EPA
United Starts
Environmental Protection
Agency
Offica of Water
Regulations and Standards
Washington, OC 20460
EPA 440/538/009
September 1988
Water
Intermittent Streams
Water Quality Standards
Criteria Summaries:
A Compilation
of State/Federal Criteria
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DISCLAIMER
This publication was prepared by Battelle under contract to
the U.S. Environmental Protection Agency (Contract 68^03-3534).
Secondary information sources were used to compile data presented
in this document. Each State was given an-opportunity to review
and provide comments on a draft of this information document. In
no event shall either the United States or Battelle have any
responsibility or liability for any use, misuse, or reliance upon
the information contained herein, nor does either warrant or
otherwise represent in any way the accuracy, adequacy, efficacy
or applicability of the contents hereof.
The reader should consult the water quality standards of a
particular State for exact regulatory language applicable to that
State. ' Copies of State water quality standards may be obtained
from the State's Water Pollution Control Agency or its
equivalent.
Additional' information may also be obtained from the:
Standards Branch
Criteria and Standards Division (WH-585)
Office of Water Regulations and Standards
U.S. Environmental Protection Agency
Washington, D.C. 20460
202-475-7315
This document may be obtained only from the National Technical
Information Service (NTIS) at the following address:
National Technical Information Service
5285 Front Royal Road
Springfield, Virginia 22161
703-487-4650
The NTIS order number is: PB89-141410
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INTRODUCTION
This digest is compiled to provide general information to the public as veil
as to Federal, State, and local officials. It contains excerpts from the
individual Federal-State vater quality standards establishing pollutant
specific criteria for interstate surface waters. The vater quality standards
program is implemented by the U. S. Environmental Protection Agency vhere
responsibility for providing vater quality recommendations, approving
State-adopted standards for interstate vaters, evaluating adherence to the
standards, and overseeing enforcement of standards compliance, has been
mandated by Congress.
Standards, a nationvide strategy for surface vater quality management, contain
three major elements: the use (recreation, drinking vater, fish and vildlife
propagation, industrial, or agricultural) to be made of the navigable vater;
criteria to protect these uses; and an antidegradation statement to protect
existing high quality vaters, from degradation by the addition of pollutants.
Guidance for the development of standards by individual States is contained'in
tvo EPA documents entitled Water Quality Standards Handbook (1983) and Quality
Criteria for Water (1986). : ' waxny
Intermittent streams provisions and policies in State vater quality standards
are the subject of this digest. These provisions and policies are included
into the standards vhen a State vishes to qualify the applicability of its
vater criteria to intermittently lov flov streams. The Agency has recommended
that vater quality standards should protect specified uses of a vatervay in
critical lov flov .situations.* Additionally, for intermittent streams, the
Agency recommends criteria be adopted to that extent necessary to assure that
conditions in the streams- or stream beds vill not impair existing or
designated uses in the stream or in dovnstream vaters.
Since vater quality standards experience revisions and upgrading from time to
time, folloving procedures set forth in the Clean Water Act, individual
entries in this digest may be superseded. As these revisions are accomplished
and alloving for the states to revise their standards accordingly, this digest
vill be updated and reissued. Because this publication is not intended for
use other than as a general information resource, to obtain the latest
information and for special purposes and applications, the reader needs to
refer to the current approved vater quality standards. These can be obtained
from the State vater pollution control agencies or the EPA or Regional Offices.
* Guidelines for State and Areavide Water Quality Management Program
Development; Chapter 5, Water Quality Standards.
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REFERENCES
19 Maine Water Classification Program, Maine Revised Statutes Annotated,
• Title 38, Article 4-A, State of Maine Department of Environmental
Protection, May, 1987, p. 10.
31 Water Quality Standards for Interstate and Intrastate Streams in Nev
Mexico, State of New Mexico Water Quality Control Commission, 1988.
40 South Carolina Water Classifications and Standards, Regulation 61-68,
Office of Environmental Quality Control, South Carolina Department of
Health and Environmental Control, 1985.
42 Tennessee's Water Quality Criteria and Stream Use Classifications for
Interstate and Intrastate Streams, Tennessee Water Quality Control Board:
Department of Health and Environment, 1987.
43 Texas Surface Water Quality Standards, . Texas Water Commission, Rule
Change, 1988.
44 Utah Standards of Quality for Waters of the State, Wastewater Disposal
Regulations: Part II, State of Utah Department of Health: Division of
Environmental Health, 1988.
