worked
with
stakeholders
under
the
Federal
Advisory
Committee
Act
(
FACA)
to
develop
the
proposed
Stage
2
Disinfection
Byproducts
Rule
(
Stage
2
DBPR)
and
Long
Term
2
Enhanced
Surface
Water
Treatment
Rule
(
LT2ESWTR).
These
rules
are
being
developed
concurrently,
using
occurrence
data
from
the
ICR
and
other
available
sources
to
ensure
that
microbial
protection
is
maintained
or
enhanced
while
exposure
to
DBPs
is
reduced.

This
occurrence
assessment
supports
the
Stage
2
DBPR
proposal.
The
remainder
of
this
chapter
is
organized
as
follows:

°
Section
1.1
summarizes
the
purpose
of
this
document.

°
Section
1.2
describes
the
history
of
drinking
water
regulations
leading
up
to
the
Stage
2
DBPR.

°
Section
1.3
provides
a
brief
synopsis
of
the
factors
affecting
DBP
formation.

°
Section
1.4
describes
the
main
data
source,
the
ICR.

°
Section
1.5
describes
other
sources
used.

°
Section
1.6
describes
the
rest
of
the
chapters
and
appendices
that
make
up
this
document.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
2
1.1
Purpose
of
the
Occurrence
Document
This
document
serves
two
main
purposes.
First,
it
presents
data
as
an
addendum
to
the
Occurrence
Assessment
for
Disinfectants/
Disinfection
Byproducts
in
Public
Drinking
Water
Supplies
document
(
USEPA
1998c)
which
supported
the
Stage
1
DBPR.
In
order
to
update
the
1998
document
to
support
the
current
rulemaking,
EPA
undertook
two
tasks.
First,
EPA
conducted
additional
searches
to
identify
articles
and
studies
from
the
scientific
literature
and
from
recent
conferences
in
the
relevant
subject
areas.
Second,
EPA
used
the
results
of
the
ICR
data
collection
effort,
which
was
the
primary
source
of
the
new
information
included
in
this
document.

The
second
purpose
of
the
document
is
to
evaluate
the
characteristics
of
DBP
occurrence
for
the
post­
Stage
1
baseline.
Because
the
compliance
deadline
for
the
Stage
1
DBPR
passed
very
recently
(
January
2002)
for
large
and
medium
surface
water
systems,
all
observed
data
in
this
document
represent
pre­
Stage
1
conditions
(
i.
e.,
conditions
before
the
implementation
of
the
Stage
1
DBPR).
Chapter
4
of
this
occurrence
document
provides
one
possible
analysis
of
DBP
formation
for
post­
Stage
1
DBPR
conditions.

ICR
and
other
occurrence
data
can
be
analyzed
in
a
variety
of
ways.
To
provide
support
to
the
Stage
2
DBPR
rulemaking,
this
document
focuses
on
analyses
of
the
following
data
types:

°
Disinfectant
use
and
residual
concentrations
°
DBP
precursors
and
other
water
quality
parameters
affecting
DBP
formation
°
Occurrence
of
regulated
DBPs
­
Total
Trihalomethanes
(
TTHM)
­
Haloacetic
Acid­
Five
(
HAA5)
­
Bromate
­
Chlorite
Alternative
and
additional
analyses
are
presented
in
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002)
(
This
includes
some
analyses
of
water
quality
data
collected
under
the
ICR
that
are
not
relevant
to
the
Stage
2
DBPR
rulemaking).

In
this
occurrence
document,
analyses
of
TTHM
and
HAA5
occurrence
are
focused
on
the
distribution
system.
Spatial
and
temporal
variability
of
TTHM
and
HAA5
occurrence
in
the
distribution
system
is
evaluated
for
the
post­
Stage
1
DBPR
baseline
in
Chapter
4.

1.2
Regulatory
Background
Exhibit
1.1
presents
a
brief
chronology
of
EPA's
rulemaking
activities
on
microbial
contaminants,
disinfectants,
and
DBPs
in
drinking
water,
starting
with
the
Total
Trihalomethane
Rule
promulgated
in
1979
(
USEPA
1979).
The
rules
that
are
bolded
in
Exhibit
1.1
are
rules
that
are
currently
in
the
Federal
Register.
Each
rule
or
rule­
making
process
presented
in
this
section
deals
with
the
removal
of
microbial
contaminants
and/
or
the
reduction
of
disinfectants
and
disinfection
byproducts
in
drinking
water.
Brief
descriptions
of
these
rulemaking
efforts
follow
the
exhibit.
3
CWSs
are
PWSs
that
serve
at
least
15
service
connections
used
by
year­
round
residents
or
that
regularly
serve
at
least
25
year­
round
residents.

Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
3
Exhibit
1.1
Chronology
of
EPA's
Drinking
Water
M­
DBP
Rulemaking
Efforts
Year
Regulation
Action
(
Federal
Register
#)

1979
Total
Trihalomethane
Rule
(
TTHM)
Promulgated
(
44
FR
68624)

1989
Surface
Water
Treatment
Rule
(
SWTR)
Promulgated
(
54
FR
27486)

1989
Total
Coliform
Rule
(
TCR)
Promulgated
(
54
FR
27544)

1992
Regulatory
Negotiation
Process
Initiated
1996
Information
Collection
Rule
(
ICR)
Promulgated
(
61
FR
24354)

Safe
Drinking
Water
Act
(
SDWA)
Reauthorized
(
Public
Law
104­
182
104th
Congress)

1997
Microbial
and
Disinfectants/
Disinfection
Byproduct
Federal
Advisory
Committee
(
M­
DBP
FACA)
(
Stage
1
DBPR)
Established
1998
Stage
1
Disinfectants
and
Disinfection
Byproduct
Rule
(
Stage
1
DBPR)
Promulgated
(
63
FR
69390)

Interim
Enhanced
Surface
Water
Treatment
Rule
(
IESWTR)
Promulgated
(
63
FR
69478)

1999
M­
DBP
FACA
(
Stage
2
DBPR)
Re­
convened
2000
Ground
Water
Rule
Proposed
(
65
FR
30194)

2001
Filter
Backwash
Recycling
Rule
(
FBRR)
Promulgated
(
66
FR
31086)

2002
Long
Term
1
Enhanced
Surface
Water
Treatment
Rule
(
LT1ESWTR)
Promulgated
(
67
FR
1812)

2003
Stage
2
Disinfectants
and
Disinfection
Byproduct
Rule
(
Stage
2
DBPR)
Planned
Proposal
Long
Term
2
Enhanced
Surface
Water
Treatment
Rule
(
LT2ESWTR)
Planned
Proposal
Ground
Water
Rule
Planned
Promulgation
1.2.1
Total
Trihalomethane
Rule
Under
the
Total
Trihalomethane
Rule
(
USEPA
1979),
EPA
set
a
maximum
contaminant
level
(
MCL)
for
TTHM,
the
sum
of
the
concentrations
of
chloroform,
bromoform,
bromodichloromethane,
and
dibromochloromethane,
of
0.10
mg/
L
as
a
running
annual
average
(
RAA)
of
quarterly
measurements.
The
TTHM
Rule
was
based
on
the
need
to
reduce
exposure
to
DBPs
and
reduce
related
cancer
risks
while
maintaining
disinfection
to
address
microbial
risks
(
USEPA
1979).
This
standard
applied
to
community
water
systems
(
CWSs)
3
using
surface
or
ground
water
that
serve
at
least
10,000
people
and
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
4
that
add
a
disinfectant
to
the
drinking
water
during
any
part
of
the
treatment
process.
This
1979
rule
was
superseded
by
the
1998
Stage
1
DBPR
(
section
1.2.8).

1.2.2
Surface
Water
Treatment
Rule
Between
1979
and
1989,
no
new
regulations
related
to
disinfection
or
DBPs
were
promulgated;
however,
interim
regulations
promulgated
in
1975
regulating
coliform
bacteria
and
turbidity
remained
in
effect.
In
1989,
in
response
to
the
requirements
of
the
1986
SDWA,
EPA
promulgated
the
Surface
Water
Treatment
Rule
(
SWTR)
(
USEPA
1989a)
that
established
maximum
contaminant
level
goals
(
MCLGs)
of
zero
for
Giardia
lamblia,
viruses,
and
Legionella,
and
established
requirements
for
all
PWSs
using
surface
water
or
ground
water
under
the
direct
influence
of
surface
water
(
GWUDI)
as
a
source.
The
SWTR
includes
treatment
technique
requirements
for
filtered
and
unfiltered
systems
that
are
intended
to
protect
against
the
adverse
health
effects
associated
with
Giardia
lamblia,
viruses,
and
Legionella,
as
well
as
many
other
pathogenic
organisms.
These
requirements
include:

°
Maintenance
of
a
disinfectant
residual
in
the
distribution
system.

°
Removal
and/
or
inactivation
requirements
of
3
logs
(
99.9
percent)
for
Giardia
and
4
logs
(
99.99
percent)
for
viruses.

°
For
filtered
systems,
meeting
a
turbidity
performance
standard
for
the
combined
filter
effluent
of
5
nephelometric
turbidity
units
(
NTUs)
as
a
maximum
and
0.5
NTU
in
95
percent
of
monthly
measurements,
based
on
4­
hour
monitoring
for
treatment
plants
using
conventional
treatment
or
direct
filtration
(
with
separate
standards
for
other
filtration
technologies).
These
requirements
were
superseded
by
the
1998
IESWTR
and
will
be
further
modified
by
the
2002
Long
Term
1
Enhanced
Surface
Water
Treatment
Rule
(
LT1ESWTR).

°
Watershed
protection
and
other
requirements
for
unfiltered
systems.

1.2.3
Total
Coliform
Rule
In
1989,
EPA
promulgated
the
Total
Coliform
Rule
(
TCR)
(
USEPA
1989b),
which
applies
to
all
PWSs,
to
provide
protection
against
the
presence
of
microbial
pathogens
in
the
distribution
system.
Prior
to
the
TCR,
the
interim
regulations
required
compliance
with
an
MCL
based
on
coliform
bacteria
density.
The
primary
provision
of
the
TCR
requires
systems
to
monitor
at
representative
locations
in
their
distribution
systems
for
total
coliforms,
a
potential
indicator
of
fecal
contamination.
Any
total
coliform
positive
sample
must
be
tested
for
E.
coli
or
fecal
coliforms,
and,
if
these
are
found,
repeat
sampling
and
other
appropriate
steps
must
be
taken
to
protect
public
health.
Monitoring
frequency
is
determined
by
system
size
(
i.
e.,
large
or
small)
and
type
(
i.
e.,
whether
the
system
is
a
community
or
noncommunity
water
system).
To
meet
the
MCL
for
this
rule,
less
than
5
percent
of
samples
collected
in
a
month
may
be
positive
for
total
coliforms.

Total
coliforms
are
bacteria
that
are
used
as
an
indicator
of
water
treatment
effectiveness
and
distribution
system
integrity.
Fecal
coliform
bacteria
are
generally
considered
indicators
of
possible
recent
fecal
contamination.
Combined,
the
SWTR
and
the
TCR
are
intended
to
address
risks
associated
with
pathogens
that
might
be
found
in
source
waters
or
associated
with
distribution
systems.

1.2.4
Regulatory
Negotiation
Process
Prompted
by
an
interest
in
balancing
health
risks
from
microbial
pathogens
and
DBPs,
EPA
initiated
a
negotiated
rulemaking
process
in
1992.
The
negotiators
included
representatives
of
State
and
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
5
local
health
and
regulatory
agencies,
PWSs,
elected
officials,
consumer
groups,
and
environmental
organizations.
The
main
concern
in
developing
the
rules
was
to
ensure
that
when
systems
changed
existing
treatment
to
comply
with
new
requirements
for
DBPs,
they
would
not
compromise
microbial
protection.
Hence,
the
negotiators
agreed
that
EPA
should
propose
a
microbial
rule
with
the
DBPR.

Early
in
the
rulemaking
process,
the
Negotiating
Committee
determined
that
sufficient
plantspecific
information
on
how
to
optimize
the
use
of
disinfectants,
while
concurrently
minimizing
pathogen
and
DBP
exposure
risk,
was
not
available.
Nevertheless,
the
Negotiating
Committee
recommended
that
EPA
propose
a
DBPR
to
extend
coverage
to
all
CWSs
and
NTNCWSs
that
use
disinfectants.
As
a
result
of
the
negotiations,
the
Committee
recommended
that
EPA
develop
three
sets
of
rules.
These
rules
include
a
two­
stage
DBP
rule,
an
"
interim"
and
"
final"
microbial
rule
to
address
large
and
small
systems
respectively,
and
an
ICR
to
gather
data
on
microbial
and
DBP
occurrence.

1.2.5
Information
Collection
Rule
EPA
promulgated
the
ICR,
a
monitoring
and
data­
reporting
rule,
on
May
14,
1996
(
USEPA
1996a).
The
ICR
authorized
EPA
to
collect
occurrence
and
treatment
information
from
water
treatment
plants
in
large
systems
to
help
evaluate
the
possible
need
for
changes
to
the
current
microbial
requirements
and
existing
microbial
treatment
practices,
and
to
help
evaluate
the
need
for
future
regulation
of
disinfectants
and
DBPs.
The
ICR
provided
EPA
with
additional
information
on
the
national
occurrence
of
(
1)
chemical
byproducts
that
form
when
disinfectants
used
for
microbial
control
react
with
naturally
occurring
compounds
and
ions
present
in
source
water;
and
(
2)
disease­
causing
microorganisms
including
Cryptosporidium,
Giardia,
and
viruses.
The
ICR
also
mandated
the
collection
of
treatment
train
data
on
how
water
systems
currently
control
for
contaminants.

The
ICR
data
collection
focused
on
large
PWSs,
which
serve
populations
of
over
100,000
people.
A
more
limited
set
of
ICR
requirements
covered
ground
water
systems
serving
50,000
to
100,000
people.
This
extensive
data
collection
effort
surveyed
296
PWSs
operating
512
treatment
plants.
A
detailed
description
of
the
ICR
is
provided
in
Section
1.4.

1.2.6
Safe
Drinking
Water
Act
Reauthorization
In
1996,
Congress
reauthorized
the
Safe
Drinking
Water
Act.
The
1996
SDWA
Amendments
include
provisions
related
to
the
DBPR
and
the
ESWTR.
Those
provisions
established
a
deadline
of
November
1998
for
the
promulgation
of
both
the
Stage
1
DBPR
and
an
interim
ESWTR.
The
Amendments
also
set
deadlines
for
a
long­
term
ESWTR
and
for
the
final
Stage
2
DBPR.
No
mandatory
deadline
was
established
for
LT2ESWTR.
However,
to
ensure
a
proper
balance
between
microbial
and
DBP
risks,
EPA
believes
it
is
important
to
finalize
the
LT2ESWTR
in
conjunction
with
the
Stage
2
DBPR.

1.2.7
M­
DBP
Advisory
Committee
(
Stage
1
DBPR)

In
May
1996,
EPA
initiated
a
series
of
public
meetings
to
exchange
information
on
issues
related
to
the
development
of
the
IESWTR
and
the
Stage
1
DBPR.
EPA
established
the
M­
DBP
Advisory
Committee
under
the
FACA
on
February
12,
1997,
to
collect,
share,
and
analyze
new
information
and
data,
as
well
as
to
build
consensus
on
the
regulatory
implications
of
this
new
information.
The
M­
DBP
Advisory
Committee
was
comprised
of
20
members
representing
EPA,
State
and
local
public
health
and
regulatory
agencies,
local
elected
officials,
drinking
water
suppliers,
chemical
and
equipment
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
6
manufacturers,
and
public
interest
groups.
The
M­
DBP
Advisory
Committee
agreed
that
the
Stage
1
DBPR
and
IESWTR
should:

1)
Include
proposed
MCLs
for
total
trihalomethanes,
haloacetic
acids,
and
bromate.

2)
Require
enhanced
coagulation
and
enhanced
softening.

3)
Require
microbial
profiling
to
ensure
that
DBP
control
does
not
compromise
microbial
protection.

4)
Continue
to
give
credit
for
complying
with
disinfection
requirements.

5)
Establish
stricter
turbidity
limits.

6)
Establish
a
Cryptosporidium
MCLG
and
requirements
for
removing
Cryptosporidium.

7)
Use
a
multiple
barrier
approach.

8)
Strengthen
existing
sanitary
survey
requirements
(
USEPA
1997a).

1.2.8
Stage
1
Disinfectants
and
Disinfection
Byproducts
Rule
The
Stage
1
DBPR
(
USEPA
1998a)
applies
to
all
CWSs
and
NTNCWSs
that
add
a
chemical
disinfectant
to
their
water.
Certain
requirements
designed
to
provide
protection
against
acute
health
effects
from
chlorine
dioxide
also
apply
to
transient
noncommunity
water
systems
(
TNCWSs).
Compliance
for
surface
water
and
GWUDI
systems
serving
at
least
10,000
people
began
in
January
2002.
Surface
water
and
GWUDI
systems
serving
fewer
than
10,000
people
and
all
ground
water
systems
must
comply
by
January
2004.

Exhibit
1.2
summarizes
standards
set
by
the
Stage
1
DBPR.
Maximum
residual
disinfectant
levels
(
MRDL)
and
maximum
residual
disinfectant
level
goals
(
MRDLG)
were
set
for
chlorine,
chloramines,
and
chlorine
dioxide
at
4
mg/
L,
4
mg/
L,
and
0.8
mg/
L
respectively.
The
MRDLs
and
MRDLGs
were
established
at
levels
at
which
no
known
or
anticipated
health
effects
occur
and
allowing
for
an
adequate
margin
of
safety
while
reflecting
that
these
disinfectants
have
beneficial
disinfection
properties.
In
addition,
maximum
contaminant
levels
(
MCL)
and
maximum
contaminant
level
goals
(
MCLG)
were
established
for
bromate,
chlorite,
TTHM
(
including
separate
MCLs
for
bromoform,
bromodichloromethane,
chloroform,
and
dibromochloromethane),
and
HAA5
(
including
separate
MCLs
for
dichloroacetic
acid
and
trichloroacetic
acid).

In
addition
to
these
standards,
the
Stage
2
DBPR
required
systems
that
use
surface
water
or
GWUDI
and
employ
conventional
treatment
to
remove
a
specified
percentage
of
organic
materials,
measured
as
total
organic
carbon
(
TOC),
unless
they
meet
high
source
water
quality
standards.
This
is
important
because
these
organic
materials,
or
precursors,
react
with
disinfectants
to
form
DBPs.
Precursors
can
be
removed
through
treatment
techniques
(
enhanced
coagulation
or
enhanced
softening),
which
are
described
in
the
Stage
1
DBPR
(
USEPA
1998a).
Exhibit
1.3
lists
the
required
percentage
of
TOC
reduction
for
various
influent
TOC
and
alkalinity
levels.

In
addition
to
these
requirements,
monitoring,
reporting,
and
recordkeeping
are
required
for
the
regulated
contaminants.
The
Stage
1
DBPR
was
promulgated
concurrently
with
the
IESWTR
to
coordinate
the
control
of
DBPs
and
microbial
contaminants.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
7
Exhibit
1.2
Stage
1
DBPR
Standards
Maximum
Residual
Disinfectant
Level
Goals
(
MRDLG)
(
mg/
L)
Maximum
Residual
Disinfectant
Levels
(
MRDL)
(
mg/
L)
Maximum
Contaminant
Level
Goal
(
MCLG)
(
mg/
L)
Maximum
Contaminant
Level
(
MCL)
(
mg/
L)

Disinfectants
Chlorine
4
(
as
Cl2)
4.0
(
as
Cl2)

Chloramine
4
(
as
Cl2)
4.0
(
as
Cl2)

Chlorine
Dioxide
0.8
(
as
ClO2)
0.8
(
as
ClO2)

DBPs
Bromate
0
0.010
Chlorite
0.8
1.0
Total
Trihalomethanes
(
TTHMs)
­­
0.080
Bromoform
0
­­

Bromodichloromethane
(
BDCM)
0
­­

Chloroform
N/
A1
­­

Dibromochloromethane
(
DBCM)
0.06
­­

Haloacetic
Acid­
Five
(
HAA5)
­­
0.060
Monochloroacetic
acid
(
MCAA)
2
­­
­­

Dichloroacetic
acid
(
DCAA)
0
­­

Trichloroacetic
acid
(
TCAA)
0.3
­­

Monobromoacetic
acid
(
MBAA)
2
­­
­­

Dibromoacetic
acid
(
DBAA)
2
­­
­­

Notes:
1
The
Stage
1
DBPR
included
a
MCLG
of
zero
for
chloroform.
The
MCLG
was
challenged,
and
the
U.
S.
Court
of
Appeals
for
the
District
of
Columbia
Circuit
issued
an
order
vacating
the
zero
MCLG
(
U.
S.
Court
of
Appeals,
DC
Circuit
2000).
On
May
30,
2000,
EPA
removed
the
MCLG
for
chloroform
from
its
National
Primary
Drinking
Water
Regulations
(
NPDWRs)
(
USEPA
2000a).
EPA
is
proposing
a
new
MCLG
for
chloroform
of
0.070
mg/
L
in
the
proposed
Stage
2
DBPR
(
USEPA
2003c).
2
There
are
no
MCLs
or
MCLGs
for
these
individual
HAA5
compounds.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
8
Exhibit
1.3
TOC
Percent
Reduction
Requirements
for
Systems
Employing
Enhanced
Coagulation
and
Enhanced
Softening
Source
Water
TOC
(
mg/
L)
Source
Water
Alkalinity
(
mg/
L
as
CaCO3)

0
 
60
>
60
 
120
>
120
>
2.0
 
4.0
35
%
25
%
15
%

>
4.0
 
8.0
45
%
35
%
25
%

>
8.0
50
%
40
%
30
%

Notes:
Systems
meeting
at
least
one
of
the
conditions
in
Section
141.135(
a)(
2)(
i)­(
vi)
of
the
Stage
1
DBPR
are
not
required
to
meet
the
percent
reduction
requirements
in
this
table.
Systems
employing
enhanced
softening
must
meet
the
TOC
removal
requirements
for
systems
with
source
water
alkalinity
greater
than
120
mg/
L
unless
they
meet
one
of
the
two
alternative
compliance
criteria
in
Section
141.135(
a)(
3)
of
the
Stage
1
DBPR,
in
which
case
they
are
not
required
to
meet
the
percent
reduction
requirements
in
this
table.

1.2.9
Interim
Enhanced
Surface
Water
Treatment
Rule
The
IESWTR
(
USEPA
1998b)
enhances
the
1989
SWTR.
It
applies
to
PWSs
serving
at
least
10,000
people
and
using
surface
water
or
GWUDI
as
a
source.
These
systems
began
compliance
with
the
IESWTR
in
January
2002.
The
purpose
of
the
IESWTR
is
to
improve
control
of
the
protozoan
Cryptosporidium
and
to
address
risk­
risk
tradeoffs
between
microbial
pathogens
and
DBPs.
The
requirements
include:

°
An
MCLG
of
zero
for
Cryptosporidium.

°
Removal
of
99
percent
(
2
logs)
of
Cryptosporidium
for
systems
that
use
filters.

°
Strengthened
performance
standards
for
combined
filter
effluent
turbidity
and
individual
filter
turbidity.

°
Disinfection
profiling
and
benchmarking
to
assess
the
level
of
microbial
protection
provided
as
facilities
change
their
disinfection
practices
to
meet
the
requirements
of
the
Stage
1
DBPR.

°
Inclusion
of
Cryptosporidium
in
the
definition
of
GWUDI
and
in
the
watershed
control
requirements
for
unfiltered
PWSs.

°
Covers
for
all
new,
finished
water
storage
facilities.

°
A
primacy
provision
that
requires
States
to
conduct
sanitary
surveys
for
all
surface
water
systems,
including
those
serving
fewer
than
10,000
people.

For
performance
standards,
the
turbidity
levels
in
combined
filtered
water
must
be
no
greater
than
0.3
NTU
in
at
least
95
percent
of
samples
taken
each
month;
turbidity
must
not
exceed
1.0
NTU
at
any
time.
In
addition,
individual
filters
must
be
monitored
and
systems
must
provide
an
exceptions
report
to
the
State
(
if
required)
monthly.
Exceptions
to
be
reported
include
the
following:

°
Any
individual
filter
with
a
turbidity
level
greater
than
1.0
NTU
in
2
consecutive
measurements
taken
15
minutes
apart.
Systems
must
also
either
identify
and
report
an
obvious
reason
for
exceedance
or
produce
a
filter
profile
for
that
filter.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
9
°
Any
individual
filter
with
a
turbidity
level
greater
than
0.5
NTU
after
4
hours
of
filter
operation,
based
on
2
consecutive
measurements
taken
15
minutes
apart.
If
no
obvious
reason
for
abnormal
filter
performance
can
be
identified,
a
filter
profile
must
be
produced
within
7
days
of
the
exceedance.

°
An
assessment
by
the
system
of
any
individual
filter
that
has
turbidity
levels
greater
than
1.0
NTU
in
2
consecutive
measurements
taken
15
minutes
apart
in
each
of
3
consecutive
months.

°
A
Comprehensive
Performance
Evaluation
by
the
State,
or
by
a
third
party
approved
by
the
State,
of
any
individual
filter
that
has
turbidity
levels
greater
than
2.0
NTU
in
2
consecutive
measurements
taken
15
minutes
apart
in
each
of
2
consecutive
months.

The
IESWTR
was
promulgated
concurrently
with
the
Stage
1
DBPR
so
that
systems
could
coordinate
their
response
to
the
risks
posed
by
DBPs
and
microbial
pathogens.

1.2.10
Proposed
Ground
Water
Rule
In
May
2000,
EPA
proposed
the
Ground
Water
Rule
to
address
fecal
contamination
in
ground
water
systems.
The
proposed
Ground
Water
Rule
also
builds
on
the
TCR
through
provisions
based
on
further
evaluation
of
E.
coli
monitoring
results
measured
under
the
TCR.
EPA
plans
to
publish
a
final
rule
in
2003.
Key
components
of
the
multibarrier
approach
for
protection
of
ground
water
included
in
the
proposed
rule
are:

°
Periodic
sanitary
surveys
for
all
ground
water
systems
requiring
the
evaluation
of
eight
elements
and
the
identification
of
significant
deficiencies.

°
Hydrogeologic
assessments
to
identify
wells
sensitive
to
fecal
contamination.

°
Source
water
monitoring
for
systems
drawing
from
sensitive
ground
water
sources.

°
Compliance
monitoring
to
ensure
that
disinfection
treatment
is
reliably
operated
when
it
is
used.

°
Correction
of
significant
deficiencies
and
fecal
contamination
through
the
following
actions:

­
Eliminate
the
source
of
contamination
­
Correct
the
significant
deficiency
­
Provide
an
alternative
source
of
water
­
Provide
inactivation
and/
or
removal
of
99.99
percent
(
4
logs)
of
viruses
1.2.11
Filter
Backwash
Recycling
Rule
The
Filter
Backwash
Recycling
Rule
(
FBRR),
promulgated
on
June
8,
2001
(
USEPA
2001b),
regulates
systems
where
filter
backwash
is
returned
to
the
treatment
process.
The
rule
applies
to
surface
water
and
GWUDI
systems
that
use
direct
or
conventional
filtration
and
recycle
spent
filter
backwash
water,
sludge
thickener
supernatant,
or
liquids
from
dewatering
processes.

The
following
filter
backwash
requirements
will
reduce
the
potential
risks
associated
with
recycling
contaminants
removed
during
filtration:
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
10
°
Recycling
systems
are
required
to
return
spent
filter
backwash,
sludge
thickener
supernatant,
and
liquids
from
dewatering
processes
through
all
processes
of
a
system's
existing
conventional
or
direct
filtration,
or
at
an
alternate
location
approved
by
the
State.

°
Conventional
and
direct
filtration
systems
that
recycle
specific
flows
must
notify
the
State
that
they
practice
recycling
and
must
provide
schematics
and
other
information
about
their
recycling
processes.

°
Systems
must
collect
and
maintain
information
for
review
by
the
State.

1.2.12
Long
Term
1
Enhanced
Surface
Water
Treatment
Rule
Like
the
IESWTR,
the
proposed
LT1ESWTR
is
an
enhancement
of
the
1989
SWTR,
but
for
small
systems.
The
LT1ESWTR
(
USEPA
2002a),
promulgated
in
January
2002,
extends
control
of
Cryptosporidium
and
other
disease­
causing
microbes
to
surface
water
and
GWUDI
systems
that
serve
fewer
than
10,000
people
annually.
Key
provisions
in
the
LT1ESWTR
are
very
similar
to
those
for
the
IESWTR
but
provide
additional
flexibility
for
small
systems.
LT1ESWTR
requirements
include
the
following:

°
Conventional
and
direct
filtration
systems
must
comply
with
specific
combined
filter
effluent
turbidity
requirements
and
individual
filter
turbidity
requirements.

°
Systems
must
develop
a
disinfection
profile
to
help
ensure
that
if
changes
are
made
to
the
disinfection
practices
in
order
to
comply
with
the
new
DBP
standards,
current
microbial
inactivation
treatment
is
maintained.

°
Finished
water
reservoirs
for
which
construction
begins
after
the
effective
date
of
the
rule
must
be
covered.

°
Inclusion
of
Cryptosporidium
in
the
definition
of
GWUDI
systems
and
in
the
watershed
control
requirements
for
unfiltered
PWSs.

1.2.13
M­
DBP
Advisory
Committee
(
Stage
2
DBPR)

In
March
1999,
EPA
reconvened
the
M­
DBP
Advisory
Committee
to
develop
recommendations
on
issues
pertaining
to
the
development
of
the
Stage
2
DBPR
and
LT2ESWTR.
The
Committee
consisted
of
organizational
members
representing
EPA,
State
and
local
public
health
and
regulatory
agencies,
local
elected
officials,
Native
American
tribes,
drinking
water
suppliers,
chemical
and
equipment
manufacturers,
and
public
interest
groups.
The
Committee
evaluated
recent
health
effects
information
and
the
potential
benefits
of
a
Stage
2
DBPR
and
LT2ESWTR.
The
Committee
considered
new
information
from
the
ICR
and
other
data
sources
on
the
occurrence
of
DBPs
and
pathogens
as
well
as
the
treatment
performance
and
costs
of
various
technologies.
The
Committee
established
a
Technical
Working
Group
(
TWG)
to
provide
technical
support
for
the
Committee's
discussions.

Despite
the
evaluation
of
a
large
amount
of
data,
the
Committee
recognized
that
substantial
uncertainty
remains
regarding
the
nature
and
magnitude
of
risk
associated
with
DBPs
and
pathogens
in
drinking
water.
In
light
of
this
uncertainty,
the
Committee
recommended
steps,
based
on
the
extensive
analysis
discussed
in
this
document
and
in
EPA's
economic
analysis,
to
address
the
areas
of
greatest
concern
without
placing
an
undue
burden
on
PWSs.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
11
In
September
2000,
the
Committee
signed
the
Agreement
in
Principle
 
a
full
statement
of
the
consensus
recommendations
of
the
group.
The
Agreement
was
published
by
EPA
in
a
December,
2000
Federal
Register
notice
(
USEPA
2000c).
The
Agreement
is
divided
into
Parts
A
and
B,
as
summarized
below.

Part
A
Stage
2
DBPR
°
MCLs
for
TTHM
and
HAA5
will
remain
at
0.080
and
0.060
mg/
L,
respectively.

°
Compliance
with
MCLs
for
TTHM
and
HAA5
will
be
based
on
the
locational
running
annual
average
(
LRAA).

°
In
Phase
1
of
the
rule,
systems
must
comply
with
TTHM
and
HAA5
MCLs
of
0.080
and
0.060
mg/
L
as
a
RAA
and
0.120
and
0.100
mg/
L
calculated
as
a
LRAA
at
sample
location.

°
In
Phase
2,
compliance
with
TTHM
and
HAA5
MCLs
of
0.080
and
0.060
mg/
L
is
calculated
as
a
LRAA
for
each
of
the
new
monitoring
locations
identified
in
the
Individual
Distribution
System
Evaluation
(
IDSE).

°
Systems
will
carry
out
an
IDSE
to
select
new
compliance
monitoring
sites
that
more
accurately
capture
the
highest
TTHM
and
HAA5
levels.
The
studies
will
be
based
either
on
system­
specific
monitoring
or
other
system
specific
data
that
provides
equivalent
or
better
information
on
site
selection.

°
MCL
for
bromate
will
remain
at
0.010
mg/
L.

LT2ESWTR
°
Additional
treatment
requirements
for
Cryptosporidium
will
be
based
on
the
results
of
source
water
monitoring.

°
Systems
that
are
required
to
provide
additional
removal/
inactivation
can
choose
technologies
from
a
`
toolbox'
of
options.

°
The
monitoring
burden
for
small
systems
will
be
reduced
through
the
use
of
indicators.

°
Systems
will
conduct
future
monitoring
to
determine
if
source
water
quality
has
changed
following
completion
of
the
initial
monitoring.

°
Unfiltered
systems
will
achieve
at
least
2
logs
of
Cryptosporidium
removal,
and
unfiltered
systems
will
meet
overall
inactivation
requirements
with
a
minimum
of
two
disinfectants.

°
Systems
will
cover
all
uncovered
finished
water
reservoirs
unless
the
reservoir
effluent
is
treated
to
achieve
4
logs
of
virus
inactivation
or
the
State
determines
that
existing
risk
mitigation
is
adequate.

°
EPA
will
develop
guidance
and
criteria
to
facilitate
the
use
of
UV
for
compliance
with
drinking
water
disinfection
requirements.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
12
Part
B
°
Beginning
in
January
2001,
as
part
of
the
6­
year
review
of
the
TCR,
EPA
will
initiate
a
stakeholder
process
to
address
distribution
system
requirements
related
to
significant
health
risks.

°
The
Committee
recommends
that
EPA
develop
a
national
water
quality
criteria
under
the
Clean
Water
Act
for
microbial
pathogens
for
stream
segments
designated
by
States
for
drinking
water
use.

These
recommendations
reflect
the
Committee's
emphasis
on
targeted,
risk­
based
rulemaking.
They
incorporate
substantial
initial
monitoring
to
identify
systems
with
the
highest
potential
risk.
Additional
treatment
steps
are
required
only
where
systems
exceed
limits
on
locational
average
DBP
concentrations
or
source
water
Cryptosporidium
occurrence
levels.

1.3
Factors
Affecting
DBP
Formation
Organic
DBPs
(
and
oxidation
byproducts)
are
formed
by
the
reaction
between
organic
substances
and
oxidizing
agents
that
are
added
to
water
during
treatment.
In
most
water
sources,
natural
organic
matter
(
NOM)
is
the
major
constituent
of
organic
substances
and
DBP
precursors.
NOM
is
typically
measured
as
TOC
and
as
such
the
two
terms
are
used
interchangeably
in
much
of
the
discussion
presented
here.
Major
factors
affecting
the
type
and
amount
of
DBPs
formed
include:

°
Type
of
disinfectant,
dose,
and
residual
concentration
°
Contact
time
and
mixing
conditions
between
disinfectant
(
oxidant)
and
precursors
°
Concentration
and
characteristics
of
precursors
°
Water
temperature
°
Water
chemistry
(
including
pH,
bromide
ion
concentration,
organic
nitrogen
concentration,
and
presence
of
other
reducing
agents
such
as
iron
and
manganese)

A
description
of
these
factors
follows.

1.3.1
Impact
of
Disinfection
Method
on
Organic
DBP
Formation
Organic
DBPs
can
be
subdivided
into
halogenated
and
non­
halogenated
byproducts.
Halogenated
organic
disinfection
byproducts
are
formed
when
organic
compounds
in
water
react
with
free
chlorine,
free
bromine,
or
free
iodine.
The
formation
reactions
may
take
place
in
the
treatment
plant
or
the
distribution
system.
Free
chlorine
can
be
introduced
to
water
directly
as
a
primary
or
secondary
disinfectant,
or
as
a
byproduct
of
the
manufacturing
of
chlorine
dioxide
and
chloramines.
Reactions
between
NOM
and
chlorine
lead
to
the
formation
of
a
variety
of
halogenated
DBPs
including
THMs
and
HAAs.

Free
chlorine
and
ozone
oxidize
bromide
ion
to
hypobromite
ion/
hypobromous
acid,
which
in
turn
can
react
with
NOM
to
form
brominated
DBPs
(
e.
g.,
bromoform).
The
presence
of
bromide
affects
both
the
rate
and
yield
of
DBPs.
As
the
ratio
of
bromide
to
NOM
increases,
the
percentage
of
brominated
DBPs
increases.
For
example,
Krasner
(
1999)
reported
the
rate
of
THM
formation
is
higher
in
waters
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
13
with
increased
concentrations
of
bromide.
Oxidation
of
organic
nitrogen
can
lead
to
the
formation
of
DBPs
containing
nitrogen,
such
as
haloacetonitriles
(
HAN4),
halopicrins,
and
cyanogen
halide
(
Reckhow
et
al.
1990;
Hoigné
and
Bader
1988).
Brominated
DBPs
can
also
form
by
bromine
substitution
in
the
chlorinated
byproducts.
Hypobromous
acid
is
a
more
effective
substituting
agent,
while
hypochlorous
acid
is
a
better
oxidant
(
Krasner
1999).

Non­
halogenated
DBPs
may
form
when
precursors
react
with
strong
oxidants.
For
example,
the
reaction
of
organics
with
ozone
and
hydrogen
peroxide
results
in
the
formation
of
aldehydes,
aldo­
and
keto­
acids,
and
organic
acids
(
Singer
1999).
Chlorine
can
also
trigger
the
formation
of
some
nonhalogenated
DBPs
(
Singer
and
Harrington
1993).
Many
of
the
non­
halogenated
DBPs
are
biodegradable.

Studies
have
documented
that
chloramines
produce
significantly
lower
DBP
levels
than
free
chlorine,
and
there
is
no
clear
evidence
that
the
reaction
of
NOM
and
chloramine
leads
to
the
formation
of
THMs
(
Singer
and
Reckhow
1999;
USEPA
1999a).
Predictions
of
an
empirical
DBP
formation
model
calibrated
using
ICR
data
indicated
that
THMs
and
HAAs
are
formed
in
full­
scale
plants
and
distribution
systems
under
chloraminated
conditions
as
a
fraction
of
the
amount
that
would
be
expected
based
on
observations
of
DBP
formation
under
free
chlorine
conditions.
The
amount
of
formation
with
chloramines
varied
from
5
percent
to
35
percent
of
that
calculated
for
free
chlorine,
depending
on
the
individual
DBP
species
(
Swanson
et
al.
2001).

It
is
possible
that
DBPs
might
form
during
the
mixing
of
chlorine
and
ammonia,
when
free
chlorine
might
react
with
NOM
before
the
complete
formation
of
chloramines.
In
addition,
monochloramine
slowly
hydrolyzes
to
release
free
chlorine
in
water.
This
free
chlorine
may
contribute
to
the
formation
of
small
amounts
of
additional
DBPs
in
the
distribution
system.
The
benefits
of
low
DBP
formation
with
chloramines
are
especially
important
at
the
extremities
of
the
distribution
system
where
high
DBP
levels
can
found.

The
application
of
chlorine
dioxide
does
not
produce
significant
amounts
of
organic
halogenated
DBPs.
Only
small
amounts
of
total
organic
halides
(
TOXs,
the
class
of
halogenated
organic
by­
products
that
includes
THMs
and
HAAs)
are
formed.
However,
THMs
and
HAAs
will
form
if
excess
chlorine
is
added
to
water
to
ensure
complete
reaction
with
sodium
chlorite
during
the
production
of
chlorine
dioxide.

To
date,
there
is
no
evidence
to
suggest
that
use
of
UV
results
in
the
formation
of
any
disinfection
byproducts;
however,
little
research
has
been
performed
in
this
area.
Most
of
the
research
regarding
application
of
UV
and
DBP
formation
has
focused
on
chlorinated
DBP
formation
as
a
result
of
UV
application
prior
to
the
addition
of
chlorine
or
chloramines.
The
evidence
suggests
UV
does
not
affect
chlorinated
DBP
formation.

Ozone
does
not
produce
chlorinated
DBPs;
however,
ozone
can
alter
the
reactions
between
chlorine
and
NOM
and
affect
the
speciation
of
chlorinated
DBPs
when
chlorine
is
added
downstream.
In
waters
with
sufficient
bromide
concentrations,
ozonation
can
lead
to
the
formation
of
bromate
and
other
brominated
DBPs.
Bromate,
like
THMs
and
HAAs,
is
a
regulated
DBP.
Ozonation
of
natural
waters
also
produces
aldehydes,
haloketones,
ketoacids,
carboxylic
acids,
and
other
types
of
biodegradable
organic
material.
The
biodegradable
fraction
of
organic
material
can
serve
as
a
nutrient
source
for
microorganisms,
and
should
be
removed
to
prevent
microbial
regrowth
in
the
distribution
system.

