1Under
section
303(
d)(
1)
of
the
CWA,
states,
territories,
and
authorized
tribes
must
identify
waterbodies
for
which
technology­
based
controls
required
by
the
Act
are
not
sufficient
to
implement
applicable
water
quality
standards
(
i.
e.,
are
impaired),
and
prioritize
such
waterbodies
for
TMDL
establishment.

Page
1
of
4
Memorandum
From:
Carey
A.
Johnston,
P.
E.
USEPA/
OW/
OST
ph:
(
202)
566
1014
johnston.
carey@
epa.
gov
To:
304(
m)
Record
(
EPA
Docket
Number
OW­
2003­
0074)

Date:
December
4,
2003
Re:
Use
of
STORET
Ambient
Monitoring
Data
and
Water
Quality
Standards
in
Future
Effluent
Guidelines
Program
Plans
Overview
Under
the
Clean
Water
Act
(
CWA),
EPA
establishes
technology­
based
national
regulations,
termed
"
effluent
guidelines,"
to
reduce
pollutant
discharges
from
industrial
facilities
to
waters
of
the
United
States.
Section
304(
m)
of
the
Clean
Water
Act
(
CWA)
requires
EPA
to
publish
an
Effluent
Guidelines
Program
Plan
every
two
years.
In
order
incorporate
the
Agency's
goal
of
reducing
the
number
of
impaired
waterbodies
into
effluent
guidelines
planning,
EPA
attempted
to
quantify
the
number
of
facilities
in
an
industrial
point
source
category
that
discharge
the
same
pollutant
(
or
class
of
pollutants)
that
is
causing
the
impairment
of
the
receiving
waterbody.
1
The
CWA
requires
states
to
identify
waters
not
meeting
water
quality
standards
and
to
develop
Total
Maximum
Daily
Loads
(
TMDLs)
for
those
waters
(
Section
303(
d)
of
the
CWA).
A
TMDL
is
essentially
a
prescription
designed
to
restore
the
health
of
the
polluted
body
of
water
by
indicating
the
amount
of
pollutants
that
may
be
present
in
the
water
and
still
meet
water
quality
standards.
More
than
20,000
bodies
of
water
across
America
have
been
identified
as
impaired
.
These
waters
include
more
than
300,000
river
and
shoreline
miles
and
five
million
acres
of
lakes.
EPA
estimates
that
more
than
40,000
TMDLs
must
be
established.
The
CWA
set
up
both
TMDLs
and
effluent
guidelines
as
complementary
regulatory
programs
as
both
are
necessary
for
restoring
the
quality
of
the
Nation's
waters
and
for
striving
towards
the
national
goal
of
eliminating
the
discharge
of
all
pollutants.
2A
major
facility
is
any
NPDES
facility
or
activity
classified
as
such
by
the
Regional
Administrator,
or,
in
the
case
of
approved
State
Programs,
the
Regional
Administrator
in
conjunction
with
the
State
Director.
Major
industrial
facilities
are
determined
based
on
specific
ratings
criteria
developed
by
EPA/
State.

3See
http://
www.
epa.
gov/
storet/.

4See
http://
www.
epa.
gov/
tri/.

5See
http://
www.
epa.
gov/
enviro/
html/
pcs/
index.
html.

Page
2
of
4
Impairments
Analyses
in
Current
Effluent
Guidelines
Program
Plan
For
the
Effluent
Guidelines
Program
Plan
for
2004/
2005,
EPA
linked
available
data
to
water
quality
impairments
with
point
sources
discharges.
EPA
focused
this
impaired
waters
analysis
on
those
point
source
dischargers
discharging
the
most
pounds
of
toxic
and
nonconventional
pollutants.
For
example,
if
a
"
major"
facility2
discharges
copper
or
a
"
minor"
facility
is
likely
to
discharge
copper,
and
the
facility
is
located
on
a
waterbody
that
is
impaired
for
copper,
the
facility
was
"
matched"
to
that
water
body.
Unfortunately,
the
current
analyses
linking
point
source
dischargers
to
impaired
waterbodies
is
limited
and
requires
improvement
for
future
effluent
guidelines
program
plans
(
see
"
Factor
1
Analysis:
Human
Health
and
Environmental
Impacts
­
Status
of
Screening
Level
Review
Phase,"
DCN
00545,
Section
2.1).

Impairments
Analyses
for
Future
Effluent
Guidelines
Program
Plans
The
current
impairment
analyses
only
identify
spatial
relationships
between
point
source
dischargers
and
impaired
waterbodies.
The
current
analyses
do
not
suggest
the
actual
correlations/
causal
relationships
between
point
source
dischargers
and
impaired
waterbodies.
EPA
will
need
to
conduct
more
analyses
before
determining
whether
there
is
any
actual
causal
relationship
between
industrial
point
sources
and
impaired
waters.
EPA
will
examine
the
possibility
of
using
the
STORET
(
data
STOrage
and
RETrieval
system)
database3
in
impairment
analyses
for
future
effluent
guidelines
program
plans.
STORET
is
EPA's
main
repository
of
water
quality
monitoring
data.
It
contains
water
quality
information
from
a
variety
of
organizations
across
the
country,
from
small
volunteer
watershed
groups
to
State
and
Federal
environmental
agencies.