48 Water Quality Standards, West Virginia Legislative Rules, State Water
Resources .Board, 1985. ' - >
ENVIRONMENT REPORTER, The Bureau of National Affairs, Inc. Washington, D.C.
20037
1 Pages 701:1008-1010, June 26, 1981
3 Page 711: 1005, February 7, 1986
4 Page 716:1005, August 30, 1985
6 Page 726:1005, March 22, 1985
7 Page 731:1003, May 14, 1982
8 Pages 736:1001-1002, March 28, 1986
10 Page 751:0505, December 27, 1985
13 Pages 766:0504-0505, March 28, 1986
14 Page 771:1002, January 10, 1986
15 Page 776:1004, February 13, 1987
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16 Page 781:1003, March 27, 1987
*8 Pages 791:1003-1004, January 18, 1982
19 Page 796:0521, January 23, 1987
20 Page 801:1004, April 19, 1985
21 Pages 806:1002-1003, June 21, 1985
22 Page 811:1008, February 13, 1987
23 Page 816:1003, June 25, 1983
24 Page 821:1001, October 25, 1985
26 Page 831:1011, October 4, 1985
27 Page 836:1002, March 27, 1987
28 Page 841:1013, February 22, 1985
29 Page 846:1002, October 5, 1984
30 Page 851:1004, April 11, 1986
33 Page 866:1006» September 6, 1985
34 Page 871:1003, June 7, 1985
36 Page 881:1002, September 26, 1986
37 Page 891:1003, August 9, 1985
39 Page 901:1006, August 9, 1985
41 Page 911:003, March 22, 1985
45 Page 931:1004, March 22, 1985
46 'Page 936:1002, February 28, 1986
49 Page 951:1003, December 19, 1986
50 Page 956:1004, July 5, 1985
52 Page 741:1005, March 28, 1986
55 Page 896:1002, December 23, 1983
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State and Water Use
Intermittent Stream Policy
Alabama1
Agricultural and
Industrial Water
Supply & Indus-
trial Operations
& Navigation
This category includes vatercourses in vhich natural
flov is intermittent and non-existent during droughts
and vhich may,.of necessity receive treated wastes
from existing municipalities and industries, both now
and in the future. In such instances, recognition
must be given to the lack of opportunity for mixture
of the treated wastes with the receiving stream for
purposes of compliance. It is also understood in
considering waters for this classification that urban
runoff or natural conditions may impact any waters so
classified.
Alaska"
Not specified
Arizona"
When the flow in a natural watercourse, that would
otherwise be dry at that time and place, is effluent
from a wastewater treatment facility or agricultural
irrigation return flow or combination thereof, the
Council may, upon application by the discharger
determine that all or part of R9-21-208 does not apply
where the council finds that such entire flow does not
present, a substantial danger to the health of .the
public.
Arkansas
Specific standards (Section 6, Regulation No. 2, As
Amended "Regulation Establishing Water Quality
Standards for Surface Waters of the State of
Arkansas") shall apply at all times except during
periods when flows are less than the average minimum
7-day flow which occurs once in ten years (Q7-10).
Streams with regulated flow will be addressed on a
case-by-case basis to maintain designated instream
uses. These standards apply outside the mixing zone
to conditions resulting in frequent, persistent or
long-term modification of the water quality and are
not applicable to naturally-occuring excursions'
outside the standards.
California'
Colorado6
Not specified
Low Flow Exceptions - Water quality standards shall
apply at all times except vhere surface waters are
below the empirically based average 30-day low flow
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State and ¥ater Use Intermittent Stream Policy
vith am average l-in-3-year recurrence interval for
chronic (30-day) standards or the empirically based
1-day low flow with an average l-in-3--year recurrence
interval for acute (1-day) standards, or the
equivalent statistically-based flow. For certain
substances, such as ammonia, the low flow exceptions
may be based on periodic or seasonal flows. The
length of the periods will be determined on a
case-by-case basis by the Division. •
Connecticut The minimum average daily flow for seven consecutive
days that can be expected to occur once in ten years
under natural conditions is the minimum flow to which
the standard for surface water apply, except when a
stream has been historically regulated to result in
low flows below that level, in which case the
standards apply to the absolute low flow resulting
from such regulation.
