Appendix
D
Changes
in
Distribution
System
Operation
Significant
Excursions
Identified
Using
the
"
Maximum
Concentration
Approach"
This
page
intentionally
left
blank.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
1
The
first
part
of
this
appendix
includes
general
system
information
and
a
summary
of
TTHM
and
HAA5
data
that
resulted
in
Elm
City
having
to
perform
a
significant
excursion
evaluation.
This
information
is
not
required
e
as
part
of
the
documenntation
of
a
significant
excursion.
Only
the
Significant
Excursion
Report
is
required
to
be
completed
by
systems
that
experience
a
significant
excursion.

This
appendix
is
provided
as
an
example
of
a
system
in
which
changes
in
distribution
system
operations
led
to
a
DBP
Significant
Excursion.
Possible
strategies
to
reduce
excursions
are
presented
in
Chapter
4,
but
they
are
not
to
be
included
in
the
identification
and
documentation
process.
Appendices
B,
C,
and
E
provide
similar
examples
for
systems
in
which
changes
in
source
water
quality,
changes
in
treatment
plant
operations,
and
multiple
causes
resulted
in
a
significant
excursion.

This
example
assumes
the
state
has
chosen
to
use
100
µ
g/
L
TTHM
and
75
µ
g/
L
HAA5
as
the
trigger
levels
for
determining
that
a
significant
excursion
has
occurred
and
that
a
significant
excursion
evaluation
is
required.

Background
Information
for
this
Example
System
Description:

General
system
characteristics:
Service
area:
Elm
City
plus
surrounding
suburban
areas
Production:
Annual
average
daily
demand
15
MGD
Source
Water
Information:
Hardwood
Lake
(
surface
water)
pH:
from
6.9
to
7.5
Alkalinity:
from
82
to
98
mg/
L
as
CaCO
3
TOC:
from
2.1
to
4.0
mg/
L
as
C
Bromide:
from
0.04
to
0.1
mg/
L
Turbidity:
1
to
100
ntu
Softwood
River
(
surface
water)
pH:
from
6.8
to
7.9
Alkalinity:
from
77
to
94
mg/
L
as
CaCO
3
TOC:
from
1.6
to
9.4
mg/
L
as
C
Bromide:
from
0.03
to
0.1
mg/
L
Turbidity:
2
to
115
ntu
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
2
Treatment
Provided:
Hardwood,
conventional
(
15
MGD
design,
7.5
MGD
average)
Softwood
River,
conventional
with
GAC
(
20
MGD
design,
7.5
MGD
average)
Primary
and
residual
disinfection:
Chlorine/
chlorine
at
both
plants
Summary
of
Stage
2
DBPR
Monitoring
Locations:
Table
D.
1
summarizes
the
Stage
2
DBPR
monitoring
locations
used
by
Elm
City.
Sample
locations
are
marked
in
the
distribution
system
schematic
presented
in
Figure
D.
1.

Table
D.
1
Stage
2
DBPR
Monitoring
Locations
Location
Description
Location
#
1
Hardwood
Plant
­
average
residence
time
Location
#
2
Hardwood
Plant
­
high
TTHM
Location
#
3
Hardwood
Plant
­
high
HAA5
Location
#
4
Hardwood/
Softwood
Mix
Zone
­
high
TTHM
Location
#
5
Hardwood/
Softwood
Mix
Zone
­
high
TTHM
Location
#
6
Hardwood/
Softwood
Mix
Zone
­
high
TTHM
Location
#
7
Softwood
Plant
­
average
residence
time
Location
#
8
Softwood
Plant
­
high
HAA5
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
3
Pineville
MIXING
ZONE
Softwood
River
WTP
Hardwood
WTP
Elevated
Storage
Tank
Ground
storage
tank
Booster
disinfection
2
Oakville
1
3
Elmville
5
Downtown
Appleville
Weeping
Willow
Poplarville
Cedarville
Cypressville
6
7
4
8
Peak
DBP
site
Figure
D.
1
Schematic
of
Elm
City
Distribution
System
and
Stage
2
DBPR
Monitoring
Locations
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
4
DBP
Excursion
Investigation:

During
the
last
sampling
period
which
took
place
in
September
2004,
Elm
City
experienced
unusually
high
TTHM
values
(
relative
to
the
LRAA)
at
monitoring
location
#
2.
DBP
data
from
the
previous
year
and
most
recent
sampling
period
(
five
quarters
total)
are
presented
in
Table
D.
2.