In
particular,
EPA
will
attempt
to
use
the
Toxic
Release
Inventory
(
TRI)
4,
Permit
Compliance
System
(
PCS)
5,
and
STORET
databases
and
a
new
water
quality
standards
database
to
estimate
the
magnitude
of
the
pollutant
discharges
from
industrial
point
source
categories.
This
will
allow
EPA
to
rank
those
industrial
point
source
categories
with
the
largest
impact
on
impaired
waterbodies.
EPA
will
likely
use
a
simple
dilution
model
to
estimate
the
impact
of
pollutant
discharges
to
rivers
from
point
source
dischargers.
The
simple
dilution
model
is
described
in
Equation
1.
6The
7Q10
refers
to
the
lowest
consecutive
7
day
streamflow
that
is
likely
to
occur
in
a
ten
year
period.
It
is
often
used
in
setting
discharge
limits
in
National
Pollutant
Discharge
Elimination
System
(
NPDES)
water
quality
permits.

7See
http://
www.
epa.
gov/
wqsdatabase/
index.
html.

Page
3
of
4
Q
1*
C
1
+
Q
2*
C
2
=
Q
3
*
C
3
(
1)

Where,

Q
1
=
waterbody
flow
(
7Q10)
6
before
mixing
with
facility
effluent,
ft3/
s
C
1
=
ambient
pollutant
concentration
in
watebody
before
mixing
with
facility
effluent,
mg/
L
Q
2
=
facility
effluent
flow,
ft3/
s
C
2
=
pollutant
concentration
in
facility
effluent,
mg/
L
Q
3
=
waterbody
flow
after
mixing
with
facility
effluent,
ft3/
s
C
3
=
pollutant
concentration
in
watebody
after
mixing
with
facility
effluent,
mg/
L
Since
the
waterbody
flow
after
mixing
with
facility
effluent
(
Q
3)
is
the
sum
of
the
waterbody
flow
before
mixing
with
facility
effluent
(
Q
1)
and
the
facility
effluent
(
Q
2),
Equation
1
can
rewritten
as:

C
3
=
[
Q
1
*
C
1
+
Q
2*
C
2]/[
Q
1
+
Q
2]
(
2)

EPA
will
use
STORET
to
estimate
waterbody
flow
before
mixing
with
facility
effluent
(
Q
1)
and
ambient
pollutant
concentration
in
watebody
before
mixing
with
facility
effluent
(
C
1).
EPA
will
use
the
TRI
and
PCS
databases
to
estimate
facility
effluent
(
Q
2)
and
pollutant
concentration
in
facility
effluent
(
C
2).

EPA
will
then
attempt
to
compare
the
pollutant
concentration
in
watebody
after
mixing
with
facility
effluent
(
C
3)
with
the
applicable
water
quality
criteria
from
the
new
Water
Quality
Standards
Database
(
WQSDB).
7
At
this
time,
the
WQSDB
contains
criteria
for
Missouri
and
Mississippi
and
EPA
is
working
to
include
data
from
Florida
and
Illinois.
EPA
expects
that
data
from
Florida
and
Illinois
to
be
integrated
into
the
WQSDB
by
September
2004.
If
the
WQSDB
program
receives
sufficient
funding,
it
will
take
at
least
3
years
(
as
early
as
2005
to
2007)
to
incorporate
water
quality
criteria
for
all
states
into
the
database.
After
the
WQSDB
is
sufficiently
complete,
EPA
will
attempt
to
rank
industrial
point
source
categories
based
this
comparison
of
the
pollutant
concentration
in
watebody
after
mixing
with
facility
effluent
with
the
applicable
water
quality
criteria.
8See
http://
www.
epa.
gov/
watertrain/
hydrogis.
html.

Page
4
of
4
Limitations
of
Simple
Dilution
Model
The
actual
number
of
facilities
discharging
to
impaired
waters
is
currently
unknown
and
can
only
be
estimated
from
PCS
and
TRI.
There
are
significant
data
limitations
is
these
databases
(
see
"
Factor
1
Analysis,
DCN
00545,
Section
2.1).
EPA
is
working
to
address
these
data
limitations
in
future
effluent
guidelines
planning.
Moreover,
the
effect
of
upstream
facilities
(
and
non­
point
sources)
are
not
included
in
this
simple
dilution
model.
Additionally,
ambient
water
quality
flow
and
pollutant
concentration
data
must
be
estimated
from
nearby
stream­
gaging
and
monitoring
stations.
Results
from
the
simple
dilution
model
will
be
limited
by
the
extrapolation
methods
used
to
estimate
ambient
water
quality
flow
and
pollutant
concentration
data.

There
are
also
limitations
in
water
quality
monitoring
data.
In
particular,
not
all
pollutants
are
monitored
at
each
water
quality
monitoring
station
and
many
pollutants
do
not
have
approved
water
quality
criteria.
Finally,
EPA
is
working
to
develop
a
database
listing
the
approved
water
quality
standards
for
each
waterbody
segment.
Currently
only
a
few
states
have
their
approved
water
quality
standards
in
EPA's
new
water
quality
standards
database.

Next
Steps
EPA
will
continue
to
populate
the
WQSDB
with
data
from
the
States.
Additionally,
EPA
will
continue
to
replace
missing
data
in
the
TRI,
PCS,
and
STORET
databases
to
enable
EPA
to
conduct
future
impairments
analyses.
Finally,
EPA
will
enhance
the
TRI,
PCS,
STORET,
and
WQSDB
databases
to
ensure
that
they
are
linked
to
the
National
Hydrography
Dataset
(
NHD)
8
and
linkable
with
each
other
for
future
impairments
analyses.
EPA
will
not
be
able
to
perform
this
analysis
in
the
current
effluent
guidelines
planning
cycle
but
will
continue
to
explore
the
use
of
the
TRI,
PCS,
STORET,
and
WQSDB
databases
for
estimating
impacts
of
point
sources
on
impaired
water
bodies
in
future
planning
cycles.