Q
Delaware, , In water which do not meet certain water quality
standards or support certain designated uses, the
Department may propose that specific standards and/or
uses be downgrades. Any such action may be taken only
after a public hearing is held pursuant to 7 Del.C,
6006. Justification for' .such action may include:
'Natural, ephemeral, intermittent or low flow
conditions or water levels inclusive of existing or
proposed discharge flows, where lack of water prevents
the attainment of the use.
Critical Flows - For the following situations, the
numerical and narrative water quality criteria
contained in this document (with exceptions noted
below) shall not apply:
(a) For perennial freshwater streams, at those
times when the flow in the stream falls below that
value that is equal to the flow of seven-day duration
with recurrence interval of 10 years (generally know
as the 7Q10 or the Q7-10).
Exceptions: All waters under (a) above shall be
free of the materials and substances as listed in
Section 5.5 (a) through (e).
q
Florida Not specified
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State and Water Use
Georgia
10
Intermittent Stream Policy
Streamflovs - Specific criteria or standards set for
the various parameters apply to all flows on regulated
streams. On unregulated streams, they shall apply to
all stream-flows equal to or exceeding to 7-day,
10-year minimum flow.
Hawaii11
Not specified
Idaho
12
Not specified
Illinois
13
Stream Flows - Except as otherwise provided in this
Chapter with respect to temperature, the water quality
standards in this Part shall apply at all times except
during periods when flows are less than the average
minimum seven day flow which occurs once in ten years.
Indiana14
All water quality standards in Section 6 of this
Regulation, except those provided in subsection 6(a),
will cease to be applicable when the stream flows are
less than the average minimum seven-consecutive-day
low flow which occurs once in ten years. This
determination will be made- using "Low-Flow
Characteristics of Indiana Streams" by Paul B. Rohn,
Jr., 1978, United States Department of Interior,
Geological Survey, or any additional information
compiled on a comparable basis.
Iowa
15
Implementation strategy - These water quality
standards shall be met at all times when the flow of
the receiving stream equals or exceeds the average
seven-day low flow which occurs once in ten years.
^Exceptions may be made for intermittent or low flow
streams. Where intermittent or low flow streams are
classified for class B aquatic life protection the
department may waive the seven-day, ten-year low flow
requirement and establish a minimum flow in lieu
thereof.
Kansas
16
Low Flow - Classified surface waters shall be excluded
from the application of K.A.R. 28-16-28e(c) when the
receiving stream flow is less than the greater of the
seven-day 10-year low flow, or 1.0 cfs. The low flow
exclusion shall also include consideration of the
minimum desirable stream flov established pursuant to
K.S.A. 82a-703(a).
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State and ?ater Use
Intermittent Stream Policy
Kentucky
17
On occasion surface water quality may be outside of
the limits established to protect designated uses
because of natural conditions. When this condition
occurs during periods vhen stream flows are below the
low flow which is used by the cabinet to establish
effluent limits for wastewater treatment facilities
consistent with the definition contained in 401 KAR
5:029, Section l(l)(n), a discharger shall not be
considered a contributor to instreara violations of
water quality standards, provided that treatment in
compliance with permit requirements is maintained.
Louisiana
18
Intermittent Stream Policy - Certain watercourses may
be considered for application of an excepted water use
classification of the basis of being an intermittent
stream. Only those streams which have low flow
conditions or water levels that preclude the
attainment of recreation and the propagation of
desirable species of fish and wildlife will be
considered for classification as intermittent. At a
minimum, the "General Criteria" of these Standards
shall apply to all watercourses approved as
intermittent streams.
An intermittent stream is defined as a natural
watercourse which because of natural conditions, of
flow, width' and depth preclude the attainment of
recreational uses and the propagation of a balanced
population of aquatic fauna. Such streams because of
one or more of these conditions provide only an
ephemeral aquatic habitat which is not conducive to
the establishment of a balanced population of aquatic
biota or to the support of recreational activities.
This definition does not include those watercourses
that contain enduring pools which support recreational
uses and contain desirable species of aquatic biota or
watercourses which are subject to tidal effects and
may contain standing water with no flow during periods
of slack tide.
In order for a stream .to be considered for this
excepted water use classification the stream must not
have a duffi-' ^t drainage area to maintain a
perennial flow and/or the 7Q10 for the stream must be
less than a projected or measured 0.1 cfs. The no
flow condition must be natural and not a result of
man's activities. The no flow condition is generally
characterized by dry stream reaches during dry weather
conditions; however, the watercourse may exhibit flow
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State and Vater Use Intermittent Stream Policy
or contain pools for short periods after rainfall.