1.3.2
Disinfectant
Dose
The
concentration
of
disinfectant
can
affect
the
formation
of
DBPs.
In
general,
changes
in
the
disinfectant
dose
have
a
great
impact
on
DBP
formation
during
primary
disinfection
because
the
disinfectant
is
typically
the
limiting
reactant
in
DBP
formation
reactions.
Although
disinfectant
dose
can
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
14
affect
DBP
formation
during
secondary
disinfection,
the
effect
is
less
significant
than
in
primary
disinfection.
During
secondary
disinfection
DBP
formation
reactions
may
be
precursor
limited
since
an
excess
of
disinfectant
is
added
to
the
water.
In
the
distribution
system,
DBP
formation
reactions
become
disinfectant­
limited
when
the
free
chlorine
residual
drops
to
low
levels.
(
Singer
and
Reckhow
[
1999]
suggested
a
chlorine
concentration
of
0.3
mg/
L
as
a
rule
of
thumb).

In
many
systems
booster
disinfection
is
applied
to
raise
disinfectant
residual
concentration,
especially
in
remote
areas
of
the
distribution
system
or
near
storage
tanks
where
water
age
may
be
high
and
disinfectant
residuals
can
be
low.
The
additional
chlorine
dose
applied
to
the
water
at
these
booster
facilities
can
increase
THM
and
HAA
levels.
Further,
booster
chlorination
can
maintain
high
HAA
concentrations
because
the
increased
disinfection
residuals
can
prevent
the
biodegradation
of
HAAs.

1.3.3
Time
Dependency
of
DBP
Formation
In
general,
DBPs
continue
to
form
in
drinking
water
as
long
as
disinfectant
residuals
and
reactive
DBP
precursors
are
present.
Thus,
the
longer
the
contact
time
between
disinfectant/
oxidant
and
NOM,
the
greater
the
amount
of
DBPs
that
can
be
formed.
This
accumulation
is
a
consequence
of
the
formation
of
THMs
and
HAAs
and
their
associated
chemical
stabilities,
which
are
generally
quite
high
in
the
disinfected
drinking
water
as
long
as
a
significant
disinfectant
residual
is
still
present
(
Singer
and
Reckhow
1999).

High
TTHM
values
usually
occur
where
the
water
age
is
the
oldest.
Unlike
THMs,
HAAs
cannot
be
consistently
related
to
water
age
because
HAAs
are
known
to
biodegrade
over
time
when
the
disinfectant
residual
is
low.
This
might
result
in
relatively
low
HAA
concentrations
in
areas
of
the
distribution
system
where
disinfectant
residuals
are
depleted.

In
contrast
to
chlorination
byproducts,
ozonation
byproducts
form
more
rapidly
and
their
period
of
formation
is
much
lower
than
that
of
chlorination
byproducts
(
Singer
and
Reckhow
1999).
This
is
the
result
of
the
quick
dissipation
of
ozone
residuals
in
drinking
water
treatment
plants.

1.3.4
Concentration
and
Characteristics
of
Precursors
The
formation
of
halogenated
DBPs
is
related
to
the
concentration
of
NOM
at
the
point
of
chlorination.
Greater
DBP
levels
are
formed
in
waters
with
high
concentrations
of
precursors.
Studies
conducted
with
different
fractions
of
NOM
have
indicated
the
reaction
between
chlorine
and
NOM
with
high
aromatic
content
tends
to
form
higher
DBP
levels
than
NOM
with
low
aromatic
content.
For
this
reason,
UV
absorbance
(
typically
indicated
by
UV
absorbance
at
254
nm
[
UV­
254]),
which
is
generally
attributed
to
the
aromatic
and
unsaturated
components
of
NOM,
is
considered
a
good
predictor
of
the
tendency
of
a
source
water
to
form
THMs
and
HAAs
(
Owen
et
al.
1998;
Singer
and
Reckhow
1999).
It
should
be
noted,
however,
that
the
more
highly
aromatic
precursors,
characterized
by
high
UV­
254,
in
source
waters
are
more
easily
removed
by
coagulation.
Thus,
it
is
the
UV­
254
measurement
immediately
upstream
of
the
point(
s)
of
chlorination
within
a
treatment
plant
that
is
more
directly
related
to
THM
and
HAA
formation
potential.

1.3.5
Water
Temperature
The
rate
of
formation
of
THMs
increases
with
increasing
temperature.
HAA
formation
rates
may
also
increase
with
temperature,
though
the
effects
are
less
pronounced.
Consequentially,
the
highest
THM
and
HAA
levels
may
occur
in
the
warm
summer
months.
However,
water
demands
are
often
higher
in
warmer
months,
resulting
in
lower
water
age
within
the
distribution
system
and
helping
to
control
DBP
formation.
Furthermore,
high
temperature
conditions
in
the
distribution
system
promote
the
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
15
accelerated
depletion
of
residual
chlorine,
which
can
mitigate
DBP
formation
and
promote
biodegradation
of
HAAs
(
unless
chlorine
dosages
are
increased
to
maintain
high
residuals).
(
Singer
and
Reckhow
1999).
For
these
reasons,
depending
on
the
specific
system,
the
highest
THM
and
HAA
levels
may
be
observed
during
months
which
are
warm,
but
not
necessarily
the
warmest.

Seasonal
trends
affect
where
high
THM
and
HAA
concentrations
might
be
found.
For
example,
when
water
is
colder,
microbial
activity
is
typically
lower
and
DBP
formation
kinetics
are
slower.
Under
these
conditions,
the
highest
THM
and
HAA
concentrations
might
appear
coincident
with
the
oldest
water
in
the
system.
In
warmer
water,
the
highest
HAA
concentrations
might
appear
in
fresher
water,
which
is
likely
to
contain
higher
disinfectant
residuals
that
can
prevent
the
biodegradation
of
HAAs.

1.3.6
Water
pH
In
the
presence
of
NOM
and
chlorine,
THM
formation
increases
with
increasing
pH,
whereas
the
formation
of
HAAs
and
other
DBPs
increase
with
decreasing
pH.
The
increase
of
THMs
at
higher
pH
values
is
likely
due
to
base
catalyzed
reactions
that
lead
to
THM
formation.
The
HAA
formation
pathway
can
be
altered
at
high
pH
since
their
precursors
can
hydrolyze
(
Singer
and
Reckhow
1999).

The
major
byproducts
of
ozonation
are
not
affected
by
base
hydrolysis.
However,
the
rate
of
decomposition
of
ozone
to
hydroxyl
radical
is
accelerated
as
pH
increases.
This
occurrence
is
thought
to
be
responsible
for
the
decrease
of
some
byproducts
(
e.
g.,
aldeydes)
and
the
increase
of
others
(
e.
g.,
carbonyl
byproduct
and
total
organic
halides;
Singer
and
Reckhow
1999).
The
application
of
ozone
to
bromide
containing
waters
leads
to
the
formation
of
hypobromite
and
hypobromous
acid.
At
low
pH,
the
equilibrium
shifts
to
hypobromous
acid
which
can
react
with
NOM
to
form
halogenated
byproducts
such
as
bromoform
and
dibromoacetic
acid
(
Singer
and
Reckhow
1999).

1.4
The
Primary
Data
Source:
Information
Collection
Rule
The
main
source
of
occurrence
data
for
large
PWSs
is
the
ICR.
ICR
monitoring
requirements
applied
to
surface
and
ground
water
CWSs
serving
at
least
100,000
people
(
296
systems
total).
The
monitoring
began
in
July
1997
and
ended
in
December
1998.
The
ICR
generated
data
sets
for
512
plants
(
which
includes
the
11
blended
source
water
plants),
that
characterize
the
water
quality
in
each
plant's
source
water,
in
several
steps
in
the
treatment
process,
and
at
several
points
in
the
distribution
system
(
reflecting
finished
water).

This
section
describes
the
ICR
data
collected,
ICR
implementation
activities,
ICR
sampling
plans,
data
management
activities,
quality
assurance
activieis,
and
the
development
of
the
auxiliary
databases.
The
last
two
subsections
(
1.4.8
and
1.4.9)
describe
the
methods
used
to
analyze
ICR
data
and
how
the
data
analyses
are
documented.
Appendix
C
summarizes
the
uses
of
the
ICR
data
and
document
how
data
quality
objectives
are
met.
For
more
detailed
information
on
the
ICR
data
collection
methodology
and
results,
refer
to
the
following
publications:

°
ICR
Sampling
Manual
(
USEPA
1996b)

°
Information
Collection
Rule
Data
Analysis
(
McGuire
et
al.
2002)

1.4.1
Description
of
the
ICR
Data
Set
ICR
monitoring
requirements
depended
on
the
system
size
and
type.
Surface
water
systems
serving
more
than
100,000
people
were
required
to
monitor
for
DBPs
and
related
parameters
(
e.
g.,
DBP
precursors,
disinfectants),
conduct
microbial
monitoring,
collect
treatment
plant
design
and
operating
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
16
information,
and
monitor
for
treatment
study
applicability
(
which
determined
if
a
treatment
study
was
required).
Ground
water
systems
serving
more
than
100,000
people
were
required
to
monitor
for
DBPs
and
related
parameters
and
for
treatment
study
applicability.
Ground
water
systems
serving
more
then
50,000
but
fewer
than
100,000
people
were
required
to
monitor
only
for
treatment
study
applicability.

The
following
subsections
describe
ICR
analytical
requirements,
sample
locations,
monitoring
frequency,
and
minimum
reporting
levels.
A
summary
of
all
requirements
follows
the
discussion
(
Exhibit
1.4).
For
more
detailed
information,
such
as
specific
treatment
sampling
locations,
refer
to
the
ICR
Sampling
Manual
(
USEPA
1996b).

Analytical
Requirements
Samples
were
analyzed
for
the
following:

°
Water
quality
parameters,
including
DBP
precursors
(
temperature,
pH,
alkalinity,
total
organic
carbon,
etc.)

°
Disinfectants
(
free
chlorine
residual,
chloramine
residual,
etc.)

°
DBPs
(
TTHM
and
individual
THM
species
such
as
chloroform;
HAA5,
HAA6,
HAA9,
and
individual
HAA
species;
chlorite;
bromate,
etc.)

Since
DBP
formation
depends
on
the
type
of
disinfectant
used,
monitoring
for
each
DBP
did
not
occur
at
every
plant.
For
example,
chlorite
is
a
byproduct
primarily
related
to
disinfection
with
chlorine
dioxide
and
was
therefore
monitored
only
by
plants
that
use
chlorine
dioxide.

Microbial
analyses
were
also
performed
on
some
samples.
Microbial
results
are
not
covered
in
this
document;
see
the
LT2ESWTR
Occurrence
Document
(
USEPA
2003b)
for
microbial
regulations
and
results
from
the
ICR.

Sample
Locations
ICR
samples
were
generally
collected
at
the
treatment
plant
influent,
sites
throughout
the
treatment
plant
(
e.
g.,
before
and
after
filtration,
before
and
after
each
point
of
disinfection),
a
finished
water
location
(
typically
the
same
as
the
entry
point
sample
except
for
plants
that
blend
finished
water
from
multiple
treatment
plants),
and
sites
within
the
distribution
system.
A
total
of
four
distribution
system
monitoring
locations
were
required
for
the
ICR:

°
Average
Residence
Time
in
the
Distribution
System
(
AVG1
and
AVG2):
two
sample
points
in
the
distribution
system,
each
representing
an
approximate
average
residence
time,
as
designated
by
the
water
system.

°
Maximum
Residence
Time
in
the
Distribution
System
(
DS
Maximum):
the
samples
from
the
point
in
the
distribution
system
that
has
the
longest
residence
time,
as
designated
by
the
water
system.

°
Distribution
System
Equivalent
(
DSE)
:
a
sample
from
the
point
in
the
distribution
system
that
has
a
well
characterized
detention
time
equivalent
to
a
simulated
distribution
sample
(
SDS).

Plant
characteristics,
including
source
water
and
disinfectant
type,
determined
the
specific
sampling
location
and
frequency
for
certain
parameters.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
17
Monitoring
Frequency
General
water
quality
parameters,
DBP
precursors,
and
disinfectant
concentrations
were
monitored
monthly,
while
most
DBPs
were
monitored
quarterly.
Targeted
DBP
monitoring
for
bromate
and
chlorite
was
conducted
monthly.
Monthly
samples
were
supposed
to
reflect
typical
operating
conditions
at
the
plant
and
each
set
was
required
to
be
collected
within
a
72­
hour
period.
A
minimum
of
14
days
was
required
between
monthly
sampling
periods.
A
minimum
of
two
months
was
required
between
quarterly
sampling
periods
(
USEPA
1996b).

Minimum
Reporting
Levels
The
method
detection
limit
(
MDL)
is
defined
as
the
minimum
concentration
of
a
substance
that
can
be
measured
and
reported
with
99
percent
confidence
that
the
reported
analyte
concentration
is
greater
than
zero.
Usually,
measurements
below
the
MDL
concentration
are
considered
qualitative,
not
quantitative,
because
they
are
not
adequately
precise
to
meet
the
needs
of
the
data
user(
s).
MDLs
vary
from
laboratory
to
laboratory
based
on
the
method
used,
equipment,
etc.

Because
method
detection
limits
vary
from
method
to
method
and
from
laboratory
to
laboratory,
EPA
established
Minimum
Reporting
Levels
(
MRL)
for
the
ICR.
MRLs
were
based
on
(
1)
a
review
of
available
occurrence
data
to
confirm
that
most
are
above
the
MRL;
(
2)
whether
the
concentration
at
the
MRL
could
be
measured
taking
use,
burden,
and
status
of
analytical
methods
into
consideration;
and
(
3)
recommendations
of
an
expert
panel.
Although
EPA
recognizes
that
some
laboratories
could
provide
reliable
data
at
concentrations
below
the
MRL,
a
concentration
measured
below
the
MRL
was
not
required
to
be
reported;
instead,
"
below
the
MRL"
was
reported.
Exhibit
1.4
presents
the
ICR
MRLs
for
water
quality
parameters,
disinfectants,
and
DBPs.
Section
1.4.8
explains
how
results
that
are
"
below
the
MRL"
were
handled
in
the
ICR
data
analysis.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
18
Exhibit
1.4
ICR
Plant
Monitoring
Requirements
Analyte
Plant
Types
Required
to
Test
Sampling
Locations
(#
of
Sampling
Locations)
1
Frequency
Minimum
Reporting
Level
(
MRL)

Water
Quality
Parameters
Total
Organic
Carbon
(
TOC)
All
Influent,
Treatment,
Finished
Monthly
0.7
mg/
L
as
C
pH
All
Influent,
Treatment,
Finished
Monthly
 
All
Distribution
System
(
4)
Quarterly
Hypochlorite
Disinfectant
Stock
Solution
Quarterly
Alkalinity
2
All
Influent,
Treatment,
Finished
Monthly
 
All
Distribution
System
(
4)
Quarterly
Total
Hardness
2
All
Influent,
Treatment,
Finished
Monthly
 
All
Distribution
System
(
4)
Quarterly
Turbidity
2
All
Influent,
Treatment,
Finished
Monthly
 
All
Distribution
System
(
4)
Quarterly
Temperature
2
All
Influent,
Treatment,
Finished
Monthly
 
All
Distribution
System
(
4)
Quarterly
Hypochlorite
Disinfectant
Stock
Solution
Quarterly
Bromide
All
Influent,
Treatment
Monthly
0.02
mg/
L
UV­
254
absorbance
All
Influent,
Treatment,
Finished
Monthly
0.009
cm­
1
Disinfectants
Free
Chlorine
Residual
2
Free
chlorine
as
residual
disinfectant
Treatment,
Finished
Monthly
 
Distribution
System
(
4)
Quarterly
Hypochlorite
Disinfectant
Stock
Solution
Quarterly
Total
Chlorine
Residual
2
All
Treatment,
Finished
Monthly
 
Distribution
System
(
4)
Quarterly
Chlorine
Dioxide
(
ClO2)
2
Chlorine
Dioxide
Treatment,
Finished,
and
Distribution
System
(
3)
Monthly
 
Ozone
2
Ozone
Treatment
Monthly
 
DBPs
Total
Trihalomethanes
(
TTHM)
2
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
 
Chloroform
(
CHCl3)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
1.0
µ
g/
L
Bromodichloro­
methane
(
BDCM)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
1.0
µ
g/
L
Dibromochloro­
methane
(
DBCM)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
1.0
µ
g/
L
Bromoform
(
CHBr3)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
1.0
µ
g/
L
Haloacetic
Acid­
Five
(
HAA5)
2
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
 
Analyte
Plant
Types
Required
to
Test
Sampling
Locations
(#
of
Sampling
Locations)
1
Frequency
Minimum
Reporting
Level
(
MRL)

Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
19
Haloacetic
Acid­
Six
(
HAA6)
2
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
 
Haloacetic
Acid­
Nine
(
HAA9)
2
All
Encouraged
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
 
Monochloroacetic
Acid
(
MCAA)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
2.0
µ
g/
L
Dichloroacetic
Acid
(
DCAA)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
1.0
µ
g/
L
Trichloroacetic
Acid
(
TCAA)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
1.0
µ
g/
L
Monobromoacetic
Acid
(
MBAA)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
1.0
µ
g/
L
Dibromoacetic
Acid
(
DBAA)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
1.0
µ
g/
L
Bromochloracetic
acid
(
BCAA)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
1.0
µ
g/
L
Bromodichloroacetic
acid
(
BDCAA)
All
Encouraged
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
1.0
µ
g/
L
Chlorodibromoacetic
acid
(
CDBAA)
All
Encouraged
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
2.0
µ
g/
L
Tribromoacetic
acid
(
TBAA)
All
Encouraged
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
4.0
µ
g/
L
Bromate
(
low­
level)
Chlorine
Dioxide
Treatment,
Finished
Monthly
0.2
µ
g/
L
Ozone
Treatment,
Finished
Monthly
Bromate
(
Method
300.0)
Ozone
Treatment,
Finished
Monthly
5.0
µ
g/
L
Chlorite
(
ClO2
!
)
Chlorine
Dioxide
Treatment,
Finished,
and
Distribution
System
(
3)
Monthly
20
µ
g/
L
Chlorate
(
ClO3
!
)
Chlorine
Dioxide
Treatment,
Finished,
and
Distribution
System
(
3)
Monthly
20
µ
g/
L
Hypochlorite
Influent,
Disinfectant
Stock
Solution,
and
Finished
Quarterly
Haloacetonitriles­
Four
(
HAN4)
2
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
 
Dichloroacetonitrile
(
DCAN)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
0.5
µ
g/
L
Trichloroacetonitrile
(
TCAN)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
0.5
µ
g/
L
Bromochloro­
acetonitrile
(
BCAN)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
0.5
µ
g/
L
Dibromoacetonitrile
(
DBAN)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
0.5
µ
g/
L
Cyanogen
chloride
(
CNCl)
Chloramine
Finished
and
Distribution
System
(
Max)
Quarterly
0.5
µ
g/
L
Analyte
Plant
Types
Required
to
Test
Sampling
Locations
(#
of
Sampling
Locations)
1
Frequency
Minimum
Reporting
Level
(
MRL)

Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
20
Chloral
Hydrate
(
CH)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
0.5
µ
g/
L
Chloropicrin
(
CP)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
0.5
µ
g/
L
Trichloropropanone
(
TCP)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
0.5
µ
g/
L
Dichloropropanone
(
DCP)
All
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
0.5
µ
g/
L
Formaldehyde3
Ozone
Treatment,
Finished
Quarterly
5.0
µ
g/
L
Chlorine
Dioxide
Treatment,
Finished
Quarterly
Acetaldehyde
3
Ozone
Treatment,
Finished
Quarterly
5.0
µ
g/
L
Chlorine
Dioxide
Treatment,
Finished
Quarterly
Butanol
Ozone
Treatment,
Finished
Quarterly
5.0
µ
g/
L
Chlorine
Dioxide
Treatment,
Finished
Quarterly
Glyoxal
Ozone
Treatment,
Finished
Quarterly
5.0
µ
g/
L
Chlorine
Dioxide
Treatment,
Finished
Quarterly
Methyl
Glyoxal
Ozone
Treatment,
Finished
Quarterly
5.0
µ
g/
L
Chlorine
Dioxide
Treatment,
Finished
Quarterly
Pentanol
Ozone
Treatment,
Finished
Quarterly
5.0
µ
g/
L
Chlorine
Dioxide
Treatment,
Finished
Quarterly
Propanol
Ozone
Treatment,
Finished
Quarterly
5.0
µ
g/
L
Chlorine
Dioxide
Treatment,
Finished
Quarterly
Total
Organic
Halides
(
TOX)
All
Influent,
Treatment,
Finished,
and
Distribution
System
(
4)
Quarterly
50
µ
g/
L
as
Cl­

Notes:
1
"
Influent"
refers
to
the
point
where
the
water
enters
the
plant.
"
Treatment"
may
include
one
or
multiple
sample
locations
along
the
treatment
process
train,
depending
on
the
water
quality
parameter,
DBP,
and
type
of
plant
and/
or
disinfectant
used.
"
Finished"
refers
to
the
point
of
exit
from
the
plant.
"
Distribution
System
(
4)"
refers
to
the
four
points
within
the
distribution
system
where
samples
were
taken:
the
distribution
system
equivalent,
two
points
with
average
residence
time,
and
one
point
with
maximum
residence
time.
"
Distribution
System
(
3)"
refers
to
3
points
in
the
distribution
system
where
samples
were
taken:
a
location
near
the
first
customer,
one
point
of
average
residence,
and
one
point
with
maximum
residence
time.
Plants
that
purchase
water
were
also
required
to
sample
most
DBPs
at
their
plant
influent.
Plants
that
blend
water
sources
within
the
treatment
plant
also
monitored
water
quality
parameters
prior
to
blending.
2
No
MRLs
were
set
for
alkalinity,
total
hardness,
turbidity,
temperature,
free
chlorine
residual,
total
chlorine
residual,
chlorine
dioxide,
and
ozone;
however,
the
data
entry
software
did
not
allow
"
0"
to
be
entered.
Also,
there
are
no
MRLs
for
analyte
summations
(
e.
g.,
TTHM,
HAA5)
because
they
are
determined
by
adding
or
averaging
several
individual
concentrations,
rather
than
by
measuring
directly.
3
Aldehyde
samples
were
also
analyzed
for
optional
aldehydes
(
benzaldehyde,
decanal,
hexanal,
heptanal,
nonanal,
octanal).

Source:
USEPA
1996c.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
21
1.4.2
ICR
Implementation
Activities
EPA,
along
with
other
agencies,
such
as
the
American
Water
Works
Association
(
AWWA)
and
the
Association
of
Metropolitan
Water
Agencies
(
AMWA),
provided
technical
assistance
before
and
during
the
ICR.
ICR
reference
manuals
and
videos
were
created
to
provide
guidance
on
various
technical
aspects
of
the
rule,
such
as
microbial
sample
collection
and
database
use.
See
Chapter
1
of
the
Information
Collection
Rule
Data
Analysis
(
McGuire
et
al.
2002)
for
a
full
listing
of
these
materials.
Email
and
telephone
support
was
provided
for
questions
during
the
early
stages
the
of
the
ICR
implementation.

During
ICR
implementation,
laboratories
analyzing
ICR
samples
for
DBPs,
DBP
surrogates,
and
other
water
quality
parameters
were
required
to
apply
for
ICR
approval
to
ensure
data
quality.
Over
400
commercial,
utility,
State,
university,
and
Federal
laboratories
applied,
of
which
380
received
approval.
Initial
approval
was
based
on
criteria
developed
by
EPA
and
a
panel
of
experts
and
was
given
based
on
method
and
analyte.
To
maintain
approval,
laboratories
had
to
successfully
conduct
six
quarterly
ICR
performance
evaluations
(
PE)
studies.
On­
site
audits
were
performed
as
an
additional
mechanism
to
maintain
data
quality.

1.4.3
ICR
Sampling
Plans
To
ensure
that
ICR
requirements
were
correctly
applied,
EPA
required
each
system
to
submit
an
Initial
Sampling
Plan
(
ISP)
for
approval.
The
ISPs
included
Initial
Sampling
Schematics
(
ISSs)
and
which
were
used
to
determine
requirements.
As
reported
in
the
Information
Collection
Rule
Data
Analysis
(
McGuire
et
al.
2002),
nearly
80
percent
of
the
ISPs
required
modifications
such
as
correcting
chemical
additions
and
sampling
locations
after
an
initial
review.
After
a
second
review,
nearly
90
percent
of
the
ISPs
were
approved.

1.4.4
Data
Management
Activities
The
ICR
data
were
reported
and
tracked
through
the
ICR
Data
Management
System.
The
ICR
Data
Management
System
consists
of
three
systems:

°
ICR
Water
Utility
Database
System,
used
by
PWSs
to
report
data
°
ICR
Laboratory
Quality
Control
(
QC)
Database
System,
used
by
independent
laboratories
to
report
information
on
sample
quality
control
°
ICR
Federal
Database
System
(
ICR
FED),
used
to
upload
and
maintain
data
from
systems
and
laboratories
in
a
central
database
The
data
reported
each
month
by
ICR
systems
on
diskettes
included
unit
process
data
for
each
ICR
plant,
and
collection
information
and
analytical
results
for
each
ICR
sample.
Once
data
were
validated,
they
entered
the
ICR
FED.
The
ICR
FED
is
an
Oracle
 
database
available
to
the
public.

1.4.5
Quality
Assurance
Activities
The
ICR
data
were
developed
based
on
the
Quality
Assurance
Project
Plan
for
the
Implementation
of
the
Information
Collection
Rule
that
was
finalized
in
July
1997
(
USEPA
1997c).
This
Plan
included
data
objectives
and
measurement
criteria,
training
requirements,
and
instructions
for
records
and
documentation.
It
specified
use
of
the
ICR
Sampling
Manual
(
EPA
814­
B­
96­
001),
the
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
22
DBP/
ICR
Analytical
Methods
Manual
(
EPA
814­
B­
96­
002),
and
the
ICR
Manual
for
Bench­
and
Pilot­
Scale
Treatment
Studies
(
EPA
814­
B­
96­
003).
It
specified
oversight
activities
needed
to
ensure
data
quality
and
the
data
system
to
be
used
for
collecting
and
reporting
the
measurement
data.
The
ICR
data
were
highly
important
to
the
decision­
making
process.
EPA
validated
in
several
ways
that
these
procedures
specified
in
the
Plan
were
being
followed
.

°
On
a
monthly
basis,
EPA
received
data
on
diskettes
from
systems
and
labs.
The
QC
requirements
established
by
the
ICR
were
more
extensive
than
those
included
in
the
analytical
methods.
Laboratories
and
systems
were
required
to
report
most
of
the
QC
data
to
EPA
along
with
the
monitoring
data.

°
Once
the
data
were
uploaded
into
the
computer
system,
the
data
were
processed
using
validation
algorithms.
These
algorithms
tested
whether
the
procedures
were
being
followed
by
verifying,
for
example,
that
the
laboratory
was
approved
to
preform
the
analysis
and
the
sample
was
analyzed
using
an
approved
method.
Information
about
the
samples
was
used
to
cross­
check
data
submitted
by
laboratories
and
water
systems.
Examples
of
validation
failures
include
exceeding
a
sample
holding
time
or
failing
the
calibration
standard.
See
Chapter
2
of
the
Information
Collection
Rule
Data
Analysis
(
McGuire
et
al.
2002)
for
a
list
of
QC
data
used
to
validate
ICR
monitoring
data.
Laboratories
and
plants
received
reports
containing
validation
failures
and
monthly
results
generated
by
ICR
FED.
They
were
given
an
opportunity
to
correct
errors
and
resubmit
data
for
the
data
validation
process.
Only
data
that
met
the
QC
criteria
were
maintained
in
ICR
FED.

°
As
noted
above,
laboratories
had
to
successfully
conduct
six
quarterly
ICR
performance
evaluations
(
PE)
studies
and
on­
site
audits
were
performed
as
an
additional
mechanism
to
maintain
data
quality.

Not
only
were
the
data
were
collected
with
rigorous
QA
procedures
in
place,
but
the
data
and
methods
were
also
extensively
technically
reviewed.
This
level
of
attention
to
assessing
the
technical
quality
of
the
ICR
data
was
used
for
several
reasons.
Most
important
was
the
recognition
that
these
data
were
critical
to
the
development
of
a
future
rule,
and
that
importance
was
underscored
by
the
data
collection
effort
being
specified
in
a
separate
federal
rule
with
the
force
of
law.
It
entailed
substantial
effort
and
expense
on
the
part
of
water
systems
and
the
government.
The
data
collection
effort
took
place
over
18
months,
which
allowed
for
technical
review
to
take
place
while
data
were
being
collected
and
for
feedback,
additional
training,
or
other
corrections
to
be
made
if
particular
water
systems
or
laboratories
appeared
to
have
consistent
data
problems.
This
technical
review
was
more
extensive
than
what
would
normally
occur
during
a
peer
review
process.

Some
of
the
technical
review
steps
undertaken
were
as
follows:

°
EPA
set
high
QC
criteria
and
monitored
the
failure
rate
for
each
data
element
and
the
reasons
for
failures
so
that
it
could
adjust
the
validation
process
to
accept
more
lower­
quality
data
or
to
work
with
utilities
and
laboratories
to
fix
the
problems
(
See
Chapter
2
of
the
Information
Collection
Rule
Data
Analysis
[
McGuire
et
al.
2002]
for
a
discussion
of
these
and
related
data
quality
issues
discussed
below.)

°
As
noted
above,
EPA
received
monthly
updates
of
data
from
systems
and
laboratories.
EPA
had
automated
some
review
of
the
technical
quality
or
reasonableness
of
the
data,
such
as
whether
the
analysis
was
sensitive
enough
to
meet
the
reporting
requirements.
Further,
the
process
had
built
in
the
requirement
for
many
fortified
and
duplicate
samples
so
that
precision
could
be
verified
and
those
data
elements
that
did
not
pass
could
be
removed.
Overall,
92
percent
of
the
analytical
data
met
the
ICR
QC
requirements
(
McGuire
et
al.
2002).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
23
°
After
review
by
EPA,
the
data
that
had
passed
the
QC
criteria
were
released
for
use
by
analysts.
"
Evaluations
of
the
QC
data
for
DBPs
and
DBP
surrogates
indicate
the
national
database 
contain
high­
quality
data
suitable
to
support
regulation
development"
(
McGuire
et
al.
2002).
The
data
were
judged
to
be
of
sufficient
quality
based
on
the
combination
of
using
only
reviewed
and
approved
laboratories
to
conduct
the
analyses,
using
specific
analytical
methods,
requiring
all
analyses
to
be
performed
within
a
specified
amount
of
time,
and
continuously
reviewing
data
throughout
the
18
months
of
data
collection.

°
In
addition
to
the
internal
EPA
process
of
reviewing,
accepting,
and
releasing
ICR
data,
these
data
were
also
carefully
scrutinized
upon
release
by
EPA
analysts,
EPA
contractors,
and
members
of
the
M­
DBP
FACA
Technical
Work
Group
(
TWG).
The
data
were
released
for
use
in
three
6­
month
blocks.
Hundreds
of
statistical
summaries
and
graphs
were
made
available
to
the
TWG
through
a
web
site
that
received
extensive
use.
These
reviewers
were
users
of
the
information
and
many
had
extensive
knowledge
of
the
surveyed
systems.
The
virtually
unlimited
availability
of
the
data
to
interested
experts
ensured
additional
technical
review
of
the
data
and
ensured
high
data
quality
because
any
identified
problems
were
discussed
and
brought
to
EPA's
attention
for
explanation
or
correction.

1.4.6
Development
of
Auxiliary
Databases
The
M­
DBP
FACA
Technical
Work
Group
determined
that
data
in
ICR
FED
needed
to
be
available
in
a
more
user­
friendly
format.
To
this
end,
EPA
created
seven
auxiliary
databases
from
ICR
FED.
The
Auxiliary
Database
1
(
AUX1)
(
USEPA
2000d)
is
the
primary
Microsoft
Access
 
database,
containing
all
system­
and
plant­
level
data
extracted
from
ICR
FED,
such
as
sampling
and
treatment
operation
data.
The
AUX1
database
is
structured
"
vertically",
i.
e.,
it
is
designed
to
facilitate
analyses
of
a
single
parameter
across
all
plants
or
subsets
of
plants.

Six
other
auxiliary
databases
were
derived
from
AUX1
that
focused
on
"
horizontal"
data,
i.
e.,
data
that
represented
source
water,
plant,
finished
water,
and
in
some
cases,
distribution
data
for
an
individual
plant
for
specific
analytes:

°
Auxiliary
Database
2
(
AUX2):
Contact
Time
(
CT)
and
Disinfection
°
Auxiliary
Database
3
(
AUX3):
Enhanced
Coagulation
°
Auxiliary
Database
4
(
AUX4):
Sludge
Production
°
Auxiliary
Database
5
(
AUX5):
Washwater
Return
°
Auxiliary
Database
6
(
AUX6):
Disinfection
Byproducts
°
Auxiliary
Database
8
(
AUX8):
Input
and
output
data
for
modeling
For
the
data
in
AUX1
to
be
presented
in
an
user­
friendly
format,
fields
were
added
as
necessary
and
some
data
manipulation
occurred.
Additional
information
on
data
transformation
can
be
obtained
from
the
dictionary
and
documentation
of
AUX1
(
USEPA
2000m).
Because
all
other
auxiliary
databases
were
extracted
from
AUX1,
the
same
data
manipulation
criteria
were
used.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
24
1.35
11.21
0.45
0.90
1.79
2.69
0.00
0.00
2.69
0.00
0.00
0.45
0.45
1.79
1.35
7.62
0.90
1.35
1.79
1.35
1.35
0.90
3.59
2.24
2.24
3.59
0.45
5.38
6.28
1.35
0.45
2.69
1.35
3.14
2.24
0.45
2.24
4.48
1.35
VT­
0.00
NH­
0.45
MA­
2.24
RI­
0.90
CT­
1.79
NJ­
4.48
DE­
0.45
MD­
0.90
DC­
0.45
0.45
0.00
2.69
1.35
1.4.7
Representativeness
of
ICR
Data
It's
important
to
characterize
the
representativeness
of
the
time
period
over
which
the
ICR
data
was
collected.
The
representativeness
of
the
time
period
can
be
assessed
by
considering
several
factors
including
geographic
distribution,
climate,
and
source
water
quality
of
the
systems
included
in
the
ICR.
See
Chapter
3
of
the
Information
Collection
Rule
Data
Analysis
(
McGuire
et
al.
2002)
for
further
discussion
of
these
topics.
The
national
representative
of
ICR
data
are
discussed
in
more
detail
in
both
the
ICR
handbook
(
McGuire
2002)
and
the
Stage
2
DBPR
EA
(
USEPA
2003a).

Geographic
Distribution
The
geographic
distribution
of
the
surface
and
ground
water
systems
represented
in
the
ICR
data
is
shown
in
Exhibits
1.5a
and
1.5b.
As
mentioned
previously,
ICR
monitoring
was
conducted
by
systems
serving
more
than
100,000
people.
Therefore,
ICR
systems
were
most
concentrated
in
five
States
with
large
populations
(
CA,
NY,
TX,
FL,
and
PA).
Four
States
(
VT,
MT,
ND,
and
WY)
had
neither
surface
or
ground
water
ICR
systems.
Note
that
the
majority
of
Florida's
systems
are
ground
water,
though
it
ranks
second
in
the
total
number
of
ICR
systems
per
State.
About
half
of
the
U.
S.
population
served
by
CWSs
is
represented
by
ICR
data
(
see
Chapter
2,
Exhibit
2.3
for
estimate
of
population
served
by
various
system
sizes).

Exhibit
1.5a
Percentage
of
Surface
Water
Systems
(
by
State)
Sampled
for
the
ICR
Note:
Maps
are
not
drawn
to
scale.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
25
0.00
26.03
0.00
1.37
0.00
1.37
0.00
0.00
0.00
1.37
0.00
0.00
1.37
0.00
0.00
5.48
0.00
0.00
1.37
0.00
2.74
1.37
2.74
1.37
2.74
1.37
0.00
5.48
0.00
0.00
0.00
1.37
1.37
0.00
0.00
0.00
0.00
0.00
30.14
VT­
0.00
NH­
0.00
MA­
0.00
RI­
0.00
CT­
0.00
NJ­
2.74
DE­
0.00
MD­
1.37
DC­
1.37
0.00
2.74
0.00
2.74
Exhibit
1.5b
Percentage
of
Ground
Water
Systems
(
by
State)
Sampled
for
the
ICR
Note:
Maps
are
not
drawn
to
scale.

Climate
and
Source
Water
Quality
In
Chapter
3
of
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002),
the
authors
evaluated
ICR
data
representativeness
by
comparing
rainfall
data
and
other
weather
patterns
that
occurred
during
the
ICR
monitoring
period
to
historical
weather
patterns
using
data
from
the
National
Weather
Service.
Results
showed
that
the
calendar
year
1998
was
the
warmest
and
fifth
wettest
year
on
record
in
the
United
States
since
1895.
Rainfall
amounts
varied,
however,
across
the
country
(
approximately
22
percent
of
the
country
was
much
wetter
than
normal;
however
about
2
percent
was
much
drier
than
normal).
National
trends
and
generalizations
on
the
representativeness
of
the
ICR
data
are
not
possible
due
to
the
regional
variations.

1.4.8
Methods
and
Assumptions
for
Analyzing
ICR
Results
Description
of
Data
Set
Evaluated
The
majority
of
ICR
data
described
in
this
chapter
are
derived
from
the
ICR
AUX1
Database,
CD
version
5.0
(
USEPA
2000d),
representing
monitoring
results
from
512
plants,
including
11
blended
source
water
plants.
Some
analyses
in
Chapter
2
are
based
on
data
from
AUX2
(
USEPA
2000i)
(
results
are
from
AUX1
unless
otherwise
noted).
Data
analyses
in
Chapters
2,
3,
and
4
of
the
document
represent
ICR
results
from
the
last
12
months,
or
last
4
quarters,
of
ICR
collection
period
(
January
through
December
1998).
Appendix
A
provides
results
for
the
full
18
months
of
the
ICR
(
July
1997
through
December
1998).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
26
Plant
Source
Water
Type
Plants
reported
the
following
source
water
types
for
each
month
of
the
ICR:
"
surface
water",
"
ground
water,"
"
mixed,"
"
blended,"
or
"
purchased
water."
For
the
purposes
of
this
document,
plant
source
water
type
is
based
on
data
from
the
last
12
months
of
the
ICR.
Because
there
are
plants
that
reported
more
than
one
source
water
type
during
this
period,
designation
of
plant
source
water
type
was
done
using
a
hierarchical
approach.
Specifically,
the
plant
source
water
type
was
designated
as
the
first
type
to
appear
in
this
list:
surface
water,
mixed,
ground
water,
and
purchased.
In
other
words,
if
an
ICR
plant
treated
surface
water
for
any
month,
it
was
classified
as
a
surface
water
plant.
Refer
to
Appendix
B
for
the
query
language
for
source
categorization
(
see
the
query
"
Plant
Source
Type,
Last
12
Months").

ICR
data
analyses
in
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002)
and
in
other
documents
may
have
designated
plant­
source
types
differently.
Because
there
are
a
small
number
of
plants
that
reported
more
than
one
source
type,
the
differences
in
methodology
should
not
create
a
large
discrepancy
in
results.

Plants
With
Multiple
Quarterly
Samples
Some
of
the
plants
in
ICR
data
set
reported
multiple
sampling
results
for
a
single
quarter
for
a
given
distribution
system
location.
In
these
circumstances,
the
data
were
averaged
for
the
sampling
location
and
quarter.
The
averaged
results
were
used
in
the
plant
screening
analysis
(
see
next
section)
and
in
all
calculations.
A
total
of
15
plants
have
at
least
one
quarter
that
was
analyzed
in
this
manner,
including
all
eleven
blended
plants.
This
does
not
apply
to
samples
collected
on
a
monthly
basis.

Screening
of
Plants
For
DBP
analyses
in
Chapters
3
and
4
of
this
document,
ICR
plants
are
screened
to
include
only
those
with
at
least
3
of
the
last
4
quarters
of
the
ICR
having
at
least
3
of
4
distribution
system
locations
with
both
TTHM
and
HAA5
data.
This
screening
was
done
to
reduce
the
seasonal
bias
that
could
occur
if
TTHM
and
HAA5
data
represented
only
one
or
two
of
the
four
quarters
(
e.
g.,
if
TTHM
data
represent
the
summer
only,
yearly
average
results
would
most
likely
be
skewed
high),
or
only
one
or
two
of
the
distribution
system
locations
(
e.
g.,
if
data
from
the
max
location
was
missing,
TTHM
average
results
for
the
distribution
system
could
be
skewed
low).

For
all
other
analytes
(
e.
g.,
TOC,
temperature,
etc.),
plants
were
screened
to
include
only
those
with
at
least
9
of
the
last
12
months
or
3
of
the
last
4
quarters
of
the
ICR
to
reduce
potential
seasonal
biases.

See
Appendix
B,
section
B.
3
for
the
query
language
for
plant
screening.