Table
D.
2
TTHM
and
HAA5
Monitoring
Data
Loc
atio
n
TTHM
(
ug/
L)
HAA5
(
ug/
L)

Quarterly
Pre­
Sept
2004
Data1
LRAA
Pre­
Sept
2004
Sept
2004
Data
LRAA
incl.
Sept
2004
Quarterly
Pre­
Sept
2004
Data1
LRAA
Pre­
Sept
2004
Sept
2004
Data
LRAA
incl.
Sept
2004
#
1
54,
67,
58,
75
65
72
68
52,
37,
30,
41
40
53
40
#
2
49,
39,
50,
76
52
122
72
43,
39,
41,
45
42
49
44
#
2
68,
68,
55,
69
63
69
65
38,
45,
28,
19
33
40
33
#
3
66,
52,
71,
72
64
76
68
41,
46,
45,
39
43
58
47
#
4
50,
55,
51,
61
55
82
60
42,
43,
38,
34
39
54
42
#
5
34,
48,
55,
50
44
68
48
32,
43,
55,
38
42
37
43
#
6
44,
62,
58,
60
49
70
63
45,
33,
41,
40
40
53
42
#
7
40,
41,
37,
46
41
58
46
21,
38,
28,
19
27
29
29
#
8
68,
68,
55,
69
63
69
65
38,
45,
28,
19
33
40
33
1Data
for
sampling
conducted
on
September
2003,
December
2003,
March
2004
and
June
2004.
Data
relevant
to
peak
excursions
are
bold
and
underlined.

Unusually
high
TTHM
concentrations
were
observed
at
location
#
2.
The
results
are
significantly
higher
than
both
the
LRAA
at
those
locations
for
the
previous
12­
month
period
and
the
historic
TTHM
and
HAA5
values
at
those
locations
for
the
years
1999­
2003
(
see
Significant
Excursions
Evaluation
Report).
Data
for
September
2004
meets
the
criteria
of
peak
excursion.
The
city
staff
does
not
believe
that
treatment
plant
or
source
water
quality
changes
caused
the
increase
in
the
DBP
level
because
such
changes
would
likely
impact
all
locations
supplied
by
the
treatment
plant
or
source
water,
but
only
one
location
was
affected
by
high
DBP
level.
The
city
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
5
staff
believes
that
distribution
system
operations
in
the
vicinity
of
the
location
caused
the
increase
in
the
DBP
level.

Significant
Excursion
Report
date:
October
16th,
2004
Evaluation
Report
Report
prepared
by:
Ronald
Doe,
P.
E.

Page
1
System
name:
Elm
City
1)
When
was
the
significant
excursion
sample(
s)
collected?
What
were
the
TTHM
and
HAA5
concentrations?

Location
No.
#
2
#
______
#
______
#
______

Location
description
Hardwood
Plant
­
high
TTHM
Sample
collection
date
Sept.
4,
2004
Sample
collection
time
2
p.
m.

TTHM
LRAA
Concentration
(
ug/
L)
72
TTHM
Concentration
(
ug/
L)
122
HAA5
LRAA
Concentration
(
ug/
L)

HAA5
Concentration
(
ug/
L)

Note:
Attach
additional
sheets
if
you
observed
more
than
four
significant
excursions
during
this
round
of
sampling.

2)
Where
did
the
excursion(
s)
occur?
Attach
a
schematic
of
your
system,
sketch
your
system
in
the
space
below,
or
have
a
schematic
of
your
system
available
to
review
with
your
state
at
the
time
of
your
next
sanitary
survey.
Indicate
the
location(
s)
of
the
significant
excursion(
s)
on
your
schematic.

Location
#
2
B
Represents
high
residence
time
of
water
leaving
the
Hardwood
Plant.
It
is
located
in
the
Pineville
neighborhood.
An
elevated
storage
tank
also
supplies
water
to
this
subdivision.