The State administrative authority and the EPA must
approve and designate a stream for the intermittent
classification. Candidate streams for intermittent
status will be considered on a case-by-case basis. To
be approved as intermittent, a watercourse must meed
the conditions belov:
1. The watercourse is not used as a source of public
water supply
2. The watercourse is not used for water contact
recreation to any reasonable extent.
3. The watercourse is not used for preservation or
propagation of desirable species of aquatic biota
such as indigenous species of fish, shellfish and
wildlife to any reasonable extent and does not
have a reasonable potential for such purposes as
determined by the Louisiana Department of
Wildlife and Fisheries.
In the event that a wastewater discharge is proposed
for an approved and designated intermittent stream the
following conditions must be met:
1. The discharge will not by itself or in conjunction
with other discharges violate the "General
Criteria" of State of Louisiana Water Quality
Standards.
2. The discharge will not by itself or in conjunction
with other discharges violate the numerical
criteria of any perennial stream which receives
water from an intermittent stream.
3. The discharge will be disinfected to protect from
health hazards that may result from inadvertent
primary contact.
19
Minimum Flow - Regulated Rivers and Streams - For
regulated rivers and streams, the Department may
establish a minimum flow necessary to maintain water
quality standards. This flow will be based upon
achieving the assigned classification, criteria and
protection of the uses of the stream. The Department
will cooperate with appropriate Federal, State and
private interests in the development and maintenance
of stream flow requirements.
For the purpose of computing whether a discharge will
violate the classification of any river or stream, the
assimilative capacity of the river or stream shall be
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State and ¥ater Use
Intermittent Stream Policy
computed using the minimum 7-day low flow which can be
expected to occur with a frequency of once in 10
years.
Maryland
20
1. Discharges to intermittent streams are not
permitted when feasible alternatives are available.
2. Effluent limitation for discharges to specific
intermittent streams may be determined by the
Department on a case-by-case basis.
3. Effluent
than:
a.
limitations may not be less stringent
The minimum national effluent guidelines
established under the Federal Act; or
Those levels necessary to maintain the water
quality standards of downstream segments; or
Those levels necessary to protect the
biological community of the intermittent
stream.
Those levels necessary to protect p.ublic
health.
Hassachusetts
21
Hydrologic Conditions - The division will determine
the most severe hydrologic condition at which water
quality standards must be met. In classifying the
inland surface waters and in applying these standards
to such waters, the critical low flow condition at and
above which these standards must be met is the average
minimum consecutive seven day flow to be expected once
in ten years, unless otherwise stated by the Division
in these standards. In artificially regulated waters,
the critical low flow will be established by the
Division through agreement with the Federal, State or
private interest controlling the flow. The minimum
flow established in such agreement will become the
critical low flow under this section for those waters
covered by the agreement.
Protection of Low Flow Waters - Certain waters will be
designated by the Division in Regulation 5.5 of these
standards for protection under this section due to
their inability to accept pollutant discharges. New
or increased discharges of pollutants to waters so
designated are prohibited unless a variance is granted
by the Division as provided in 314 CMR 4.04(6).
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State and Water Use Intermittent Stream Policy
22
Michigan Water quality standards shall apply at all flows equal
to or exceeding the design flow. The design flow is
equal to the most restrictive of the 12 monthly 95%
exceedance flows, except where the commission
determines that a more restrictive design flow is
necessary or where the commission determines that
seasonal design flows may be granted pursuant to R
323.1090(4). The 95Z exceedance flow is the flow
equal to or exceeded 95% of the time for the specified
month.
23
Minnesota Discharges of sewage, industrial waste or other waste
effluents shall be controlled so that the water
quality standards will be maintained at all stream
flows which are equal to or exceeded by 902 of the
seven consecutive daily average flows or record (the
lowest weekly flow with a once in ten year recurrence
interval) for the critical month(s). The period of
record for determining the specific flow for the
stated recurrence interval, where records are
available, shall include at least the most recent ten
years of record, including flow records obtained after
establishment of flow regulation devices, if any.
Such calculations shall riot be applied to lakes and
their embayments which have no comparable flow
recurrence interval. Where stream flow records are
not available, • the flow may be estimated on the basis
of available information on the watershed
characteristics, precipitation, run-off and other
relevant data.