Assumptions
for
Data
Below
the
MRL
Any
data
reported
to
be
below
the
MRL
for
a
particular
water
quality
parameter,
DBP,
or
disinfectant
were
assigned
a
value
of
zero.
Because
levels
below
the
MRL
were
assigned
values
of
zero,
the
means
for
each
water
quality
parameter,
DBP,
and
disinfectant
are
probably
slightly
lower
than
they
would
be
if
the
actual
values
were
known
and
used
in
the
calculations.
In
addition,
median
concentrations
that
appear
to
be
zero
are
not
necessarily
zero
but
are
below
the
MRL.
There
is
no
MRL
for
analyte
summations
(
e.
g.,
TTHM,
HAA5)
and
DS
Average
values
because
they
are
determined
by
adding
or
averaging
several
individual
concentrations,
rather
than
by
measuring
directly.
Therefore,
if
each
THM,
HAA,
HAN4,
or
haloketone
concentration
is
below
its
MRL,
the
resulting
value
for
the
corresponding
TTHM,
HAA5,
HAA6,
HAA9,
HAN4,
and
haloketones
is
zero.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
27
1.4.9
Documentation
of
ICR
Data
Analyses
ICR
data
are
available
to
the
public
through
the
EPA
website.
Because
there
are
different
methods
that
could
potentially
be
used
to
analyze
ICR
data,
EPA
has
included
several
features
in
this
document
to
ensure
transparancy
and
reproducability
of
all
ICR­
based
results:

°
Section
1.4.8
described
the
overall
methods
and
assumptions
used
by
EPA
to
evaluate
the
ICR
data.

°
All
tables
and
graphs
in
Chapters
2
through
4
show
the
number
of
observations
(
or
N­
count)
used
to
generate
results.
The
N­
count
will
be
the
first
data
column
in
all
tables
and
will
be
in
either
the
title,
axis
heading,
or
legend
of
each
chart.

°
All
Microsoft
Access
 
queries
(
in
Structured
Query
Language
[
SQL]
code)
used
to
extract
ICR
data
from
AUX1
are
provided
in
Appendix
B.
Queries
are
organized
alphabetically
by
query
name.

°
Query
names,
corresponding
to
queries
in
Appendix
B,
are
included
at
the
bottom
of
each
applicable
table
and
chart
in
Chapters
2
through
4.

°
An
Excel
reference
file
is
also
provided
for
those
analyses
that
were
conducted
in
Microsoft
Excel.
All
Excel
files
are
included
an
accompanying
CD.

1.5
Other
Data
Sources
Occurrence
data
for
medium
and
small
water
treatment
plants
were
not
included
in
the
ICR
data
collection.
Data
were
obtained
from
the
ICRSS,
NRWA
Survey,
the
Water
Utility
Database
(
WATER:\
STATS)
(
AWWA
2000),
the
Ground
Water
Supply
Survey
(
GWSS),
and
several
States
in
order
to
examine
the
occurrence
patterns
of
medium
and
small
water
treatment
plants.
Exhibit
1.6
briefly
outlines
these
data
sources,
while
the
subsections
that
follow
describe
the
sources
in
greater
detail,
including
the
level
of
quality
assurance.
Appendix
C
summarizes
how
each
data
source
is
used
in
this
document
and
shows
how
the
data
quality
objectives
are
met.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
28
Exhibit
1.6
Summary
of
Non­
ICR
Occurrence
Survey
Data
Data
Source
Data
Collected
Time
Frame
Geographic
Representation
Number
of
plants
(
By
Population
Served)

ICR
Supplemental
Survey
(
ICRSS)
°
Raw
source
water­
(
Large
Systems)
TOC
°
Raw
source
water­
(
Small
&
Medium
Systems)
TOC,
UV
254,
bromide,
turbidity,
pH,
&
temperature
March
1999
­
February
2000
Random
national
distribution
by
SW
source
type1
°
47
serving
100,000
or
more
°
40
serving
10,000­
99,999
°
40
serving
fewer
than
10,000
NRWA
Survey
°
Population
served
and
flows
°
Raw
source
watertemperatures
turbidity,
pH,
and
source
water
type,
bromide,
TOC,
UV
254,
alkalinity,
calcium
and
total
hardness
°
Finished
water­
residence
time
estimate,
total
and
individual
THMs,
individual
HAAs
and
HAA5,
HAA6,
HAA9,
TOC,
UV
254,
Bromide,
Temperature,
pH,
free
and
total
chlorine
residual
levels
°
Treatment­
unit
processes,
disinfectant
used
November
1999
­
March
2000
Random
national
distribution
117
serving
fewer
than
10,000
WATER:\
STATS
°
Population
served
and
flows
°
Raw
source
water
­
Water
Quality
Parameters
(
WQPs),
Source
water
type
°
Finished
water­
WQPs,
TTHM,
HAAs
°
Treatment­
unit
processes,
disinfectant
used
1996
Random
national
distribution
°
219
serving
100,000
or
more
°
623
serving
10,000­
99,999
°
30
serving
fewer
than
10,000
Ground
Water
Supply
Survey
TOC
and
TTHM
(
one
sample
for
each
parameter
at
the
entry
point
to
distribution
system.)
December
1980
­
December
1981
Combination
of
random
national
sample
and
nonrandom
sample
945
total
(
466
random,
479
nonrandom)

State
Data
­
Ground
Water
Distribution
system
TTHM
occurrence
data
Varies
AK,
CA,
FL,
IL,
NC,
TX,
WA2
562
serving
fewer
than
10,000
State
Data
­
Surface
Water
Distribution
system
TTHM
occurrence
data
Varies
AK,
CA,
IL,
MN,
MS,
NC,
TX,
WA
2336
serving
fewer
than
10,000
1
Source
type
designations
include
flowing
stream
and
lake/
reservoir
(
Except
for
7
large
plants
pre­
selected).
2
Over
50
percent
of
each
State's
systems
are
represented.
In
total
there
are
approximately
20
percent
of
the
nation's
small
systems
included
in
these
data.
EPA
believes
that
the
data
reasonably
represent
a
full
range
of
source
water
quality
in
small
systems
at
the
national
level.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
29
1.5.1
ICR
Supplemental
Survey
EPA
conducted
the
ICRSS
to
supplement
ICR
information
on
microbial
and
byproduct
occurrence.
The
ICRSS
was
conducted
at
120
randomly
selected
plants,
40
of
which
were
classified
as
small
surface
water
plants
serving
fewer
than
10,000
people,
40
as
medium
surface
water
plants
serving
10,001
to
100,000
people,
and
40
as
large
surface
water
plants
serving
more
than
100,000
people.
Seven
very
large
systems
(>
1
million
people
served)
were
also
included
in
the
survey
effort.
Monitoring
was
conducted
for
12
consecutive
months
beginning
in
March
1999.
Large
systems
collected
protozoa
and
limited
precursor
data
(
i.
e.,
TOC),
while
medium
and
small
systems
monitored
water
quality
parameters
(
i.
e.,
temperature,
pH
and
alkalinity)
and
DBP
precursors
(
i.
e.,
TOC,
UV
254
and
bromide).
EPA
used
this
data
to
compare
relative
treatability
among
different
system
size
categories
for
achieving
compliance
with
the
Stage
2
DBPR
regulatory
alternatives.
A
discussion
of
the
protozoa
data
is
included
in
the
Draft
Occurrence
and
Exposure
Assessment
for
the
LT2ESWTR
(
USEPA
2003b).

These
measurement
data
were
generated
based
on
the
Quality
Assurance
Project
Plan
for
the
Implementation
of
the
Information
Collection
Rule
Supplemental
Surveys,
finalized
in
March
1999
(
USEPA
1999c).
It
employed
a
QA
process
similar
to
that
used
for
ICR
data,
and
covered
measurement
and
data
acquisition,
assessment
and
oversight,
and
data
validation
and
usability.
Also
similar
to
the
review
of
ICR
data,
a
technical
review
more
rigorous
than
a
peer
review
process
was
implemented.

1.5.2
National
Rural
Water
Association
Survey
The
National
Rural
Water
Association
(
NRWA)
Survey
was
conducted
to
provide
information
on
DBPs
and
their
precursors
in
small
surface
water
systems.
Results
have
been
published
the
document,
Summary
Report:
NRWA
Small
System
Study
of
D/
DBP
(
Trax,
2003).

The
NRWA,
in
conjunction
with
EPA
and
NRWA
State
chapters,
conducted
a
survey
of
117
randomly
selected
small
PWSs.
A
minimum
number
of
112
systems
was
targeted
to
ensure
that
the
results
from
the
survey
(
in
particular,
the
90
percent
confidence
intervals)
would
be
statistically
representative
lf
the
universe
of
small
water
systems.
Also
to
ensure
representativeness
of
water
quality
conditions,
the
survey
collected
detailed
treatment
process
information,
source
water
quality
data,
and
DBP
samples
for
both
a
cold­
weather
period
in
1999­
2000
and
a
warm­
weather
period
in
2000.
NRWA
data
are
presented
in
Chapter
3
and
support
the
analyses
of
small
systems.

The
NRWA
conducted
this
survey
with
the
assistance
of
EPA,
although
EPA
did
not
direct
this
effort.
EPA
helped
to
train
sample
takers
and
provided
QA
on
the
data
provided
by
the
NRWA.
EPAapproved
laboratories
were
used
for
the
analysis
of
samples.
The
measurement
data
were
generated
based
on
the
procedures
used
for
the
ICR.
An
extensive
quality
assurance
protocol
was
followed
which
resulted
in
careful
monitoring,
control,
and
documentation
of
the
quality
of
the
analytical
data.
These
included:

°
Samples
from
ten
percent
of
the
112
sites
were
replicated.

°
Fifteen
percent
of
the
samples
for
each
analyte
were
randomly
replicated.

°
The
contractor
was
provided
with
a
THM
"
blank"
sample.
It
was
analyzed
when
results
appeared
erroneous
or
deviated
greatly
from
expected
values.

°
All
analytical
methods
and
QA/
QC
procedures
were
consistent
with
the
requirements
listed
in
the
DBP/
ICR
Analytical
methods
Manual
(
EPA
814­
B­
96­
002).
For
HAA9,
the
contractor
had
the
flexibility
to
use
Standard
Method
6251B.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
30
°
The
selection
of
the
contractor
was
based
on
the
demonstration
of
historical
ability
to
meet
or
exceed
the
QA/
QC
requirements.

1.5.3
The
Water
Utility
Database
Published
by
the
American
Water
Works
Association
(
AWWA),
WATER:\
STATS
is
derived
from
the
AWWA
Water
Industry
Database
resulting
from
a
1996
survey
of
approximately
900
water
utilities,
mostly
entities
serving
at
least
10,000
people.
The
effort
collected
a
range
of
financial
and
operational
information
on
these
utilities,
including
data
on
the
occurrence
of
DBPs
in
finished
water
(
however,
many
systems
did
not
respond
to
all
sections).
WATER:\
STATS
does
not
contain
individual
sample
results;
rather
it
contains
minimum,
maximum,
and
average
values
reported
by
each
system.
The
WATER:\
STATS
data
used
here
are
aimed
mainly
at
characterizing
relevant
treatment
and
byproduct
information
for
medium
surface
water
plants.

The
survey
was
progressively
improved
upon
since
1989,
when
WATER:\
STATS
was
first
developed.
Over
the
years,
it
has
been
technically
reviewed
by
the
AWWA
and
AWWARF
Advisory
Committees
and
by
the
Technical
and
Education
Committees
of
the
AWWA,
and
modified
based
on
their
inputs.
Prior
to
sending
the
survey
questionnaire
out
to
all
participants,
it
was
field
tested
with
25
utilities
and
adjusted
accordingly.

Responses
to
the
survey
questions
were
screened
to
ensure
they
were
applicable
and
pertinent.
The
determination
was
done
by
a
team
of
experts
from
AWWA.
Their
staff
also
reviewed
data
for
magnitude
and
units
related
issues.
Standard
procedures
were
adopted
to
identify
the
"
outlier"
data,
following
which,
the
respective
utilities
were
contacted
again
and
the
data
adjusted
accordingly.

1.5.4
Ground
Water
Supply
Survey
There
are
few
national
studies
of
the
occurrence
of
contaminants
in
ground
water.
Although
two
decades
old,
the
GWSS,
conducted
by
EPA
from
December
1980
through
December
1981,
remains
one
of
the
most
extensive
and
useful
studies
of
ground
water.
The
GWSS
was
a
sampling
and
analysis
study
of
the
levels
of
volatile
organic
compounds
(
VOCs)
in
ground
water.
Results
are
presented
in
the
report,
The
Ground
Water
Supply
Survey:
Summary
of
Volatile
Organic
Contaminant
Occurrence
Data
(
USEPA
1983).
The
data
are
presented
in
Chapter
3
and
support
the
analyses
of
medium
and
small
systems.

The
data
were
collected
from
945
systems,
approximately
half
selected
randomly
and
half
selected
nonrandomly.
Random
selection
was
intended
to
provide
a
broad
national
perspective
on
the
incidence
of
VOC
contamination;
the
nonrandom
selection
allowed
States
to
identify
sites
that
were
presumed
to
have
high
levels
of
VOCs
for
further
investigation.
Included
in
the
sampling
parameters
were
levels
of
finished
water
TOC
and
TTHM.

The
random
sample
included
186
systems
from
a
random
list
of
systems
serving
a
population
of
greater
than
10,000,
and
280
systems
from
a
random
list
of
systems
serving
a
population
of
less
than
or
equal
to
10,000.
The
nonrandom
sample
consisted
of
479
systems
that
were
selected
by
State
agencies.
States
were
encouraged
to
choose
systems
for
which
no
prior
VOC
data
were
available
and
those
they
believed
had
a
high
probability
of
contamination
by
VOCs,
based
on
their
knowledge
of
local
conditions
(
e.
g.
proximity
to
landfills,
industrial
activity,
etc.)

An
extensive
quality
assurance
protocol
was
followed
which
resulted
in
careful
monitoring,
control,
and
documentation
of
the
quality
of
the
analytical
data.
These
included:
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
31
°
Analysis
of
EPA
reference
samples:
The
reference
samples
contained
known
concentrations
of
compounds
including
four
common
trihalomethanes
(
THMs)
and
nine
frequently
detected
VOCs.
They
were
run
by
the
contractor
once
a
week
for
each
instrument
to
determine
whether
the
precision
and
accuracy
of
the
instruments
were
within
acceptable
limits
per
the
quality
protocol.

°
Analysis
of
duplicate
samples
by
the
contractor:
Duplicate
analyses
were
performed
on
at
least
10
percent
of
the
samples.
They
were
to
agree
within
40
percent,
for
compounds
present
below
5
µ
g/
L,
and
within
20
percent,
for
compounds
present
above
5
µ
g/
L,
in
order
to
comply
with
the
quality
protocol.

°
Confirmatory
analysis:
All
samples
found
or
suspected
to
contain
purgeable
aromatic
and
halocarbon
compounds
other
than
THMs
were
re­
analyzed
using
different
chromatographic
columns
that
elute
compounds
in
different
orders.
Samples
containing
chloroform
at
concentrations
greater
than
40
µ
g/
L
were
re­
analyzed
using
the
confirmatory
column
since
chloroform
concentrations
at
this
level
(
i.
e.
equal
to
or
greater
than
40
µ
g/
L)
could
potentially
mask
1,2­
dichloroethane.
Additionally,
5
percent
of
all
samples
were
re­
analyzed
by
gas
chromatography/
mass
spectrometry
(
GC/
MS)
to
identify
or
confirm
unknown/
tentatively
known
compounds.

°
Blind
samples:
EPA
used
five
blind
samples
during
the
initial
phase
of
the
survey
to
evaluate
the
contractor's
ability
to
identify
and
measure
specific
compounds.
The
samples
consisted
of
five
different
mixtures
of
compounds,
spiked
into
organic­
free
distilled
water.
The
contractor
correctly
identified
the
spiked
compounds
in
every
case.

°
Analysis
of
duplicate
samples
by
EPA:
Replicate
samples
were
collected
in
separate
bottles
and
stored
at
EPA's
laboratories.
They
were
analyzed
as
an
additional
check
on
the
contractor's
results.

1.5.5
State
Data
A
number
of
State
agencies
have
collected
data
on
influent
water
quality
and
DBP
occurrence
for
small
surface
water
plants.
As
part
of
the
data
synthesis
effort
for
small
and
medium
systems,
some
of
these
States
provided
data
sets
to
EPA.
The
Agency
reviewed
them
for
apparent
conclusions
and
applicability
to
analysis
of
DBP
occurrence.
The
following
States
collected
sufficient
DBP
occurrence
data
to
include
in
further
surface
water
analyses:
Alaska,
California,
Illinois,
Minnesota,
Missouri,
North
Carolina,
Texas,
and
Washington.
In
addition,
seven
States'
data
sets
were
used
to
analyze
small
ground
water
systems
(
Alaska,
California,
Florida,
Illinois,
North
Carolina,
Texas,
and
Washington).
Their
data
met
several
initial
criteria
that
ensured
the
data
were
nationally
representative.
The
criteria
were:

°
For
each
State's
data
set,
the
small
surface
water
systems
sampled
by
the
State
were
representative
of
at
least
50
percent
of
the
total
number
of
small
surface
water
systems
in
the
State.

°
TTHM
data
were
collected
and
reported
in
a
manner
that
approximated
a
typical
monitoring
approach,
and
in
some
cases
included
individual
species
of
THMs.

The
data
available
from
each
State
are
not
exactly
comparable;
some
States
reported
individual
sample
data,
while
others
reported
only
plant
averages.
Some
of
the
data
appear
to
be
from
distribution
system
locations,
while
other
samples
are
from
locations
in
the
plant
or
from
raw
water.
Samples
in
some
States
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
1­
32
were
collected
quarterly,
while
in
others
the
sample
frequency
ranged
from
one
every
two
months
to
less
than
one
per
year.

These
data
are
from
existing
sources
and
are
typically
summaries
of
data
rather
than
measurement
data.
Although
a
QA
plan
did
not
exist
during
data
collection
and
data
were
not
peer
reviewed,
it
is
assumed
that
the
data
were
reviewed
by
States
before
submission
to
EPA.
The
usage
of
State's
data
for
characterizing
national
DBP
occurrence
for
small
surface
water
systems
is
discussed
in
the
Stage
2
DBPR
EA
(
USEPA
2003a).

1.6
Document
Organization
The
remainder
of
this
document
is
organized
into
the
following
three
chapters,
plus
reference
section
and
appendices.

°
Chapter
2
 
Use
of
Disinfectants
in
the
United
States.
The
universe
of
systems
using
disinfectants
and
their
population­
served
are
presented
by
system
size
and
source
water
type
category.
This
chapter
also
presents
information
on
disinfection
use.
An
overview
of
disinfection
processes
is
provided,
followed
by
information
on
the
four
most
commonly
used
disinfectants:
free
chlorine,
chloramine
(
combined
chlorine),
chlorine
dioxide,
and
ozone.
Each
disinfectant
is
briefly
described,
including
its
method
of
application,
use
and
distribution,
advantages
and
disadvantages,
dosage
requirements,
and
potential
byproducts.

°
Chapter
3
 
National
Occurrence
Data.
This
chapter
presents
data
related
to
DBP
occurrence
in
public
drinking
water
supplies.
Graphical
presentations
of
source
water
quality
parameters,
disinfectant
residuals,
and
DBPs
are
included.
Data
are
from
the
ICR
data
set
and
other
sources.

°
Chapter
4
 
Predicted
Occurrence
of
Disinfection
Byproducts
 
Post­
Stage
1
DBPR.
This
chapter
describes
predicted
post­
Stage
1
occurrence
for
TTHM
and
HAA
based
on
ICR
data.

°
Chapter
5
 
References.

°
Appendix
A
 
ICR
Occurrence
Data.
This
appendix
supplements
ICR
analyses
in
Chapters
2
and
3
by
showing
results
for
additional
analytes
and
results
for
the
entire
18
months
of
the
ICR
collection
period.

°
Appendix
B
 
ICR
Data
Queries.
This
appendix
provides
the
Access
 
Queries
(
in
SQL
code)
used
in
the
data
presentations
in
Chapters
2,
3,
and
4.
Queries
are
organized
alphabetically
by
query
name
and
include
a
one
to
two
sentence
description
of
their
function.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
1
2.
Use
of
Disinfectants
in
the
United
States
Many
water
treatment
processes
can
remove
or
inactivate
microorganisms,
including
pathogens
that
can
cause
waterborne
diseases.
Treatment
is
especially
important
for
systems
that
use
surface
water
sources
or
ground
water
under
the
direct
influence
of
surface
water
(
GWUDI).
In
many
cases,
surface
water
supplies
receive
discharges
from
upstream
wastewater
treatment
plants,
industrial
facilities,
stormwater
runoff,
or
animal
feed
lots.
In
the
treatment
plant,
certain
treatment
processes,
such
as
sedimentation
and
filtration,
remove
most,
if
not
all,
of
the
microorganisms
that
cause
waterborne
diseases.
However,
there
is
a
need
to
inactivate
the
pathogens
that
pass
through
the
filters,
grow
in
the
distribution
system
(
e.
g.,
biofilm
growth),
or
breach
the
distribution
system
(
e.
g.,
entering
through
crossconnections
or
negative
pressure).
Water
systems
have
relied
primarily
upon
filtration
supplemented
by
disinfection
to
control
pathogens.

This
chapter
describes
the
disinfection
processes
used
in
the
treatment
of
drinking
water
and
their
effects
on
finished
water
quality.
Sections
2.1
and
2.2
provide
background
information
on
the
disinfection
process
and
the
resulting
formation
of
DBPs,
respectively.
Section
2.3
provides
the
inventory
of
disinfecting
community
water
systems
(
CWSs)
with
respect
to
source
water
type
and
population
served.
Section
2.4
shows
data
on
the
proportion
of
plants
using
various
types
of
disinfection.
Sections
2.5
through
2.8
describe
the
four
main
disinfectants
used
by
drinking
water
systems:
chlorine,
chloramines,
chlorine
dioxide,
and
ozone.
Included
for
each
disinfectant
is
a
description
of
chemistry
and
method
of
application,
use
and
distribution,
typical
dosages,
and
potential
byproducts.
Chapter
3,
Section
3.1.2,
builds
on
this
chapter
by
examining
disinfectant
residual
concentrations
in
treated
water.
For
additional
information
on
disinfectant
practices
of
surface
water
systems
and
for
an
inventory
of
disinfecting
systems,
refer
to
Chapter
15
of
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002).

2.1
Overview
of
Disinfection
Processes
The
1995
Community
Water
Systems
Survey
(
CWSS)
(
USEPA
1997b)
reports
that
99
percent
of
surface
water
systems
in
the
United
States
provide
some
level
of
water
treatment
before
distribution
to
customers,
and
99
percent
of
these
treatment
systems
use
disinfection
in
the
treatment
process
(
disinfection
is
required
for
all
surface
water
systems).
Disinfection
can
be
accomplished
in
several
ways.
The
most
common
method
used
to
achieve
disinfection
is
to
add
a
chemical
disinfectant
to
the
water.
Disinfectants
can
be
applied
in
the
plant
(
this
is
referred
to
as
primary
disinfection)
and/
or
after
treatment
(
secondary
disinfection).
Secondary
disinfection
ensures
the
presence
of
a
disinfectant
residual
after
treated
water
leaves
the
plant
and
enters
the
distribution
system.
Some
systems
use
booster
chlorination,
the
adding
of
chlorine
or
chloramines
at
a
point
within
the
distribution
system,
to
raise
the
disinfectant
residuals
to
required
levels.
The
most
commonly
used
disinfectants,
in
both
plants
and
distribution
systems,
are
chlorine
and
chloramines.
Chlorine
dioxide,
ozone,
membrane
systems
(
physical
removal
treatments),
and
ultraviolet
light
(
UV)
(
a
non­
chemical
disinfection
process)
are
also
used
on
a
limited
basis
to
meet
disinfection
goals.
Chlorine
or
chloramines
are
the
most
common
disinfectants
used
to
achieve
secondary
disinfection.

Chlorine,
chloramines,
ozone,
and
chlorine
dioxide
are
oxidants,
and,
in
addition
to
inactivating
pathogens,
are
used
to
treat
drinking
water
for
the
following
purposes:

°
Controlling
Asiatic
clams
and
zebra
mussels
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
2
°
Oxidizing
iron,
manganese,
and
sulfides
°
Preventing
microbial
regrowth
in
the
distribution
system
and
maintaining
biological
stability
°
Removing
undesirable
tastes
and
odors
through
chemical
oxidation
°
Improving
coagulation
and
filtration
efficiency
°
Preventing
algal
growth
in
sedimentation
basins
and
filters
°
Oxidizing
organic
micropollutants
such
as
pesticides
and
volatile
organic
compounds
The
effectiveness
of
disinfection
depends
on
the
contact
time
(
the
amount
of
time
a
disinfectant
is
in
contact
with
the
water)
and
the
residual
disinfectant
concentration.
The
efficacy
of
disinfection
also
depends
on
other
factors,
including
pH,
temperature,
and
the
type
and
amount
of
disinfectant
used.

2.2
Disinfection
Byproducts
(
DBPs)

Disinfectants
react
with
naturally
occurring
organic
matter
(
NOM)
to
form
DBPs.
Three
main
types
of
DBPs
are
discussed
in
this
document.

°
Halogenated
organic
byproducts
°
Organic
oxidation
byproducts
°
Inorganic
DBPs
Halogenated
organic
byproducts
form
during
reactions
with
free
chlorine
or
free
bromine.
Although
bromine
is
not
used
as
a
disinfectant,
bromide
ions
can
be
naturally
present
in
water
and,
when
oxidized,
form
free
bromine.
Organic
oxidation
byproducts,
such
as
acetaldehyde,
form
during
oxidation
reactions
with
the
disinfectants.
Inorganic
DBPs
are
usually
formed
during
reactions
with
chlorine
dioxide
and
ozone.

Temperature,
pH,
alkalinity,
total
hardness,
turbidity,
disinfectant
type,
and
the
composition
of
NOM
(
usually
measured
as
total
organic
carbon,
or
TOC)
affect
the
types
and
rates
of
DBP
formation.
It
should
be
noted
that
many
DBPs
have
been
identified,
but
only
a
select
subset
(
shown
in
Exhibit
2.1)
were
monitored
during
the
ICR
and
are
the
focus
of
this
analysis.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
3
Exhibit
2.1
List
of
Disinfection
Byproducts
(
DBPs)
Measured
During
the
ICR
Halogenated
Organic
Byproducts1
Trihalomethanes
Chloroform
(
CHCl3)
Bromodichloromethane
(
BDCM)
Dibromochloromethane
(
DBCM)
Bromoform
(
CHBr3)

Haloacetic
Acids
(
HAA)
HAA5:
Monochloroacetic
acid
(
MCAA)
Dichloroacetic
acid
(
DCAA)
Trichloroacetic
acid
(
TCAA)
Monobromoacetic
acid
(
MBAA)
Dibromoacetic
acid
(
DBAA)

HAA6:
HAA5
plus
Bromochloroacetic
acid
(
BCAA)

HAA9:
HAA6
plus
Bromodichloroacetic
acid
(
BDCAA)
Chlorodibromoacetic
acid
(
CDBAA)
Tribromoacetic
acid
(
TBAA)

Haloacetonitriles
(
HAN4)
Dichloroacetonitrile
(
DCAN)
Bromochloroacetonitrile
(
BCAN)
Dibromoacetonitrile
(
DBAN)
Trichloroacetonitrile
(
TCAN)

Haloketones
1,1­
Dichloropropanone
1,1,1­
Trichloropropanone
Chloropicrin
(
CP)

Chloral
Hydrate
(
CH)

Cyanogen
Chloride
(
CNCl)

Total
Organic
Halides
(
TOX)
Organic
Oxidation
Byproducts
Aldehydes
Formaldehyde
Acetaldehyde
Propanal
Butanal
Pentanal
Glyoxal
Methyl
Glyoxal
Inorganic
Byproducts
Chlorate
Ion
Chlorite
Ion
Bromate
Ion
1
Not
all
individual
organic
halides
could
be
measured
during
the
ICR.
TOX
is
used
to
estimate
the
total
quantity
of
dissolved
halogenated
organic
material
in
water.

Source:
Cohn
et
al.
(
1999).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
4
System
Size
(
Population
Served)
Ground
Water
(
Percent
of
Total)
Surface
Water
(
Percent
of
Total)
Total
(
Percent
of
Total)
Small
(<
10,001)
37,980
(
73.6%)
9,921
(
19.2%)
47,901
(
92.8%)

Medium
(
10,001
­
100,000)
1,365
(
2.6%)
2,013
(
3.9%)
3,378
(
6.5%)

Large
(>
100,000)
63
(
0.1%)
290
(
0.6%)
353
(
0.7%)

Total
39,408
(
76.3%)
12,224
(
23.7%)
51,632
(
100.0%)
2.3
Inventory
of
Disinfecting
Water
Systems
and
Population
Served
Both
CWSs
and
nontransient
noncommunity
water
systems
(
NTNCWSs)
that
disinfect
their
water
supplies
are
regulated
under
the
Stage
2
DBPR.
All
surface
water
systems
are
required
to
disinfect,
but
only
an
estimated
68
percent
of
ground
water
CWSs
and
37
percent
of
ground
water
NTNCWSs
disinfect
(
USEPA
2003a).
Exhibit
2.2
shows
the
combined
CWS
and
NTNCWS
estimated
system
size
distribution
of
disinfecting
systems,
classified
by
source
water
type
(
systems
using
GWUDI
are
included
in
the
surface
water
category)
and
by
population
served.
Exhibit
2.2
shows
that
approximately
76
percent
of
disinfecting
CWSs
and
NTNCWSs
are
ground
water
systems.

Exhibit
2.3
show
other
size
distribution
findings.
The
distribution
of
the
population
served
by
disinfecting
systems
is
nearly
the
opposite
of
the
distribution
of
systems:
63
percent
of
the
population
is
served
by
surface
water
systems,
and
37
percent
is
served
by
ground
water.
This
is
because
most
large
systems
serving
more
than
100,000
people
are
surface
water
systems.

Exhibits
2.2
and
2.3
also
show
the
distribution
of
systems
and
population
between
different
size
categories.
Approximately
93
percent
of
all
disinfecting
CWSs
and
NTNCWSs
are
small
systems
serving
less
than
10,000
people,
while
fewer
than
one
percent
are
large
systems
serving
more
than
100,000
people.
Although
there
are
many
more
small
systems
than
large
in
the
United
States,
an
estimated
140
million
people
(
55
percent)
are
served
by
large
disinfecting
systems,
77
million
(
30
percent)
by
medium
disinfecting
systems,
and
only
38
million
(
15
percent)
by
small
disinfecting
systems.

Exhibit
2.2
Number
(
and
Percent)
of
Disinfecting
CWSs
and
NTNCWSs
Detail
may
not
add
due
to
independent
rounding.

Notes:
The
"
surface
water"
designation
includes
GWUDI
systems.

Percent
disinfecting
based
on
1995
CWSS,
as
summarized
in
the
Drinking
Water
Baseline
Handbook,
and
adjusted
for
potential
impacts
of
the
Ground
Water
Rule.
See
Chapter
3
of
the
Stage
2
DBPR
Economic
Analysis
(
USEPA
2003a)
for
further
details.

Source:
Derived
from
Chapter
3,
Exhibit
3.3
of
the
Stage
2
DBPR
Economic
Analysis
(
USEPA
2003a).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
5
System
Size
(
Population
Served)
Ground
Water
(
Percent
of
Total)
Surface
Water
(
Percent
of
Total)
Total
(
Percent
of
Total)
Small
(<
10,001)
29,413,975
(
11.6%)
8,197,640
(
3.2%)
37,611,615
(
14.8%)

Medium
(
10,001
­
100,000)
37,986,723
(
14.9%)
38,616,140
(
15.2%)
76,602,863
(
30.1%)

Large
(>
100,000)
26,392,250
(
10.4%)
113,871,860
(
44.7%)
140,264,110
(
55.1%)

Total
93,792,948
(
36.9%)
160,685,640
(
63.1%)
254,478,588
(
100.0%)
Exhibit
2.3
Population
Total
(
and
Percent)
Served
by
Disinfecting
CWSs
Detail
may
not
add
due
to
independent
rounding.

Notes:
The
"
surface
water"
designation
includes
GWUDI
systems.

Percent
disinfecting
based
on
1995
CWSS,
as
summarized
in
the
Drinking
Water
Baseline
Handbook,
and
adjusted
for
potential
impacts
of
the
Ground
Water
Rule.
See
Chapter
3
of
the
Stage
2
DBPR
Economic
Analysis
(
USEPA
2003a)
for
further
details.
NTNCWSs
are
typically
schools,
restaurants,
etc.,
and
their
population
is
already
counted
in
the
CWS
population,
thus
only
population
served
by
CWSs
is
shown
in
this
exhibit.

Source:
Derived
from
Chapter
3,
Exhibit
3.5
of
the
Stage
2
DBPR
Economic
Analysis
(
USEPA
2003a).

2.4
Disinfection
Types
This
section
presents
data
on
chemical
disinfection
practices
among
large
surface
and
ground
water
plants
as
derived
from
the
Information
Collection
Rule
Auxiliary
Database
1
(
ICR
AUX1)
(
USEPA
2000d).
It
also
presents
disinfectant
dose
data
for
chlorine,
ozone,
and
chlorine
dioxide
from
the
Information
Collection
Rule
Auxiliary
Database
2
(
ICR
AUX2)
(
USEPA
2000i).
See
Chapter
1,
section
1.4.6
for
a
description
of
these
databases.

In
the
ICR
databases,
disinfectant
types
associated
with
a
treatment
plant
are
classified
based
on
disinfectant
usage
within
the
plant
and
distribution
system.
At
the
plant
level,
five
disinfectant
types
are
defined
in
the
ICR
AUX1
and
AUX2
databases
as:

°
CL2
 
Free
chlorine
when
only
Cl
2
is
used
as
a
disinfectant.

°
CLM
 
Chloramine
when
Cl
2
and
ammonia
(
NH
3)
are
added
simultaneously
into
a
unit
process
in
the
plant
where
no
earlier
point
of
chlorination
exists.

°
CL2_
CLM
 
Free
chlorine
followed
by
chloramine
(
CLM)
when
NH
3
is
added
after
free
chlorine
has
previously
been
applied
in
one
or
more
preceding
unit
processes.

°
CLX
 
Chlorine
dioxide
(
ClO
2)
if
chlorine
dioxide
is
used
anywhere
in
the
plant.

°
O3
 
Ozone
if
ozone
is
used
anywhere
in
the
plant.

At
the
distribution
system
level,
two
disinfectant
types
are
defined
(
i.
e.,
CL2
and
CLM)
according
to
the
disinfectant
type
applied
at
the
last
disinfectant
application
point
before
the
entry
point
to
the
distribution
system.

In
order
to
characterize
disinfection
practices
of
surface
water
plants,
the
ICR
AUX2
database
was
used
to
derive
information
for
plants
that
reported
both
plant­
and
distribution
system­
level
disinfectant
use
for
the
last
12
months
of
the
ICR
collection
period.
Because
some
plants
switched
disinfectants
during
the
12­
month
period,
the
analysis
was
done
for
each
plant­
month
individually.
Exhibit
2.4
shows
the
findings
of
the
analysis
for
surface
water
plants
for
each
combination
of
plant
and
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
6
53.7%

23.1%

6.5%
5.1%

2.7%
3.7%
3.0%
2.1%
0.1%
0%
10%
20%
30%
40%
50%
60%

CL2/
CL2
CL2_
CLM/
CLM
CL2/
CLM
CLM/
CLM
CLX/
CLM
CLX/
CL2
O3/
CLM
O3/
CL2
CL2_
CLM/
CL2
Percentage
of
Plant­
Months
(
N
=
3,927)
distribution
system
disinfectant
for
3,927
plant­
months.
Chapter
15,
Table
15.1,
in
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002)
provides
additional
information
on
the
type
of
disinfectants
used
for
different
treatment
plant
types
(
e.
g.,
conventional
softening,
unfiltered).

For
ground
water
plants,
the
ICR
AUX2
database
was
also
used
to
derive
information.
Information
was
extracted
for
ground
water
plants
that
reported
both
plant­
and
distribution
system­
level
disinfectant
use
for
the
last
12
months
of
the
ICR
collection
period.
Exhibit
2.5
shows
the
results
of
the
ground
water
plant
analysis
for
chlorine
only,
chloramines
only,
and
each
combination
of
plant
and
distribution
system
disinfectant
for
647
plant­
months.
The
"
CL2
only"
category
includes
plants
that
reported
chlorine
use
for
both
the
plant
and
distribution
system
category,
and
includes
plants
that
reported
chlorine
use
only
in
the
distribution
system.

Exhibit
2.4
Percentage
of
Surface
Water
Plants
Applying
Specific
Disinfection
Types
for
Combined
Plant/
Distribution
System
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Screened
Plant
Disinfectant
Type.
See
Appendix
B
for
details.

Excel
File:
Plant­
Distribution
Disinfectant
Types.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
7
84.9%

13.4%

0.0%
0.8%
0.0%
0.0%
0.0%
0.8%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%

CL2
Only
CLM
Only
CL2_
CLM/
CL2
CL2/
CLM
CLX/
CL2
CLX/
CLM
O3/
CL2
O3/
CLM
Percent
of
Plant­
Months
(
N=
647)
Exhibit
2.5
Percentage
of
Ground
Water
Plants
Applying
Specific
Disinfection
Types
for
Individual
and
Combined
Plant/
Distribution
System
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Screened
Plant
Disinfectant
Type.
See
Appendix
B
for
details.

Excel
File:
Plant­
Distribution
Disinfectant
Types.
xls
Among
medium
surface
water
plants,
chlorine
is
the
most
common
disinfectant
(
see
Exhibit
3.30,
which
compares
disinfectant
use
in
medium
and
large
plants).
This
is
expected,
since
both
medium
and
large
plants
are
subject
to
the
1979
Total
Trihalomethane
(
TTHM)
rule.
The
National
Rural
Water
Association
(
NRWA)
Survey
indicates
that
almost
all
small
surface
water
systems
use
free
chlorine
(
see
Exhibit
3.39).

2.5
Chlorine
Chlorine
is
the
most
commonly
used
disinfectant
in
public
water
systems
in
the
United
States.
Through
filtration
and
chlorination,
waterborne
diseases,
including
typhoid
and
cholera,
have
been
virtually
eliminated
in
this
country.
For
example,
in
only
four
years
(
between
1911
and
1915),
the
number
of
typhoid
cases
in
Niagara
Falls,
New
York
dropped
from
185
deaths
for
every
100,000
people
to
nearly
zero
following
the
introduction
of
filtration
and
chlorination
(
White
1986).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
8
Disinfection
with
chlorine
is
simple,
economical,
efficient,
measurable,
and
practical.
Several
types
of
chlorine
are
available
for
use
as
a
disinfectant.

°
Chlorine
gas
(
Cl
2)

°
Sodium
hypochlorite
(
liquid)
(
NaOCl)

°
Calcium
hypochlorite
(
tablet,
granular,
or
powdered)
(
Ca(
OCl)
2)

2.5.1
Description
of
Chemistry
The
chemistries
of
these
disinfectants
are
similar;
they
all
react
with
water
to
form
disinfecting
agents.
Chlorine
hydrolyzes
in
water
to
form
hypochlorous
acid
(
HOCl).
HOCl
is
a
weak
acid
and
ionizes
to
yield
hypochlorite
ion,
or
OCl­.
Free
residual
chlorine
is
the
sum
of
HOCl
and
OClconcentrations
the
relative
quantity
of
each
depends
on
pH.
Both
hypochlorous
acid
and
hypochlorite
inactivate
or
kill
pathogens,
but
hypochlorous
acid
is
more
effective.

Upon
addition
to
water,
free
chlorine
chemically
reacts
with
constituents
in
the
water
by
various
mechanisms.
Chlorine
oxidizes
soluble
iron,
manganese,
and
sulfides
typically
found
in
drinking
water
sources.
Once
oxidized,
the
resulting
products
precipitate
and
are
primarily
removed
by
clarification
and
filtration
processes.
When
chlorine
reacts
with
natural
organic
matter
in
the
water,
it
reacts
with
electron­
rich
sites
to
form
halogenated
organic
byproducts
(
e.
g.,
trihalomethanes
and
chlorophenols),
some
of
which
have
been
shown
to
be
possible
human
carcinogens
(
Weisel
et
al.
1999).
Chlorine
also
oxidizes
organic
matter
to
form
compounds
that
do
not
contain
a
halogen,
such
as
aldehydes,
carboxylic
acids,
ketones,
and
alcohols
(
Richardson
1998).
The
occurrence
of
halogenated
byproducts
has
been
studied
the
most
because
halogenated
DBPs
are
easily
detected.

The
three
forms
of
chlorine
that
are
typically
used
at
water
treatment
plants
(
chlorine
gas,
sodium
hypochorite,
and
calcium
hypochlorite)
are
described
below.

Chlorine
gas
is
often
referred
to
as
elemental
chlorine.
Chlorine
is
produced,
collected,
purified,
compressed,
cooled,
packaged,
and
shipped
as
a
liquefied
gas
under
pressure.
Systems
then
inject
chlorine
gas
into
the
water
stream,
where
hydrolysis
and
ionization
(
as
described
above)
produce
the
disinfecting
agents.