The
location
of
these
sample
locations
is
illustrated
in
Figure
D.
1.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
6
Significant
Excursion
Evaluation
Report
Page
2
Report
date:
October
16th,
2004
3)
Attach
(
or
provide
in
the
Supplemental
Data
Form)
all
available
water
quality
data
for
the
round
of
sampling
in
which
the
significant
excursion
occurred.
At
a
minimum,
include
all
TTHM
and
HAA5
results
from
the
sampling
period.
You
should
also
consider
including
pH,
temperature,
alkalinity,
TOC,
disinfectant
residual,
and
any
other
data
that
you
think
would
be
useful.

a)
Were
there
any
unusual
circumstances
associated
with
this
round
of
sampling?

Yes
No
X
If
yes,
please
explain.

b)
Were
all
analytical
QA/
QC
measures
met?

Sample
preservation
Yes
X
No
Sample
holding
time
Yes
X
No
Other
If
no,
please
explain.

4)
Attach
(
or
provide
in
the
Supplemental
Data
Form)
historical
TTHM
and
HAA5
data
for
the
location(
s)
at
which
the
significant
excursion(
s)
occurred.
Provide
at
least
three
years
of
data,
if
available.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
7
Significant
Excursion
Evaluation
Report
Page
3
Report
date:
October
16th,
2004
5)
What
caused
your
excursion(
s)
to
occur?

Sections
A
through
F
starting
on
page
4
can
help
you
determine
the
possible
cause(
s)
of
your
excursion.
Please
note
there
may
be
more
than
one
factor
which
resulted
in
your
excursion.

Section
A:
Source
water
quality
change
Section
B:
Process
upset
at
treatment
plant
Section
C:
Planned
change
or
maintenance
activities
at
plant
Section
D:
Planned
distribution
system
operations
or
maintenance
activities
Section
E:
Unplanned
events
in
distribution
system
If
you
already
suspect
a
cause,
go
directly
to
that
section.
If
you
read
Sections
A
through
E
and
are
unable
to
determine
a
cause
of
your
excursion,
then
complete
Section
F.

Consecutive
systems
should
also
contact
their
wholesaler
to
identify
the
cause(
s)
of
the
significant
excursion(
s).

6)
List
steps
taken
or
planned
to
reduce
DBP
peak
levels.

Considering
modifications
to
configuration
of
inflow
piping
at
the
Pineville
tank
to
improve
mixing.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
8
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
9
Significant
Excursion
Evaluation
Report
Page
4
Report
date:
October
16th,
2004
A.
Source
Water
Quality
Changes
°
Did
any
of
the
events
listed
below
take
place
before
the
DBP
excursion
to
cause
TOC
levels
to
increase?
 
Heavy
rain
fall
 
Flooding
 
Spring
snow­
melt/
runoff
 
Significant
decrease
in
rainfall
or
source
flow
 
Algae
bloom
°
Did
any
of
the
events
listed
below
take
place
before
the
DBP
excursion
to
cause
bromide
levels
to
increase?
 
Significant
decrease
in
rainfall
or
source
flow
 
Brackish
or
seawater
intrusion
°
Did
pH
and/
or
alkalinity
significantly
change?

°
If
two
or
more
supplies
are
used,
was
a
greater
portion
of
water
drawn
from
the
one
with
higher
TOC?

°
Was
raw
water
stored
for
an
unusually
long
period
of
time
resulting
in
a
significant
increase
in
water
temperature?

Conclusions:

Did
source
water
quality
changes
cause
or
contribute
to
your
significant
excursion(
s)?

Yes
No
X
If
yes,
please
explain:

Attach
all
supporting
operational
or
other
data
which
led
you
to
conclude
this
was
the
cause
of
your
excursion(
s)
or
make
sure
this
data
is
available
during
your
sanitary
survey.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
10
Significant
Excursion
Evaluation
Report
Page
5
Report
date:
October
16th,
2004
B.
Process
Upset
at
Treatment
Plant
°
Was
raw
water
stored
for
an
unusually
long
time,
providing
additional
contact
time
for
DBP
formation
after
prechlorination?

°
Were
there
changes
in
coagulation
practices?

S
Were
there
any
changes
or
malfunctions
of
the
coagulation
process
in
the
days
leading
to
the
excursion?

S
Were
the
coagulant
dose
and
pH
properly
adjusted
for
incoming
source
water
conditions?

°
Were
there
changes
in
chlorination
practices?
 
Were
there
any
changes
in
chlorine
dose
at
any
location
in
the
plant?
 
Were
there
changes
in
plant
flow
that
may
have
resulted
in
longer
than
normal
residence
time
at
any
location
in
the
plant?