Allowance shall not be made in the design of treatment
works for low stream flow augmentation unless such
flow augmentation of minimum flow is dependable and
controlled under applicable laws or regulations.
Mississippi All criteria contained herein shall apply to all
stages of streamflow greater than or equal to the
7-day, 10-year minimum flow in unregulated, natural
streams, and the legally guaranteed minimum flow in
regulated streams. This requirement shall not be
interpreted to pe=^..,it any unusual waste discharges
during periods of lower flow.
25
Missouri Not specified
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State and Vater Use
Montana
26
Intermittent Stream Policy
Until such time as minimum stream flovs are
established for devatered streams, the minimum
treatment requirements for discharges to devatered
receiving streams must be no less than the minimum
treatment requirements set forth in ARM 16.20.631 (2)
& (3).
Nebraska
27
These standards, except criteria associated with
aesthetics and public health (Chapter 4-005), will not
apply to:
1. Waters during periods vhen the flov is less than
0.1 cfs or the 7-day, 10-year low flow, unless an
assigned beneficial use still exists under these
conditions. Flow conditions apply to rivers and
streams and not to lakes and resevoirs.
2. Effluent dominated streams during periods when the
daily flow is totally composed of effluent, excluding
minor amounts of bank seepage.
Nevada
28
The specified standards are not considered violated
when the natural conditions of the receiving water are
outside the established limit, including periods of
extreme high or low flow. Where effluents are
discharged to such waters, the discharges are not
considered a contributor to substandard conditions
provided maximum treatment in compliance with permit
requirements is maintained.
79
Nev Hampshire
Low Flow - The water quality standards appearing in
RSA 149s3-1, II, and III and in Ws 432 shall apply at
all times except during periods when receiving stream
flows are less than the minimum average seven day flow
which occurs once in 10 years (7 Q 10).
New Jersey'
.30
Water quality criteria are expected to be maintained
during periods when stream flows are at or greater
than the MA7CD10 flow.
Water quality criteria are expected to be maintained
in intermittent streams during all natural flow
conditions. When the intermittent stream does not
contain natural flow of sufficient magnitude to
determine water quality, the criteria to be maintained
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State and Water Use Intermittent Stream Policy
in the intermittent stream vill be those pertaining to
the measurable .natural flov immediately downstream of
the intermittent stream.
31
Nev Mexico The general standards and numeric standards may not be
attainable vhen streamflow is less than critical low
flow .of the stream in question. The critical low flow
of a stream at a particular site is the minimum
average seven consecutive day flow which occurs with
a frequency of once in ten years (7Q10). Critical
low-flow numeric values may be determined on an
annual, a seasonal or a monthly basis, as appropriate,
after due consideration of site-specific conditions.
32
New York Not specified
33
North Carolina The governing flow criterion for water quality
standards except toxic substances, generally shall be
the minimum average flow for a period of seven
consecutive days that has an average recurrence of
once in 10 years (7Q10).
These governing criteria are established specifically
for setting effluent limitations and for the design of
wastewater treatment facilities. In addition, the
governing flow also establishes a value below which
deviations from water quality standards can be
anticipated.
/s /
North Dakota When The flow in the stream is less than the ten-year,
seven-day low flow level, the department reserves the
right to make a case-by-case evaluation of application
of these standards. However, no substances shall be
present in concentrations or combinations that
materially interfere with, or prove hazardous to, the
intended water usage.
Ohio35 Not specified
Oklahoma Numerical standards apply at all times downstream from
the mixing zone and within the zone of passage for all
waters of the State except in two instances:
1. When a discharge into a primary warm water
fishery or a secondary warm water fishery
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State and Water Use
Intermittent Stream Policy -
complies with and meets the discharge permit
limitations but the flov immediately upstream
from the discharge is less than one (1) cubic
foot per second (cfs) or vhen the flow falls
below the 7-day, 2-year, low-flow, whichever is
larger.
2. When the low-flow is unknown or less than the
larger of the 7-day, 2-year, low-flow or 1 cfs, a
dilution flow of the larger of 1 cfs or the
7-day,2-year, low-flow will be assumed for
permitting and enforcement activities except for
seasonal criteria which apply at other than
summer conditions. If more than one narrative or
numerical criterion is assigned to a stream, the
most stringent shall be maintained.