Sodium
hypochlorite
is
produced
by
reacting
chlorine
with
sodium
hydroxide.
Sodium
hypochlorite
solutions
are
also
referred
to
as
liquid
bleach
or
Javelle
water.
Generally,
commercial
or
industrial
grade
solutions
have
hypochlorite
strengths
of
10
to
16
percent.
Low
concentrations
(
i.
e.,
5.25
percent
or
less)
are
sold
as
common
household
bleach.
The
stability
of
a
sodium
hypochlorite
solution
depends
on
the
hypochlorite
concentration,
storage
temperature,
time
in
storage,
impurities,
pH,
and
exposure
to
light.
Decomposition
of
hypochlorite
solution
over
time
can
affect
the
feed
rate
and
dosage,
as
well
as
produce
undesirable
byproducts
such
as
chlorite
or
chlorate
ions
(
Gordon
et
al.
1995).
Because
of
these
storage
problems,
many
systems
are
investigating
onsite
generation
of
sodium
hypochlorite
in
lieu
of
purchasing
hypochlorite
stock
supplies
in
the
granular
or
tablet
form
from
a
manufacturer
or
vendor.

Calcium
hypochlorite
is
a
crystal
and
can
be
produced
by
combining
equivalent
amounts
of
sodium
hypochlorite
and
calcium
chloride
(
known
as
the
Perchloron
process).
A
slurry
of
lime
and
caustic
soda
is
chlorinated
and
cooled
so
that
crystals
are
formed.
These
crystals
are
centrifuged,
then
added
to
a
chlorinated
lime
slurry;
when
warmed,
the
calcium
hypochlorite
precipitates.
Generally,
the
final
product
contains
up
to
70
percent
available
chlorine
and
less
than
3
percent
lime
(
White
1992).
Storage
of
calcium
hypochlorite
is
a
major
safety
consideration.
It
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
9
should
never
be
stored
where
it
is
subject
to
heat
or
allowed
to
contact
any
easily
oxidized
organic
material.

Based
on
analysis
of
the
ICR
AUX2
data,
gaseous
chlorine
is
by
far
the
most
common
form
of
chlorine
used
for
water
system
disinfection
(
chlorine
was
used
in
its
gaseous
form
91
percent
of
the
time).
See
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002)
for
more
details.

2.5.2
Use
and
Distribution
Chlorine
gas
feeders
used
to
treat
drinking
water
can
be
either
direct
feed
or
solution
feed.
Direct
gas
feeders
deliver
chlorine
gas
under
pressure
directly
to
the
point
of
application.
Because
direct
feeders
are
less
safe
than
solution
feed
chlorinators,
solution
feed
is
typically
used.
In
a
solution
feeder,
chlorine
gas
is
metered
under
vacuum
conditions
and
mixed
with
water
in
an
injector
to
produce
a
chlorine
solution,
which
is
injected
at
the
appropriate
application
point(
s).
With
this
type
of
system,
the
flow
of
chlorine
gas
automatically
shuts
off
if
there
is
a
loss
of
vacuum,
stoppage
of
the
solution
discharge
line,
or
loss
of
operating
solution
water
pressure.
This
safety
mechanism
is
important
because
chlorine
gas
released
into
the
atmosphere
can
cause
acute
health
problems
or
even
death
if
inhaled.

Sodium
hypochlorite
is
normally
fed
directly
with
a
motor­
driven
diaphragm
and
plunger­
type
chemical
metering
pump(
s)
to
the
appropriate
application
point(
s).
Although
unusual,
feeding
sodium
hypochlorite
using
a
hydraulic
injector
or
simple
gravity
flow
is
possible.

When
calcium
hypochlorite
is
used
as
a
treatment
process
for
continuous
disinfection,
it
is
mixed
with
water
to
form
a
dilute
hypochlorite
solution
and
fed
in
the
same
manner
as
sodium
hypochlorite.
For
spot
disinfection
in
a
basin
or
pipe,
calcium
hypochlorite
tablets
are
deposited
in
the
appropriate
location,
water
is
added,
and
the
tablets
allowed
to
dissolve
to
form
a
liquid
hypochlorite
solution.

According
to
the
1995
Community
Water
Systems
Survey
(
USEPA
1997b),
most
surface
water
and
ground
water
systems
that
have
primary
disinfection
use
chlorine.
Exhibits
2.4
and
2.5
(
displayed
previously)
show
that
54
percent
of
large
ICR
surface
water
and
85
percent
of
large
ICR
ground
water
systems
use
chlorine.
Additionally,
these
exhibits
show
that
chlorine
is
also
the
most
widely
used
secondary
disinfectant.

2.5.3
Advantages
and
Disadvantages
The
following
list
presents
selected
advantages
and
disadvantages
of
using
chlorine
to
disinfect
drinking
water
(
Masschelein
1992;
Process
Applications,
Inc.
1992).

°
Advantages
 
Chlorine
is
an
effective
biocide.
 
Chlorine
oxidizes
soluble
iron,
manganese,
and
sulfides.
 
Chlorine
enhances
color
removal.
 
Chlorine
controls
taste
and
odor.
 
The
use
of
chlorine
is
the
easiest
and
least
expensive
disinfection
method,
regardless
of
system
size.
 
Chlorine
is
the
most
widely
used
disinfection
method
and,
therefore,
the
most
well
known.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
10
 
Chlorine
is
available
as
calcium
and
sodium
hypochlorite,
which
are
more
advantageous
for
smaller
systems
than
chlorine
gas
because
they
are
easier
to
use,
safer,
and
need
less
equipment
compared
to
chlorine
gas.
 
Chlorine
provides
a
residual
(
for
a
prolonged
treatment
effect).

°
Disadvantages
 
Chlorine
forms
both
halogenated
and
non­
halogenated
organic
byproducts
(
some
of
which
pose
health
concerns).
 
Chlorine
gas
is
a
hazardous
corrosive
gas,
and
special
leak
containment
and
scrubber
facilities
could
be
required
to
ensure
safety.
 
Sodium
hypochlorite
degrades
over
time
and
with
exposure
to
light
(
which
diminishes
its
treatment
effectiveness).
 
Sodium
hypochlorite
is
a
corrosive
chemical.
 
Calcium
hypochlorite
requires
proper
storage.
It
must
be
stored
in
a
cool,
dry
place
to
reduce
potential
reactions.
Also,
an
antiscalant
chemical
may
be
needed
since
impurities
may
cause
a
precipitate
to
form.
 
Higher
concentrations
of
hypochlorite
solutions
are
unstable
and
will
produce
chlorate
as
a
decomposition
byproduct.
 
Hypochlorite
can
contain
bromate
as
a
contaminant,
resulting
in
an
inadvertent
introduction
of
low
concentrations
of
bromate
to
drinking
water.
 
Chlorine
is
less
effective
in
water
with
higher
pH.
 
Chlorine
forms
biodegradable
oxygenated
byproducts
that
can
lead
to
regrowth
of
biological
material
in
the
distribution
system.

Because
of
the
variety
of
forms
and
dosage
of
chlorine
and
their
different
usage
depending
on
system
size
and
water
quality,
not
all
of
these
advantages
and
disadvantages
apply
to
all
systems.

2.5.4
Dose
Ranges
and
Points
of
Application
Two
key
operational
parameters
that
affect
DBP
formation
are
disinfectant
dose
and
point
of
application.
The
chlorine
dose
range
guideline
used
in
reviewing
public
water
systems'
(
PWSs)
ICR
initial
sampling
plans
was
based
on
dosages
provided
in
engineering
design
manuals
and
published
articles
(
see
the
Occurrence
Assessment
for
Disinfectants/
Disinfection
Byproducts
in
Public
Drinking
Water
Supplies
[
USEPA
1998c]
for
further
information).
This
range
of
doses,
shown
in
Exhibit
2.6,
includes
primary
and
secondary
disinfection.
Note
that
these
ranges
represent
the
extreme
upper
and
lower
dose
values,
with
normal
doses
well
within
these
ranges.
The
combination
of
chlorination
at
the
treatment
plant
and
strategic
locations
in
the
distribution
system
may
be
more
effective
at
maintaining
residuals
than
an
equivalent
single
dosage
at
the
treatment
plant
(
Tryby
et
al.
1999).
Public
health
benefits
of
booster
chlorination
can
include
decreased
DBP
formation
and
better
control
of
biological
regrowth
and
biofilm
formation
in
the
distribution
system.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
11
Exhibit
2.6
Chlorine
Dose
Ranges
Derived
from
in
ICR
Initial
Sampling
Plans
Chlorine
Compound
Range
of
Doses
(
mg/
L)

Calcium
hypochlorite
0.5
­
5
Sodium
hypochlorite
0.2
­
2
Chlorine
gas
1
­
16
Source:
USEPA
1998c.

Exhibit
2.7
illustrates
the
difference
in
total
chlorine
dose
in
large
surface
water
plants
using
only
free
chlorine
versus
those
using
chloramines
(
median
of
2.7
mg/
L
as
Cl
2
for
chlorine­
only
plants
versus
a
median
of
5.0
mg/
L
as
Cl
2
for
chloramine
plants).
Chapter
15
in
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002)
provides
additional
information
on
chlorine
dose
for
different
plant
types
(
e.
g.,
direct
filtration,
softening)
and
different
influent
TOC
concentrations.

Exhibit
2.8
shows
the
difference
in
total
chlorine
dose
in
ground
water
plants
using
only
free
chlorine
versus
those
using
chloramines
(
median
of
1.6
mg/
L
as
Cl
2
for
chlorine­
only
plants
versus
a
median
of
5.0
for
chloramine
plants).
Higher
chlorine
doses
applied
in
plants
using
chloramines
may
be
due
to
higher
levels
of
organic
material,
higher
chlorine
demand,
and
thus
higher
chlorine
doses
are
needed
to
achieve
adequate
disinfection.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
12
0%
20%
40%
60%
80%
100%

0
2
4
6
8
10
12
14
Plant­
Mean
Total
Cl2
Doses
(
mg
Cl2/
L)
Percentile
of
Plants
CL2
Only
Plants
(
N=
166)

CL2_
CLM
or
CLM
Only
Plants
(
N=
85)
Exhibit
2.7
Cumulative
Distributions
of
Mean
Total
Chlorine
Dose
for
Surface
Water
Plants
Source:
ICR
AUX2
Database
(
USEPA
2000i).

Query:
Screened
SW
Plant­
Mean
CL2
Doses
(
w
AUX2).
See
Appendix
B
for
details.

Excel
File:
ICR
Dose
Data
and
Graphs.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
13
0%
20%
40%
60%
80%
100%

0
2
4
6
8
10
12
14
Plant­
Mean
Total
Cl2
Dose
(
mg
Cl2/
L)
Percentile
of
Plants
CL2
Plants
(
N=
28)

CLM
Plants
(
N=
14)
Exhibit
2.8
Cumulative
Distributions
of
Mean
TotalChlorine
Dose
for
Ground
Water
Plants
Source:
ICR
AUX2
Database
(
USEPA
2000i)

Query:
Screened
SW
Plant­
Mean
CL2
Doses
(
w
AUX2).
See
Appendix
B
for
details.

Excel
File:
ICR
Dose
Data
and
Graphs.
xls
Table
15.3
in
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002)
shows
the
number
of
disinfectant
application
points
for
various
types
of
surface
water
plants
using
free
chlorine
only.
The
data
indicate
that
most
plant
types
used
either
one
or
two
application
points.
Approximately
10
percent
of
direct
filtration,
in­
line
filtration
plants,
and
conventional
plants
used
three
Cl2
application
points.
Plants
with
multiple
application
points
were
most
likely
using
Cl2
to
address
multiple
treatment
objectives
(
e.
g.,
disinfection,
preoxidation,
taste
and
odor
control,
and
prevention
of
microbial
growth
within
unit
processes).

Figure
15.3
in
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002)
shows
the
proportion
of
plants
using
specific
chlorine
dose
locations
(
e.
g.,
rapid
mix).
Results
are
shown
separately
for
subsets
of
plants
with
one,
two,
or
three
points
of
application.
Results
for
the
three
subsets
were
consistent:
plants
apply
disinfection
primarily
at
the
clearwell,
at
a
point
just
prior
to
filtration,
or
at
the
rapid
mix
stage.
For
plants
with
one
application
point,
rapid
mix
is
the
application
point
36
percent
of
the
time,
the
point
just
prior
to
filtration
28
percent,
and
the
clearwell
is
used
27
percent
of
the
time.
For
plants
with
two
application
points,
the
rapid
mix
is
used
53
percent,
the
point
just
prior
to
filtration
32
percent,
and
the
clearwell
is
used
80
percent
of
the
time.
Given
the
prevalence
of
the
rapid
mix
stage
and
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
14
the
point
just
prior
to
filtration
as
the
application
points,
chlorine­
only
systems
may
have
some
flexibility
to
move
the
point
of
chlorination
to
reduce
the
formation
of
DBPs.

2.5.5
Byproducts
Although
disinfection
of
water
destroys
microbes
that
can
transmit
disease,
it
has
the
drawback
of
producing
hundreds
of
DBPs,
some
of
which
are
considered
to
be
harmful
to
humans
(
Carlson
and
Hardy
1998;
Chen
and
Weisel
1998).
Exhibit
2.1
listed
the
halogenated
organic
byproducts
that
were
measured
during
the
ICR.
The
two
most
abundant
groups
of
DBPs
are
trihalomethanes
(
THMs)
and
haloacetic
acides
(
HAAs)
(
Weisel
et
al.
1999;
Hoyer
1998).

Halogenated
organic
byproducts
form
when
NOM
reacts
with
free
chlorine
or
free
bromine.
Free
chlorine
is
normally
introduced
into
water
directly
as
a
primary
or
secondary
disinfectant.
Free
bromine
results
from
the
oxidation
of
naturally
occurring
bromide
ion
by
chlorine.
Factors
affecting
the
rate
of
formation
and
concentration
of
halogenated
organic
DBPs
include
type
and
concentration
of
NOM,
form
and
dose
of
chlorine,
contact
time,
bromide
ion
concentration,
pH,
organic
nitrogen
concentration,
and
temperature
(
Chen
and
Weisel
1998;
Clark
and
Sivaganesan
1998).
Organic
nitrogen
significantly
influences
the
formation
of
nitrogen­
containing
DBPs,
including
the
haloacetonitriles
and
halopicrins
(
Reckhow
et
al.
1990;
Hoigne
and
Bader
1988).
See
Chapter
1
for
a
full
discussion
of
factors
affecting
DBP
formation.

Other
DBPs
can
result
from
impurities
in
feed
chemicals.
Sodium
hypochlorite
is
formed
by
combining
chlorine
gas
and
sodium
hydroxide.
Both
chemicals
are
manufactured
by
electrolysis
of
sodium
chloride
(
table
salt),
which
can
contain
naturally
occurring
impurities,
such
as
bromide
ions,
that
are
difficult
to
remove.
While
manufacturing
sodium
chloride,
bromide
is
converted
to
bromate,
which
has
been
found
in
small
amounts
in
sodium
hypochlorite
solutions
(
The
Chlorine
Institute
2000).

2.6
Chloramines
Chloramines
were
first
considered
for
use
in
disinfection
after
scientists
observed
that
disinfection
still
occurred
when
ammonia
was
present,
even
though
free
available
chlorine
had
dissipated.
This
lingering
disinfection
was
caused
by
inorganic
chloramines.

Chloramines
were
used
regularly
for
disinfection
during
the
1930s
and
1940s
to
provide
a
residual
disinfectant
and
to
control
taste
and
odor.
Because
of
an
ammonia
shortage
during
World
War
II,
however,
the
popularity
of
chloramination
declined.
In
recent
years,
choramines
were
recognized
as
being
more
stable
than
free
chlorine
in
the
distribution
system
and,
consequently,
were
found
to
be
effective
in
controlling
bacterial
regrowth
in
the
distribution
system
(
LeChevallier
et
al.
1996).
The
concern
over
halogenated
organic
byproduct
(
THM
and
HAA)
formation
in
water
treatment
and
distribution
systems
has
increased
interest
in
chloramines
because
they
react
differently
with
NOM
than
chlorine,
generally
producing
lower
concentrations
of
DBPs
(
Symons
et
al.
1998).
Currently,
monochloramine
is
used
to
disinfect
drinking
water
in
approximately
25
percent
of
U.
S.
municipalities
(
Kool
et
al.
1999).

2.6.1
Description
of
Chemistry
Chloramines
are
formed
by
the
reaction
of
ammonia
with
aqueous
chlorine.
In
aqueous
solutions,
hypochlorous
acid
from
the
chlorine
reacts
with
ammonia
to
form
inorganic
chloramines
in
a
series
of
Occurrence
Assessment
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Stage
2
DBPR
Proposal
July
2003
2­
15
competing
reactions.
In
these
reactions,
monochloramine
(
NH
2
Cl),
dichloramine
(
NHCl
2),
or
nitrogen
trichloride
(
NCl
3),
also
referred
to
as
trichloramine,
is
formed.
These
competing
reactions
depend
primarily
on
pH
and
are
controlled
to
a
large
extent
by
the
chlorine:
ammonia
nitrogen
ratio
(
Cl
2:
NH
3­
N).
Temperature
and
contact
time
also
regulate
this
reaction.
Monochloramine
is
formed
primarily
when
the
applied
Cl
2:
NH
3­
N
ratio
is
less
than
5:
1
by
weight.
When
certain
ratios
of
chlorine
and
ammonia
nitrogen
are
present,
chloramines
may
not
form,
and
ammonia
and
chlorine
may
be
converted
to
other
molecules
that
do
not
act
as
disinfectants
and
are
not
detected
when
chlorine
residual
is
measured.
For
instance,
as
the
applied
Cl
2:
NH
3­
N
ratio
increases
from
5:
1
to
7.6:
1,
a
"
breakpoint"
reaction
occurs,
reducing
the
residual
chloramine
and
ammonia
nitrogen
level
to
a
minimum.
Breakpoint
chlorination
results
in
the
formation
of
nitrogen
gas
or
nitrate
and
hydrochloric
acid.
At
Cl
2:
NH
3­
N
ratios
above
7.6:
1,
free
chlorine
and
nitrogen
trichloride
are
present;
being
quite
volatile,
the
latter
usually
dissipates.
To
avoid
breakpoint
reactions,
utilities
normally
maintain
a
Cl
2:
NH
3­
N
ratio
of
between
3:
1
and
5:
1
by
weight.
A
ratio
of
6:
1
is
actually
optimum
for
disinfection
because
dichloramine
predominates
(
dichloramine
is
a
stronger
disinfectant
than
monochloramine),
but
maintaining
a
stable
operation
at
that
point
on
the
breakthrough
curve
is
difficult.
Therefore,
as
noted
above,
a
Cl
2:
NH
3­
N
ratio
of
3:
1
to
5:
1
is
typically
accepted
as
optimal
for
chloramination.

2.6.2
Use
and
Distribution
Monochloramine
is
used
primarily
as
a
secondary
disinfectant
for
maintaining
a
residual
in
the
distribution
system.
Monochloramine
can
be
formed
by
adding
ammonia
first
and
then
chlorine,
by
adding
chlorine
first
and
then
ammonia,
or
by
concurrently
adding
both
reactants.
Ammonia
is
added
first
when
the
formation
of
objectionable
taste
and
odor
compounds
caused
by
the
reaction
of
chlorine
and
organic
matter
are
a
concern.
Currently,
most
drinking
water
systems
add
chlorine
first
and
then
ammonia,
in
order
to
meet
the
EPA
Surface
Water
Treatment
Rule
(
SWTR)
disinfection
requirements.
The
point
of
ammonia
addition
typically
is
selected
to
"
quench"
the
free
chlorine
residual
after
the
optimal
contact
time
has
been
achieved.

2.6.3
Advantages
and
Disadvantages
The
following
list
highlights
selected
advantages
and
disadvantages
of
using
chloramines
as
a
method
of
disinfecting
drinking
water
(
Masschelein
1992).

°
Advantages
 
The
monochloramine
residual
is
more
stable
and
lasts
longer
than
free
chlorine
or
chlorine
dioxide
 
thereby
providing
better
bacterial
regrowth
protection
in
the
distribution
system.
 
Chloramines
are
very
effective
in
addressing
taste
and
odor
problems.
 
Chloramines
are
inexpensive
and
easy
to
produce.
 
Production
of
chlorinated
DBPs
is
minimized
if
Cl
2:
NH
3
ratio
is
maintained
at
a
low
level.

°
Disadvantages
 
The
disinfecting
properties
of
chloramine
are
not
as
strong
as
other
disinfectants,
such
as
chlorine,
ozone,
and
chlorine
dioxide.
 
Chloramines
cannot
oxidize
iron,
manganese,
or
sulfides.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
16
0
10
20
30
40
50
60
70
80
90
100
0
5
10
15
20
25
30
35
40
45
50
Cl2:
N
Weight
Ratios
(
Plant
Averages
[
indicated
by
o],
Minimums,
and
Maximums)
Percentiles
of
Plants
(
N=
82)
 
When
using
chloramine
as
the
secondary
disinfectant,
it
may
be
necessary
to
periodically
convert
to
free
chlorine
for
biofilm
control
in
the
water
distribution
system
(
chloramine
does
not
effectively
control
biofilm).
 
Excess
ammonia
in
the
distribution
system,
in
the
presence
of
chloramine,
may
lead
to
nitrification
problems.
 
Monochloramine
is
less
effective
in
waters
with
high
pH.
 
Dichloramines
can
pose
problems
for
taste
and
odor.
 
Chloramines
must
be
made
on
site.
 
As
Cl
2:
NH
3
ratio
approaches
the
breakpoint,
the
greater
the
potential
for
DBP
formation.

Because
of
the
different
forms
and
dosages
of
chloramine,
and
different
usages
depending
on
system
size
and
water
quality,
not
all
of
these
advantages
and
disadvantages
apply
to
all
systems.

2.6.4
Dose
Ranges
and
Points
of
Application
The
normal
primary
disinfection
dose
range
for
monochloramine
is
1.0
to
4.0
mg/
L.
The
minimum
dosage
of
monochloramine
in
the
distribution
system
is
typically
0.5
mg/
L
(
Texas
Natural
Resource
Conservation
Commission
1996).
Exhibit
2.7
showed
the
cumulative
distributions
of
mean
chloramine
dose
for
surface
water
plants.
Another
way
to
characterize
total
chlorine
dose
is
by
Cl
2:
NH
3­
N
weight
ratios.
These
weight
ratios
determine
the
species
of
chloramines
formed
(
e.
g.,
monochloramine,
dichloramine,
trichloramine).
Exhibit
2.9
shows
the
distribution
of
Cl
2:
NH
3­
N
weight
ratios
in
plants
using
chloramines.
The
distributions
indicate
that
approximately
95
percent
of
plants
using
chloramines
had
a
plant
average
Cl
2:
NH
3­
N
weight
ratio
above
2.5,
which
is
the
stoichiometric
ratio
for
formation
of
monochloramine
in
chlorine­
demand­
free
water
(
McGuire
et
al.
2002).

Exhibit
2.9
Cl2:
NH3­
N
Weight
Ratios
in
Surface
Water
CL2_
CLM
and
CLM
Plants
Source:
McGuire
et
al.
2002.

Approximately
92
percent
of
ICR
plants
using
CL2_
CLM
have
one
point
of
application
and
the
remaining
8
percent
have
two
points
of
application.
For
CLM
plants,
78
percent
have
one
point
of
Occurrence
Assessment
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2
DBPR
Proposal
July
2003
2­
17
application
and
22
percent
have
two
points
of
application.
Figures
15.4A
and
B
in
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002)
show
the
point
of
application
of
ammonia
for
CL2_
CLM
and
CLM
plants.
For
CL2_
CLM
plants
with
one
point
of
application,
53
percent
applied
it
at
the
clearwell,
while
approximately
19
percent
applied
ammonia
at
the
rapid
mix
stage
(
the
remaining
plants
added
ammonia
during
flocculation,
sedimentation,
or
prior
to
filtration).
For
plants
with
two
points
of
application,
most
plants
applied
ammonia
at
the
rapid
mix
and
clearwell
points.
For
CLM
plants,
the
rapid
mix
point
was
the
predominant
point
of
application
for
plants
with
both
one
and
two
points
of
application.
The
predominance
of
the
rapid
mix
point
indicates
that
ammonia
is
already
being
added
early
in
the
treatment
train
to
minimize
DBP
formation.

2.6.5
Byproducts
The
effectiveness
of
chloramines
in
controlling
DBP
production
depends
upon
a
variety
of
factors,
notably
the
chlorine
to
ammonia
ratio,
the
point
of
addition
of
ammonia
relative
to
that
of
chlorine,
the
extent
of
mixing,
and
pH
levels
in
the
water.

Direct
reactions
between
monochloramine
and
organic
matter
in
water
produce
very
few
halogenated
organic
compounds.
However,
some
dichloroacetic
acid
can
be
formed,
and
cyanogen
chloride
formation
is
greater
than
with
free
chlorine
(
Jacangelo
et
al.
1989;
Smith
et
al.
1993;
Cowman
and
Singer
1994;
Symons
et
al.
1998).
If
chlorine
and
NH
3
are
added
separately
to
water
(
not
preformed
then
some
free
chlorine
is
available
to
react
with
organic
matter.
Another
potential
source
of
free
chlorine
is
monochloramine,
which
slowly
hydrolyzes
to
free
chlorine
in
an
aqueous
solution.
Therefore,
halogen­
substitution
reactions
occur
even
when
pre­
formed
monochloramine
is
used
(
Rice
and
Gomez­
Taylor
1986).
The
closer
the
Cl
2:
NH
3­
N
ratio
is
to
the
breakpoint,
the
greater
the
formation
of
DBPs
(
Speed
et
al.
1987).

The
application
of
chloramines
results
in
the
formation
of
total
organic
halide
(
TOX),
which
includes
unidentified
organic
byproducts.
However,
TOX
formation
occurs
to
a
much
lesser
degree
than
it
would
given
an
equivalent
dose
of
free
chlorine.
Little
is
known
about
the
nature
of
these
byproducts,
except
that
they
are
more
hydrophilic
and
larger
in
molecular
size
than
the
organic
halides
produced
from
free
chlorine
(
Jensen
et
al.
1985;
Singer
1992;
Symons
et
al.
1998).

2.7
Chlorine
Dioxide
Chlorine
dioxide
is
a
powerful
oxidant
originally
used
by
industries
as
a
bleaching
agent
and
disinfectant.
Chlorine
dioxide
was
first
used
for
drinking
water
treatment
in
1944
at
the
Niagara
Falls,
New
York
Water
Treatment
Plant.
Currently,
the
major
use
of
chlorine
dioxide
is
as
a
pre­
oxidant
to
control
tastes
and
odors
and
to
reduce
THM
formation
in
finished
water
(
DeMers
and
Renner
1992).

2.7.1
Description
of
Chemistry
Chlorine
dioxide
(
ClO
2)
is
a
neutral
compound
of
chlorine
in
the
+
IV
oxidation
state.
ClO
2
is
a
yellow
to
red
colored
gas
at
temperatures
above
11
 
12
°
C.
Because
ClO
2
does
not
hydrolyze
in
water,
it
exists
as
a
dissolved
gas
as
long
as
the
pH
of
the
water
ranges
from
2
to
10.
In
strongly
alkaline
solutions
(
pH
greater
than
9
or
10),
however,
formation
rates
of
DBPs
increase
with
increasing
concentrations
of
chlorine
dioxide.
Chlorine
dioxide
is
a
volatile
free
radical
that
functions
as
an
oxidant
by
way
of
a
oneelectron
transfer
mechanism
in
which
it
is
reduced
to
chlorite
(
ClO
2
!
)
(
Hoehn
et
al.
1996;
Doerr
1981).
During
drinking
water
treatment,
chlorite
is
the
predominant
reaction
byproduct,
with
50
to
70
percent
of
Occurrence
Assessment
for
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Stage
2
DBPR
Proposal
July
2003
2­
18
the
reacted
chlorine
dioxide
being
converted
to
chlorite
and
30
percent
to
chlorate
(
ClO
3
!
)
or
chloride
(
Cl
!
)
depending
on
the
secondary
disinfectant.

Although
chlorine
dioxide
can
be
produced
from
sodium
chlorate
(
NaClO
3),
for
most
potable
water
applications,
chlorine
dioxide
is
generated
from
sodium
chlorite
(
NaClO
2).
The
proportion
of
chlorine
dioxide
relative
to
impurities,
including
chlorite,
chlorate,
or
free
chlorine,
is
important
when
chlorine
dioxide
is
applied
to
drinking
water
(
Aieta
and
Berg
1986).
Although
a
significant
amount
of
chlorite
ion
can
appear
in
drinking
water
from
the
application
and
subsequent
reduction
of
chlorine
dioxide,
both
precursor
chlorite
and
chlorate
ions
can
be
constituent
contaminants
in
generated
solutions.
EPA
recommends
that
systems
limit
the
formation
of
chlorite
and
chlorate
by
maintaining
high
generator
purity
(
i.
e.,
more
than
95­
percent
efficiency)
and
limiting
excess
chlorine
to
no
more
than
5
percent
of
the
applied
dose
of
chlorine
dioxide.
Two
feed
chemical
combinations
that
generate
chlorine
dioxide
yield
in
excess
of
95
percent
are
chlorine­
sodium
chlorite
and
acid­
sodium
hypochlorite­
sodium
chlorite.

Several
feed
chemical
combinations
that
are
used
in
the
water
industry
are
described
below.

Acid
 
Chlorite
Solution.
Chlorine
dioxide
can
be
generated
by
acidification
of
a
sodium
chlorite
solution,
usually
with
hydrochloric
acid,
and
several
stoichiometric
reactions
have
been
reported
for
such
processes
(
Gordon
et
al.
1972).
When
catalyzed
by
the
presence
of
chloride
ions,
acid
activation
of
sodium
chlorite
has
a
maximum
possible
yield
of
80
percent
of
the
quantity
of
chlorine
dioxide
that
could
be
produced
from
a
reaction
of
the
same
amount
of
sodium
chlorite
with
chlorine
(
Petochelli
1995).
The
reaction
is
relatively
slow,
and
production
rates
using
this
method
are
practically
limited
to
about
25
to
30
pounds
per
day,
due
to
the
exothermic
nature
of
the
reactions.

Chlorine
Solution
 
Chlorite
Solution.
Chlorite
ions
(
from
dissolved
sodium
chlorite)
will
react
in
aqueous
solutions
with
chlorine
or
hypochlorous
acid
to
form
chlorine
dioxide.
Two
moles
of
chlorite
ions
will
theoretically
react
with
one
mole
of
chlorine
to
produce
two
moles
of
chlorine
dioxide.
To
fully
utilize
the
sodium
chlorite
solution,
excess
chlorine
is
often
used,
reducing
the
pH
and
driving
the
reaction
further
toward
completion.
The
reaction
is
faster
than
the
acid
 
chlorite
solution
method,
but
much
slower
than
the
other
commercial
methods
described
in
the
following
discussion.
Chlorine
dioxide
production
by
this
method
is
limited
to
about
1,000
pounds
per
day.

Chlorine
Gas
 
Chlorite
Solution.
Sodium
chlorite
solution
can
be
"
vaporized"
and
reacted
in
a
vacuum
with
molecular
gaseous
chlorine.
This
process
uses
concentrated
reactants
and
is
much
more
rapid
than
chlorine
solution
 
chlorite
solution
methods
(
Petochelli
1995).
If
the
chlorine
and
chlorite
ions
react
stoichiometrically,
the
resulting
pH
is
close
to
7.
Production
rates
are
virtually
unlimited,
and
some
systems
have
reported
producing
more
than
60,000
pounds
per
day.

Chlorine
Gas
 
Solid
Chlorite.
This
process
reacts
dilute,
humidified
chlorine
gas
with
specially
processed
solid
sodium
chlorite
contained
in
sealed
reactor
cartridges.
The
reaction
is
rapid
and
produces
high­
purity
chlorine
dioxide
gas
inherently
free
of
chlorine
and
chlorate
ions
because
these
ions
do
not
carry
into
the
gas
phase.
Using
multiple
cartridges
in
series
ensures
an
excess
of
sodium
chlorite;
thus,
all
chlorine
is
reacted
and
the
chlorine
dioxide
produced
is
chlorine­
free.
Because
the
chlorine
dioxide
production
rate
is
solely
a
function
of
the
chlorine
gas
feed
rate,
generators
that
use
chlorine
gas
 
solid
chlorite
technology
are
capable
of
infinite
turndown
(
i.
e.,
the
chlorine
dioxide
production
rate
can
be
adjusted
without
requiring
recalibration
between
settings)
(
Petochelli
1995;
Hoehn
and
Rosenblatt
1996).
Chlorine
gas
 
solid
chlorite
solution
method
production
capacities
are
limited
to
2,000
pounds
per
day.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
19
In
addition
to
the
commercial
processes
discussed
previously,
other
potential
methods
for
generating
chlorine
dioxide
include
electrolysis
of
a
sodium
chlorite
solution
(
with
or
without
the
use
of
membranes
to
purify
the
chlorine
dioxide
product),
irradiation
of
dilute
sodium
chlorite
solution
with
UV
light,
and
reduction
of
sodium
chlorate
with
concentrated
sulphuric
acid
and
50
percent
hydrogen
peroxide.

2.7.2
Use
and
Distribution
Chlorine
dioxide
is
almost
never
used
commercially
as
a
gas
because
it
cannot
be
safely
compressed
and
shipped.
For
potable
water
treatment
process,
it
is
predominantly
generated
in
aqueous
solutions.
Because
of
the
volatile
nature
of
the
gas,
chlorine
dioxide
works
extremely
well
in
plug
flow
reactors,
such
as
pipe
lines.
It
can
be
easily
removed
from
dilute
aqueous
solution
by
aerated
turbulence,
such
as
in
a
rapid
mix
tank
or
aerated
cascade.
For
post­
disinfection,
chlorine
dioxide
can
be
added
before
clearwells
or
transfer
pipelines.

An
estimated
700
to
900
U.
S.
drinking
water
systems
use
chlorine
dioxide,
largely
to
oxidize
iron
and
manganese,
control
taste
and
odor,
and
reduce
THM
levels
(
Hoehn
et
al.
1992).
Some
systems
are
looking
to
the
higher
disinfection
efficacy
of
chlorine
dioxide
to
decrease
contact
time
needed
for
Cryptosporidium
control.
Nineteen
plants
(
3.7
percent)
that
participated
in
the
ICR
reported
using
chlorine
dioxide
for
at
least
9
of
the
last
12
months
of
the
ICR
collection
period
(
USEPA
2000i).

2.7.3
Advantages
and
Disadvantages
The
following
list
highlights
selected
advantages
and
disadvantages
of
using
chlorine
dioxide
to
disinfect
drinking
water
(
Masschelein
1992;
DeMers
and
Renner
Inc.
1992;
Gallagher
et
al.
1994).

°
Advantages
 
More
effective
than
chlorine
and
chloramines
for
inactivation
of
viruses
(
with
longer
contact
times),
Cryptosporidium,
and
Giardia
(
with
shorter
contact
times).
 
Oxidizes
iron,
manganese,
and
sulfides.
 
Provides
taste,
odor,
and
color
control.
 
Under
proper
generation
conditions
(
i.
e.,
no
excess
chlorine),
TTHM
is
not
formed.
 
Biocidal
properties
are
not
influenced
by
pH.

°
Disadvantages
 
Incomplete
generation
of
chlorine
dioxide
leaves
unreacted
chlorite
and
chlorate.
 
Generator
inefficiency
and
optimization
difficulty
can
result
in
excess
chlorine
feed
at
the
application
point,
leading
to
formation
of
halogenated
organic
DBPs.
 
Costs
are
a
concern:
training,
sampling,
and
laboratory
testing
for
chlorite
and
chlorate
are
expensive;
in
many
cases
equipment
must
be
rented;
and
the
cost
of
the
sodium
chlorite
is
high.
 
Measuring
a
chlorine
dioxide
residual
for
determining
disinfection
credit
is
difficult.
 
Chlorine
dioxide
gas
is
explosive,
so
it
must
be
generated
on­
site
and
requires
careful
handling.
 
Chlorine
dioxide
decomposes
in
sunlight.
 
Chlorine
dioxide
can
lead
to
production
of
noxious
odors
in
some
systems.
 
It
is
difficult
to
maintain
a
chlorine
dioxide
residual
in
the
distribution
system.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
20
Because
of
the
wide
variation
in
system
size,
water
quality,
and
resulting
dosages
of
chlorine
dioxide
applied,
not
all
of
these
advantages
and
disadvantages
apply
to
all
systems.

2.7.4
Dose
Ranges
Before
chlorine
dioxide
is
selected
as
a
primary
disinfectant,
an
oxidant
demand
study
must
be
completed.
Ideally,
this
study
should
consider
the
seasonal
variations
in
water
quality,
temperature,
and
application
points.
EPA
recommends
that
the
combined
concentrations
of
chlorine
dioxide,
chlorate,
and
chlorite
not
exceed
1.0
mg/
L
in
finished
water.
This
means
that
if
the
desired
oxidant
dosage
is
greater
than
about
1.4
mg/
L,
the
chlorite/
chlorate
byproduct
concentrations
would
already
be
at
the
maximum
level;
therefore,
chlorine
dioxide
would
not
be
acceptable
as
a
disinfectant.
The
range
of
doses
includes
both
primary
and
secondary
disinfection,
although
chlorine
dioxide
typically
is
used
for
primary
disinfection.
Note
that
these
ranges
represent
the
extremes;
normal
doses
fall
within
these
ranges.

Exhibit
2.10
presents
chlorine
dioxide
doses
(
average,
minimum,
and
maximum
of
all
plant­
months
where
data
was
reported
for
9
of
the
last
12
months
of
the
ICR
collection
period)
for
surface
water
plants
using
chlorine
dioxide.
A
number
of
surface
water
plants
using
chlorine
dioxide
(
58
percent)
had
average
chlorine
dioxide
doses
between
1.0
and
1.5
mg/
L
as
ClO
2.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
21
0%
20%
40%
60%
80%
100%

0
0.5
1
1.5
2
2.5
3
3.5
Chlorine
Dioxide
Dose
(
mg
ClO2/
L)
Percentile
(
N=
20)
Exhibit
2.10
Chlorine
Dioxide
Doses
(
Plant
Minimum,
Mean,
and
Maximum)

Note:
Open
circles
represent
plant
means
and
lines
represent
minimum
and
maximum
values.

Source:
ICR
AUX2
Database
(
USEPA
2000i).

Query:
Screened
SW
Plant­
Mean
CLX
Doses
(
w
AUX2).
See
Appendix
B
for
details.

Excel
File:
ICR
Dose
Data
and
Graphs.
xls
2.7.5
Byproducts
Small
amounts
of
chlorine
are
often
present
when
chlorine
dioxide
is
used,
so
halogenated
organic
DBPs
are
often
detected
in
small
quantities.
However,
the
application
of
chlorine­
free
chlorine
dioxide
does
not
form
THMs
and
produces
only
a
small
amount
of
TOX
(
Werdehoff
and
Singer
1987)
and
other
halogenated­
substituted
compounds
at
very
low
concentrations
(
Richardson
1998).
Chlorine
dioxide
oxidizes
NOM
to
form
organic
DBPs.
Primarily,
however,
the
application
of
chlorine
dioxide
to
water
results
in
oxidation/
reduction
reactions
that
form
two
inorganic
DBPs:
chlorite
and
chlorate
(
Rav­
Acha
et
al.
1984;
Werdehoff
and
Singer
1987).
Chlorite
and
chlorate
frequently
are
found
as
contaminants
in
chlorine
dioxide
feed
streams,
and
chlorite
is
formed
as
a
byproduct
from
disinfection
with
chlorine
dioxide
(
Griese
et
al.
1991).
However,
chlorine
dioxide
does
not
generate
bromine­
substituted
byproducts
to
the
same
extent
as
ozone
in
bromide­
containing
waters.
Chlorite
in
drinking
water
results
from
two
parts
of
the
chlorine
dioxide
disinfection
process:
.
°
Unreacted
chlorite
from
the
chlorine
dioxide
generation
process
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
22
°
Reduction
of
chlorine
dioxide
when
it
reacts
with
organic
matter
in
water
Incomplete
reaction
or
non­
stoichiometric
addition
of
the
sodium
chlorite
and
chlorine
reactants
can
result
in
unreacted
chlorite
or,
more
likely,
chlorate
in
the
chlorine
dioxide
feed
stream.
Upon
application
to
water,
chlorine
dioxide
is
fairly
unstable
and
rapidly
dissociates
into
chlorite
and
chlorate
at
pHs
above
10.
This
occurs
only
to
a
limited
extent
where
residuals
of
chlorine
dioxide
are
greater
than
1
percent.
Chlorite
ions
are
the
primary
product
of
chlorine
dioxide
reduction,
but
the
percentage
of
chlorite
and
chlorate
present
is
influenced
by
pH
and
sunlight,
as
well
as
the
efficiency
of
the
chlorine
dioxide
generator.