S
Did
the
pH
change
at
the
point
of
chlorine
addition?

°
Were
there
changes
in
settling
practices?

S
Was
there
excess
sludge
build­
up
in
the
settling
basin
that
may
have
carried
over
to
the
point
of
disinfectant
addition?

S
Was
there
any
disruption
in
the
sludge
blanket
that
may
have
resulted
in
carryover
to
the
point
of
disinfection?

°
Were
there
changes
in
filtration
practices?

S
Have
filter
run
times
been
changed
to
meet
raw
water
quality
changes?

S
Were
there
any
spikes
in
individual
filter
effluent
turbidity
(
which
may
indicate
particulate
or
colloidal
TOC
breakthrough)
in
the
days
leading
to
the
excursion?

S
Did
chlorinated
water
sit
in
the
filter
for
an
extended
period
of
time?

S
Were
all
filters
run
in
a
filter­
to­
waste
mode
during
initial
filter
ripening?

S
Were
any
filters
operated
beyond
their
normal
filter
run
time?

S
If
GAC
filters
are
used:
Is
it
possible
the
adsorptive
capacity
of
the
GAC
bed
was
reached
before
reactivation
occurred?

S
If
biological
filtration
is
used:
Were
there
any
process
upsets
that
may
have
resulted
in
breakthrough
of
TOC
(
particularly
biodegradable
TOC)?

°
Were
there
changes
in
plant
flow
that
may
have
resulted
in
an
unusually
high
residence
time
in
the
clearwell
on
the
days
prior
to
the
excursion?

S
For
example,
a
temporary
plant
shutdown.

Continued
on
next
page
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
11
Significant
Excursion
Evaluation
Report
Page
6
Report
date:
October
16th,
2004
B.
Process
Upset
at
Treatment
Plant
(
Continued)

Conclusions:

Did
a
process
upset
in
the
treatment
plant
cause
or
contribute
to
your
significant
excursion(
s)?

Yes
No
X
If
yes,
please
explain:

Attach
all
supporting
operational
or
other
data
which
led
you
to
conclude
this
was
the
cause
of
your
excursion(
s)
or
make
sure
this
data
is
available
during
your
sanitary
survey.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
12
Significant
Excursion
Evaluation
Report
Page
7
Report
date:
October
16th,
2004
C.
Planned
Change
or
Maintenance
Activities
for
the
Treatment
Plant
°
Was
there
a
recent
change
(
or
addition)
of
pre­
oxidant?

°
Was
there
any
maintenance
in
the
basin
that
may
have
stirred
sludge
from
the
bottom
of
the
basin
and
caused
it
to
carry
over
to
the
point
of
disinfectant
addition?

°
Did
you
change
the
type
or
manufacturer
of
the
coagulant?

°
Were
there
any
changes
in
disinfection
practices
in
the
days
prior
to
the
excursion?

S
For
example,
a
switch
from
chloramines
to
free
chlorine
for
burnout
period.

S
Discontinuation
of
ozone
which
forms
very
little
TTHM.

°
Was
a
filter(
s)
taken
off­
line
for
an
extended
period
of
time
that
caused
the
other
filters
to
operate
near
maximum
design
capacity
and
creating
the
conditions
for
possible
breakthrough?

°
Were
any
pumps
shut
down
for
maintenance,
leading
to
changes
in
flow
patterns
or
hydraulic
surges?

Conclusions:

Did
a
planned
maintenance
or
operational
activity
in
the
treatment
plant
cause
or
contribute
to
your
significant
excursion(
s)?

Yes
No
X
If
yes,
please
explain:

Attach
all
supporting
operational
or
other
data
which
led
you
to
conclude
this
was
the
cause
of
your
excursion(
s)
or
make
sure
this
data
is
available
during
your
sanitary
survey.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
13
Significant
Excursion
Evaluation
Report
Page
8
Report
date:
October
16th,
2004
D.
Planned
Distribution
System
Operations
or
Maintenance
Activities
°
Was
a
tank
drained
for
cleaning
or
other
maintenance?

S
Was
the
tank
drained
to
waste
or
to
the
distribution
system?

S
Was
a
larger
volume
than
normal
drained
to
the
distribution
system?

°
If
booster
disinfection
is
used,
was
the
booster
disinfectant
dose
higher
than
the
normal
booster
disinfectant
dose
for
that
season?