Oregon
37
Not specified
38
Pennsylvania
The accepted design stream flow, to which the water
quality criteria as set forth in this chapter shall
apply, is the actual or estimated lowest
seven-consecutive-day average flow that occurs once in
ten years for .a stream with unregulated flow, or the
estimated minimum flow for a stream with regulated
flows, except where the Department determines that a
more restrictive application is necessary to protect a
particular designated or existing use. Where the
lowest seven-consecutive-day average flow that occurs
once in ten years is zero, the Department shall
specify the design flow based on the- identified or
estimated flow at that point where a use identified in
section 93.4 of this title (relating to statewide
water uses) becomes possible.
Rhode Island
39
The water quality standards apply under the most
adverse conditions, as determined by the Director
according to sound engineering and scientific
practices. For fresh water, most adverse conditions
shall include a minimum average daily flow for seven
consecutive days that can be expected to occur once in
ten years. for tidal waters, most adverse conditions
shall mean when the most unfavorable hydrographic and
pollution conditions occur at the particular point of
evaluation.
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State and Water Use
South Carolina
40
Intermittent Stream Policy
Intermittent streams and ephemeral streams shall be
considered waters of the State. The use
classification' and numeric standards of the class or
the stream to which intermittent and ephemeral streams
are tributary shall apply, disregarding any
site-specific numeric standards for that tributary.
South Dakota'
41
Flow rates for high quality waters - When flow in
streams classified for the beneficial use of coldwater
permanent fish life propagation, coldwater marginal
fish life propagation, or warmwater permanent fish
life propagation falls below the minimum 7-day average
flow that can be accepted to occur once in every 25
years, water quality criteria set forth in 74:03:02:33
to 74:03:02:45, inclusive, do not apply to the water
but applicable effluent regulations remain in force.
Flow rates for low quality fishery waters - When the
flow in streams classified for the beneficial use of
warmwater semipermanent fish life propagation falls
below the minimum seven day average flow that can be
expected to occur once in every five years or 1.0
cubic foot per second, whichever is greater, water
quality criteria set forth in 74:03:02:33 to
74:03.: 02:45, inclusive, do'not apply to the water but
any applicable effluent regulations remain in force.
Tennessee
42
The criteria set forth shall be applied on the basis
of the following stream flows:
Unregulated Streams - stream flows equal to or
exceeding the 3-day minimum, 20-year recurrence
interval;
Regulated Streams - all flows in excess of the minimum
critical flow occurring once in twenty (20) years as
determined by an analysis of records of operation and
approved by the Commissioner or the Tennessee
Department of Health and Environment.
Wet Weather Conveyance - Wet weather conveyances are
natural watercourse, including natural watercourse
that have been modified by channelization, that flow
only in direct response to precipitation in'their
immediate locality and whose channel are above the
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State and Vater Use Intermittent Stream Policy
groundwater table and vhich do not support fish or
aquatic life and are not suitable for drinking water
supp'lies. Statutory Authority: T.C.A. Section
4-5-202, T.C.A. Section 69-3-105.
Texas (a) Low-flow conditions.
(1) The following standards do not apply .below seven-
day, two-year low flows in unclassified waters, or
below low-flow conditions specified in Appendix B of
§307.10 of this title (relating to Appendices A
through C) for designated segments:
(A) site-specific criteria, as defined in §307.7 of
this title (relating to Site-specific Criteria and
Uses) and listed for each classified segment in
Appendix A of §307.10 of this title (relating to
Appendices A through C);
(B) numerical chronic criteria for toxic materials as
established in §307.6 of this title (relating to Toxic
Materials);
(C) total chronic toxicity restrictions as
established in §307.6 of this title (relating to Toxic
Materials); and •
(D) maximum temperature differentials as established
in §307.4(f) of this title (relating to General
Criteria).
(E) dissolved oxygen criteria for unclassified
waters, as established in §307.4(h) of this title
(relating to General Criteria).
(F) dissolved oxygen criteria for intermittent
streams and barge canals, as established in §307.4(j)
of this title (relating to General Criteria).
(G) fecal coliform criteria for unclassified waters,
as established in §307.4(k) of this title (relating to
General Criteria).
(2) Numerical acute criteria for toxic materials and
preclusion of total acute toxicity as established in
§307.6 of this title (relating to Toxic Materials) are
applicable at all flow conditions.