The
quantity
of
chlorate
produced
during
chlorine
dioxide
generation
increases
with
excess
chlorine
addition.
Similarly,
low
pH
can
increase
the
quantity
of
chlorate
during
chlorine
dioxide
generation.
The
predominant
source
of
chlorate
ions
in
finished
water,
however,
results
from
the
oxidation
of
chlorite
(
from
the
applied
chlorine
dioxide)
by
free
available
chlorine
used
as
a
final
distribution
system
disinfectant
(
Gallagher
et
al.
1994).
Consequently,
chlorate
concentrations
are
expected
to
increase
with
increasing
contact
time
in
water
containing
chlorite
and
chlorine.
Once
formed,
chlorate
is
stable
in
finished
drinking
water.

2.8
Ozonation
Ozone
(
O
3)
is
used
in
water
treatment
for
disinfection
and
oxidation.
Early
application
of
ozone
was
primarily
for
non­
disinfection
purposes,
such
as
color
removal
or
taste
and
odor
control.
Since
implementation
of
the
SWTR,
Stage
1
DBPR,
and
IESWTR,
ozone
usage
for
disinfection
has
increased.
Ozone
is
a
powerful
oxidant
capable
of
oxidizing
many
organic
and
inorganic
compounds
in
water.

Ozone
was
first
used
for
drinking
water
treatment
in
1893
in
the
Netherlands.
While
used
frequently
in
Europe
to
disinfect
drinking
water,
ozonation
technology
was
slow
to
transfer
to
the
United
States.
In
1991,
approximately
40
water
treatment
plants
serving
more
than
10,000
people
in
the
United
States
used
ozone
(
Langlais
et
al.
1991).
This
number
had
grown
to
201
by
1997
(
Rice
and
Dimitrou
1997).
Most
of
these
facilities
are
small:
90
plants
treat
fewer
than
1
million
gallons
per
day
(
mgd)
and
only
6
exceeded
100
mgd
as
of
May
1997.
ICR
data
show
that
14
large
surface
water
plants
reported
using
ozone
for
at
least
9
of
the
last
12
months
of
the
ICR
collection
period
(
USEPA
2000d).
Another
source
cites
that
as
of
January
2000,
275
plants
were
using
ozone,
with
another
16
plants
expected
to
come
on
line
in
the
next
year
(
Rice
2000).
Many
of
these
plants
are
using
ozone
for
purposes
besides
disinfection.
Rice
also
estimates
that
many
very
small
systems
in
California,
many
of
which
may
be
noncommunity
systems,
use
ozone
as
a
disinfectant
in
their
storage
tanks.

2.8.1
Description
of
Chemistry
A
gas
at
room
temperature,
ozone
is
highly
corrosive
and
toxic.
The
gas
is
colorless
with
a
pungent
odor
readily
detectable
at
concentrations
as
low
as
0.01
to
0.05
parts
per
million
(
ppm),
which
is
below
concentrations
that
would
cause
a
health
problem.

Ozone
decomposes
spontaneously
in
water
by
a
complex
reaction
involving
the
generation
of
oxygen
and
hydroxyl
free
radicals.
Hydroxyl
radicals
are
among
the
most
reactive
oxidizing
agents
in
water
due
to
their
unpaired
electrons
(
Hoigne
and
Bader
1983a;
Hoigne
and
Bader
1983b;
Glaze
1987).
Ozone
reacts
in
two
modes
in
aqueous
solutions:
direct
oxidation
of
compounds
by
aqueous
ozone
(
O
3(
aq))
and
oxidation
of
compounds
by
hydroxyl
radicals
produced
during
the
spontaneous
decomposition
of
ozone
(
Hoigne
and
Bader
1977).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
23
2.8.2
Use
and
Distribution
Ozone
is
used
in
drinking
water
treatment
for
various
purposes.

°
Disinfection
°
Inorganic
pollutant
oxidation,
including
iron,
manganese,
and
sulfide
°
Organic
micropollutant
oxidation,
including
taste
and
odor
compounds,
phenolic
pollutants,
and
pesticides
°
Organic
macropollutant
oxidation,
including
color
removal,
increasing
the
biodegradability
of
organic
compounds,
THM
and
TOX
precursor
control,
and
destruction
of
chlorine
demand
°
Improvement
of
coagulation
and
filtration
Ozone
is
unstable,
so
it
must
be
generated
at
the
point
of
application.
It
is
generally
formed
by
combining
an
oxygen
atom
with
an
oxygen
molecule
(
O
2).
This
reaction
is
endothermic
and
requires
considerable
energy.
Ozone
can
be
produced
several
ways,
including
by
irradiating
an
oxygen­
containing
gas
with
electrolytic
reactions,
ultraviolet
light,
or
high­
energy
radiation.
These
are
all
processes
that
produce
free
oxygen
radicals
from
electron
or
photon
energy
input.

One
method,
corona
discharge,
predominates
in
the
water
industry.
Corona
discharge,
also
known
as
silent
electrical
discharge,
consists
of
passing
an
oxygen­
containing
gas
through
two
electrodes
separated
by
a
dielectric
and
an
air
gap.
A
voltage
is
applied
to
the
electrodes,
causing
an
electron
flow
across
the
air
gap.
These
electrons
provide
the
energy
to
dissociate
the
oxygen
molecules,
leading
to
the
formation
of
ozone
directly
in
the
water
source.
Therefore,
no
chemical
inputs
are
needed.

For
most
applications,
ozone
is
applied
either
to
the
raw
water
or
after
some
type
of
clarification
process.
Turbidity
and
ozone
demand
(
the
amount
of
ozone
required
to
oxidize
all
the
constituents
in
the
water)
influence
the
way
ozone
is
used
in
the
treatment
process.
By
moving
the
ozonation
process
further
downstream,
the
ozone
demand
and
production
of
oxidation
byproducts
are
reduced.
The
advantage
of
placing
ozone
ahead
of
filtration
is
that
biodegradable
organics
produced
during
ozonation
can
be
removed
in
the
filters
if
they
are
operated
with
biological
processes.
Bacteria
living
in
the
biofilm
growing
on
filters
can
break
down
and
feed
on
NOM.
Biological
filtration
is
often
necessary
for
waters
that
have
high
levels
of
NOM.

2.8.3
Advantages
and
Disadvantages
The
following
list
highlights
selected
advantages
and
disadvantages
of
using
ozone
to
disinfect
drinking
water
(
Masschelein
1992).

°
Advantages
 
Ozone
is
more
effective
than
chlorine,
chloramines,
and
chlorine
dioxide
for
inactivation
of
viruses,
Cryptosporidium,
and
Giardia.
 
Ozone
oxidizes
iron,
manganese,
and
sulfides.
 
Ozone
can
sometimes
enhance
the
clarification
process
and
turbidity
removal.
 
Ozone
improves
color,
taste,
and
odors.
 
Ozone
requires
a
very
short
contact
time.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
24
 
Halogenated
organic
DBPs
are
not
formed
by
ozonation
if
bromide
is
absent.
 
Enhances
the
biodegradability
of
natural
and
synthetic
organic
compounds
and
destroys
many
organic
compounds.
 
Created
in
the
water
to
be
treated,
so
does
not
require
storage
space
for
disinfection
chemicals.

°
Disadvantages
 
DBPs
formed
include
bromate
and
bromine­
substituted
DBPs
(
when
bromide
is
present),
as
well
as
aldehydes
and
ketones
(
if
there
is
incomplete
oxidation
of
some
organic
compounds).
 
The
initial
cost
of
ozonation
equipment
is
high.
 
The
generation
of
ozone
is
energy­
intensive
and
must
be
generated
on
site.
 
Ozone
is
highly
corrosive
and
toxic.
 
Ozone
decays
rapidly
at
high
pH
and
warm
temperatures.
 
Ozone
provides
no
residual.
 
Ozone
plants
require
a
higher
level
of
maintenance
and
operator
skill.

Because
of
the
wide
variation
in
system
size,
water
quality,
and
ozonation
dosages
applied,
not
all
of
these
advantages
and
disadvantages
apply
to
all
systems.

2.8.4
Dose
Ranges
Engineering
design
manuals
and
published
articles
were
used
in
developing
an
ozone
dose
range
for
the
guideline
used
to
review
PWSs'
ICR
initial
sampling
plans.
This
range
of
doses
is
for
primary
disinfection
only.
Note
that
these
ranges
represent
extremes,
and
normal
values
fall
between
these
values.
Ozone
plants
participating
in
the
ICR
also
reported
the
doses
of
ozone
they
used.
Exhibit
2.11
presents
ozone
doses
(
average,
minimum,
and
maximum
of
all
plant­
months
where
data
was
reported
for
9
of
the
last
12
months
of
the
ICR
collection
period)
for
surface
water
plants
using
ozone.
Approximately
86
percent
of
surface
water
plants
using
ozone
had
an
average
ozone
dose
below
3.0
mg/
L
as
O
3.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
25
0%
20%
40%
60%
80%
100%

0
2
4
6
8
10
12
14
16
18
Ozone
Dose
(
mg
O3/
L)
Percentile
(
N=
14)
Exhibit
2.11
Ozone
Doses
(
Plant
Minimum,
Mean,
and
Maximum)

Note:
Open
circles
represent
plant
means
and
lines
represent
minimum
and
maximum
values.

Source:
ICR
AUX2
Database
(
USEPA
2000i).

Query:
Screened
SW
Plant­
Mean
O3
Doses
(
w
AUX2).
See
Appendix
B
for
details.

Excel
File:
ICR
Dose
Data
and
Graphs.
xls
2.8.5
Byproducts
A
variety
of
organic
and
inorganic
byproducts
have
been
observed
following
ozonation
of
water.
Ozone
can
react
with
bromide
naturally
present
in
water
to
form
bromate.
If
bromide
is
present
in
the
source
water,
however,
bromine­
substituted
DBPs
can
also
be
formed.
The
primary
factors
affecting
the
speciation
and
concentrations
of
bromine­
substituted
byproducts
are
pH
and
the
ratios
of
ozone­
tobromide
and
total
organic
carbon­
to­
bromide
(
Singer
1992).
Refer
to
Chapter
15
of
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002)
for
data
on
source
water
bromide
concentrations
for
plants
using
ozone.

The
principal
benefit
of
using
ozone
to
control
THM
formation
is
that
ozone
allows
free
chlorine
to
be
applied
at
lower
doses
later
in
the
treatment
process,
after
some
of
the
DBP
precursors
have
been
removed,
thereby
reducing
the
potential
for
DBP
formation.
However,
application
of
a
secondary
disinfectant
following
ozonation
requires
special
consideration
for
potential
interaction
between
disinfectants.
For
example,
chloral
hydrate
formation
has
been
observed
to
increase
when
chlorine
is
used
as
a
secondary
disinfectant
after
ozone
(
McKnight
and
Reckhow
1992;
Logsdon
et
al.
1992).
One
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
2­
26
byproduct
of
ozonation,
acetaldehyde,
is
a
known
precursor
of
chloral
hydrate.
Enhancement
of
chloral
hydrate
formation
has
not
been
observed
when
monochloramine
is
applied
as
the
secondary
disinfectant,
or
if
biologically
active
filtration
is
used
following
ozonation
and
prior
to
chlorination
(
Singer
1992).
Chloropicrin
formation
from
free
chlorine
also
appears
to
be
enhanced
by
pre­
ozonation
(
Hoigne
and
Bader
1988).

Organic
oxidation
byproducts,
including
aldehydes,
ketones,
aldo­
acids,
ketoacids,
and
assimilable
organic
carbon
(
AOC)
can
be
formed
upon
ozonation
of
water
containing
a
high
level
of
NOM.
The
primary
aldehydes
that
have
been
detected
are
formaldehyde,
acetaldehyde,
glyoxal,
and
methyl
glyoxal
(
Glaze
et
al.
1991).
The
ICR
data
provided
occurrence
information
on
these
substances
along
with
propanal,
pentanal,
and
butanal.
Total
aldehyde
concentration
in
drinking
water
disinfected
with
ozone
ranges
from
less
than
5
to
300
:
g/
L,
depending
on
the
TOC
concentration
and
the
applied
ozone­
toorganic
carbon
ratio
(
Van
Hoof
et
al.
1985;
Yamada
and
Somiya
1989;
Glaze
et
al.
1989;
Krasner
et
al.
1989;
Glaze
et
al.
1991;
LeLacheur
et
al.
1991).

Ozonation
of
water
containing
bromide
can
produce
hypobromous
acid
and
hypobromite,
which,
in
turn,
contribute
to
the
formation
of
bromine­
substituted
byproducts,
the
brominated
analogues
of
the
chlorinated
DBPs.
These
bromine­
substituted
byproducts
include:
bromoform;
the
bromine­
substituted
acetic
acids,
acetonitriles,
and
aldo­
acids;
bromopicrin;
and
cyanogen
bromide.
An
ozone
dose
of
2
mg/
L
produced
53
:
g/
L
of
bromoform
and
17
:
g/
L
of
dibromoacetic
acid
in
water
containing
2
mg/
L
of
bromide
ion
(
McGuire
et
al.,
1990).
Ozonation
of
the
same
water
spiked
with
2
mg/
L
bromide
ion
showed
cyanogen
bromide
formation
of
10
:
g/
L
(
McGuire
et
al.
1990).
An
ICR
plant
with
the
median
ozone
dose
of
1.84
mg/
L
had
influent
bromide
levels
of
0.133
mg/
L
and
finished
water
bromate
levels
of
3.1
:
g/
L.
Dibromoacetic
acid
levels
of
3.5
:
g/
L
were
also
detected,
but
all
other
brominated
DBPs
were
below
their
minimum
reporting
levels.

Ozone
can
react
with
the
hypobromite
ion
to
form
bromate
(
Siddiqui
and
Amy
1993;
Krasner
et
al.
1993;
Amy
et
al.
1997).
Bromate
formation
is
affected
by
NOM,
pH,
bromide
ion
concentrations,
inorganic
carbon,
and
ozone
dose.
Decreasing
pH
(
8.5
 
6.5)
generally
decreases
bromate
formation
because
the
equilibrium
is
shifted
to
hypobromous
acid,
which
does
not
form
bromate.
Lower
pH,
however,
enhances
the
formation
of
bromine­
substituted
DBPs
formed
by
the
reaction
of
hypobromous
acid
and
NOM.
Higher
bromide
ion
concentrations
and
high
inorganic
carbon
concentrations
have
been
noted
with
increased
bromate
ion
formations
(
Amy
et
al.
1997).

The
amount
of
bromide
incorporated
into
the
detected
DBPs
accounts
for
only
one­
third
of
the
total
source
water
bromide
concentration.
This
indicates
that
other
bromine­
substituted
DBPs
exist
that
are
not
yet
identified
(
McGuire
et
al.
1989;
AWWARF
1991).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
1
3.
National
Occurrence
Data
This
chapter
summarizes
the
data
collected
to
assess
disinfectants
and
disinfection
byproduct
(
DBP)
occurrence
in
public
drinking
water
supplies.
Because
the
compliance
deadline
for
the
Stage
1
Disinfectants
and
Disinfection
Byproducts
Rule
(
DBPR)
passed
recently
(
January
2002)
for
large
and
medium
surface
water
systems,
all
occurrence
data
presented
in
this
chapter
represent
pre­
Stage
1
conditions
(
i.
e.,
conditions
before
the
implementation
of
the
Stage
1
DBPR).
Chapter
4
provides
a
prediction
of
post­
Stage
1
DBP
occurrence.

The
main
source
of
DBP
data
is
the
Information
Collection
Rule
(
ICR),
which
authorized
EPA
to
collect
occurrence
and
treatment
information
from
water
systems
serving
at
least
100,000
people.
The
ICR
data
described
in
this
chapter
are
from
the
AUX1
Database,
CD
version
5.0
(
USEPA
2000d).
Information
about
medium
(
10,001
to
100,000
people
served)
and
small
(
10,000
or
fewer
people
served)
systems
comes
from
the
National
Rural
Water
Association
(
NRWA)
Survey
(
USEPA
2001g),
ICR
Supplemental
Surveys,
the
Water
Utility
Database
(
WATER:\
STATS),
and
data
provided
by
several
States.
Because
the
data
available
for
medium
and
small
systems
are
not
as
extensive
as
the
ICR
data,
the
majority
of
this
chapter
is
a
presentation
of
ICR
data
for
individual
water
quality
parameters
and
DBPs
for
large
systems.
EPA
found
that
there
are
significant
similarities
between
large
systems
and
medium
and
small
systems
with
regard
to
source
water
quality
(
affecting
DBP
formation)
and
use
of
treatment
technologies.
Because
of
these
similarities,
EPA
expects
that
small
and
medium
systems
would
find
DBP
distribution
system
levels
similar
to
those
found
in
large
systems
following
compliance
with
the
Stage
1
DBPR
requirements.

The
organization
of
the
remainder
of
this
chapter
is
as
follows:

°
Section
3.1
presents
large
system
occurrence
data
provided
through
the
ICR
for
DBP
precursors
and
other
parameters
that
affect
DBP
formation,
disinfectant
residuals,
and
DBPs.
°
Section
3.2
presents
medium
and
small
system
occurrence
data
derived
from
sources
other
than
the
ICR.

°
Section
3.3
evaluates
co­
occurrence
among
certain
ICR
water
quality
parameters
and
the
relationships
of
these
interactions.

°
Section
3.4
evaluates
regional
occurrence
trends
for
some
DBP
precursors
Data
analyses
in
this
chapter
are
supported
by
two
appendices.
Appendix
A
supplements
section
3.1
by
describing
additional
analyses
of
ICR
data
presented
in
this
chapter
and
additional
data
related
to
DBP
formation
that
were
gathered
during
the
ICR.
Appendix
B
provides
the
Microsoft
AccessTM
query
language
that
was
used
to
extract
data
from
the
ICR
AUX1
database.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
2
3.1
ICR
Data
Sections
3.1.1
through
3.1.3
present
the
ICR
summary
data
for
large
systems
with
a
description
of
analyte
characteristics
as
follows:

Section
3.1.1
DBP
Precursors
Section
3.1.2
Disinfectant
Residuals
Section
3.1.3
DBPs
Summary
statistics
in
this
section
are
generally
for
"
plant­
mean"
data
 
that
is,
for
each
plant,
the
mean
concentration
of
an
analyte
is
calculated
using
all
reported
data
during
the
last
12
months
of
the
ICR
collection
period.
Summary
statistics
were
then
generated
based
on
the
distribution
of
all
plant­
means.
See
section
1.4.8
for
a
detailed
description
of
the
methodology
used
to
generate
ICR
data
summaries
in
this
section.

3.1.1
DBP
Precursors
This
section
summarizes
plant­
mean
data
for
water
quality
parameters
that
can
affect
the
formation
of
DBPs.
These
water
quality
parameters
are
total
organic
carbon
(
TOC),
temperature,
bromide,
and
UV­
254
absorbance.
Summary
statistics,
calculated
using
the
last
12
months
of
the
ICR
collection
period
for
plants
that
have
at
least
9
months
of
data
for
each
parameter,
are
shown
in
Exhibit
3.1.
Exhibits
3.2
through
3.5
compare
the
cumulative
distributions
of
plant­
mean
values
for
ground
and
surface
water
plants.
Exhibit
3.6
characterizes
plant­
level
variability
by
showing
the
distribution
of
the
maximum
value
minus
the
minimum
value
at
each
plant
for
each
water
quality
parameter.
Analyses
of
individual
observations
for
these
and
other
water
quality
parameters
(
pH,
alkalinity,
total
hardness,
and
turbidity)
are
presented
in
Appendix
A.

All
data
in
this
section
represent
samples
collected
from
the
influent
water
sampling
location.
Although
the
ICR
required
samples
to
be
collected
throughout
the
treatment
plant,
the
influent
water
sampling
point
was
selected
to
illustrate
parameters
of
the
influent
water
quality
matrix
that
ICR
systems
consider
during
treatment.
Although
the
water
quality
characteristics
that
directly
affect
DBP
formation
are
present
at
the
point
of
disinfectant
addition,
this
section
focuses
on
influent
characteristics
with
the
understanding
that
treatment
will
change
the
parameters.

Observations
regarding
the
data
follow
the
exhibits.
Appendix
A
contains
additional
discussion
and
background
information
on
each
parameter.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
3
Source
Water
Number
of
Plants
Mean
of
Plant­
Means
Median
of
Plant­
Means
90th
Percentile
of
Plant­
Means
Range
of
Plant­
Means
Total
Organic
Carbon
(
mg/
L
as
Carbon
[
C])

Surface
307
3.14
2.71
5.29
<
0.7
­
21.4
Ground
103
1.46
0.19
3.36
<
0.7
­
16.1
All1
423
2.71
0.08
0.73
<
0.7
­
21.4
Temperature
(
degrees
Celsius)

Surface
334
16.0
16.1
20.7
3.7
­
27.7
Ground
121
19.9
20.1
26.3
9.5
­
30.5
All1
473
17.1
17.0
24.5
3.7
­
30.5
Bromide
(
mg/
L)
2
Surface
320
0.055
0.027
0.115
<
0.02
­
1.325
Ground
118
0.103
0.066
0.190
<
0.02
­
1.325
All1
449
0.068
0.036
0.151
<
0.02
­
1.325
UV­
254
Absorbance
(
cm­
1)

Surface
306
0.098
0.079
0.176
<
0.009
­
0.880
Ground
104
0.062
0.009
0.266
<
0.009
­
0.606
All1
424
0.091
0.069
0.180
<
0.009
­
0.880
Exhibit
3.1
Summary
of
Influent
Water
Quality
Parameter
ICR
Data
for
All
Large
Plants
Notes:
1"
All"
plants
include
those
with
surface,
ground,
blended,
mixed,
or
purchased
source
water
types,
so
"
All"
does
not
equal
the
sum
of
surface
and
ground.
2Plant
402
was
removed
from
the
analysis
for
bromide.
Its
plant­
mean
bromide
value
of
2.36
mg/
L
was
calculated
based
on
one
month
of
bromide
levels
of
28
mg/
L.
All
the
other
values
for
that
plant
in
the
last
12
months
of
the
ICR
were
below
0.1
mg/
L.
The
28
mg/
L
value
is
most
likely
a
reporting
error
as
laboratories
often
report
bromide
values
in
µ
g/
L
rather
than
mg/
L,
and
this
value
may
not
have
been
converted
to
mg/
L.

Source:
ICR
AUX1
database
(
USEPA
2000d).

Queries:
Screened
TOC
INF,
Screened
TEMP
INF,
Screened
BROMIDE
INF,
and
Screened
UV_
254
INF.
See
Appendix
B
for
query
language.

Excel
File:
ICR
Influent
WQP.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
4
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
2
4
6
8
10
12
14
16
18
20
22
24
Plant­
Mean
TOC
(
mg/
L
as
C)
Percentile
SW
ICR
TOC
Plant­
Means
(
N=
307)

GW
ICR
TOC
Plant­
Means
(
N=
103)
Exhibit
3.2
Cumulative
Distribution
of
Plant­
Mean
TOC
Concentrations
of
Influent
Samples
Based
on
ICR
Data
for
Large
Surface
and
Ground
Water
Plants
(
mg/
L
as
C)

Source:
ICR
AUX1
database
(
USEPA
2000d).

Query:
Screened
TOC
INF.
See
Appendix
B
for
query
language.

Excel
File:
ICR
Influent
WQP.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
5
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
5
10
15
20
25
30
35
Plant­
Mean
Temperature
(
degrees
Celsius)
Percentile
SW
ICR
Temperature
Plant­
Means
(
N=
334)

GW
ICR
Temperature
Plant­
Means
(
N=
121)
Exhibit
3.3
Cumulative
Distribution
of
Plant­
Mean
Water
Temperature
of
Influent
Samples
Based
on
ICR
Data
for
Large
Surface
and
Ground
Water
Plants
(
degrees
Celsius)

Source:
ICR
AUX1
database
(
USEPA
2000d).

Query:
Screened
TEMP
INF.
See
Appendix
B
for
query
language.

Excel
File:
ICR
Influent
WQP.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
6
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
0.2
0.4
0.6
0.8
1
1.2
1.4
Plant­
Mean
Bromide
(
mg/
L)
Percentile
SW
ICR
Bromide
Plant­
Means
(
N=
320)

GW
ICR
Bromide
Plant­
Means
(
N=
118)
Exhibit
3.4
Cumulative
Distribution
of
Plant­
Mean
Bromide
Concentrations
of
Influent
Samples
Based
on
ICR
Data
for
Large
Surface
and
Ground
Water
Plants
(
mg/
L)

Note:
Plant
402
was
removed
from
the
analysis
for
bromide.
Its
plant
mean
bromide
value
of
2.36
mg/
L
was
calculated
based
on
one
month
of
bromide
levels
of
28
mg/
L.
All
the
other
values
for
that
plant
in
the
last
12
months
of
the
ICR
were
below
0.1
mg/
L.
The
28
mg/
L
value
is
most
likely
a
reporting
error
as
laboratories
often
report
bromide
values
in
µ
g/
L
rather
than
mg/
L,
and
this
value
may
not
have
been
converted
to
mg/
L.

Source:
ICR
AUX1
database
(
USEPA
2000d).

Query:
Screened
BROMIDE
INF.
See
Appendix
B
for
query
language.

Excel
File:
ICR
Influent
WQP.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
7
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Plant­
Mean
UV­
254
(
cm­
1)
Percentile
SW
ICR
UV­
254
Plant­
Means
(
N=
306)

GW
ICR
UV­
254
Plant­
Means
(
N=
104)
Exhibit
3.5
Cumulative
Distribution
of
Plant­
Mean
UV­
254
Concentrations
of
Influent
Samples
Based
on
ICR
Data
for
Large
Surface
and
Ground
Water
Plants
(
mg/
L)

Source:
ICR
AUX1
database
(
USEPA
2000d).

Query:
Screened
UV_
254
INF.
See
Appendix
B
for
query
language.

Excel
File:
ICR
Influent
WQP.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
8
TOC
is
a
measure
of
the
organic
content
of
water.
This
organic
matter
contributes
to
the
formation
of
DBPs.
In
unpolluted
source
water,
humic
and
fulvic
acids
from
the
decay
of
vegetation
are
the
major
constituents
of
TOC;
in
polluted
water,
pesticides
and
other
manmade
chemicals
may
be
constituents
of
TOC
as
well
(
Amirtharajah
and
O'Melia
1990).
Researchers
have
found
that
TOC
can
be
a
good
indicator
of
the
amount
of
THMs
and
other
DBPs
that
may
form
as
a
result
of
chemical
disinfection
(
Singer
and
Chang
1989).
Correlations
between
TOC
and
DBPs
are
presented
in
section
3.3.

Mean
TOC
concentrations
for
ICR
influent
samples
at
surface
water
plants
are
more
than
double
the
mean
influent
TOC
concentrations
in
ground
water
plants.
Approximately
42
percent
of
ground
water
plants
have
mean
TOC
concentrations
less
than
or
equal
to
0.1
mg/
L
as
C,
whereas
less
than
1
percent
of
surface
water
plants
have
mean
TOC
concentrations
less
than
0.1
mg/
L
as
C.
However,
as
shown
in
the
cumulative
distribution
of
TOC
concentrations
in
Exhibit
3.2,
TOC
concentrations
in
the
upper
95th
percentile
are
similar
for
ground
water
and
surface
water
plants.

Temperature,
like
pH,
can
affect
many
aspects
of
water
chemistry
and
treatment.
Generally,
as
temperature
increases
so
do
chemical
reaction
rates
which
increase
the
amount
of
DBPs
formed
(
specifically
trihalomethanes).
Temperature
also
affects
the
solubility
of
different
substances
in
water
(
including
calcium
carbonate,
which
can
change
pH,
alkalinity,
and
hardness)
and
rates
of
chemical
reaction.
Also,
increased
temperature
often
means
increased
efficiency
of
chlorine
disinfection.

Temperature
fluctuates
much
more
in
surface
water
than
in
ground
water.
Plant­
mean
temperature
can
be
lower
in
surface
water
than
in
ground
water,
since
the
surface
water
is
directly
exposed
to
the
air
and
ground
water
sources
are
insulated
by
the
ground.
The
mean
of
plant­
mean
temperature
level
for
surface
water
plants
is
16.0
°
C,
while
the
mean
of
plant­
mean
temperature
levels
for
ground
water
plants
is
19.9
°
C.

Bromide
can
be
present
as
a
result
of
salt
water
intrusion
into
an
aquifer,
human
activities
such
as
pesticide
and
road
salt
application,
and
dissolution
of
minerals
in
geologic
formations
(
Siddiqui
et
al.
1995).
The
presence
of
bromide
in
source
water
can
affect
the
type
and
amount
of
DBPs
formed,
shifting
the
distribution
of
DBPs
generated
to
the
more
brominated
species
(
Krasner
et
al.
1989).
In
addition,
bromide
can
react
with
strong
oxidants,
such
as
ozone
or
chlorine
dioxide,
to
form
bromate,
another
byproduct
of
concern.

Bromide
concentrations
are
typically
higher
in
ground
water
than
in
surface
water
sources,
in
part
because
ground
water
has
long
contact
time
with
geologic
formations
that
can
act
as
sources
of
bromide.
This
is
reflected
by
the
ICR
results
 
mean
bromide
concentration
was
0.1
:
g/
L
for
ground
water
plants
compared
to
0.055
:
g/
L
for
surface
water
plants.
Peak
values,
however,
were
identical
for
surface
and
ground
water
plants,
calculated
at
1.33
:
g/
L.
Bromide
levels
can
be
impacted
by
seasonal
climate
conditions.
Concentrations
tend
to
be
higher
during
drought
periods
because
of
concentration
of
ions
in
a
smaller
volume
of
water.
Bromide
occurrence
also
varies
regionally.
Section
3.4
shows
analysis
of
regional
trends
for
influent
bromide.
See
Chapter
14
of
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002)
for
additional
information
regarding
bromide
occurrence.

The
absorbance
of
UV
radiation
at
a
wavelength
of
254
nanometers
correlates
with
the
amount
of
unsaturated
organic
compounds,
particularly
dissolved
matter
such
as
humic
substances,
in
the
water
(
USEPA
1999a).
UV­
254
absorbance
can
be
used
as
an
alternative
to
measuring
TOC
or
dissolved
organic
carbon
(
DOC)
as
an
indicator
of
DBP
precursors.
Exhibits
3.2
and
3.5
show
that
the
distributions
of
TOC
and
UV­
254
absorbance
for
ground
and
surface
water
plants
follow
very
similar
trends,
with
surface
water
plants
generally
showing
higher
plant­
mean
values
(
except
in
the
upper
5th
percentile).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
9
Source
Water
Number
of
Plants
Mean
25th
Percentile
50th
Percentile
75th
Percentile
90th
Percentile
95th
Percentile
Total
Organic
Carbon
(
mg/
L
as
Carbon
[
C])

Surface
307
2.26
0.95
1.55
2.70
4.10
5.60
Ground
103
1.01
0.00
0.80
1.30
1.95
2.75
All1
423
1.93
0.80
1.30
2.30
3.75
5.35
Temperature
(
degrees
Celsius)

Surface
334
17.0
13.2
18.0
21.0
23.0
24.5
Ground
121
4.3
2.0
3.8
5.2
8.2
12.0
All1
473
13.5
6.9
14.3
19.8
22.0
24.0
Bromide
(
mg/
L)
2
Surface
320
0.078
0.023
0.040
0.091
0.160
0.260
Ground
118
0.060
0.024
0.043
0.082
0.110
0.210
All1
449
0.073
0.024
0.041
0.090
0.150
0.260
UV­
254
Absorbance
(
cm­
1)

Surface
306
0.121
0.034
0.070
0.134
0.302
0.448
Ground
104
0.033
0.000
0.015
0.036
0.085
0.127
All1
424
0.106
0.023
0.049
0.120
0.280
0.412
Exhibit
3.6
provides
statistics
for
the
difference
between
the
plant­
highest
and
plant­
lowest
monthly
values
(
as
reported
during
the
last
12
months
of
the
ICR)
for
TOC,
temperature,
bromide,
and
UV­
254.
On
average,
the
difference
between
the
highest
and
lowest
values
is
roughly
three
to
four
times
greater
in
plants
using
surface
waters
than
in
plants
using
ground
waters
for
TOC,
temperature,
and
UV­
254.
The
difference
between
the
highest
and
lowest
bromide
value
is
also
greater,
on
average,
for
surface
water
plants
compared
to
ground
water
plants,
but
not
by
as
much.
These
general
trends
are
consistent
across
the
range
of
percentiles.
These
findings
are
consistent
with
general
observations
that
ground
water
varies
less
over
a
year
than
surface
water.

Exhibit
3.6
Cumulative
Distribution
of
Differences
Between
Highest
and
Lowest
Monthly
Parameter
Values
for
Influent
Water
Sample
Location
Based
on
ICR
Data
for
All
Large
Plants
Notes:
1"
All"
plants
include
those
with
surface,
ground,
blended,
mixed,
or
purchased
source
water
types,
so
"
All"
does
not
equal
the
sum
of
surface
and
ground.
2Plant
402
was
removed
from
the
analysis
for
bromide.
Its
plant
mean
bromide
value
of
2.36
mg/
L
was
calculated
based
on
one
month
of
bromide
levels
of
28
mg/
L.
All
the
other
values
for
that
plant
in
the
last
12
months
of
the
ICR
were
below
0.1
mg/
L.
The
28
mg/
L
value
is
most
likely
a
reporting
error
as
laboratories
often
report
bromide
values
in
µ
g/
L
rather
than
mg/
L,
and
this
value
may
not
have
been
converted
to
mg/
L.

Source:
ICR
AUX1
database
(
USEPA
2000d).

Queries:
Screened
TOC
INF,
Screened
TEMP
INF,
Screened
BROMIDE
INF,
and
Screened
UV_
254
INF.
See
Appendix
B
for
query
language.

Excel
File:
ICR
Influent
WQP.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
10
Source
Data
Sample
Location
Number
of
Plants
Mean
of
Plant­
Means
Median
of
Plant­
Means
90th
Percentile
of
Plant­
Means
Range
of
Plant­
Means
Free
Chlorine
Residual
(
mg/
L)
1
Surface
Finished
183
1.23
1.14
1.98
0.00­
4.37
Ground
Finished
33
1.13
1.04
2.06
0.17­
2.61
All3
Finished
224
1.22
1.13
1.98
0.00­
4.37
Total
Chlorine
Residual
(
mg/
L)

Surface
­
CL2
1
Finished
187
1.56
1.33
2.53
0.33­
4.58
Ground
­
CL2
1
Finished
37
1.45
1.17
3.25
0.17­
3.73
All3
­
CL2
1
Finished
232
1.55
1.33
2.58
0.17­
4.58
Surface
­
CLM2
Finished
89
2.51
2.35
3.58
1.07­
5.19
Ground
­
CLM2
Finished
14
3.07
3.23
4.57
1.33­
4.62
All3
­
CLM2
Finished
105
2.58
2.46
3.66
1.07­
5.19
Chlorine
Dioxide
Residual
(
mg/
L)

Surface
Finished
20
0.61
0.21
2.13
0.00­
2.74
Ozone
Residual
(
mg/
L)

Surface
After
Last
Contact
Chamber
13
0.08
0.06
0.13
0.01­
0.21
3.1.2
Disinfectant
Residuals
This
section
summarizes
residual
concentrations
for
chlorine,
chloramine,
and
chlorine
dioxide
in
finished
water
and
ozone
residuals
after
the
last
contact
chamber
(
see
Chapter
2
for
a
discussion
of
disinfectant
use
and
doses).
Disinfectants
were
monitored
monthly,
although
there
are
no
ground
water
data
for
some
of
the
disinfectant
types.
Summary
statistics,
calculated
using
the
last
12
months
of
the
ICR
collection
period
for
plants
that
have
at
least
9
months
of
data
for
each
parameter,
are
shown
in
Exhibit
3.7.
Further
analyses
of
individual
observations
are
presented
in
Appendix
A.
General
observations
regarding
the
data
follow
Exhibit
3.7.

Exhibit
3.7
Summary
of
Disinfectant
Residual
ICR
Data
for
All
Large
Plants
Notes:
1
For
plants
using
chlorine
only.
2
For
plants
using
chlorine
and
chloramines
or
chloramines
only.
3
"
All"
plants
include
those
with
surface,
ground,
blended,
mixed,
or
purchased
source
water
types.

Source:
ICR
AUX1
database
(
USEPA
2000d).

Queries:
Screened
EXFCLRES
FIN,
Screened
EXTCLRES
FIN,
Screened
EXCLXRES
FIN,
and
Screened
EXO3RES.
See
Appendix
B
for
query
language.

Excel
File:
ICR
Disinfectant
Residuals.
xls
In
water,
chlorine
exists
as
hypochlorous
acid
(
HOCl)
and
hypochlorite
(
OCl­).
Free
chlorine
is
defined
as
the
sum
of
the
concentrations
of
HOCl,
OCl­,
and
gaseous
Cl
2
measured
as
Cl
2.
The
Surface
Water
Treatment
Rule
sets
minimum
requirements
for
residual
disinfectant
concentration.
For
instance,
the
residual
disinfectant
concentration
at
the
point
of
entry
to
the
distribution
system
may
not
drop
below
0.2
mg/
L
for
more
than
four
hours,
although
the
regulations
do
not
state
that
the
disinfection
concentration
must
be
measured
as
free
chlorine
residual.
The
rule
also
sets
CT
(
the
product
of
contact
time
and
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
11
disinfectant
concentration)
requirements
for
systems
using
free
chlorine
as
a
disinfectant
(
USEPA
1989a).

The
mean
of
all
plant­
mean
free
chlorine
residual
concentrations
were
similar
for
surface
water
(
1.23
mg/
L)
and
ground
water
plants
(
1.13
mg/
L),
with
the
mean
for
all
plants
of
approximately
1.22
mg/
L.
Although
surface
water
plants
exhibit
a
higher
upper
range
value
(
4.37
mg/
L),
ground
water
plants
have
a
slightly
higher
90th
percentile
of
plant
means
(
2.06
mg/
L).

Total
chlorine
is
defined
as
the
sum
of
free
chlorine
and
combined
chlorine
(
chloramine)
concentrations,
and
is
expressed
in
mg/
L
as
Cl
2.
Total
chlorine
residuals
for
surface
and
ground
water
plants
that
use
chloramines
are
higher
than
total
chlorine
residuals
for
surface
and
ground
water
plants
that
use
only
free
chlorine.
Higher
total
chlorine
residual
concentrations
in
chloramine
systems
may
be
due
to
organic
material
and
DBP
precursors
and
thus,
higher
chlorine
demand
in
those
systems.

Only
twenty
surface
water
plants
reported
using
chlorine
dioxide
for
at
least
9
of
the
last
12
months
of
the
ICR
collection
period.
Although
not
in
effect
at
the
time
of
the
ICR,
the
Stage
1
DBPR
sets
a
daily
maximum
residual
disinfectant
level
(
MRDL)
of
0.8
mg/
L
for
chlorine
dioxide
based
on
sampling
at
the
entry
point
to
the
distribution
system
(
which
can
be
interpreted
in
most
cases
to
mean
finished
water).
Average
chlorine
dioxide
residuals
range
from
0
to
2.74,
with
4
plants
(
or
20
percent)
having
mean
residual
concentrations
greater
than
0.8
mg/
L.

Ozone
(
O
3)
is
a
colorless
gas
that
is
unstable
and
decomposes
rapidly,
reacting
with
hydroxide
ions
(
OH­)
to
form
hydroxyl
radicals
and
organic
radicals.
(
Radicals
are
unstable
molecules
with
unpaired
electrons.)
As
part
of
ICR
sampling,
plants
measured
ozone
residuals
of
the
effluent
of
each
ozone
contact
chamber.
For
CT
calculation,
plants
must
take
all
contact
chambers
into
account.
For
this
current
analysis,
only
the
ozone
residual
at
the
last
contact
chamber
is
presented
to
show
the
small
potential
for
DBP
formation
outside
the
contact
chambers.
The
plant­
mean
ozone
residual
concentrations
in
the
last
ozone
contact
chamber
are
very
low,
with
an
average
of
0.08
mg/
L.
Averages
ranged
from
0.01
to
0.21
mg/
L
for
the
13
surface
water
plants
that
submitted
ICR
data.

3.1.3
DBPs
Halogenated
organic
DBPs
form
as
a
result
of
reactions
of
free
chlorine,
bromide,
or
chloramines
with
naturally
occurring
organic
matter.
Studies
show
that
some
of
these
DBPs
can
cause
adverse
reproductive
and
development
health
effects
and
some
forms
of
cancer
(
USEPA
2003a).
Inorganic
DBPs
are
also
of
concern,
and
are
usually
formed
during
reactions
of
chlorine
dioxide
with
water
and
ozone
with
bromide.

A
description
of
how
distribution
system
DBP
data
are
aggregated
is
provided
below.
Next,
this
section
summarizes
results
for
all
halogenated
DBPs
measured
during
the
ICR
(
see
Exhibit
1.4
for
a
full
list
of
DBPs
measured
during
the
ICR).
The
remainder
of
the
section
focuses
on
regulated
DBPs
(
TTHM,
HAA5,
bromate,
and
chlorite).
See
section
1.4.8
for
a
detailed
description
of
the
methodology
used
to
generate
DBP
results
using
ICR
data.