°
Were
there
any
system
maintenance
activities
in
the
days
prior
to
DBP
excursion?
Including:
 
Repairing
mains
or
installing
new
mains
 
Closure
of
valves
to
isolate
sections
of
pipes
°
Were
the
pipes
flushed
properly
or
were
the
appropriate
valves
re­
opened
after
work
was
completed?

°
Did
any
pump
or
pipeline
maintenance
occur
that
would
have
changed
the
flow
pattern
in
the
area
the
sample
was
drawn
from?

S
Change
in
flow
can
cause
water
in
stagnant
areas
to
be
drawn
into
another
area.

°
Did
any
pipeline
replacement
occur?

S
Disinfecting
piping
in
contact
with
drinking
water
could
result
in
a
high
concentration
of
chlorine
entering
the
distribution
system
and
thus
increase
DBPs.

Conclusions:

Did
a
planned
distribution
system
maintenance
or
operational
activity
cause
or
contribute
to
your
significant
excursion(
s)?

Yes
X
No
If
yes,
please
explain:

Refer
to
the
explanation
following
Section
E.

Attach
all
supporting
operational
or
other
data
which
led
you
to
conclude
this
was
the
cause
of
your
excursion(
s)
or
make
sure
this
data
is
available
during
your
sanitary
survey.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
14
Significant
Excursion
Evaluation
Report
Page
9
Report
date:
October
16th,
2004
E.
Unplanned
Distribution
System
Events
°
Were
there
increases
in
demand
that
caused
older
water
in
storage
tanks
to
be
drawn
into
the
system?

S
Were
there
any
major
fire
events?

S
Did
one
or
more
storage
tank
have
greater
than
average
drawdown
preceding
the
time
of
DBP
peak
excursion?

°
Were
there
decreases
in
demand
that
resulted
in
longer
than
normal
system
residence
times?

S
Were
there
any
large
customers
off­
line?

°
Did
any
main
breaks
occur
causing
changes
in
flow
patterns
in
the
influence
area
of
the
sample
location?

°
If
you
collect
water
temperature
inside
storage
tanks,
was
the
temperature
inside
the
tank
higher
than
normal
for
the
season?

°
Were
any
storage
tanks
hydraulically
locked
out
of
the
system
for
an
extended
period
and
then
used
preceding
the
time
of
DBP
peak
excursion?

°
Did
changes
in
overall
water
demand
cause
a
change
in
water
demand
patterns
in
the
vicinity
of
dead
ends
and/
or
stagnant
zones
in
the
system?

°
Were
there
large
variations
in
localized
system
pressures
that
were
different
from
the
normal
pressure
range
that
could
have
caused
a
change
in
water
demand
patterns
in
the
vicinity
of
dead
ends
and/
or
stagnant
zones
in
the
system?

Conclusions:

Did
an
unplanned
distribution
system
maintenance
or
operational
activity
cause
or
contribute
to
your
significant
excursion(
s)?

Yes
X
No
If
yes,
please
explain:

The
city
staff
believes
distribution
system
operations
caused
the
peak
THM
excursion.
Therefore,
the
likelihood
that
distribution
issues
contributed
to
the
peak
THM
excursion
has
been
explored
first.
To
determine
the
cause
of
the
THM
peak
excursion,
the
city
staff
reviewed
the
following
information
for
a
period
of
two
weeks
prior
to
the
occurrence
of
peak
THM
excursion:

°
System
maintenance
activities
°
Main
breaks
°
System
pressure
fluctuations
°
Overall
system
demand
°
Water
level
in
storage
tanks
°
Boost
disinfection
operation
Attach
all
supporting
operational
or
other
data
which
led
you
to
conclude
this
was
the
cause
of
your
excursion(
s)
or
make
sure
this
data
is
available
during
your
sanitary
survey.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
15
System
maintenance
activities:
Installation
of
a
new
12­
inch
main
for
a
new
development
in
Elmville
subdivision
was
completed.
The
city
staff
reviewed
the
main
disinfection
logbook
which
indicated
that
the
new
main
was
flushed
properly,
and
chlorine
residual
in
the
pipe
was
1
mg/
L
before
it
was
connected
to
the
rest
of
the
water
system.
Three
valves
were
closed
to
isolate
sections
of
pipes
from
the
rest
of
the
water
system.
during
installation
of
the
new
main.
These
valves
were
checked
to
make
sure
that
they
were
all
opened
after
installation
of
the
new
main
was
completed.
One
valve
was
found
to
be
inadvertently
left
in
the
closed
position.
However,
the
closure
of
this
valve
did
not
affect
the
water
quality
in
Pineville
subdivision
where
the
peak
THM
concentration
occurred.
The
city's
hydraulic
model
indicated
that
water
does
not
flow
from
Elmville
to
Pineville
and
closing
the
valve
in
the
pipe
in
Elmville
does
not
alter
the
water
flow
patters
in
Pineville.