(3) Low-flow criteria in Appendix B of §307.10 of
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State and Water Use
Intermittent Stream Policy
this title (relating to Appendices A through C) are
solely .for the,:purpose of defining the flow conditions
under whi'ch water quality standards apply to a given
water body. Low-flow criteria listed in Appendix B of
§307.10 of this title (relating to Appendices A
through C) are not for the purpose of regulating flows
in water bodies in any manner, or requiring that
minimum flows be maintained in classified segments.
(4) Low-flow criteria defined in this section and
listed in Appendix B of §307.10 of this title
(relating to Appendices A through C) apply only to
river basin and coastal basin waters. They do not
apply to bay or gulf waters or reservoirs or estuaries.
Utah
44
(5) Seven-day, two-year low flows (7Q2) in Appendix B
of §307.10 of this title (relating to Appendices A
through C) were calculated from historical U.S.
Geological Survey (USGS) daily streamflow records
where available. Where a USGS flow station was not
located at a commission monitoring station, the
low-flow condition was interpolated/ extrapolated from
the nearest comparable USGS stations. The low-flow
criterion was set at 0.1 of one cubic foot per second
(fts/s) when the calculated 7Q2 was equal to or less
than 0.1 of one. ft,/s. •
(6) Flow values will be periodically recomputed to
reflect alterations in the hydrologic characteristics
of a segment, including reservoir construction,
climatological trends, and other phenomena.
(7) The general criteria are applicable at all flow
conditions except as specified in this section or in
§307.4 of this title (relating to General Criteria).
Intermittent Waters - Failure of a stream to meet
water quality standards when stream flow is either
unusually high or less than the 7-day, 10-year minimum
flow shall not be cause for action against persons
discharging wastes which meet both the requirements of
PART I of these regulations and the requirements of
applicable permits.
Vermont
45
Unregulated Waters - The applicable water quality
criteria shall apply at all times except when the
average daily flow is less than the seven day low
flow, ten year return period (7Q10). This rule shall
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State and Water Use
Intermittent Stream Policy
not be construed to allow less than the normal design
operation of any wastevater treatment facility during
periods of low stream flow or to otherwise waive the
terms of any permit issued under the Act.
Regulated Waters - The applicable water quality
criteria shall apply at the agreed minimum flow, or
7Q10, .which ever is less. In the absence of such an
agreement, the water quality criteria shall apply at
the absolute low flow resulting from regulation, or
7Q10, whichever is less.
Virginia46
Stream Standards shall apply whenever flows are equal
to, or greater than, the lowest flow which, on a
statistical basis, would occur for a 7-consecutive-day
period once every 10 years.
Washington
47
Not specified
Vest Virginia'
48
Water quality standards shall not apply in wet weather
streams (or intermittent streams, when they are dry or
have no measurable flow) provided that the designated
uses of downstream waters are not adversely affected.
Wisconsin
49
Water quality standards will not be maintained under
all natural occurrences of flow, temperature or other
water quality characteristics. The design of water
quality related effluent limitations or other
management practices shall be based upon:
a. The average minimum 7-day low stream flow which
occurs once in 10 years (7-day QIO)> or
b. In the case of dissolved oxygen and wherever
sufficient data on stream flow and temperature
are available, by application of a 0.274% level
of nonattainment. this is equivalent to an
expected nonattainment of the dissolved oxygen
criterion of one day per year.
Wyoming
.50
Where stream flow data are available, these standards
shall apply at all times except during periods when
flows are less than the average of the minimum seven
consecutive day flow which has the probability of
occurring once in ten years.
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State and Water Use Intermittent Stream Policy
During periods when stream flows are less than the
minimums .described above, the Wyoming Game and Fish
Department and the Department may require the
discharger to institute operational modifications as
necessary to Insure the protection of aquatic life.
Where stream flow data are not available, the
Department must take into consideration the possible
existence of markedly abnormal flows when determining
violations of these standards.
In addition, Sections 15, 16, 17 and 28 shall apply at
all stream-flow conditions.
American Samoa Not specified
District of Columbia52 The numerical standards shall not apply at flows less
than the average seven (7) day low flow which has a
. . - probability of occurrence of once in ten (10) years.
53
Guam Not specified
$4
Mariana Islands Not specified . '
Puerto Rico Water Quality standards shall apply at all times,
except in surface waters during periods when their
flows are less than the average minimum seven day lov
flow which occurs once in any two consecutive years.
Trust Territory Not specified
Virgin Islands57 Not specified
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