Chapter
4
builds
on
this
section
by
providing
additional
analyses
of
TTHM
and
HAA5
occurrence
(
e.
g.
spatial
and
temporal
variation
in
the
distribution
system
(
DS))
for
only
those
plants
in
compliance
with
the
Stage
1
DBPR.
Appendix
A
presents
individual
observation
results
for
halogenated
DBPs
(
including
individual
species
for
each
grouping),
organic
DBPs
(
e.
g.,
butanol
and
propanol)
and
inorganic
DBPs
(
e.
g.,
chlorate).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
12
Aggregation
of
DBP
Data
As
explained
in
section
1.4.1,
each
ICR
plant
collected
samples
from
a
single
finished
water
location
and
from
four
distribution
system
sample
locations
(
DSE,
AVG1,
AVG2,
DS
Maximum)
for
the
ICR.
DBP
data
in
this
section,
in
Chapter
4,
and
in
Appendix
A
are
aggregated
into
the
following
data
types
for
analyses:

°
Finished
Water
means
a
sample
taken
from
the
end
of
the
treatment
plant,
before
water
enters
the
distribution
system.
The
plant­
mean
finished
water
concentration
is
the
average
of
the
last
four
quarters
of
finished
water
data
for
that
plant.

°
DS
Average
(
or
RAA)
is
the
calculated
average
of
four
distribution
system
samples
(
DSE,
AVG
1,
AVG
2,
and
DS
Maximum).
The
plant­
mean
DS
Average
concentration
is
the
average
of
the
last
four
quarters
of
calculated
DS
Average
data
for
that
plant.
The
plantmean
DS
Average
concentration
is
equivalent
to
the
running
annual
average
(
RAA)
concentration
for
that
year.

°
Single
Highest
is
the
highest
concentration
of
the
four
distribution
system
samples
collected
by
a
plant
in
the
last
four
quarters
of
the
ICR
(
16
possible
values).
This
value
may
represent
any
of
the
four
distribution
system
locations
 
DSE,
AVG1,
AVG2,
or
DS
Maximum.

°
Locational
Running
Annual
Average
(
LRAA)
is
the
average
of
four
quarters
of
data
from
a
single
distribution
system
location
(
DSE,
AVG1,
AVG2,
and
DS
Maximum).
For
example,
the
LRAA
for
the
DSE
location
would
be
the
average
of
the
last
four
quarters
of
data
collected
from
that
location.
The
highest
LRAA
is
the
maximum
of
the
four
(
DSE,
AVG1,
AVG2,
and
DS
Maximum)
calculated
LRAAs.
Since
the
LRAA
covers
one
year's
worth
of
data,
it
already
represents
a
plant­
mean
value.

°
Max­
Min
is
the
highest
concentration
of
the
four
distribution
system
samples
collected
by
a
plant
during
the
last
four
quarters
of
the
ICR
(
16
possible
values)
minus
the
lowest
concentration
of
the
four
distribution
system
samples
reported
during
the
last
four
quarters
of
the
ICR.
In
other
words,
Max­
Min
is
a
single
value
that
represents
the
difference
between
the
maximum
and
minimum
concentrations
from
all
four
distribution
system
samples
collected
during
the
last
four
quarters
of
the
ICR.

All
Measured
Halogenated
DBPs
Exhibit
3.8
summarizes
DS
Average
results
for
all
halogenated
DBPs
measured
under
the
ICR
(
results
for
individual
species
are
shown
Appendix
A).
As
can
be
seen
from
the
measured
concentrations
for
all
plants,
TTHMs
and
HAA5
comprise
approximately
50
percent
of
the
measured
total
organic
halides
(
TOX),
whereas
the
other
measured
organic
halides
(
HAN4,
CH,
CP,
DCP,
and
TCP)
represent
approximately
7
percent
of
the
TOX
concentration.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
13
Source
Parameter
Number
of
Plants
Mean
of
Plant­
Means
Median
of
Plant­
Means
90th
Percentile
of
Plant­
Means
Range
of
Plant­
Means
TTHM
213
68.68
63.90
118.70
0­
177
HAA5
213
24.60
20.85
45.78
0­
104
HAN4
209
3.79
3.20
7.62
0­
17.5
CH
208
4.82
4.36
9.91
0­
18.7
CP
208
0.34
0.19
0.94
0­
2.4
DCP
209
0.54
0.37
1.35
0­
2.8
TCP
209
1.50
1.23
0.00
0­
6.4
TOX
213
144.19
138.16
241.25
0­
305
TTHM
82
15.36
6.79
36.95
0­
123
HAA5
82
6.35
0.33
18.83
0­
97
HAN4
80
2.22
0.75
6.01
0­
14.8
CH
80
0.59
0.03
2.18
0­
5.5
CP
79
0.03
0.00
0.13
0­
0.6
DCP
80
0.19
0.00
0.91
0­
2.0
TCP
80
0.07
0.00
0.00
0­
1.2
TOX
81
54.40
7.88
160.00
0­
482
TTHM
304
25.78
23.13
53.83
0­
119
HAA5
304
19.40
16.20
41.45
0­
104
HAN4
305
3.37
2.69
7.32
0­
17.5
CH
304
3.63
2.76
8.56
0­
18.7
CP
303
0.25
0.07
0.74
0­
2.4
DCP
305
0.44
0.20
1.24
0­
2.8
TCP
305
1.09
0.53
3.02
0­
6.4
TOX
310
119.40
115.86
237.19
0­
482
All
Ground
Surface
Exhibit
3.8
Summary
of
Halogenated
DBP
Data
Measured
During
the
ICR,
DS
Average
(
Parameter
Occurrence
Values
in
µ
g/
L)
for
All
Large
Plants
Source:
ICR
AUX1
database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
RAA
­
Other
DBPs
and
Plants
min
3x3,
RAA
and
Max
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
Other
DBP
Data,
Pre­
Stage
1.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
14
Source
Data
Type
1
Number
of
Plants
Mean
of
Plant­
Means
Median
of
Plant­
Means
90th
Percentile
of
Plant­
Means
Range
of
Plant­
Means
Finished
Water
213
31.60
28.75
55.53
0­
97
DS
Average
(
or
RAA)
213
42.28
40.36
69.82
0­
117
Single
Highest
213
68.68
63.90
118.70
0­
177
Highest
LRAA
213
49.29
45.80
80.67
0­
124
Max
­
Min
213
50.01
44.30
91.90
0­
129
Finished
Water
82
9.69
1.48
24.75
0­
119
DS
Average
(
or
RAA)
82
15.36
6.79
36.95
0­
123
Single
Highest
82
32.32
18.50
74.40
0­
300
Highest
LRAA
82
20.21
11.80
52.63
0­
127
Max
­
Min
82
26.53
15.40
60.00
0­
300
Finished
Water
304
25.78
23.13
53.83
0­
119
DS
Average
(
or
RAA)
311
34.98
33.16
65.88
0­
123
Single
Highest
311
58.48
54.00
113.80
0­
300
Highest
LRAA
311
41.38
39.50
78.20
0­
127
Max
­
Min
311
43.15
38.40
85.20
0­
300
Surface
Ground
All2
TTHM
TTHM
measurements
are
the
sum
of
concentrations
of
chloroform
(
CHCl
3),
bromodichloromethane
(
BDCM),
dibromochloromethane
(
DBCM),
and
bromoform
(
CHBr
3).
Exhibit
3.9
presents
summary
statistics
of
plant­
mean
TTHM
data
collected
under
the
ICR
by
source
water
and
data
type.
(
See
Appendix
A
and
Chapter
6
of
the
Information
Collection
Rule
Data
Analysis
document
[
McGuire
et
al.
2002]
for
occurrence
data
on
individual
TTHM
constituents.)
Exhibit
3.10
shows
the
cumulative
distribution
of
the
plant­
mean
DS
Average
(
or
RAA)
TTHM
data
for
ICR
surface
and
ground
water
plants.
Exhibits
3.11
and
3.12
show
the
cumulative
distributions
of
plant­
mean
TTHM
single
highest
and
plant­
mean
highest
TTHM
LRAA,
respectively.
Appendix
A
contains
additional
discussion
and
background
information
on
each
individual
THM.
Discussions
of
the
findings
follow
the
exhibits.

Exhibit
3.9
Summary
of
TTHM
(
:
g/
L)
ICR
Data
for
All
Large
Plants
Notes:
1
For
a
description
of
the
data
types,
see
"
Aggregation
of
DBP
Data"
at
the
beginning
of
the
subsection.
2
The
"
All"
plants
include
those
with
surface,
ground,
blended,
mixed,
or
purchased
source
water
types.
Finished
water
data
were
not
available
for
blended
plants.

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
average
by
finish
location
­
TTHM
&
HAA5,
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5
and
Plants
min
3x3,
Single
High
­
TTHM
&
HAA5,
Plants
min
3x3,
Max­
Min
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
15
0%
20%
40%
60%
80%
100%

0
20
40
60
80
100
120
140
Plant­
Mean
TTHM
(
ug/
L)
Cumulative
Percentile
Surface
Water
TTHM
(
N=
213)

Ground
Water
TTHM
(
N=
82)
Exhibit
3.10
Cumulative
Distribution
of
Plant­
Mean
DS
Average
(
RAA)
for
ICR
TTHM
Occurrence
Data
for
All
Large
Plants
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
16
0%
20%
40%
60%
80%
100%

0
50
100
150
200
250
300
350
Plant­
Mean
TTHM
(
ug/
L)
Cumulative
Percentile
Surface
Water
TTHM
(
N=
213)

Ground
Water
TTHM
(
N=
82)
Exhibit
3.11
Cumulative
Distribution
of
Single
Highest
ICR
TTHM
Occurrence
Data
for
All
Large
Surface
and
Ground
Water
Plants
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
Single
High
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
1
See
Chapter
4
of
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002)
for
a
thorough
analysis
of
historical
TTHM
occurrence
in
large
systems
since
the
mid­
to
late­
1970'
s.

Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
17
0%
20%
40%
60%
80%
100%

0
20
40
60
80
100
120
140
Plant­
Mean
TTHM
(
ug/
L)
Cumulative
Percentile
Surface
Water
TTHM
(
N=
213)

Ground
Water
TTHM
(
N=
82)
Exhibit
3.12
Cumulative
Distribution
of
Highest
LRAA
for
ICR
TTHM
Occurrence
Data
for
Large
Surface
and
Ground
Water
Plants
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
TTHM
has
been
regulated
by
EPA
since
the
interim
TTHM
Rule,
promulgated
in
1979.1
The
TTHM
Rule
established
an
MCL
of
100
µ
g/
L,
calculated
as
an
RAA
of
distribution
system
TTHM
data
measured
at
four
locations,
collected
quarterly.
As
explained
at
the
beginning
of
this
section,
an
RAA
is
the
average
of
the
most
recent
four
quarters
of
data;
when
data
from
a
new
quarter
is
obtained
it
replaces
the
data
from
the
oldest
quarter
in
the
four
quarter
averaging.
The
Stage
1
DBPR
sets
an
MCL
for
TTHM
of
80
µ
g/
L,
calculated
as
an
RAA.
However,
compliance
with
the
Stage
1
DBPR
was
not
required
until
2002
for
large
surface
water
systems
and
2004
for
ground
water
and
small
surface
water
systems
(
USEPA
1998a).
Thus,
TTHM
ICR
data,
collected
in
1997
and
1998
and
presented
in
this
section,
represents
pre­
Stage
1
DBPR
conditions.

Plant­
mean
DS
Average
(
or
RAA)
TTHM
data
can
be
used
to
estimate
the
percentage
of
plants
that
may
have
exceeded
the
Stage
1
MCLs
at
the
time
of
the
ICR.
Although
the
90th
percentile
RAA
concentrations
for
ground
and
surface
plants
are
less
than
the
Stage
1
DBPR
MCL
of
80
:
g/
L,
the
maximum
plant­
mean
RAA
concentrations
are
higher
than
80
:
g/
L
for
both
plant
types.
From
the
cumulative
distributions
of
TTHM
RAA
data
(
Exhibit
3.10),
the
following
information
can
be
derived:
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
18
°
For
surface
water
plants,
approximately
4
percent
had
TTHM
RAA
levels
above
80
:
g/
L;
however,
13
percent
had
TTHM
RAA
levels
above
64
:
g/
L
(
20
percent
less
than
the
Stage
1
DBPR
MCL).
The
64
:
g/
L
level
represents
the
safety
margin
occurrence
level
that
utilities
may
try
to
achieve
to
avoid
noncompliance.

°
For
ground
water
plants,
approximately
2
percent
had
TTHM
RAA
levels
above
80
:
g/
L;
however,
4
percent
had
TTHM
RAA
levels
greater
than
64
:
g/
L.

It
is
important
to
note
that
ICR
sampling
locations
may
not
be
the
locations
that
will
be
used
for
compliance
with
the
Stage
1
DBPR.
Also,
because
compliance
is
based
on
a
RAA
for
the
water
system
rather
than
the
plant,
it
is
possible
for
a
plant
to
report
TTHM
data
that
is
above
the
Stage
1
DBPR
MCLs
but
for
the
system
to
still
be
in
compliance
with
this
regulation.

The
Single
Highest
and
Highest
LRAA
TTHM
values
in
Exhibit
3.9
indicate
that
concentrations
at
some
locations
in
the
distribution
system
are
much
higher
than
DS
Average
concentrations.
Many
of
these
high
values
may
not
be
reduced
through
compliance
with
the
Stage
1
DBPR.
Chapter
4
provides
additional
analyses
of
peak
TTHM
data
as
it
relates
to
the
Stage
1
DBPR
and
proposed
Stage
2
DBPR.

HAA5
HAA5
measurements
represent
the
sum
of
concentrations
of
monochloroacetic
acid
(
MCAA),
dichloroacetic
acid
(
DCAA),
trichloroacetic
acid
(
TCAA),
monobromoacetic
acid
(
MBAA),
and
dibromoacetic
acid
(
DBAA).
Exhibit
3.13
presents
summary
statistics
of
plant­
mean
HAA5
data
collected
under
the
ICR
by
source
water
and
data
type.
(
See
Appendix
A
and
Chapter
6
of
the
Information
Collection
Rule
Data
Analysis
document
[
McGuire
et
al.
2002]
for
occurrence
data
on
individual
HAA5
constituents.)
Exhibit
3.14
shows
the
cumulative
distribution
of
the
plant­
mean
DS
Average
(
or
RAA)
for
HAA5
data
for
ICR
surface
and
ground
water
plants.
Exhibits
3.15
and
3.16
show
the
cumulative
distributions
of
plant­
mean
HAA5
single
highest
and
plant­
mean
highest
HAA5
LRAA,
respectively.
Appendix
A
contains
additional
discussion
and
background
information
on
each
individual
HAA.
Observations
follow
the
exhibits.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
19
Source
Data
Type
1
Number
of
Plants
Mean
of
Plant­
Means
Median
of
Plant­
Means
90th
Percentile
of
Plant­
Means
Range
of
Plant­
Means
Finished
Water
213
24.60
20.85
45.78
0­
104
DS
Average
(
or
RAA)
213
29.07
24.38
52.31
0­
116
Single
Highest
213
47.77
40.00
86.00
0­
189
Highest
LRAA
213
33.66
28.30
58.37
0­
124
Max
­
Min
213
34.85
28.20
68.00
0­
150
Finished
Water
82
6.35
0.33
18.83
0­
97
DS
Average
(
or
RAA)
82
8.45
2.24
21.53
0­
71
Single
Highest
82
17.79
6.30
46.30
0­
124
Highest
LRAA
82
11.13
3.80
30.43
0­
93
Max
­
Min
82
14.68
6.20
43.60
0­
94
Finished
Water
304
19.40
16.20
41.45
0­
104
DS
Average
(
or
RAA)
311
22.98
19.11
47.14
0­
116
Single
Highest
311
38.66
31.40
75.30
0­
189
Highest
LRAA
311
26.93
22.53
55.73
0­
124
Max
­
Min
311
28.48
23.30
59.00
0­
150
Surface
Ground
All2
Exhibit
3.13
Summary
of
HAA5
ICR
Data
for
All
Large
Plants
(
:
g/
L)

Notes:
1
For
a
description
of
the
data
types,
see
"
Aggregation
of
DBP
Data"
at
the
beginning
of
the
subsection.
2
The
"
All"
plants
include
those
with
surface,
ground,
blended,
mixed,
or
purchased
source
water
types.
Finished
water
data
were
not
available
for
blended
plants.

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
average
by
finish
location
­
TTHM
&
HAA5,
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5
and
Plants
min
3x3,
Single
High
­
TTHM
&
HAA5,
Plants
min
3x3,
Max­
Min
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
20
0%
20%
40%
60%
80%
100%

0
20
40
60
80
100
120
140
Plant­
Mean
HAA5
(
ug/
L)
Cumulative
Percentile
Surface
Water
HAA5
(
N=
213)

Ground
Water
HAA5
(
N=
82)
Exhibit
3.14
Cumulative
Distribution
of
Plant­
Mean
DS
Average
(
RAA)
for
ICR
HAA5
Occurrence
Data
for
Large
Surface
and
Ground
Water
Plants
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
21
0%
20%
40%
60%
80%
100%

0
20
40
60
80
100
120
140
160
180
200
Plant­
Mean
HAA5
(
ug/
L)
Cumulative
Percentile
Surface
Water
HAA5
(
N=
213)

Ground
Water
HAA5
(
N=
82)
Exhibit
3.15
Cumulative
Distribution
of
Single
Highest
ICR
HAA5
Occurrence
Data
for
Large
Surface
and
Ground
Water
Plants
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
Single
High
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
22
0%
20%
40%
60%
80%
100%

0
20
40
60
80
100
120
140
Plant­
Mean
HAA5
(
ug/
L)
Cumulative
Percentile
Surface
Water
HAA5
(
N=
213)

Ground
Water
HAA5
(
N=
82)
Exhibit
3.16
Cumulative
Distribution
of
Highest
LRAA
ICR
HAA5
Occurrence
Data
for
Large
Surface
and
Ground
Water
Plants
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
The
Stage
1
DBPR
sets
an
HAA5
MCL
of
60
µ
g/
L,
with
the
HAA5
regulated
value
calculated
as
the
RAA
of
distribution
system
data
measured
at
four
locations,
collected
quarterly.
As
noted
previously,
compliance
with
the
Stage
1
DBPR
was
not
required
until
2002
for
large
surface
water
systems
and
2004
for
ground
water
and
small
surface
water
systems.
Thus,
HAA5
ICR
data
in
this
section
represent
pre­
Stage
1
conditions.

Plant­
mean
DS
Average
(
or
RAA)
HAA5
data
can
be
used
to
estimate
the
percent
of
plants
that
may
have
exceeded
the
Stage
1
MCLs
at
the
time
of
the
ICR.
Although
the
90th
percentile
RAA
concentrations
for
ground
and
surface
water
plants
are
less
than
the
Stage
1
DBPR
MCL
of
60
:
g/
L,
the
maximum
plant­
mean
RAA
concentrations
are
higher
than
60
:
g/
L
for
both
plant
types.
From
the
cumulative
distributions
of
HAA5
RAA
data
(
Exhibit
3.14),
the
following
information
can
be
derived:

°
For
surface
water
plants,
approximately
6
percent
had
HAA5
RAA
levels
above
60
:
g/
L;
however,
12
percent
had
HAA5
RAA
levels
greater
than
48
:
g/
L
(
20
percent
less
than
the
Stage
1
DBPR
MCL).
The
48
:
g/
L
level
represents
the
safety
margin
occurrence
level
that
utilities
may
try
to
achieve
to
avoid
noncompliance.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
23
°
For
ground
water
plants,
approximately
2
percent
had
HAA5
RAA
levels
above
60
:
g/;
however,
4
percent
had
HAA5
RAA
levels
greater
than
48
:
g/
L.

It
is
important
to
note
that
ICR
sampling
locations
may
not
be
the
locations
used
for
compliance
with
the
Stage
1
DBPR.
Also,
because
compliance
is
based
on
a
RAA
for
the
water
system
rather
than
the
plant,
it
is
possible
for
a
plant
to
report
HAA5
data
that
is
above
the
Stage
1
DBPR
MCLs
but
still
be
in
compliance
with
current
regulations.

The
Single
Highest
and
Highest
LRAA
HAA5
values
in
Exhibit
3.13
indicate
that
concentrations
at
some
locations
in
the
distribution
system
are
much
higher
than
DS
Average
concentrations.
Many
of
these
high
values
may
not
be
reduced
by
the
Stage
1
DBPR.
Chapter
4
provides
additional
analysis
of
peak
HAA5
data
as
it
relates
to
the
Stage
1
DBPR
and
proposed
Stage
2
DBPR.

Bromate
ICR
requirements
for
bromate
monitoring
pertained
to
plants
that
use
oxygenated
disinfectants
 
ozone
or
chlorine
dioxide.
Bromate
forms
when
these
disinfectants
react
with
bromide,
which
is
commonly
found
in
many
source
waters
(
see
Exhibit
3.1
for
source
water
bromide
concentrations).
Bromate
also
occurs
as
an
impurity
in
hypochlorite
solutions.
Because
bromide
reacts
immediately
with
ozone
and
bromate
formation
does
not
increase
with
residence
time
in
the
absence
of
a
residual,
monthly
monitoring
was
required
at
the
finished
water
sampling
point
but
not
in
the
distribution
system.
However,
bromate
formation
does
increase
with
contact
time
if
there
is
a
residual
present.

Split
samples
for
bromate
were
collected
during
the
ICR:
one
set
was
analyzed
by
plant
laboratory
personnel
and
one
was
analyzed
by
EPA.
EPA's
laboratory
used
a
different
laboratory
analytical
method
and
was
able
to
detect
bromate
at
much
lower
levels
than
most
utility
laboratories.
The
MRL
for
the
utility
method
is
5.0
µ
g/
L,
while
the
MRL
for
the
EPA
method
is
0.20
µ
g/
L.
Plant­
mean
bromate
data
are
summarized
in
Exhibit
3.17.
Ground
water
plant
data
were
not
included
in
this
analysis
 
no
ground
water
plants
used
chlorine
dioxide,
and
only
one
used
ozone.

For
surface
water
plants
using
chlorine
dioxide
disinfection,
approximately
47
percent
of
plantmean
finished
water
results
were
less
than
the
MRL
based
on
the
EPA
method,
and
88
percent
were
less
than
the
MRL
based
on
the
utility
method.
Bromate
concentrations
for
plants
using
ozone
are
much
higher
than
for
plants
using
chlorine
dioxide.
Plant­
mean
finished
water
concentrations
were
as
high
as
7.2
µ
g/
L
based
on
the
EPA
method
and
6.4
µ
g/
L
based
on
the
plant
laboratory
method.
It
is
difficult
to
compare
values
obtained
by
the
EPA
and
plant
laboratory
methods.
Because
the
MRL
for
the
utility
method
is
so
high,
most
individual
values
were
below
the
MRL
of
5.0
µ
g/
L
and
thus
were
assigned
a
value
of
zero,
affecting
the
calculation
of
the
medians
and
means.
For
plants
treating
with
chlorine
dioxide,
the
median
of
the
EPA
method
data
was
0.02
µ
g/
L,
while
the
median
of
the
plant
laboratory
data
was
0
µ
g/
L.
For
plants
using
ozone,
the
mean,
median,
and
90th
percentile
plant­
mean
bromate
concentrations
were
higher
based
on
the
EPA
method
versus
the
plant
laboratory
method.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
24
Data
Type
Number
of
Plants
Mean
of
Plant­
Means
Median
of
Plant­
Means
90th
Percentile
of
Plant­
Means
Range
of
Plant­
Means
Chlorine
Dioxide
Plants
EPA
Analytical
Method
19
0.06
0.02
0.10
0­
0.7
Plant
Laboratory
Analytical
Method
16
0.09
0.0
0.64
0­
0.8
Ozone
Plants
EPA
Analytical
Method
16
2.42
2.2
5.64
0­
7.2
Plant
Laboratory
Analytical
Method
14
1.75
0.0
5.09
0­
6.4
Exhibit
3.17
Summary
of
Bromate
in
Finished
Water,
Plant­
Mean
ICR
Data
for
All
Large
Plants
(
:
g/
L)

Note:
EPA
laboratory
analytical
method
has
an
MRL
of
0.02
µ
g/
L
and
the
plant
laboratory
analytical
method
has
an
MRL
of
5.0
µ
g/
L.
These
different
MRLs
greatly
affect
plant­
mean
bromate
calculations.

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Screened
BROMATE
EPA
FIN
and
Screened
BROMATE
UTIL
FIN.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
Chlorite
ICR
requirements
for
chlorite
monitoring
pertained
only
to
plants
that
use
chlorine
dioxide
for
disinfection.
Monthly
monitoring
was
required
at
the
finished
water
sampling
location
and
at
three
rather
than
four
locations
in
the
distribution
system.
The
three
required
monitoring
locations
were:
(
1)
a
location
near
the
first
customer;
(
2)
a
location
with
average
residence
time
(
AVG1),
and;
(
3)
the
location
with
maximum
residence
time
(
DS
Max).

Exhibit
3.18
summarizes
plant­
mean
chlorite
data.
All
data
is
for
surface
water
systems
(
there
were
no
ICR
ground
water
systems
that
used
chlorine
dioxide).
Different
plant­
mean
data
types
are
displayed
to
reflect
the
Stage
1
DBPR
compliance
calculations:
(
1)
Plant­
mean
finished
water
chlorite
concentrations
reported
by
a
plant;
(
2)
Maximum
of
monthly
finished
water
chlorite
concentrations
reported
by
a
plant;
(
3)
Plant­
mean
DS
Average
concentration
(
DS
Average
for
chlorite
is
the
average
of
data
from
the
3
distribution
system
sample
locations
described
above)
for
a
plant;
(
4)
Maximum
of
monthly
calculated
DS
Average
concentration
for
a
plant,
and;
(
5)
Single
Highest
concentration
reported
in
one
year
in
the
distribution
system
for
a
plant.

The
Stage
1
DBPR
requires
daily
monitoring
for
chlorite
at
the
finished
water
location
and
monthly
monitoring
at
three
locations
in
the
distribution
system.
Under
that
rule,
if
a
single
daily
sample
at
the
finished
water
location
exceeds
1,000
µ
g/
L,
additional
monitoring
(
outside
the
monthly
monitoring
requirement)
at
the
three
distribution
system
locations
is
then
required.
The
MCL
for
chlorite
is
1.0
mg/
L
(
1,000
µ
g/
L),
based
on
the
average
of
the
three
distribution
system
locations.
The
maximum
of
monthly
finished
water
chorite
concentrations
ranged
from
0
to
1,719
µ
g/
L.
Approximately
78
percent
of
maximum
finished
water
samples
are
below
1,000
µ
g/
L.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
25
Data
Type
Number
of
Plants
Mean
of
Plant­
Means
Median
of
Plant­
Means
90th
Percentile
of
Plant­
Means
Range
of
Plant­
Means
Finished
Water,
Plant­
Mean
18
432
461
768
2­
1,105
Finished
Water,
Maximum
Plant
Month
18
720
690
1,300
20­
1,719
DS
Average,
Plant­
Mean
16
345
409
645
5­
650
DS
Average,
Maximum
Plant
Month
16
572
653
871
20­
1,100
Single
Highest
16
645
700
886
41­
1,200
Exhibit
3.18
Summary
of
Chlorite
ICR
Data
(
µ
g/
L)
for
Large
Surface
Water
Plants
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Screened
Chlorite
DSAVG,
Screened
CHLORITE
FIN,
and
Screened
Chlorite
Single
High.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
3.2
Medium
and
Small
Systems
As
discussed
in
Chapter
2,
an
estimated
12,224
surface
water
systems
and
39,408
ground
water
systems
(
51,632
systems
total)
use
disinfection
and
are
subject
to
the
Stage
1
and
Stage
2
DBPRs.
Although
less
than
1
percent
of
disinfecting
systems
fall
into
the
large
system
size
category
(
serving
more
than
100,000
people),
they
serve
55.1
percent
of
the
total
population
served
by
disinfecting
systems
(
see
Exhibit
2.3).
This
is
one
reason
that
the
ICR
data
collection
effort
focused
on
large
plants.
However,
because
roughly
45
percent
of
the
population
served
by
disinfecting
systems
obtains
water
from
small
and
medium
systems,
it
is
also
important
to
characterize
DBP
occurrence
in
drinking
water
provided
by
these
systems.

There
is
no
extensive,
focused
database
similar
to
the
ICR
that
provides
information
on
DBP
occurrence
in
small
and
medium
systems.
Consequently,
it
is
necessary
to
use
more
limited
and
disparate
sets
of
occurrence
data,
together
with
inferences
drawn
from
the
ICR
data
on
large
plants,
to
characterize
DBP
occurrence
in
medium
and
small
systems.

This
section
presents
available
information
on
DBP
occurrence,
the
occurrence
of
DBP
precursors
(
e.
g.,
TOC,
bromide),
and
operational
characteristics
for
small
and
medium
systems
in
order
to
compare
them
to
large
system
ICR
data.
One
important
factor
to
note
when
considering
the
possible
similarities
and
differences
in
DBP
levels
among
small,
medium,
and
large
systems
is
that
the
1979
interim
standards
for
TTHMs
do
not
apply
to
systems
serving
fewer
than
10,000
people.
Some
States
do
have
DBP
standards
in
place
for
small
systems,
but
it
is
expected
that
nationally,
a
larger
percentage
of
small
systems
will
have
higher
DBP
levels
than
large
systems,
due
to
the
absence
of
that
regulatory
"
driver."
Similarly,
it
is
expected
that
DBP
levels
in
medium
systems
(
serving
10,000
to
100,000
people)
will
be
closer
to
those
in
large
systems
than
the
levels
in
small
systems
will,
because
these
systems
are
currently
regulated
under
the
1979
TTHM
Rule.

3.2.1
Overview
of
Available
Data
for
Medium
and
Small
Systems
In
addition
to
the
ICR
data
on
large
plants,
which
can
be
used
to
draw
inferences
about
small
and
medium
systems,
several
data
sets
provide
information
specifically
useful
for
evaluating
small
and
medium
systems.
Chapter
1,
section
1.5
describes
each
data
set
in
full.
A
summary
of
each
is
provided
below.
°
ICR
Supplemental
Survey
(
ICRSS).
The
ICRSS,
conducted
by
EPA
from
March
1999
through
February
2000,
was
designed
to
provide
information
to
supplement
the
ICR
data
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
26
collection
effort
for
microbiological
and
byproduct
occurrence
data.
The
ICRSS
involved
40
randomly
selected
surface
water
systems
in
each
of
the
small,
medium,
and
large
system
size
categories,
as
well
as
7
very
large
systems.
The
ICRSS
did
not
collect
DBP
occurrence
data,
but
did
collect
information
on
byproduct
precursors
in
influent
source
waters,
notably
TOC
and
bromide
levels.

°
The
National
Rural
Water
Association
(
NRWA)
Survey.
Developed
in
cooperation
with
EPA,
the
NRWA
Survey
was
designed
to
obtain
relevant
treatment,
influent
water
quality,
and
byproduct
occurrence
information
for
a
random
sample
of
117
small
surface
water
systems
(
serving
fewer
than
10,000
people).
The
survey
collected
water
quality
and
byproduct
data
during
a
cold
weather
period
(
November
1999
to
March
2000)
and
a
warm
weather
period
(
July
2000
to
November
2000).

DBP
samples
were
collected
at
a
finished
water
location,
a
distribution
system
site
with
average
residence
time,
and
a
distribution
system
site
with
maximum
residence
time.
For
small
system
DBP
analyses
presented
in
Section
3.2.2.2,
samples
at
the
average
residence
time
location
are
given
a
weight
three
times
that
of
data
at
the
maximum
residence
location
to
produce
a
"
DS
Weighted
Avg"
result.
The
weighted
average
was
used
to
make
NRWA
data
comparable
to
ICR
DS
Average
(
or
RAA)
data,
which
is
calculated
by
averaging
data
at
four
locations
approximating
the
average
residence
time
and
at
the
maximum
residence
location.

°
Water
Utility
Database
(
WATER:\
STATS).
Published
by
the
American
Water
Works
Association
(
AWWA),
WATER\:
STATS
is
derived
from
the
AWWA
Water
Industry
Database
resulting
from
a
1996
survey
of
approximately
900
water
utilities,
mostly
entities
serving
at
least
10,000
people.
The
WATER:\
STATS
data
used
here
are
aimed
mainly
at
characterizing
relevant
treatment
and
byproduct
information
for
medium
surface
water
plants.

Although
900
systems
participated
in
the
1996
survey,
the
relevant
table
in
WATER:\
STATS
contains
data
only
from
those
systems
that
chose
to
respond
to
the
section
on
water
quality.
WATER:\
STATS
does
not
contain
data
on
individual
samples;
it
contains
averages,
minima,
and
maxima
for
each
parameter
for
each
plant.

°
The
Ground
Water
Supply
Survey
(
GWSS).
This
survey,
conducted
by
EPA
in
1981
 
82,
was
designed
to
collect
treatment,
influent
water
quality,
and
finished
water
contaminant
occurrence
information
on
979
small,
medium,
and
large
ground
water
systems
from
across
the
United
States.
Although
TTHM
data
from
this
survey
are
available,
they
are
probably
not
representative
of
current
TTHM
levels
for
large
and
medium
systems
because
they
were
collected
more
than
20
years
ago,
prior
to
the
implementation
of
the
1979
TTHM
standard.
In
addition,
the
TTHM
data
were
collected
only
at
the
entry
point
to
the
distribution
system,
not
from
the
distribution
system
itself.
Due
to
the
rolling
implementation
schedule
of
the
TTHM
Rule,
systems
may
or
may
not
have
been
in
compliance
with
the
rule
in
1981
and
1982.

°
State
Data.
Data
from
several
States
were
used
to
gain
insights
into
the
occurrence
of
DBPs
and
DBP
precursors
in
surface
water
and
ground
water.
For
surface
water,
the
data
were
available
from
eight
States:
Alaska,
California,
Illinois,
Minnesota,
Missouri,
North
Carolina,
Texas,
and
Washington.
The
data
from
these
States
represent
562
small
surface
water
systems.
While
the
systems
in
these
data
sets
were
not
randomly
selected,
they
include
at
least
50
percent
of
the
small
systems
in
each
State.
Also,
all
the
small
surface
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
27
water
systems
in
these
eight
States
together
account
for
approximately
one­
third
of
all
small
non­
purchased
surface
water
systems
in
the
United
States,
which
is
a
significant
sample.
There
were
also
some
ground
water
data
on
DBPs
available
from
seven
States:
Alaska,
California,
Florida,
Illinois,
North
Carolina,
Texas,
and
Washington.

The
data
available
from
each
State
are
not
exactly
comparable;
some
States
reported
individual
sample
data,
while
others
reported
only
plant
averages.
Some
of
the
data
appear
to
be
from
distribution
system
locations,
while
other
samples
are
from
the
plant
or
from
raw
water.
Samples
in
some
States
were
collected
quarterly,
while
in
others,
the
time
between
samples
at
some
plants
was
anywhere
from
two
months
to
more
than
a
year.

3.2.2
Surface
Water
Systems
DBP
precursor
occurrence
data
for
medium
and
small
surface
water
systems
from
the
sources
described
in
Section
3.2.1
are
summarized
in
Exhibits
3.19
and
3.20.
Exhibit
3.19
shows
plant­
mean
data,
while
Exhibit
3.20
shows
individual
observations
for
the
plants
included
in
Exhibit
3.19.
NRWA
data
were
included
only
if
both
summer
and
winter
data
were
available
for
a
plant.
ICRSS
data
were
included
only
for
plants
that
had
data
for
at
least
three­
fourths
of
the
total
possible
number
of
samples.
Detailed
discussion
of
medium
and
small
system
data
are
provided
in
the
next
two
subsections.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
28
System
Size
&
Type
Source
of
Data
Number
of
Plants
Mean
of
Plant­
Means
Median
of
Plant­
Means
90th
Percentile
of
Plant­
Means
Range
of
Plant­
Means
Source
Water
TOC
(
mg/
L
as
C)
NRWA
96
3.0
2.6
5.4
0.3­
9.0
ICRSS
38
2.4
2.1
4.5
0.1­
7.1
ICRSS
40
3.6
3.7
5.5
0.2­
7.9
WATER:\
STATS
102
5.6
3.2
6.4
0.0­
200
Medium
Ground
Water
WATER:\
STATS
51
2.3
0.8
7.0
0.0­
25
Source
Water
Bromide
(
mg/
L)
NRWA
95
0.063
0.021
0.108
0­
1.724
ICRSS
38
0.020
<
0.02
0.044
<
0.02­
0.274
Medium
Surface
Water
ICRSS
40
0.050
0.016
0.092
<
0.02­
0.534
Source
Water
UV­
254
(
cm­
1)
NRWA
96
0.082
0.074
0.127
0.012­
0.228
ICRSS
38
0.074
0.051
0.113
0.016­
0.444
Medium
Surface
Water
ICRSS
40
0.093
0.083
0.171
0.029­
0.208
Small
Surface
Water
Medium
Surface
Water
Small
Surface
Water
Small
Surface
Water
System
Size
&
Type
Source
of
Data
Number
of
Observations
Mean
Median
90th
Percentile
Range
Source
Water
TOC
(
mg/
L
as
C)
NRWA
192
3.0
2.6
5.5
0.3­
9.9
ICRSS
384
2.4
1.8
5.7
0.0­
17.0
Medium
Surface
Water
ICRSS
478
3.6
3.2
7.0
0.0­
21.6
Source
Water
Bromide
(
mg/
L)
NRWA
190
0.063
0.019
0.114
0­
1.862
ICRSS
384
0.020
0.000
0.056
0­
0.355
Medium
Surface
Water
ICRSS
473
0.050
0.014
0.116
0­
0.865
Source
Water
UV­
254
(
cm­
1)

NRWA
192
0.082
0.070
0.150
0­
0.350
ICRSS
380
0.074
0.053
0.118
0.004­
0.676
Medium
Surface
Water
ICRSS
467
0.1
0.1
0.2
0­
0.805
Small
Surface
Water
Small
Surface
Water
Small
Surface
Water
Exhibit
3.19
Summary
of
Non­
ICR
DBP
Precursor
ICR
Data
for
Large
Surface
and
Ground
Water
Plants,
Plant­
Means
Notes:
Small
systems
are
those
that
serve
fewer
than
10,000
people;
medium
systems
serve
between
10,000
and
100,000
people.
See
text
in
Section
3.2.1
for
a
description
of
"
Source
of
Data."

Sources:
USEPA
2001g;
USEPA
2000k;
AWWA
2000.

Exhibit
3.20
Summary
of
Non­
ICR
DBP
Precursor
ICR
Data
for
Large
Surface
Water
Plants,
Individual
Observations
Notes:
Small
systems
are
those
that
serve
fewer
than
10,000
people;
medium
systems
serve
between
10,000
and
100,000
people.
See
text
in
Section
3.2.1
for
a
description
of
"
Source
of
Data."

Sources:
USEPA
2001g;
USEPA
2000k.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
29
3.2.2.1
Medium
Surface
Water
Systems
The
main
purpose
of
this
section
is
to
evaluate
medium
surface
water
system
DBP
occurrence
and
water
quality
data
and
determine
if
these
parameters
in
medium
surface
water
systems
are
similar
to
those
in
large
surface
water
systems.
The
data
in
the
WATER:\
STATS
(
AWWA
2000)
and
ICRSS
(
USEPA
2000k)
data
were
primarily
used
for
this
purpose.
All
WATER:\
STATS
data
in
this
section
represent
plant­
average
values.

WATER:\
STATS
occurrence
data
shows
that
source
water
types
and
quality
in
medium
and
large
surface
water
systems
are
similar
on
a
national
level.
Exhibit
3.21
indicates
that
medium
and
large
surface
water
systems
use
very
similar
types
of
water
sources.
Exhibits
3.22
and
3.23
compare
TOC
data
for
different
system
sizes
using
WATER:\
STATS
and
ICRSS
data,
respectively.
These
graphs
show
similar
distributions
of
TOC
occurrence
in
large
and
medium
surface
water
systems.
TOC
occurrence
can
also
be
assessed
by
comparing
medium
system
TOC
data
in
Exhibit
3.19
to
large
system
TOC
data
in
Exhibit
3.1.
WATER:\
STATS
and
ICRSS
values
are
similar
to
ICR
TOC
data,
with
median
values
of
3.2
mg/
L,
3.7
mg/
L,
and
2.7
mg/
L,
respectively.
ICRSS
data
on
bromide
and
UV­
254
levels,
shown
in
Exhibit
3.19,
are
quite
close
to
ICR
plant
levels
(
see
Exhibit
3.1).
Exhibits
3.24
and
3.25
show
that
medium
and
large
systems
have
similar
distributions
of
other
parameters
affecting
treatability
and,
indirectly,
DBP
formation,
such
as
turbidity
and
alkalinity.