Main
breaks:
A
road
repair
worker
in
Pineville
subdivision
damaged
a
12­
inch
water
main
that
runs
along
that
road.
The
broken
section
of
the
water
main
was
isolated
and
shut
off
within
two
hours.
However,
it
is
anticipated
that
there
was
significant
loss
of
water
during
those
two
hours.
Hydraulic
analyses
using
the
city's
hydraulic
model
have
indicated
that
the
piping
network
in
Pineville
does
not
have
any
stagnant
zones
with
high
residence
time.
Also,
using
the
city's
hydraulic
model
to
simulate
the
main
break
by
creating
artificial
demand
at
the
location
of
the
main
break
indicated
that
the
influence
of
the
main
break
did
not
draw
water
from
any
stagnant
zones
towards
the
sample
location
where
peak
THM
excursion
occurred.

System
pressure
fluctuations:
The
distribution
system
pressure
in
the
Pineville
subdivision
was
generally
within
the
normal
range
expected
for
the
month
of
September,
approximately
52­
65
psi.
However,
the
pressure
was
about
10
psi
lower
at
the
location
of
the
main
break
for
about
two
hours.
As
soon
as
the
damaged
section
of
the
main
was
isolated,
the
pressure
at
that
location
returned
to
the
normal
pressure
range
generally
expected
for
the
month
of
September.
The
piping
network
in
Pineville
does
not
have
any
stagnant
zones.
There
may
be
stagnant
zones
outside
the
Pineville
subdivision,
but
the
lower
pressure
in
the
vicinity
of
the
peak
THM
occurrence
did
not
impact
water
flow
patterns
outside
the
Pineville
subdivision,
as
verified
by
the
city's
hydraulic
model.

Overall
system
demand:
The
total
hourly
distribution
system
demand
was
checked
using
treatment
plant
production
figures
and
tank
level
data.
The
hourly
total
system
demand
during
September
2004
ranged
between
14­
17
mgd,
which
was
also
the
general
range
for
the
system
demand
during
the
month
of
September
for
1999­
2003.
An
unusual
increase
or
decrease
in
the
total
system
demand
was
not
observed
two
weeks
prior
to
the
peak
THM
occurrence.
The
loss
of
water
due
to
the
main
break
did
not
cause
a
significant
change
in
the
overall
system
demand.
Therefore,
there
was
not
any
unusual
shift
in
the
water
demand
patterns
and
water
flow
patterns
in
the
vicinity
of
stagnant
zones
and
thus
did
not
contribute
to
the
peak
THM
occurrence.

Water
level
in
storage
tanks:
The
hourly
water
level
for
all
the
tank
in
Elm
City
was
plotted
using
the
SCADA
system
data.
The
water
levels
fluctuated
within
the
normal
range
for
all
the
tanks
except
for
the
elevated
tank
located
in
Pineville.
The
water
level
in
the
Pineville
tank
generally
fluctuates
approximately
20
feet
to
35
feet
above
the
bottom
of
the
tank.
The
water
level
in
this
tank
dropped
to
about
12
feet
above
the
bottom
of
the
tank
at
the
time
of
the
main
break
and
then
rose
to
normal
levels
once
the
broken
section
of
the
main
was
isolated.
The
increased
water
demand
and
pressure
drop
at
the
location
of
the
main
break
was
responsible
for
the
unusual
drop
in
the
water
level
of
the
Pineville
tank.
The
proximity
of
Sample
Location
2
to
the
main
break
also
decreased
the
pressure
at
the
sampling
location,
this
allowing
the
water
from
the
top
portion
of
the
tank
to
reach
that
location
during
the
main
break.
The
SCADA
data
indicated
that
the
average
inflow
rate
into
the
tank
is
1000
gpm
and
the
inlet
diameter
is
36
inches.
This
inflow
rate
and
inlet
diameter
may
not
provide
adequate
momentum
to
mix
the
water
near
the
top
portion
of
the
tank
where
the
water
came
from
during
the
main
break.
Therefore,
the
water
age
in
the
top
portion
of
the
tank
was
higher
and
may
have
caused
the
peak
DBP
level
at
Sample
Site
2.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
16
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
17
Booster
disinfection
operation:

There
is
a
booster
disinfection
station
located
in
the
Polarville
subdivision.
The
disinfectant
residual
leaving
this
booster
station
was
within
the
normal
range
of
1­
2
mg/
L.
Pineville
subdivision
receives
all
the
water
either
from
the
treatment
plant
directly
or
from
the
Pineville
tank.
It
does
not
receive
any
portion
of
its
water
from
the
booster
station.
Thus,
the
disinfectant
residuals
at
the
booster
station
did
not
contribute
to
peak
THM
occurrence
at
Location
2.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
18
Significant
Excursion
Evaluation
Report
Page
10
Report
date:
October
16th,
2004
F.
If
you
were
unable
to
identify
the
cause
of
your
significant
excursion(
s)
after
reviewing
Sections
A
through
E,
are
you
able
to
identify
another
potential
cause
of
your
increase
in
DBP
concentrations?
Explain.

Note:
If
you
are
unable
to
determine
the
cause
of
your
excursion
you
may
wish
to
consider:

°
More
frequent
raw
water
temperature
monitoring.
°
More
frequent
raw
water
TOC
monitoring.
°
Increased
disinfectant
residual
monitoring
in
the
distribution
system.
°
Tracer
studies
to
characterize
distribution
system
water
age.
°
Development
of
a
hydraulic
model
to
characterize
the
distribution
system.

Attach
all
supporting
operational
or
other
data
which
led
you
to
conclude
this
was
the
cause
of
your
excursion(
s)
or
make
sure
this
data
is
available
during
your
sanitary
survey.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
19
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
20
Supplemental
Data
Form
for
the
Significant
Excursion
Evaluation
Report
Report
date:
October
16th,
2004
Report
prepared
by:
Ronald
Doe,
P.
E.

System
name:
Elm
City
1)
Water
quality
data
from
significant
excursion
sampling
period.

Location
No.
#
1
#
2
#
3
#
4
#
5
#
6
#
7
#
8
Location
Name
TTHM
(
ug/
L)
72
122
82
68
68
70
58
69
HAA5
(
ug/
L)
53
38
58
54
37
53
29
40
Free
Chlorine
(
mg/
L)
1.5
0.1
NA
0.5
0.8
1.1
NA
0.9
Total
Chlorine
(
mg/
L)
1.7
0.2
NA
0.7
1.1
1.5
NA
1.2
pH
7.9
8.0
8.3
8.1
7.8
8.3
7.5
8.2
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
D­
21
2)
Supplemental
data
from
each
treatment
facility:

Plant
#
1:
Hardwood
Plant
Plant
#
2:
Softwood
Plant
Raw
Water
Temperature:
NA
Raw
Water
Temperature:
NA
Plant
Effluent
Water
Temperature:
20

C
Plant
Effluent
Water
Temperature:
20

C
Raw
Water
TOC:
2.2
mg/
L
(
Avg.

2.0mg/
L)
Raw
Water
TOC:
1.8
mg/
L
(
Avg.

2.0mg/
L)

Other
Data:
Other
Data:
Inf.
turb.:
25
ntu
(
Avg

20
ntu)

3)
Historical
TTHM
and
HAA5
data
at
significant
excursion
sampling
locations.

TTHM
Data
(
ug/
L)
HAA5
Data
(
ug/
L)

Monitoring
Location
#
2
#_____
#_____
#_____
Monitoring
Location
#
2
#_____
#_____
#_____

Date
­
1998
61
Date
­
1998
32
Date
­
1999
55
Date
­
1999
29
Date
­
2000
70
Date
­
2000
48
Date
­
2001
64
Date
­
2001
36
Date
­
2002
49
Date
­
2002
43
Avg.
98­
02
60
Avg.
98­
02
49
Attach
additional
sheets
if
necessary