The
type
of
treatment
technologies
used
by
medium
surface
water
systems
is
also
similar
to
those
used
by
large
systems.
As
shown
in
Exhibits
3.26
through
3.28,
medium
and
large
systems
are
similar
with
respect
to
major
categories
of
treatment
(
conventional
vs.
others),
the
use
of
key
physical
unit
processes,
and
the
use
of
specific
disinfection
methods
among
conventional
plants.
One
reason
that
medium
and
large
plants
are
similar
is
that
both
have
historically
been
subject
to
the
same
regulatory
requirements.

Exhibits
3.29
and
3.30
compare
cumulative
distributions
of
annual
average
TTHM
levels
in
finished
water
and
in
distribution
system
water
from
WATER:\
STATS
for
medium
and
large
surface
water
systems,
and
confirm
that
the
distributions
are
similar.
Also,
these
cumulative
distributions
are
consistent
with
TTHM
values
reported
for
large
ICR
plants
earlier
in
this
chapter
for
DS
Averages
(
where
the
median
plant­
mean
TTHM
value
is
41
µ
g/
L).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
30
0%
10%
20%
30%
40%
50%
60%

Reservoir/
Lake
Flowing
Stream
Mix
Percent
of
Systems
Medium
Large
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
5
10
15
20
25
30
Plant­
Mean
TOC
(
mg/
L
as
C)
Cumulative
Percentile
Medium
Surface
Water
Systems
(
N=
102)
Large
Surface
Water
Systems
(
N=
196)
Exhibit
3.21
Percentages
of
Medium
and
Large
Surface
Water
Systems
Using
Different
Source
Water
Types
Source:
WATER:\
STATS
(
AWWA
2000).

Exhibit
3.22
Comparison
of
Source
Water
TOC
for
Medium
and
Large
Surface
Water
Systems
Source:
WATER:\
STATS
(
AWWA
2000).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
31
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
1
2
3
4
5
6
7
8
9
Plant­
Mean
TOC
(
mg/
L
as
C)
Cumulative
Percentile
Large
Systems
(
N=
47)

Medium
Systems
(
N=
40)

Small
Systems
(
N=
38)

0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
50
100
150
200
250
300
Plant­
Mean
Turbidity
(
NTU)
Cumulative
Percentile
Medium
Surface
Water
Systems
(
N
=
243)

Large
Surface
Water
Systems
(
N
=
240)
Exhibit
3.23
Comparison
of
Source
Water
TOC
for
Small,
Medium
and
Large
Surface
Water
Systems
Source:
ICRSS
(
USEPA
2000k).

Exhibit
3.24
Comparison
of
Source
Water
Turbidity
For
Medium
and
Large
Surface
Water
Systems
Source:
WATER:\
STATS
(
AWWA
2000).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
32
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
50
100
150
200
250
300
350
Plant­
Mean
Alkalinity
(
mg
CaCO3/
L)
Cumulative
Percentile
Medium
Surface
Water
Systems
(
N=
224)

Large
Surface
Water
Systems
(
N=
234)

0%
10%
20%
30%
40%
50%
60%
70%
80%
90%

Conventional
Softening
Direct
Filtration
Unfiltered
Other
Percent
of
Systems
Medium
Surface
Water
Systems
(
N
=
265)

Large
Surface
Water
Systems
(
N
=
255)
100%
Exhibit
3.25
Comparison
of
Source
Water
Alkalinity
for
Medium
and
Large
Surface
Water
Systems
Source:
WATER:\
STATS
(
AWWA
2000).

Exhibit
3.26
Comparison
of
Treatment­
In­
Place
for
Medium
and
Large
Surface
Water
Systems
Source:
WATER:\
STATS
(
AWWA
2000).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
33
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

Pre­
Sedimentation
Rapid
Mix
Flocculation
Sedimentation
Filtration
Percent
of
Systems
Medium
Surface
Water
Systems
(
N
=
266)

Large
Surface
Water
Systems
(
N
=
249)

0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

PreCl2/
PostCl2
Post
Cl2
Only
PreCl2/
PostNH2Cl
w/
O3
w/
ClO2
Other
Percent
of
Systems
Medium
Surface
Water
Systems
(
N
=
266)

Large
Surface
Water
Systems
(
N
=
249)
Exhibit
3.27
Comparison
of
Physical
Unit
Processes
for
Medium
and
Large
Surface
Water
Systems
Source:
WATER:\
STATS
(
AWWA
2000).

Exhibit
3.28
Comparison
of
Disinfectant
Type
for
Medium
and
Large
Surface
Water
Systems
Using
Conventional
Filtration
Source:
WATER:\
STATS
(
AWWA
2000).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
34
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
20
40
60
80
100
120
TTHM
(
ug/
L)
Cumulative
Percentile
Medium
Surface
Water
Systems
(
N=
211)

Large
Surface
Water
Systems
(
N=
210)

0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
20
40
60
80
100
120
TTHM
(
ug/
L)
Cumulative
Percentile
Medium
Surface
Water
Systems
(
N=
207)

Large
Surface
Water
Systems
(
N=
131)
Exhibit
3.29
Comparison
of
Finished
Water
Annual
Average
TTHM
for
Medium
and
Large
Surface
Water
Systems
Source:
WATER:\
STATS
(
AWWA
2000).

Exhibit
3.30
Comparison
of
Distribution
System
TTHM
Data
for
Medium
and
Large
Surface
Water
Systems
Source:
WATER:\
STATS
(
AWWA
2000).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
35
3.2.2.2
Small
Surface
Water
Systems
The
key
sources
of
information
for
small
surface
water
systems
are
the
ICRSS,
the
NRWA
Survey,
and
some
State
data.
DBP
Precursor
data
from
these
sources
are
summarized
in
Exhibits
3.19
and
3.20.

Exhibits
3.19
and
3.23
show
that
the
distribution
of
TOC
levels
for
small
surface
water
plants
differs
somewhat
from
that
for
medium
and
large
plants.
Generally,
small
plants
appear
to
have
lower
TOC
levels
(
i.
e.,
lower
levels
of
byproduct
precursors)
than
do
the
medium
and
large
plants.
However,
at
the
upper
end
of
the
TOC
distributions,
above
approximately
the
90th
percentile,
small
plant
TOC
levels
are
very
similar
to
those
of
medium
and
large
plants
(
see
Exhibit
3.23).

Exhibits
3.31
through
3.34
provide
the
cumulative
distributions
of
influent
TOC,
bromide,
alkalinity,
and
temperature
measurements
from
the
NRWA
Survey
for
winter
and
summer
monitoring
periods.
Seasonal
variability
in
TOC,
Bromide,
and
Alkalinity
appear
low,
although
temperature
was
markedly
different
between
winter
and
summer
months
(
as
expected).
The
TOC
distribution
in
Exhibit
3.31
is
similar
to
but
slightly
higher
than
that
for
small
systems
in
the
ICRSS
(
see
Exhibit
3.19
for
summary
statistics
on
TOC).
However,
the
ICRSS
data
set
is
more
comprehensive
than
the
NRWA
data
set.
The
ICRSS
data
reflect
mean
values
for
12
months
of
sampling,
whereas
the
NRWA
data
reflect
a
single
sample
for
each
site
during
two
sampling
periods.
The
alkalinity
levels
in
Exhibit
3.33
are
higher
than
for
ICRSS
data
(
where
the
median
for
small
systems
is
50
mg/
L
as
CaCO
3),
but
are
similar
to
those
observed
for
medium
and
large
surface
water
plants
in
the
ICR
and
WATER:\
STATS.
The
bromide
levels
in
Exhibit
3.32
are
higher
than
the
small
surface
waters
in
the
ICRSS,
but
similar
to
medium
ICRSS
plants,
as
well
as
the
ICR
plants.
The
temperature
levels
in
Exhibit
3.34
are
similar
to
those
found
in
the
ICR.

Exhibits
3.35
to
3.38
illustrate
some
operational
characteristics
of
small
surface
water
plants
that
may
correlate
with
the
DBP
levels
observed
in
such
plants.
For
example,
Exhibit
3.35
shows
that
almost
50
percent
of
plants
in
the
NRWA
survey
are
in
operation
12
hours
a
day
or
less.
Some
small
plants
are
designed
for
a
peak
flow
that
may
be
seasonal,
and
the
rest
of
the
time
they
may
operate
at
reduced
flow.
In
addition,
small
plants
must
often
operate
at
a
minimum
flow
rate
based
on
the
design
of
their
package
plants
or
based
on
requirements
for
redundant
treatment
units.
At
these
rates
they
may
meet
their
production
needs
in
less
than
24
hours.
Because
they
do
not
operate
all
of
the
time,
small
water
systems
may
have
water
with
higher
residence
times
within
their
plant.
This
may
increase
DBP
formation
in
cases
where
water
stays
for
a
long
period
of
time
in
a
clearwell
or
finished
water
storage
facility
after
chlorination.

Exhibit
3.36
indicates
that
only
15
percent
of
NRWA
survey
plants
listed
DBP
control
as
a
treatment
objective.
This
is
understandable
due
to
the
fact
that
small
systems
are
not
subject
to
the
1979
TTHM
Rule.
As
shown
in
Exhibit
3.37,
almost
all
NRWA
plants
use
chlorine
as
a
disinfectant,
whereas
40
percent
of
ICR
plants
use
chloramines,
chlorine
dioxide,
and
ozone,
which
are
thought
to
contribute
less
to
DBP
formation
than
chlorine.
With
respect
to
disinfectant
dose,
small
plants
reported
larger
chlorine
doses
than
the
large
ICR
plants
(
Exhibit
3.38).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
36
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
2
4
6
8
10
12
TOC
(
mg/
L
as
C)
Cumulative
Percentile
Winter
Data
(
N=
96)

Summer
Data
(
N=
96)

0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
500
1000
1500
2000
2500
Bromide
(
ug/
L)
Cumulative
Percentile
Winter
Data
(
N=
95)

Summer
Data
(
N=
95)
Exhibit
3.31
Plant
Influent
TOC
Data
for
Small
Surface
Water
Plants
Source:
NRWA
Survey
(
USEPA
2001g).

Exhibit
3.32
Plant
Influent
Bromide
Data
for
Small
Surface
Water
Plants
Source:
NRWA
Survey
(
USEPA
2001g).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
37
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
50
100
150
200
250
300
350
Alkalinity
(
mg/
L
as
CaCO3)
Cumulative
Percentile
Winter
Data
(
N=
95)

Summer
Data
(
N=
95)

0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
5
10
15
20
25
30
35
Temperature
(
as
degrees
Celsius)
Cumulative
Percentile
Winter
Data
(
N=
73)

Summer
Data
(
N=
73)
Exhibit
3.33
Plant
Influent
Alkalinity
for
Small
Surface
Water
Systems
Source:
NRWA
Survey
(
USEPA
2001g).

Exhibit
3.34
Plant
Influent
Temperature
for
Small
Surface
Water
Systems
Source:
NRWA
Survey
(
USEPA
2001g).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
38
0%
20%
40%
60%
80%
100%

0
2
4
6
8
10
12
14
16
18
20
22
24
Time
Operated
per
Day
(
Hours)
Cumulative
Percentile
Average
(
N=
113)

Maximum
(
N=
108)

At
Time
of
Sampling
(
N=
104)

0%
20%
40%
60%
80%
100%

Disinfection
Particulate/
Turbidity
Removal
Corrosion
Control
Taste/
Odor
Control
Fluoridation
Algae
Control
Mn
Removal
Organics
Removal
Iron
Removal
DBP
Control
Softening
Arsenic
Removal
Percent
of
Systems
(
N=
112)
Exhibit
3.35
Distribution
of
Time
Operated
per
Day
Among
Small
Surface
Water
Plants
Source:
NRWA
Survey
(
USEPA
2001g).

Exhibit
3.36
Treatment
Objectives
Among
Small
Surface
Water
Plants
Source:
NRWA
Survey
(
USEPA
2001g).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
39
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

Cl2
only
Cl2
&
NH3
ClO2
O3
Percentage
of
Plants
ICR
SW
Plants
(
N=
292,
based
on
month
8)

Small
Plants
in
NRWA
Survey
(
N=
107)

0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
5
10
15
20
25
30
35
40
Total
Chlorine
Dose
(
mg
CL2/
L)
Cumulative
Percentile
ICR
SW
Plants
(
N=
166,
ave.
of
months
7­
9)

Small
Plants
in
NWRA
Survey
(
N=
94)
Exhibit
3.37
Comparison
of
Disinfectants
Used
by
Small
and
Large
Surface
Water
Plants
Sources:
ICR
AUX1
(
USEPA
2000d);
NRWA
Survey
(
USEPA
2001g).

Exhibit
3.38
Comparison
of
Total
Chlorine
Doses
in
Large
and
Small
Surface
Water
Plants
Using
Only
Chlorination
(
Cl2/
Cl2)

Sources:
ICR
AUX1
(
USEPA
2000d);
NRWA
Survey
(
USEPA
2001g).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
40
Data
Type
Number
of
Plants
Mean
of
Plant­
Means
Median
of
Plant­
Means
90th
Percentile
of
Plant­
Means
Range
of
Plant­
Means
TTHM
Finished
96
62.78
46.20
137.00
0­
326.05
Avg
Res
Time
96
80.22
56.75
181.35
0­
328.85
DS
Weighted
Average
96
82.80
62.06
179.05
0­
328.09
Single
High
96
118.40
97.20
224.80
0­
451.40
Max
Res
Time
96
90.54
67.15
188.30
0­
325.80
HAA5
Finished
96
42.19
31.75
82.50
0­
326.90
Avg
Res
Time
96
46.17
35.30
85.00
0­
327.50
DS
Weighted
Average
96
45.32
33.99
83.89
0­
261.56
Single
High
96
65.34
52.90
113.40
0­
474.90
Max
Res
Time
96
42.78
35.20
88.95
0­
182.20
Data
Type
Number
of
Observations
Mean
Median
90th
Percentile
Range
TTHM
Finished
192
62.78
45.10
132.90
0­
471.50
Avg
Res
Time
192
80.22
58.00
153.50
0­
443.90
Max
Res
Time
192
90.54
73.30
174.50
0­
451.40
HAA5
Finished
192
42.19
28.80
87.30
0­
481.10
Avg
Res
Time
192
46.17
34.10
90.10
0­
474.90
Max
Res
Time
192
42.78
34.60
87.90
0­
225.00
Although
the
NRWA
survey,
a
key
source
of
DBP
data
for
small
surface
water
systems,
paralleled
the
ICR
effort,
the
data
collection
was
not
as
extensive.
In
the
distribution
system,
NRWA
samples
were
collected
only
at
the
location
with
the
maximum
residence
time
and
one
location
with
an
average
residence
time.
Exhibits
3.39
and
3.40
summarize
the
combined
winter
and
summer
NRWA
results
for
TTHM
and
HAA5
occurrence
data.
Exhibits
3.41
through
3.43
provide
the
summer
and
winter
cumulative
distributions
of
the
NRWA
TTHM
analyses
for
finished
water,
average
residence
time,
and
maximum
residence
time
locations,
respectively.
Similar
data
are
provided
for
HAA5
in
Exhibits
3.44
through
3.46
Despite
the
fact
that
small
systems
general
have
lower
DBP
precursor
concentrations
than
medium
and
large
systems,
NRWA
results
for
small
surface
water
systems
show
higher
byproduct
levels
than
in
medium
and
large
systems.
This
is
understandable,
given
that
small
systems
have
not
been
subject
to
the
requirements
of
the
1979
TTHM
standards,
which
resulted
in
some
medium
and
large
systems
making
treatment
changes
to
limit
byproduct
formation.

Exhibit
3.39
Summary
of
NRWA
DBP
Occurrence
Data
by
Plant
Note:
DS
Weighted
Average
is
calculated
by
giving
the
average
residence
time
result
a
weight
three
times
that
of
data
at
the
maximum
residence
location.
Refer
to
section
3.2.1
for
a
full
description
of
NRWA
data
types.

Source:
USEPA
2001g.

Exhibit
3.40
Summary
of
NRWA
DBP
Individual
Observations
Note:
Refer
to
section
3.2.1
for
a
description
of
NRWA
data
types.

Source:
USEPA
2001g.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
41
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
50
100
150
200
250
300
350
400
450
500
TTHM
(
ug/
L)
Cumulative
Percentile
Winter
Data
(
N=
96)

Summer
Data
(
N=
96)
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
50
100
150
200
250
300
350
400
450
500
TTHM
(
ug/
L)
Cumulative
Percentile
Winter
Data
(
N=
96)

Summer
Data
(
N=
96)
Exhibit
3.41
Distribution
of
TTHM
Occurrence
in
Plant
Finished
Water
Source:
NRWA
Survey
(
USEPA
2001g).

Exhibit
3.42
Distribution
of
TTHM
Occurrence
at
the
Point
of
Average
Residence
Time
in
the
Distribution
System
Source:
NRWA
Survey
(
USEPA
2001g).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
42
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
50
100
150
200
250
300
350
400
450
500
TTHM
(
ug/
L)
Cumulative
Percentile
Winter
Data
(
N=
96)

Summer
Data
(
N=
96)

0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
100
200
300
400
500
600
HAA5
(
ug/
L)
Cumulative
Percentile
Winter
Data
(
N=
96)

Summer
Data
(
N=
96)
Exhibit
3.43
Distribution
of
TTHM
Occurrence
at
the
Point
of
Maximum
Residence
Time
in
the
Distribution
System
Source:
NRWA
Survey
(
USEPA
2001g).

Exhibit
3.44
Distribution
of
HAA5
Occurrence
in
Plant
Finished
Water
Source:
NRWA
Survey
(
USEPA
2001g).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
43
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
50
100
150
200
250
300
350
400
450
500
HAA5
(
ug/
L)
Cumulative
Percentile
Winter
Data
(
N=
96)

Summer
Data
(
N=
96)

0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
50
100
150
200
250
HAA5
(
ug/
L)
Cumulative
Percentile
Winter
Data
(
N=
96)

Summer
Data
(
N=
96)
Exhibit
3.45
Distribution
of
HAA5
Occurrence
at
the
Point
of
Average
Residence
Time
in
the
Distribution
System
Source:
NRWA
Survey
(
USEPA
2001g).

Exhibit
3.46
Distribution
of
HAA5
Occurrence
at
the
Point
of
Maximum
Residence
Time
in
the
Distribution
System
Source:
NRWA
Survey
(
USEPA
2001g).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
44
Exhibit
3.47
compares
cumulative
distributions
of
ICR,
NRWA,
and
State
plant­
mean
TTHM
occurrence
in
distribution
systems
for
small
and
large
surface
water
plants.
For
the
ICR,
the
running
annual
average
of
the
last
four
quarters
of
distribution
system
data,
based
on
plants
with
at
least
three
sampling
locations
each
quarter
and
at
least
three
quarters
of
data,
is
plotted.
The
NRWA
plant­
means
are
weighted
averages
of
the
winter
and
summer
average
and
maximum
residence
time
samples,
where
average
residence
time
samples
are
given
weights
three
times
those
of
maximum
residence
samples.
(
As
noted
previously,
the
NRWA
data
were
weighted
to
make
them
comparable
to
ICR
data,
for
which
the
DS
Average
is
calculated
for
each
quarter
by
averaging
results
of
three
samples
from
locations
approximating
average
residence
time
and
one
sample
at
the
maximum
residence
location.)
The
State
data
on
small
surface
water
systems
were
collected
from
over
500
small
surface
water
systems.
However,
not
all
points
on
the
graph
represent
the
same
type
of
data
 
the
points
are
plant
"
averages",
but
some
plants
took
only
one
sample,
while
others
took
multiple
samples.
The
plants
with
single
samples
may
explain
some
of
the
very
high
TTHM
plant­
means
at
the
upper
end
of
the
distribution.

The
median
TTHM
plant­
mean
value
was
66
µ
g/
L
and
62
µ
g/
L
for
State
and
NRWA
data,
respectively,
while
the
median
RAA
value
for
the
ICR
was
41
µ
g/
L.
The
upper
end
of
the
NRWA
distributions
for
TTHM
is
much
higher
than
that
of
the
ICR
distributions.
For
example,
NRWA
90th
percentile
TTHM
concentrations
are
more
than
double
their
corresponding
ICR
concentrations.
Only
5
ICR
plants
(
2
percent)
have
TTHM
levels
exceeding
100
µ
g/
L
(
the
MCL
under
the
1979
rule),
while
23
(
24
percent)
NRWA
plants
and
192
(
34
percent)
of
plants
in
the
State
data
set
do.
These
patterns
are
to
be
expected,
since
small
systems
do
not
have
to
comply
with
the
1979
TTHM
standards.

The
distribution
of
the
State
data
shows
TTHM
levels
at
the
upper
end
of
the
distribution
are
higher
than
those
observed
in
the
NRWA
data.
For
example,
the
90th
percentile
concentration
in
the
State
data
set
is
215
µ
g/
L,
while
the
NRWA
value
is
168
µ
g/
L.
This
probably
is
due
to
the
fact
that
some
of
the
data
points
in
the
State
data
set
were
not
averaged
since
some
plants
reported
only
one
observation.

Exhibit
3.48
shows
the
co­
occurrence
of
HAA5
and
TTHM
at
NRWA
plants.
The
TTHM
and
HAA5
values
are
plant­
means
weighted
as
discussed
above.
Roughly
22
percent
of
NRWA
(
small)
plants
had
both
TTHM
and
HAA5
plant­
means
exceeding
Stage
1
DBPR
limits,
as
compared
to
1.4
percent
of
ICR
SW
plants
(
see
section
3.3.3
for
ICR
large
plant
DBP
data
analyses).

Although
results
in
this
section
show
that
TTHM
levels
from
the
State
data
set
are
higher
than
the
levels
from
the
NRWA
data
set,
the
NRWA
data
may
also
be
biased
slightly
high
in
terms
of
national
DBP
concentrations.
This
is
because
some
States
with
high
TOC
(
as
compared
to
the
national
average
and
based
on
ICR
data)
are
overrepresented
in
the
survey,
while
other
States
with
low
TOC
may
be
underrepresented.
For
example,
plants
in
Louisiana,
a
high­
TOC
State,
represent
4
percent
of
plants
in
the
NRWA
survey,
but
only
1
percent
of
small
non­
purchased
surface
water
plants
in
the
country,
according
to
the
Baseline
Handbook
(
USEPA
2001e).
The
sampling
results
from
plants
in
over­
or
underrepresented
States
may
be
skewing
the
distribution
of
TOC
and
DBP
data.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
45
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
50
100
150
200
250
300
350
400
450
500
TTHM
(
ug/
L)
Cumulative
Percentile
Data
from
8
States
(
Small
plants,
1998­
1999,
N=
562)

Data
from
ICR
(
Large
Plant
RAA
of
last
4­
quarter
values,
N=
213)

NRWA
Data
(
Weighted
Small
Plant
Means,
N=
96)

80
ug/
L,
Stage
1
MCL
Exhibit
3.47
Cumulative
Distribution
of
Mean
TTHM
Occurrence
in
Distribution
Systems
for
Small
and
Large
Surface
Water
Plants
Sources:
USEPA
2000l;
USEPA
2000d;
USEPA
2001g.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
46
0
50
100
150
200
250
300
0
50
100
150
200
250
300
350
400
TTHM
RAA
(
ug/
L)
HAA5
RAA
(
ug/
L)
2.1%
21.9%

12.5%
63.5%
Exhibit
3.48
RAA
TTHM
vs.
RAA
HAA5
for
Small
Surface
Water
Plants
Source:
NRWA
Survey
(
USEPA
2001g).

Exhibit
3.49
shows
the
percent
of
plants
that
reported
the
maximum
TTHM
LRAA's
at
the
finished
water,
average
residence
time,
and
maximum
residence
time
locations.
NRWA
plants
have
the
highest
TTHM
LRAA
concentration
occurring
at
sites
other
than
the
maximum
residence
time
monitoring
site
33
percent
of
the
time.
The
highest
HAA5
LRAA
occurred
at
the
maximum
residence
time
monitoring
site
in
only
48
percent
of
the
plants.

If
TTHM
and
HAA5
occur
at
the
same
location
rather
than
different
locations,
fewer
monitoring
sites
would
be
needed
to
represent
TTHM
and
HAA5
occurrence.
However,
this
is
not
the
case.
The
NRWA
data
set
indicates
that
56
percent
of
their
plants
experienced
their
highest
LRAA
TTHM
and
HAA5
concentrations
at
different
locations
in
the
distribution
system.
For
plants
that
had
their
highest
TTHM
and
HAA5
LRAA
concentrations
at
the
same
location,
it
was
not
necessarily
at
the
maximum
residence
time
location.
Exhibit
3.50
illustrates
that
for
NRWA
plants
with
the
highest
TTHM
and
HAA5
levels
occurring
at
the
same
location,
the
highest
TTHM
and
HAA5
LRAA
simultaneously
occurred
at
a
location
other
than
the
maximum
residence
time
monitoring
location
36
percent
of
the
time.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
47
0%
10%
20%
30%
40%
50%
60%
70%
80%

Finished
Water
Point
Average
Residence
Time
Maximum
Residence
Time
Percentage
of
Systems
(
N=
96)
TTHM
HAA5
Highest
LRAA
TTHM/
HAA5
(
N=
96)
Among
Plant
with
Highest
LRAA
TTHM/
HAA5
at
Same
Location
(
N=
42)

31%
@
AVG
4.8%
@
FINISH
Maximum
occurred
at
same
locations
for
43.8%
of
plants
Maximum
occurred
at
different
locations
for
56.3%
of
plants
64.3%
@
MAX
Exhibit
3.49
Percentage
of
DS
Maximum
Observations
for
TTHM
and
HAA5
by
Sampling
Location
Source:
NRWA
Survey
(
USEPA
2001g)

Exhibit
3.50
Frequency
at
Which
Highest
TTHM
or
HAA5
LRAAs
Occurred
at
the
Same
Location
for
All
NRWA
Plants
Source:
NRWA
Survey
(
USEPA
2001g).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
48
3.2.3
Ground
Water
Systems
3.2.3.1
Medium
Ground
Water
Systems
Only
limited
data
are
available
on
precursor
and
byproduct
occurrence
for
medium
disinfecting
ground
water
systems.
The
most
relevant
information
for
assessing
byproduct
occurrence
in
ground
water
is
that
provided
in
the
WATER:\
STATS
database.
Exhibits
3.51
to
3.53
provide
comparisons
of
influent
average
TOC
levels,
treatment
used,
and
average
TTHM
levels
for
medium
and
large
ground
water
systems
in
the
WATER:\
STATS
data
set.

The
TOC
data
and
the
treatment
process
information
show
considerable
similarity
between
medium
and
large
systems.
It
should
also
be
noted
that
the
TOC
distributions
derived
from
WATER:\
STATS
for
large
and
medium
systems
are
similar
to
those
observed
for
the
large
ground
water
plants
in
the
ICR
(
see
Exhibit
3.2).
Average
TTHM
levels
in
medium
and
large
ground
water
systems
are
also
similar,
as
shown
in
Exhibit
3.53,
based
on
WATER:\
STATS
data.
The
median
average
distribution
system
concentration
for
large
ground
water
systems
was
12
µ
g/
L
and
for
medium
systems
was
10
µ
g/
L.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
49
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
5
10
15
20
25
30
Plant­
Mean
TOC
(
mg/
L
C)
Cumulative
Percent
Medium
Ground
Water
Systems
(
N=
51)

Large
Ground
Water
Systems
(
N=
38)

0%
5%
10%
15%
20%
25%
30%
35%
40%
45%

No
trmt.

Pre­
storage/
Sed
Aeration/
Air
stripping
Rapid
Mix
Floc/
Coag
Sed
Filt
Percentage
of
Systems
Medium
systems
10­
100K
(
N=
364)

Large
systems
>
100K
(
N=
110)
Exhibit
3.51
Annual
Average
TOC
in
Influent
Water
TOC
for
Ground
Water
Systems
Source:
WATER:\
STATS
(
AWWA
2000).

Exhibit
3.52
Treatment
Summary
for
Ground
Water
Systems
(
Chlorinating
and
Non­
Chlorinating)

Source:
WATER:\
STATS
(
AWWA
2000).
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
50
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
20
40
60
80
100
120
TTHM
(
ug/
L)
Cumulative
Percentile
Medium
Ground
Water
Systems
(
N=
169)

Large
Ground
Water
Systems
(
N=
68)
Exhibit
3.53
Annual
Average
Finished
Water
TTHM
for
Ground
Water
Systems
Source:
WATER:\
STATS
(
AWWA
2000)

3.2.3.2
Small
Ground
Water
Systems
As
with
the
small
surface
water
systems,
there
is
very
limited
information
available
on
DBP
precursor
levels
in
small
ground
water
systems
that
disinfect
and
insufficient
data
for
determining
national
occurrence
levels
of
DBPs
(
GWSS
DBP
data
were
not
used
because
only
distribution
system
entry
point
data
were
available).

Data
are
not
available
on
influent
TOC
levels
for
small
ground
water
systems
that
disinfect.
However,
there
are
some
data
available
on
effluent
(
finished
water)
TOC
in
small,
medium,
and
large
disinfecting
ground
water
systems
that
can
provide
some
insight
into
how
small
system
DBP
precursor
levels
compare
with
those
at
larger
systems.

Exhibit
3.54
provides
the
effluent
TOC
data
obtained
in
the
1982
GWSS.
Though
this
information
is
somewhat
dated,
it
is
reasonable
to
assume
the
following
with
respect
to
these
data:
(
1)
the
fraction
of
TOC
removed
in
ground
water
systems
is
probably
not
substantial
(
based
on
comparisons
of
influent
and
effluent
ICR
TOC
levels),
so
these
effluent
TOC
levels
are
reasonable
indicators
of
influent
TOC;
(
2)
the
levels
of
TOC
in
influent
ground
waters
probably
have
not
changed
much
since
these
data
were
collected
(
support
for
this
is
provided
by
comparing
the
effluent
data
for
the
large
systems
in
the
GWSS
data
set
to
the
observed
influent
TOC
levels
for
large
systems
in
the
ICR);
and
(
3)
the
comparison
across
system
sizes
indicates
that,
on
a
national
scale,
TOC
levels
in
small
disinfecting
ground
water
systems
are
similar
to
those
of
medium
and
large
systems.

For
TTHMs
themselves,
there
are
some
data
available
for
small
ground
water
systems.
These
data
were
collected
by
seven
States
during
1998
and/
or
1999,
as
described
in
the
beginning
of
the
chapter.
Exhibit
3.55
shows
annual
average
TTHM
levels
for
more
than
2,300
observations
and
compares
them
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
51
with
ground
water
ICR
running
annual
averages
from
the
last
four
quarters
of
data
collection.
As
with
the
surface
water
data,
the
State
data
are
inconsistent.
A
few
systems
took
only
one
sample
per
year;
the
average
of
such
a
value
cannot
easily
be
compared
to
that
of
a
system
taking
20
samples
a
year.
This
may
explain
some
of
the
very
high
ground
water
values
(
e.
g.,
the
maximum
value
is
655
µ
g/
L).
Overall,
however,
the
State
ground
water
data
compare
favorably
with
WATER:\
STATS
TTHM
data
for
medium
and
large
plants,
with
a
median
value
of
3
µ
g/
L,
much
less
than
the
median
distribution
system
values
for
the
other
size
categories
(
see
Exhibit
3.21).
The
mean
concentration,
17
µ
g/
L,
is
slightly
below
the
mean
of
19
µ
g/
L
for
medium
WATER:\
STATS
plants.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
52
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
2
4
6
8
10
12
14
16
Effluent
TOC
(
mg/
L)
Cumulative
Percentile
of
Systems
Small
Systems
(<
10K)

Medium
Systems
(
10
­
100
K)

Large
Systems
(>
100K)

Source:
GWSS
(
1981­
82)

0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%

0
20
40
60
80
100
120
140
160
180
200
TTHM
(
ug/
L)
Cumulative
Percentile
of
Systems
Data
from
7
States
(
1998­
1999,
N=
2336)

Data
from
ICR
(
RAA,
N=
82)

80
ug/
L,
Stage1
MCL
Exhibit
3.54
Comparison
of
Effluent
TOC
for
Chlorinating
Small,
Medium,
and
Large
Ground
Water
Systems
Exhibit
3.55
Cumulative
Distribution
of
TTHM
Occurrence
as
Distribution
System
Average
for
Small
and
Large
Ground
Water
Plants
Sources:
USEPA
2000l;
USEPA
2000d.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
53
3.3
Analysis
of
Co­
Occurrence
Due
to
the
extensive
data
collection
effort
of
the
ICR,
many
analyses
of
source
water
quality
parameters,
treatment
characteristics,
and
the
resulting
finished
water
quality
are
possible.
This
section
presents
the
results
of
select
analyses
of
the
relationships
between
several
source
water
quality
parameters,
disinfectants,
and
DBPs.

3.3.1
Total
Organic
Carbon
Concentration
and
Alkalinity
Organic
DBP
formation
occurs
when
disinfectants
react
with
organic
matter
in
water.
The
Stage
1
DBPR
requires
water
systems
to
remove
a
certain
percentage
of
TOC
based
on
the
TOC
and
alkalinity
levels
of
the
influent
water.
Exhibit
3.56
shows
the
percentage
removals
required
by
the
Stage
1
DBPR
in
the
3
×
3
matrix
for
conventional
plants.
The
last
column
of
the
matrix
also
applies
to
enhanced
softening
plants.
There
are
various
exceptions
and
alternative
compliance
criteria,
which
are
explained
in
detail
in
the
Stage
1
DBPR
(
USEPA
1998a).

Exhibit
3.56
Percent
TOC
Removal
Requirements
for
Systems
Employing
Enhanced
Coagulation
Source
Water
TOC
(
mg/
L)
Source
Water
Alkalinity
(
mg/
L
as
CaCO3)

0
 
60
>
60
 
120
>
120
>
2.0
 
4.0
35
%
25
%
15
%

>
4.0
 
8.0
45
%
35
%
25
%

>
8.0
50
%
40
%
30%

Source:
The
Stage
1
Disinfectants/
Disinfection
Byproducts
Rule
(
USEPA
1998a)

Exhibit
3.57
shows
the
number
of
monthly
samples
in
each
TOC
removal
category
over
the
last
12
months
(
January
to
December
1998)
of
the
ICR
monitoring
period.
Due
to
seasonal
variation
and
other
factors
affecting
source
water,
the
percentage
removal
requirements
for
each
plant
may
change
from
month
to
month
as
the
influent
TOC
and
alkalinity
vary.
Of
the
three
alkalinity
groups,
the
60­
120
mg/
L
category
had
the
fewest
samples.
The
number
of
samples
with
TOC
concentrations
greater
than
4.0
mg/
L
decreased
substantially
from
the
two
lower
TOC
concentration
groups
over
all
three
alkalinity
ranges.
In
the
4.0­
8.0
mg/
L
TOC
range
there
is
virtually
no
difference
in
the
number
of
samples
across
the
alkalinity
groups.
Many
times,
samples
are
close
to
the
limits
for
a
percentage
removal
group,
indicating
that
the
treatment
requirements
of
a
plant
can
easily
change.

Note
that
almost
40
percent
of
the
sample
points
have
TOC
observations
below
2.0
mg/
L,
and
the
few
very
high
alkalinity
observations
(
400
mg/
L
­
500
mg/
L)
are
also
in
the
below
2.0
mg/
L
TOC
category.
Also
note
that
observations
below
the
TOC
MRL
are
graphed
as
zeroes.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
54
0
100
200
300
400
500
0
5
10
15
20
25
Influent
TOC
(
mg/
L)
Influent
Alkalinity
(
mg/
L)
Percentage
<
60
60
­
120
>
120
Total
<
2.0
14%
10%
16%
39%
2.0
­
4.0
14%
14%
13%
41%
4.0
­
8.0
5%
5%
6%
16%
>
8.0
1%
0%
2%
4%
Total
34%
29%
37%
100%
Source
Water
TOC
Range
(
mg/
L)
Alkalinity
(
mg/
L)
Exhibit
3.57
Distribution
of
Monthly
TOC
(
mg/
L)
and
Monthly
Alkalinity
(
mg/
L)
Samples
Based
on
ICR
Data
for
All
Large
Plants
Source:
ICR
AUX1
database
(
USEPA
2000d).

Query:
Screened
INF
TOC
and
ALK.
See
Appendix
B
for
query
language.

Excel
File:
INF
TOC
versus
ALK.
xls
3.3.2
TOC,
Bromide,
and
TTHM
TOC
and
bromide
in
raw
water
influence
the
formation
of
DBPs.
Although
the
concentration
of
DBPs
in
the
finished
water
is
affected
by
the
treatment
applied,
higher
concentrations
of
TOC
in
the
source
water
are
expected
to
cause
a
greater
occurrence
of
DBPs
if
not
well
controlled.
Increases
in
the
concentration
of
influent
bromide
are
expected
to
shift
the
types
of
DBPs
formed
more
to
brominated
species
and
raise
the
concentration
by
weight
of
DBPs,
because
bromide
is
heavier
than
chlorine.
DBP
formation
and
speciation,
however,
depend
on
many
factors
other
than
TOC
and
bromide,
and
include
the
type
of
disinfectant,
pH,
temperature,
inorganic
demand,
and
disinfectant
residual.
This
section
examines
the
relationship
between
influent
TOC
and
bromide;
this
relationship
is
an
indicator
of
the
treatability
of
the
water.
A
comparison
of
TOC
and
bromide
source
water
occurrence
is
presented.
Additional
analyses
were
performed
relating
TOC
and
bromide
occurrence
in
source
water
to
TTHM
and
HAA5
levels
in
finished
water.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
55
Exhibits
3.58
and
3.59
contain
three­
dimensional
graphs
comparing
influent
bromide,
influent
TOC,
and
finished
water
TTHM
concentrations
for
surface
and
ground
water
plants.
Exhibits
3.60
and
3.61
contain
the
same
graphs
for
finished
water
HAA5
concentrations.
The
graphs
were
prepared
by
first
categorizing
each
ICR
plant
by
its
mean
influent
water
TOC
and
bromide
concentration
based
on
the
last
12
months
of
the
ICR
collection
period
(
TOC
and
bromide
plant­
means
were
based
on
monthly
data
for
only
those
months
that
had
corresponding
TTHM
or
HAA5
data).
This
resulted
in
a
5
by
5
matrix
according
to
the
following
bromide
and
TOC
concentrations:

°
TOC
(
mg/
L):
<
MRL
­
1;
1
­
2;
2
­
3;
3­
4;
and
>
4
°
Bromide
(
:
g/
L):
<
MRL;
MRL
­
30;
30
­
50;
50
­
100;
>
100
For
each
of
the
25
TOC/
bromide
categories,
the
mean
and
90th
percentile
of
all
plant­
mean
TTHM
and
HAA5
concentrations
were
calculated
using
data
from
all
of
the
plants
in
that
category.
Like
influent
TOC
and
bromide,
TTHM
and
HAA5
plant­
mean
data
is
based
on
the
last
12
months
of
the
ICR
collection
period.
The
highest
level
of
TTHM,
approximately
50
:
g/
L,
is
indicated
by
a
light
colored
bar
that
identifies
corresponding
values
of
TOC
of
>
4
mg/
L
and
of
bromide
of
30­
50
:
g/
L.

These
comparisons
have
some
uncertainty
because
TOC
and
bromide
levels
are
from
raw
water,
and
TTHM
and
HAA5
are
from
finished
water.
It
is
therefore
not
known
how
treatment
(
other
than
disinfection)
might
have
affected
the
TOC
and
bromide
concentrations.
If
not
controlled,
higher
influent
TOC
and
bromide
levels
result
in
higher
concentrations
of
DBPs.
However,
the
pattern
is
not
clear
in
this
data
set
because
the
different
treatment
processes
of
most
plants
reduce
DBP
formation
by
removing
TOC
at
varying
levels.
Also,
bromide
forms
many
other
brominated
acids
that
are
not
included
in
the
measurements
of
TTHM
or
HAA5,
making
a
direct
correlation
between
TTHM,
TOC
and
bromide
unlikely.

The
general
trend
from
all
graphs
is
that
TTHM
formation
increases
as
TOC
increases,
but
there
seems
to
be
no
simple
correlation
with
bromide.
These
analyses
do
not
account
for
the
effect
of
alternative
disinfectants,
which
may
have
been
used
in
plants
that
had
difficulty
treating
water
with
high
TOC
and
particularly
high
bromide
concentrations.
In
addition,
because
all
TOC,
bromide,
and
DBP
concentrations
are
calculated
as
averages
or
90th
percentiles
for
each
plant,
the
exhibits
may
not
capture
relationships
between
individual
observations
in
one
quarter.

The
formation
of
HAA5
related
to
TOC
and
bromide
in
finished
water
is
shown
in
Exhibit
3.60
and
3.61.
The
mean
and
90th
percentile
graphs
of
all
sampling
points
show
that
HAA5
formation
increases
as
TOC
increases
and
bromide
decreases.
Increasing
bromide
concentrations
are
expected
to
shift
the
speciation
of
HAAs
to
the
more
bromine­
substituted
species,
which
are
not
included
in
HAA5.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
56
<
MRL
MRL­
30
30­
50
50­
100
>
100
<
MRL­
1
1­
2
2­
3
3­
4
>
4
0
10
20
30
40
50
60
70
80
90
100
TTHM
(
ug/
L)

Bromide
(
ug/
L)
TOC
(
mg/
L)
Exhibit
3.58
Finished
Water
TTHM
Concentrations
(
Mean
of
Plant­
Means)
by
Influent
TOC
and
Bromide
Concentrations
Based
on
ICR
Data
for
All
Large
Plants
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
FW
TTHM
&
HAA5
by
Inf
Bromide
&
TOC.
See
Appendix
B
for
query
language.

Excel
File:
TTHM
and
HAA5
by
Bromide
and
TOC.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
57
<
MRL
MRL­
30
30­
50
50­
100
>
100
<
MRL­
1
1­
2
2­
3
3­
4
>
4
0
10
20
30
40
50
60
70
80
90
100
TTHM
(
ug/
L)

Bromide
(
ug/
L)
TOC
(
mg/
L)
Exhibit
3.59
Finished
Water
TTHM
Concentrations
(
90th
Percentile
of
Plant­
Means)
by
Influent
TOC
and
Bromide
Concentrations
Based
on
ICR
Data
for
All
Large
Plants
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
FW
TTHM
&
HAA5
by
Inf
Bromide
&
TOC.
See
Appendix
B
for
query
language.

Excel
File:
TTHM
and
HAA5
by
Bromide
and
TOC.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
58
<
MRL
MRL­
30
30­
50
50­
100
>
100
<
MRL­
1
1­
2
2­
3
3­
4
>
4
0
10
20
30
40
50
60
70
80
90
HAA5
(
ug/
L)

Bromide
(
ug/
L)
TOC
(
mg/
L)
Exhibit
3.60
Finished
Water
HAA5
Concentrations
(
Mean
of
Plant­
Means)
by
Influent
TOC
and
Bromide
Concentrations
Based
on
ICR
Data
for
All
Large
Plants
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
FW
TTHM
&
HAA5
by
Inf
Bromide
&
TOC.
See
Appendix
B
for
query
language.

Excel
File:
TTHM
and
HAA5
by
Bromide
and
TOC.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
59
<
MRL
MRL­
30
30­
50
50­
100
>
100
<
MRL­
1
1­
2
2­
3
3­
4
>
4
0
10
20
30
40
50
60
70
80
90
HAA5
(
ug/
L)

Bromide
(
ug/
L)
TOC
(
mg/
L)
Exhibit
3.61
Finished
Water
HAA5
Concentrations
(
90th
Percentile
of
Plant­
Means)
by
Influent
TOC
and
Bromide
Concentrations
Based
on
ICR
Data
for
All
Large
Plants
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
FW
TTHM
&
HAA5
by
Inf
Bromide
&
TOC.
See
Appendix
B
for
query
language.

Excel
File:
TTHM
and
HAA5
by
Bromide
and
TOC.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
60
0
20
40
60
80
100
120
140
0
20
40
60
80
100
120
140
RAA
TTHM
(
ug/
L)
RAA
HAA5
(
ug/
L)
4.2%

2.3%
92.0%
1.4%
3.3.3
TTHM
and
HAA5
Exhibit
3.62
through
3.67
compare
DS
Averages
and
Single
Highest
observations
for
TTHM
and
HAA5
samples
drawn
at
the
same
location
and
time.
Exhibits
3.62
and
3.63
show
RAAs
for
surface
water
and
ground
water,
respectively.
Exhibits
3.64
and
3.65
compare
each
plant's
highest
TTHM
and
HAA5
LRAA
values
during
the
last
four
quarters
of
the
ICR,
and
Exhibits
3.66
and
3.67
show
individual
Single
Highest
values.
Each
exhibit
divides
TTHM
and
HAA5
occurrence
into
quadrants,
based
on
whether
TTHM
and/
or
HAA5
levels
from
a
given
sampling
period
exceed
the
Stage
1
DBPR
MCLs
of
80
µ
g/
L
for
TTHM
and
60
µ
g/
L
for
HAA5.
Each
exhibit
shows
the
percentage
of
plants
(
or
observations)
falling
into
each
quadrant.
For
example,
in
Exhibit
3.62,
1.4
percent
of
plants
have
TTHM
and
HAA5
RAAs
that
exceed
the
contaminants
respective
MCLs.
The
graphs
demonstrate
a
slight
relation
between
TTHM
and
HAA5,
with
one
increasing
as
the
other
increases.
Most
observations
fall
below
the
Stage
1
DBPR
MCLs,
especially
for
ground
water
data.
The
exhibits
also
show
that
more
plants
would
exceed
both
the
80
and
60
µ
g/
L
TTHM
and
HAA5
levels
if
compliance
were
calculated
differently
than
under
the
Stage
1
DBPR,
which
uses
RAAs
to
determine
compliance.

Note
that
HAA5
does
not
represent
all
the
HAAs,
particularly
the
more
bromine­
substituted
HAAs.
Hence,
for
high
bromide
waters,
HAA5
may
not
be
as
representative
of
brominated
DBP
formation
as
TTHM.

Exhibit
3.62
RAA
of
TTHM
Occurrence
versus
RAA
of
HAA5
Occurrence
for
Large
Surface
Water
Plants
Based
on
ICR
Data
(
N
=
213)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
61
0
20
40
60
80
100
120
140
0
20
40
60
80
100
120
140
RAA
TTHM
(
ug/
L)
RAA
HAA5
(
ug/
L)
1.2%

1.2%
96.3%
1.2%
Exhibit
3.63
RAA
of
TTHM
Occurrence
versus
RAA
of
HAA5
Occurrence
for
Large
Ground
Water
Plants
Based
on
ICR
Data
(
N
=
82)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
62
0
20
40
60
80
100
120
140
0
20
40
60
80
100
120
140
LRAA
TTHM
(
ug/
L)
LRAA
HAA5
(
ug/
L)
4.7%

6.6%
84.5%
4.2%
Exhibit
3.64
Highest
LRAA
TTHM
versus
Highest
LRAA
HAA5
for
Large
Surface
Water
Plants
Based
on
ICR
Data
(
N
=
213)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
63
0
20
40
60
80
100
120
140
0
20
40
60
80
100
120
140
LRAA
TTHM
(
ug/
L)
LRAA
HAA5
(
ug/
L)
4.7%

6.6%
84.5%
4.2%
Exhibit
3.65
Highest
LRAA
TTHM
versus
Highest
LRAA
HAA5
for
Large
Ground
Water
Plants
Based
on
ICR
Data
(
N
=
82)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
64
0
50
100
150
200
250
300
0
50
100
150
200
250
300
Single
High
TTHM
(
ug/
L)
Single
High
HAA5
(
ug/
L)
9.4%

17.4%
58.2%
15.0%
Exhibit
3.66
Single
Highest
TTHM
versus
Single
Highest
HAA5
for
Large
Surface
Water
Plants
Based
on
ICR
Data
(
N
=
213)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
Single
High
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
65
0
50
100
150
200
250
300
0
50
100
150
200
250
300
Single
High
TTHM
(
ug/
L)
Single
High
HAA5
(
ug/
L)
6.1%

6.1%
86.6%
1.2%
Exhibit
3.67
Single
Highest
TTHM
versus
Single
Highest
HAA5
Based
on
ICR
Data
for
Large
Ground
Water
Plants
(
N
=
82)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Query:
Plants
min
3x3,
Single
High
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
1.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
66
TOC
>=
2
to
3
mg/
L
TOC
>=
3
to
4
mg/
L
No
Data
TOC
<
1
to
mg/
L
TOC
>=
1
to
2
mg/
L
TOC
>=
4
mg/
L
3.4
Analysis
of
Regional
Trends
3.4.1
Occurrence
of
TOC
EPA
evaluated
ICR
surface
and
ground
water
system
data
to
determine
if
there
were
differences
in
influent
water
quality
among
regions.
Exhibits
3.68a
and
3.68b
show
average
TOC
concentrations
by
State
for
surface
and
ground
water
systems,
respectively,
using
ICR
data.
Exhibit
3.68c
shows
average
TOC
concentrations
by
State
for
ground
water
systems
using
Ground
Water
Supply
Survey
(
GWSS)
data.
Surface
water
systems
did
not
exhibit
any
notable
regional
trends;
however,
ICR
and
GWSS
data
show
that
Florida
has
very
high
TOC
concentrations
compared
to
other
States.
Florida
also
has
the
largest
proportion
of
large
ground
water
systems
of
all
the
States.

Exhibit
3.68a
Influent
Water
TOC
Occurrence
Distribution
for
Large
ICR
Surface
Water
Systems
Source:
ICR
AUX1
Database
(
USEPA
2000d);
mean
of
all
plant­
means
for
each
State.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
67
TOC
>=
2
to
3
mg/
L
TOC
>=
3
to
4
mg/
L
No
Data
TOC
<
1
to
mg/
L
TOC
>=
1
to
2
mg/
L
TOC
>=
4
mg/
L
TOC
>=
2
to
3
mg/
L
TOC
>=
3
to
4
mg/
L
No
Data
TOC
<
1
to
mg/
L
TOC
>=
1
to
2
mg/
L
TOC
>=
4
mg/
L
Exhibit
3.68b
Influent
Water
TOC
Occurrence
Distribution
for
Large
ICR
Ground
Water
Systems
Source:
ICR
AUX1
Database
(
USEPA
2000d);
mean
of
all
plant­
means
for
each
State.

Exhibit
3.68c
Influent
Water
TOC
Occurrence
Distribution
for
Ground
Water
Systems,
Derived
from
the
Ground
Water
Supply
Survey
(
GWSS)

Source:
GWSS
(
USEPA
1983),
mean
of
all
finished
water
TOC
samples
in
the
State.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
3­
68
No
data
>
100
³
50­
100
<
MRL
(
20)

³
MRL
­
30
³
30
­
50
Mean
Bromide
(
m
g/
L)
3.4.2
Occurrence
of
Bromide
Regional
trends
in
occurrence
of
bromide
in
source
water
were
evaluated
in
the
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002).
Exhibit
3.69
shows
the
State
by
State
average
bromide
levels
in
surface
water
systems
for
each
State.
Texas
and
Florida
exhibit
the
highest
influent
bromide
concentrations,
both
over
100
µ
g/
L.
The
Midwest
region
of
the
country
exhibits
high
influent
bromide
concentrations
overall
whereas
the
Northeast
water
contains
very
little
influent
bromide.

Exhibit
3.69
Mean
Influent
Bromide
Concentrations,
Large
ICR
Surface
Water
Plants
Source:
Chapter
14
Information
Collection
Rule
Data
Analysis
document
(
McGuire
et
al.
2002).
1Note
that
the
Surface
Water
Analytical
Tool
(
SWAT)
was
used
to
predict
changes
in
average
DBP
occurrence
between
both
post­
Stage
2
and
post­
Stage
2
conditions.
SWAT
is
discussed
in
detail
in
the
Economic
Analysis
for
the
Stage
2
DBPR
(
USEPA
2003a).

Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
1
4.
Predicted
Post­
Stage
1
DBP
Occurrence
Analyses
of
disinfectants
and
disinfection
byproducts
(
DBP)
occurrence
data
to
support
the
development
of
the
Stage
2
Disinfectants
and
Disinfection
Byproducts
Rule
(
DBPR)
is
complicated
by
the
fact
that
existing
national
occurrence
data
do
not
reflect
changes
resulting
from
the
implementation
of
the
Stage
1
DBPR.
This
is
because
many
utilities
have
only
recently
changed
their
treatment
to
comply
with
the
Stage
1
DBPR
(
e.
g.,
surface
water
systems
serving
10,000
or
more
people
were
required
to
comply
by
January
2002)
or
are
about
to
make
changes
to
comply
(
e.
g.,
surface
water
systems
serving
fewer
than
10,000
people
and
all
ground
water
systems
are
required
to
comply
by
January
2004).
DBP
occurrence
data
collected
under
the
Information
Collection
Rule
(
ICR)
represent
conditions
during
late
1997
and
1998,
well
before
systems
had
to
comply
with
the
Stage
1
DBPR.
Other
occurrence
data
for
medium
and
small
systems
represent
similar
time
frames.

The
purpose
of
this
section
is
to
support
the
development
of
the
Stage
2
DBPR
by
evaluating
DBP
occurrence
likely
to
exist
after
the
Stage
1
DBPR
is
implemented.
In
this
regard,
the
analysis
presented
in
section
4.3
of
this
chapter
focuses
on
the
spatial
and
temporal
variability
in
distribution
system
total
trihalomethanes
(
TTHM)
and
haloacetic
acids
(
HAA5)
occurrence
following
the
implementation
of
the
Stage
1
DBPR.
Preceding
sections
describe
the
methodology
for
predicting
post­
Stage
1
DBP
occurrence
(
section
4.1)
and
summarize
the
results
(
section
4.2).

4.1
Methodology
for
Predicting
Post­
Stage
1
DBP
Occurrence
The
ICR
was
the
primary
data
source
used
to
characterize
post­
Stage
1
(
or
Pre­
Stage
2)
DBPR
occurrence
for
TTHM
and
HAA5
in
this
document1.
To
assess
Post­
Stage
1
DBP
occurrence,
the
analysis
in
this
section
uses
the
subset
of
ICR
plants
that
are
already
in
compliance
with
Stage
1
to
characterize
Post­
Stage
1
DBP
occurrence.
This
assumes
the
cumulative
distribution
of
TTHM
and
HAA5
concentrations
for
the
subset
of
plants
in
compliance
with
the
Stage
1
DBPR
is
unchanged
when
non­
compliant
plants
make
changes
to
meet
Stage
1.
This
may
not
be
the
case
 
systems
that
make
changes
may
be
concentrated
near
the
upper
end
of
the
cumulative
distribution
since
these
plants
will
have
poor
water
quality
with
respect
to
DBPs.
EPA
believes,
however,
that
given
the
small
number
of
plants
that
make
changes
compared
to
those
that
don't,
the
impact
on
the
Post­
Stage
1
DBPR
occurrence
distribution
is
small.

To
determine
if
an
ICR
plant
is
in
compliance
with
the
Stage
1
DBPR,
EPA
calcuated
the
TTHM
and
HAA5
running
annual
averages
(
RAAs)
using
the
last
four
quarters
of
ICR
data
(
January
to
December
1998)
at
the
four
distribution
system
locations
(
DSE,
AVG1,
AVG2,
and
DS
Maximum).
The
analysis
is
done
only
for
plants
that
meet
the
screening
criteria
discussed
in
section
1.4.8
(
plants
must
have
at
least
3
of
4
quarters
with
at
least
3
of
4
locations
having
data
for
both
TTHM
and
HAA5).

Once
TTHM
and
HAA5
RAAs
were
calculated
for
the
screened
plants,
compliance
was
determined
using
two
approaches:

°
Compare
TTHM
RAA
to
the
Stage
1
DBPR
MCL
of
80
:
g/
L,
and
HAA5
RAA
to
the
Stage
1
DBPR
MCL
of
60
:
g/
L
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
2
°
Same
as
above,
except
consider
the
Stage
1
DBPR
MCLs
with
a
20
percent
safety
factor
(
64
:
g/
L
for
TTHM
and
48
:
g/
L
for
HAA5)

Based
on
recommendations
from
the
Microbial/
Disinfection
Byproducts
Technical
Work
Group
(
M­
DBP
TWG),
EPA
uses
a
20
percent
operational
safety
factor
for
DBP
MCLs
(
TTHM,
HAA5,
bromate,
and
chlorite)
when
evaluating
all
regulatory
alternatives.
This
safety
factor
is
consistent
with
practices
in
prior
DBP
regulatory
development
efforts
and
is
intended
to
represent
the
level
at
which
systems
would
be
compelled
to
take
some
action
to
ensure
compliance
with
a
new
drinking
water
standard.
In
addition
to
reflecting
industry
practices,
the
safety
factor
also
is
intended
to
account
for
year­
to­
year
fluctuations
in
DBP
data
(
ICR
data
is
limited
to
one
year
and
may
not
reflect
the
highest
DBP
concentrations
that
occur
in
a
system).

Although
EPA
believes
that
the
use
of
a
safety
factor
generally
reflects
industry
practices,
there
is
variability
in
the
concentration
below
the
MCL
value
at
which
systems
are
confident
operating
(
e.
g.,
the
safety
factor
may
be
more
or
less
in
some
cases)
and,
therefore,
uncertainty
in
the
average
safety
factor.
In
addition
to
this
uncertainty,
EPA
believes
that
the
post­
Stage
1
DBPR
distribution
of
TTHM
and
HAA5
may
be
slightly
higher
than
the
results
using
subsets
of
Stage
1­
compliant
plants
from
the
ICR.
To
essentially
"
bound"
these
uncertainties,
analyses
of
predicted
Post­
Stage
1
TTHM
and
HAA5
occurrence
are
done
both
with
and
without
a
20
percent
safety
factor.
All
analyses
of
spatial
and
temporal
variability,
however,
(
presented
in
Section
4.3),
are
done
based
on
compliance
evaluation
without
the
safety
factor
(
i.
e.,
80/
60
RAA).

4.2
Summary
of
Post­
Stage
1
Occurrence,
Plant­
Mean
Data
Exhibits
4.1
and
4.2
summarize
post­
Stage
1
DBPR
TTHM
and
HAA5
data,
respectively.
The
data
are
presented
separately
for
different
source
water
types
(
surface,
ground,
and
all)
and
data
types
(
plant­
mean
finished
water,
running
annual
average
(
RAA),
locational
running
annual
average
(
LRAA),
and
single
high).
See
section
3.1.3
for
a
description
of
the
different
data
types.
Plant­
compliance
was
determined
by
using
the
Stage
1
DBPR
MCLs
with
and
without
a
20
percent
safety
factor.
Note
that
applying
a
20
percent
safety
factor
to
the
Stage
1
DBPR
MCLs
resulted
in
reduced
Post­
Stage
1
TTHM
and
HAA5
values
compared
to
results
without
the
safety
factor.

For
surface
water
systems
results
show
that
the
highest
LRAA
for
some
Stage
1­
compliant
plants
is
significantly
above
the
Stage
2
DBPR
MCL
of
80
:
g/
L
for
TTHM
and
60
:
g/
L
for
HAA5.
Single
highest
values
are
also
still
very
high
after
Stage
1
compliance
(
maximum
of
134
and
132
:
g/
L
for
TTHM
and
HAA5,
respectively,
based
on
compliance
without
a
safety
factor).
Ground
water
peaks
are
less,
but
LRAA
values
are
still
above
the
Stage
2
DBPR
MCLs
for
some
plants.
Section
4.3.1
provides
more
detailed
analyses
of
the
occurrence
of
individual
TTHM
and
HAA5
peak
measurements.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
3
Source
Data
Type
1
Stage
1
MCLs
With
or
Without
20%
Safety
Factor
Number
of
Plants
Mean
of
Plant­
Means
Median
of
Plant­
Means
90th
Percentile
of
Plant­
Means
Range
of
Plant­
Means
w/
o
S.
F.
196
29.29
27.37
52.13
0­
75
w/
20%
S.
F.
172
26.70
25.68
46.20
0­
75
w/
o
S.
F.
196
39.32
37.97
63.42
0­
80
w/
20%
S.
F.
172
35.83
35.65
55.86
0­
64
w/
o
S.
F.
196
46.18
43.97
75.23
0­
98
w/
20%
S.
F.
172
42.49
41.17
68.43
0­
98
w/
o
S.
F.
196
64.26
60.10
106.70
0­
142
w/
20%
S.
F.
172
58.60
56.60
94.50
0­
124
w/
o
S.
F.
79
7.59
1.40
24.57
0­
58
w/
20%
S.
F.
77
6.93
1.23
23.48
0­
58
w/
o
S.
F.
79
13.07
6.51
35.76
0­
69
w/
20%
S.
F.
77
12.23
6.42
35.39
0­
55
w/
o
S.
F.
79
17.91
11.65
49.83
0­
99
w/
20%
S.
F.
77
17.05
11.40
49.30
0­
99
w/
o
S.
F.
79
29.48
17.10
65.50
0­
300
w/
20%
S.
F.
77
28.31
16.00
63.70
0­
300
w/
o
S.
F.
284
23.42
21.48
49.90
0­
87
w/
20%
S.
F.
256
20.85
19.33
45.48
0­
87
w/
o
S.
F.
290
31.93
31.68
60.46
0­
80
w/
20%
S.
F.
262
28.57
29.39
52.89
0­
64
w/
o
S.
F.
290
38.17
37.05
69.95
0­
99
w/
20%
S.
F.
262
34.62
33.27
63.30
0­
99
w/
o
S.
F.
290
54.18
52.40
100.00
0­
300
w/
20%
S.
F.
262
49.10
49.30
89.10
0­
300
Finished,
Plant
Mean
DS
Average
(
or
RAA)

Highest
LRAA
Single
Highest
Finished,
Plant
Mean
DS
Average
(
or
RAA)

Highest
LRAA
Single
Highest
Finished,
Plant
Mean
DS
Average
(
or
RAA)

Highest
LRAA
Single
Highest
Surface
Ground
All
2
Exhibit
4.1
Summary
of
Post­
Stage
1
TTHM
Occurrence
for
ICR
Plants
in
Compliance
with
Stage
1
MCLs
with
or
without
a
Safety
Factor
Notes:
1
For
a
description
of
the
data
types.
See
"
Aggregation
of
DBP
Data"
in
section
3.1.3.
2
The
"
All"
plants
include
those
with
surface,
ground,
blended,
mixed,
or
purchased
source
water
types.
Finished
water
data
were
not
available
for
blended
plants.
MCLs
without
safety
factor:
TTHM/
HAA5=
80/
60
:
g/
L;
MCLs
with
safety
fact:
TTHM/
HAA5=
64/
48
:
g/
L
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
average
by
finish
location
­
TTHM
&
HAA5,
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5
and
Plants
min
3x3,
Single
High
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
2.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
4
Source
Data
Type
1
Stage
1
MCLs
With
or
Without
20%
Safety
Factor
Number
of
Plants
Mean
of
Plant­
Means
Median
of
Plant­
Means
90th
Percentile
of
Plant­
Means
Range
of
Plant­
Means
w/
o
S.
F.
196
21.79
20.00
40.85
0­
61
w/
20%
S.
F.
172
20.04
18.13
38.33
0­
53
w/
o
S.
F.
196
25.58
22.99
45.85
0­
59
w/
20%
S.
F.
172
23.27
22.50
40.74
0­
48
w/
o
S.
F.
196
29.81
26.87
53.10
0­
110
w/
20%
S.
F.
172
26.98
25.33
46.28
0­
60
w/
o
S.
F.
196
41.94
37.80
74.20
0­
134
w/
20%
S.
F.
172
37.88
34.30
63.50
0­
115
w/
o
S.
F.
79
4.39
0.33
17.53
0­
34
w/
20%
S.
F.
77
4.06
0.33
15.20
0­
34
w/
o
S.
F.
79
6.82
2.20
18.48
0­
49
w/
20%
S.
F.
77
6.18
2.16
17.69
0­
46
w/
o
S.
F.
79
9.24
3.33
26.97
0­
74
w/
20%
S.
F.
77
8.32
3.17
25.55
0­
58
w/
o
S.
F.
79
15.18
6.20
45.80
0­
103
w/
20%
S.
F.
77
13.97
6.20
45.00
0­
84
w/
o
S.
F.
284
16.74
15.07
37.33
0­
61
w/
20%
S.
F.
256
15.11
14.08
34.18
0­
53
w/
o
S.
F.
290
20.00
17.96
41.96
0­
59
w/
20%
S.
F.
262
17.89
17.24
36.45
0­
48
w/
o
S.
F.
290
23.62
21.17
48.60
0­
110
w/
20%
S.
F.
262
21.05
19.95
42.00
0­
60
w/
o
S.
F.
290
33.76
29.00
67.60
0­
134
w/
20%
S.
F.
262
30.19
27.20
59.80
0­
115
Highest
LRAA
Single
Highest
All
2
Finished,
Plant
Mean
DS
Average
(
or
RAA)

Highest
LRAA
Single
Highest
Surface
Finished,
Plant
Mean
DS
Average
(
or
RAA)

Highest
LRAA
Single
Highest
Ground
Finished,
Plant
Mean
DS
Average
(
or
RAA)
Exhibit
4.2
Summary
of
Post­
Stage
1
HAA5
Occurrence
for
ICR
Plants
in
Compliance
with
Stage
1
MCLs
with
or
without
a
Safety
Factor
Notes:
1
For
a
description
of
the
data
types.
See
"
Aggregation
of
DBP
Data"
in
section
3.1.3.
2
The
"
All"
plants
include
those
with
surface,
ground,
blended,
mixed,
or
purchased
source
water
types.
Finished
water
data
were
not
available
for
blended
plants.
MCLs
without
safety
factor:
TTHM/
HAA5=
80/
60
:
g/
L;
MCLs
with
safety
fact:
TTHM/
HAA5=
64/
48
:
g/
L
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
average
by
finish
location
­
TTHM
&
HAA5,
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5
and
Plants
min
3x3,
Single
High
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
2.
xls
4.3
Spatial
and
Temporal
Variability
of
TTHM
and
HAA5
Occurrence,
Post
Stage
1
Conditions
This
section
supports
the
development
of
the
Stage
2
DBPR
by
evaluating
spatial
and
temporal
variability
of
TTHM
and
HAA5
occurrence
for
Post­
Stage
1
conditions.
For
the
purposes
of
these
analyses,
EPA
uses
the
subsets
of
plants
in
compliance
with
Stage
1
DBPR
MCLs
of
80/
60
:
g/
L
for
TTHM/
HAA5,
respectively
(
no
safety
factor).
Additional
analyses
for
the
subsets
of
plants
in
compliance
with
MCLs
of
64/
48
:
g/
L
for
TTHM/
HAA5,
respectively,
were
not
done
because
they
are
expected
to
show
almost
identical
results.

Section
4.3.1
evaluates
the
occurrence
of
individual
TTHM
and
HAA5
peaks
for
post­
Stage
2
conditions.
Sections
4.3.2
and
4.3.3
characterize
the
occurrence
of
yearly
average
TTHM
and
HAA5
data
at
different
locations.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
5
4.3.1
Occurrence
of
Individual
DBP
Observations
Above
the
MCL
Exhibit
4.3
compares
the
TTHM
running
annual
average
(
RAA)
results
with
the
single
highest
TTHM
concentration
in
the
distribution
system
for
all
plants
in
compliance
with
the
Stage
1
DBPR
MCLs
of
80/
60
RAA
(
4.3a)
and
the
Stage
1
MCLs
with
a
20
percent
safety
factor
(
64/
48
RAA)
(
4.3b).
As
derived
from
data
in
Exhibit
4.3a,
twenty­
one
percent
(
61
of
290)
of
all
plants
meeting
the
Stage
1
DBPR
MCL
of
80/
60
RAA
had
single
TTHM
concentrations
higher
than
the
0.080
mg/
L
MCL.
From
Exhibit
4.3b,
about
fifteen
percent
(
38
of
262)
of
all
plants
meeting
the
Stage
1
DBPR
MCL
of
64/
48
RAA
had
single
TTHM
concentrations
higher
than
the
0.080
mg/
L
MCL.
Exhibit
4.4
makes
the
same
comparisons
for
HAA5.

Data
in
Exhibit
4.4a
show
that
fourteen
percent
(
42
of
290)
of
all
ICR
plants
meeting
the
Stage
1
DBPR
MCL
of
80/
60
RAA
had
single
HAA5
concentrations
higher
than
the
0.060
mg/
L
MCL.
From
Exhibit
4.4b,
about
ten
percent
(
25
of
262)
of
all
ICR
plants
meeting
the
Stage
1
DBPR
MCL
of
64/
48
RAA
had
single
HAA5
concentrations
higher
than
the
0.060
mg/
L
MCL.
In
systems
with
a
low
RAA
for
TTHM
and
HAA5,
the
highest
single
TTHM
and
HAA5
values
are
generally
not
much
higher
than
the
respective
Stage
1
DBPR
MCLs.
However,
as
the
RAAs
increase,
there
is
a
greater
likelihood
of
having
peak
levels
above
the
MCLs.
As
the
RAAs
approach
the
Stage
1
DBPR
MCLs,
some
of
the
distribution
system
single
highest
concentrations
approach
levels
that
are
double
the
Stage
1
DBPR
MCLs.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
6
0
50
100
150
200
250
300
350
0
10
20
30
40
50
60
70
80
90
TTHM
RAA,
ug/
L
(
N=
290)
TTHM
Single
Highest,
ug/
L
(
N=
290)
Exhibit
4.3a
Single
Highest
vs.
RAA
for
TTHM,
All
Plants
in
Compliance
with
Stage
1
MCLs
of
80/
60
RAA
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5
and
Plants
min
3x3,
Single
High
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
2.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
7
0
50
100
150
200
250
300
350
0
10
20
30
40
50
60
70
80
90
TTHM
RAA,
ug/
L
(
N=
262)
TTHM
Single
Highest,
ug/
L
(
N=
262)
Exhibit
4.3b
Single
Highest
vs.
RAA
for
TTHM,
All
Plants
in
Compliance
with
Stage
1
MCLs
with
Safety
Factor
(
64/
48
RAA)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5
and
Plants
min
3x3,
Single
High
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
2.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
8
0
25
50
75
100
125
150
175
200
0
10
20
30
40
50
60
70
HAA5
RAA,
ug/
L
(
N=
290)
HAA5
Single
Highest,
ug/
L
(
N=
290)
Exhibit
4.4a
Single
Highest
vs.
RAA
for
HAA5,
All
Plants
in
Compliance
with
Stage
1
MCLs
of
80/
60
RAA
Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5
and
Plants
min
3x3,
Single
High
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
2.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
9
0
25
50
75
100
125
150
175
200
0
10
20
30
40
50
60
70
HAA5
RAA,
ug/
L
(
N=
262)
HAA5
Single
Highest,
ug/
L
(
N=
262)
Exhibit
4.4b
Single
Highest
vs.
RAA
for
HAA5,
All
Plants
in
Compliance
with
Stage
1
MCLS
with
Safety
Factor
(
64/
48
RAA)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5
and
Plants
min
3x3,
Single
High
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
2.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
10
4.3.2
Occurrence
of
Yearly
Averages
Above
the
MCL
at
Specific
Locations
Cumulative
distributions
of
LRAA
values
for
each
distribution
system
location
(
AVG1,
AVG2,
MAX,
and
DSE)
for
all
plants
are
shown
in
Exhibit
4.5.
Exhibit
4.5a
shows
results
for
plants
in
compliance
with
Stage
1
DBPR
MCLs
of
80/
60
RAA,
while
Exhibit
4.5b
shows
results
for
plants
in
compliance
with
Stage
1
MCLs
with
a
20
percent
safety
factor
(
64/
48
RAA).
Results
show
that
there
are
still
locations
that
regularly
receive
water
over
the
MCLs
following
the
implementation
of
the
Stage
1
DBPR.
From
data
in
Exhibit
4.5a,
approximately
five
percent
of
plants
(
15
out
of
290)
in
compliance
with
Stage
1
MCLs
of
80/
60
RAA
had
one
or
more
locations
that,
on
average,
exceeded
0.080
mg/
L
as
a
TTHM
LRAA,
and
one
of
these
15
did
so
at
two
locations.
From
Exhibit
4.5b,
approximately
two
percent
of
plants
(
six
out
of
262)
in
compliance
with
Stage
1
MCLs
of
64/
48
RAA
had
one
or
more
locations
that,
on
average,
exceeded
0.080
mg/
L
as
a
TTHM
LRAA
for
that
same
year.
Customers
served
at
these
locations
regularly
received
water
with
TTHM
concentrations
higher
than
the
MCL.

Exhibit
4.6
shows
similar
results
for
HAA5.
From
Exhibit
4.6a,
three
percent
of
plants
(
eight
of
290)
in
compliance
with
Stage
1
MCLs
of
80/
60
RAA
exceeded
0.060
mg/
L
as
an
LRAA,
and
three
of
these
eight
plants
did
so
at
two
or
three
locations.
Exhibit
4.6b
shows
that
no
plants
in
compliance
with
Stage
1
MCLS
of
64/
48
RAA
exceeded
0.060
mg/
L
as
an
LRAA.

Evaluating
TTHM
and
HAA5
results
together,
23
plants
have
a
maximum
TTHM
LRAA
of
0.080
mg/
l
or
greater,
or
a
maximum
HAA5
LRAA
of
0.060
mg/
l
or
greater
(
four
plants
exceeded
both
MCLs)
among
the
290
plants
in
the
ICR
database
meeting
the
Stage
1
MCLs
of
80/
60
RAA,
Among
the
262
plants
in
the
ICR
database
meeting
the
Stage
1
MCLs
of
64/
48
RAA,
six
plants
have
a
maximum
TTHM
LRAA
of
0.080
mg/
L
or
greater,
or
a
maximum
HAA5
LRAA
of
0.060
mg/
L
or
greater.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
11
60%
65%
70%
75%
80%
85%
90%
95%
100%

50
60
70
80
90
100
110
TTHM
LRAA,
ug/
L
Cumulative
Percentage
of
Plants
TTHM
LRAA
@
DSE
(
N=
284)

TTHM
LRAA
@
AVG1
(
N=
283)

TTHM
LRAA
@
AVG2
(
N=
284)

TTHM
LRAA
@
MAX
(
N=
290)
Exhibit
4.5a
Cumulative
Percentage
of
TTHM
LRAAs,
All
Plants
in
Compliance
with
80/
60
RAA
(
Stage
1
MCL)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
2.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
12
60%
65%
70%
75%
80%
85%
90%
95%
100%

50
60
70
80
90
100
110
TTHM
LRAA,
ug/
L
Cumulative
Percentage
of
Plants
TTHM
LRAA
@
DSE
(
N=
256)

TTHM
LRAA
@
AVG1
(
N=
255)

TTHM
LRAA
@
AVG2
(
N=
256)

TTHM
LRAA
@
MAX
(
N=
262)
Exhibit
4.5b
Cumulative
Percentage
of
TTHM
LRAAs,
All
Plants
in
Compliance
with
64/
48
RAA
(
Stage
1
MCL
with
SF)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
2.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
13
70%
75%
80%
85%
90%
95%
100%

30
40
50
60
70
80
90
100
110
120
HAA5
LRAA,
ug/
L
Cumulative
Percentage
of
Plants
HAA5
LRAA
@
DSE
(
N=
284)

HAA5
LRAA
@
AVG1
(
N=
283)

HAA5
LRAA
@
AVG2
(
N=
284)

HAA5
LRAA
@
MAX
(
N=
290)
Exhibit
4.6a
Cumulative
Percentage
of
HAA5
LRAAs,
All
Plants
in
Compliance
with
80/
60
RAA
(
Stage
1
MCL)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
2.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
14
70%
75%
80%
85%
90%
95%
100%

30
40
50
60
70
80
90
100
110
120
HAA5
LRAA,
ug/
L
Cumulative
Percentage
of
Plants
HAA5
LRAA
@
DSE
(
N=
256)

HAA5
LRAA
@
AVG1
(
N=
255)

HAA5
LRAA
@
AVG2
(
N=
256)

HAA5
LRAA
@
MAX
(
N=
262)
Exhibit
4.6b
Cumulative
Percentage
of
HAA5
LRAAs,
All
Plants
in
Compliance
with
64/
48
RAA
(
Stage
1
MCL
with
SF)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
RAA
&
Max
LRAA
­
TTHM
&
HAA5
and
Plants
min
3x3,
Single
High
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
2.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
15
4.3.3
Occurrence
of
Peak
DBPs
at
Locations
Other
Than
the
DS
Maximum
The
1979
TTHM
rule
and
Stage
1
DBPR
monitoring
locations
must
include
a
site
reflecting
maximum
residence
time
in
the
distribution
system
with
the
intent
of
capturing
the
highest
DBP
levels
in
the
distribution
system.
As
described
in
Section
1.4.8,
this
location
is
referred
to
as
the
"
DS
Maximum"
for
the
ICR
data
set.
Analysis
of
the
ICR
data
in
this
section
show
two
important
results:
1)
the
monitoring
locations
identified
as
the
maximum
residence
time
locations
often
did
not
represent
those
locations
with
the
highest
DBP
levels
and
2)
the
highest
TTHM
and
HAA5
level
often
occurred
at
different
points
in
the
distribution
system.

Exhibit
4.7
illustrates
that
the
highest
TTHM
and
HAA5
concentrations
could
be
at
any
of
the
four
ICR
distribution
system
sample
locations
or,
in
some
cases,
at
the
finished
water
location.
Exhibit
4.7
shows
the
frequency
at
which
the
maximum
TTHM
or
HAA5
LRAA
occurred
at
each
distribution
sampling
location
for
all
plants
that
are
in
compliance
with
the
Stage
1
DBPR
MCLs
of
80/
60
RAA.
Results
show
that
52
percent
of
ICR
plants
have
the
highest
TTHM
LRAA
concentration
occurring
at
sites
other
than
the
maximum
residence
time
monitoring
site.
The
highest
HAA5
LRAA
occurred
at
the
maximum
residence
time
monitoring
site
in
only
36
percent
of
the
plants.
For
small
surface
water
plants,
the
frequency
at
which
the
highest
LRAA
occurred
at
different
locations
can
be
analyzed
using
National
Rural
Water
Association
(
NRWA)
data.
Because
the
post­
Stage
1
data
set
was
determined
to
be
too
small
to
produce
meaningful
results
with
respect
to
spatial
and
temporal
variability
of
DBPs,
the
analysis
was
done
for
pre­
stage
1
conditions
and
presented
in
Chapter
3
(
Section
3.2).
Results
are
similar
to
Exhibit
4.7
 
Exhibit
3.55
shows
that
33
percent
of
NRWA
plants
have
the
highest
TTHM
LRAA
concentration
occurring
at
sites
other
than
the
maximum
residence
time
monitoring
site.
The
highest
HAA5
LRAA
occurred
at
the
maximum
residence
time
monitoring
site
in
only
49
percent
of
the
plants.

The
occurrence
patterns
shown
in
Exhibit
4.7
may
be
due
to
several
factors,
such
as
HAA5
degrading
over
time
in
the
distribution
system,
maximum
residence
time
monitoring
sites
not
actually
representing
the
maximum
residence
time,
or
that
using
a
simple
estimation
of
maximum
residence
time
cannot
characterize
a
complex
distribution
system.

EPA
also
analyzed
whether
the
highest
LRAA
for
TTHM
and
HAA5
occurred
at
the
same
location.
If
TTHM
and
HAA5
occur
at
the
same
location
rather
than
different
locations,
fewer
monitoring
sites
would
be
needed
to
represent
TTHM
and
HAA5
occurrence.
However,
this
is
not
the
case.
The
ICR
and
NRWA
data
sets,
respectively
indicate,
that
49
percent
and
38
percent
of
their
plants
in
compliance
with
Stage
1
DBPR
MCLs
of
80/
60
RAA
experienced
their
highest
LRAA
TTHM
and
HAA5
concentrations
at
different
locations
in
the
distribution
system.
For
plants
that
did
have
their
highest
LRAA
TTHM
and
HAA5
concentrations
at
the
same
location,
it
was
not
necessarily
the
maximum
residence
time
monitoring
location.
Exhibit
4.8
illustrates
that
for
Stage
1­
compliant
ICR
plants
with
the
highest
TTHM
and
HAA5
levels
occurring
at
the
same
location,
the
highest
TTHM
and
HAA5
LRAA
simultaneously
occurred
at
the
maximum
residence
time
monitoring
location
in
50
percent
of
the
cases.
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
16
0%
10%
20%
30%
40%
50%
60%

FIN
DSE
AVG1
AVG2
MAX
ICR
Sampling
Locations
Percentage
of
Plants
TTHM
(
N=
290)

HAA5
(
N=
290)
Exhibit
4.7
Frequency
at
Which
Highest
TTHM
or
HAA5
LRAAs
Occurred
at
Each
Sample
Location
for
All
ICR
Plants
in
Compliance
with
80/
60
RAA
(
Stage
1
MCL)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
RAA
&
Each
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
2.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
4­
17
Highest
LRAA
TTHM/
HAA5
Among
Plants
with
Highest
LRAA
TTHM/
HAA5
at
Same
Location
Maximum
occurred
at
same
location
51.4%
of
plants
Maximum
occurred
at
different
locations
for
48.6%
of
plants
8.7%
@
FINISH
50.3%
@
MAX
16.8%
@
AVG1
15.4%
@
AVG2
8.7%
@
DSE
Exhibit
4.8
Frequency
at
Which
Highest
TTHM
or
HAA5
LRAAs
Occurred
at
the
Same
Location
for
All
ICR
Plants
in
Compliance
with
80/
60
RAA
(
Stage
1
MCL)

Source:
ICR
AUX1
Database
(
USEPA
2000d).

Queries:
Plants
min
3x3,
RAA
&
Each
LRAA
­
TTHM
&
HAA5.
See
Appendix
B
for
query
language.

Excel
File:
ICR
DBP
Data,
Pre­
Stage
2.
xls
Occurrence
Assessment
for
the
Stage
2
DBPR
Proposal
July
2003
5­
1
5.
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