TITLE 35: ENVIRONMENTAL PROTECTION
SUBTITLE C: WATER POLLUTION
CHAPTER II: ENVIRONMENTAL PROTECTION AGENCY
PART 378
EFFLUENT DISINFECTION EXEMPTIONS
SUBPART A: INTRODUCTION
Section
378.101 Purpose, Scope and Applicability
378.102 Definitions
378.103 Application Requirements
SUBPART B: PROTECTED WATER STATUS AND EXEMPTION REQUIREMENTS
Section
378.201 Year-Round Protected Waters
378.202 Seasonally Protected Waters
378.203 Unprotected Waters
378.204 Assessment of Waters for Protected Status
SUBPART C: FECAL COLIFORM DIE-OFF MODEL
Section
378.301 Die-off Equation
378.302 Cumulative Effects of Multiple Sources
APPENDIX A First Order Die-off Equation
APPENDIX B Application of the Die-off Equation
APPENDIX C Discharge and Travel Time Estimation
APPENDIX D Manning Equation
APPENDIX E Field Assessment of Die-off Rate Constant
AUTHORITY: Implementing and authorized by Sections 4, 11 and 39 of the
Environmental Protection Act (Ill. Rev. Stat. 1987, ch. 111 1/2, pars.
1004, 1011, and 1039).
SOURCE: Adopted at 13 Ill. Reg. 1190, effective January 17, 1989.
SUBPART A: INTRODUCTION
<BSection 378.101 Purpose, Scope and Applicability>>
a) The purpose of this Part is to establish requirements for
determining which National Pollutant Discharge Elimination System
(NPDES) permit dischargers may cease effluent disinfection on a
seasonal or year-round basis pursuant to standards established by
the Pollution Control Board (Board) at 35 Ill. Adm. Code 302.202,
302.209, 302.306 and 304.121.
b) This Part shall apply to National Pollutant Discharge Elimination
System permit dischargers which must comply with the fecal
coliform effluent standard of 35 Ill. Adm. Code 304.121. This
Part does not apply to discharges governed by 35 Ill. Adm. Code
306.305 or to discharges with fecal coliform limitations imposed
by any federal regulations pursuant to 35 Ill. Adm. Code 309.141.
c) The standards established by the Pollution Control Board allow
that waters unsuitable for primary contact activities, unlikely to
allow incidental contact due to remoteness from any parks or
residential areas, and unutilized for public and food processing
water supply are exempt from fecal coliform water quality
standards. National Pollutant Discharge Elimination System permit
dischargers which affect these waters may be eligible for an
exemption from 35 Ill. Adm. Code 304.121.
d) National Pollutant Discharge Elimination System permit discharges
which may prevent protected waters from complying with fecal
coliform water quality standards must continue to comply with the
fecal coliform effluent standard of 35 Ill. Adm. Code 304.121. In
order to be protected, waters must presently support or have
physical characteristics to support primary contact activities,
flow through or adjacent to parks or residential areas, or be
utilized for public and food processing water supply.
e) Exemption determinations will include consideration of potential
impacts on interstate waters.
<BSection 378.102 Definitions>>
All terms shall have the meanings set forth in the Environmental Protection
Act except, for purposes of this Part, the following definitions apply:
"Act" means the Environmental Protection Act (Ill. Rev. Stat.
1987, ch. 111 1/2, pars. 1001 et seq., as amended).
"Agency" means Illinois Environmental Protection Agency.
"Board" means Illinois Pollution Control Board.
"NPDES permit" means a permit issued under the National
Pollutant Discharge Elimination System under Section 39 of
the Act and Section 402 of the Clean Water Act, (33 U.S.C.A.
Section 1251 et seq.).
"Primary contact" means any recreational or other water use
in which there is prolonged and intimate contact with the
water involving considerable risk of ingesting water in
quantities sufficient to pose a significant health hazard,
such as swimming and water skiing.
"Residential areas" means any collection of dwellings, such
as cities, towns, and subdivisions.
"Year-round" refers to the full twelve months of the year.
<BSection 378.103 Application Requirements>>
The Agency will consider an exemption from the fecal coliform effluent
limitations of 35 Ill. Adm. Code 304.121(a) only when the holder of an
NPDES permit submits to the Agency a Disinfection Exemption Request. The
request, at a minimum, shall demonstrate and document the following:
a) The character of the receiving waters pursuant to 35 Ill. Adm.
Code 302.202, 302.209, and 302.306 in accordance with Section
378.204.
b) The discharge will not cause downstream waters to exceed
applicable fecal coliform standards pursuant to 35 Ill. Adm. Code
302.209 and 302.306.
SUBPART B: PROTECTED WATER STATUS AND EXEMPTION REQUIREMENTS
<BSection 378.201 Year-Round Protected Waters>>
Waters utilized for public and food processing water supply must comply
with the 2000 per 100 ml fecal coliform standard of 35 Ill. Adm. Code
302.306 at any intake point on a year-round basis.
<BSection 378.202 Seasonally Protected Waters>>
Waters within the following categories must comply with the 200 per 100 ml
fecal coliform standard of 35 Ill. Adm. Code 302.209(a) during the months
of May through October:
a) All large streams and rivers which support primary contact
activities;
b) All lakes and ponds which support primary contact activity;
c) Pooled areas of small streams where depth and access allow for
primary contact activities; or
d) Streams which flow through or adjacent to parks or residential
areas and are likely to create a risk of incidental or accidental
contact.
<BSection 378.203 Unprotected Waters>>
Unprotected waters are not required to comply with the fecal coliform
standards of 35 Ill. Adm. Code 302.209 and 302.306. Characteristics of
unprotected waters include but are not limited to the following, and waters
must possess one or more of these characteristics to be classified as
unprotected waters:
a) Waters with average depths of two feet or less and no pronounced
deep pools during the summer season;
b) Waters containing physical obstacles sufficient to prevent access
or primary contact activities; or
c) Waters with adjacent land uses sufficient to discourage primary
contact activities.
<BSection 378.204 Assessment of Waters for Protected Status>>
a) The permittee shall conduct surveys necessary to determine whether
affected waters currently support or have the potential to support
primary contact activities. The permittee shall determine and
document the following:
1) Whether the water body segments have potential for primary
contact use. For example, such segments must have water
depths that would ordinarily permit swimming during the
months of May through October;
2) Whether the water body segments are free of obstacles to
primary contact activities, such as unsuitable access to the
streambank or existence of logs, log jams or other debris
which render the water body hazardous or unattractive to
swimmers;
3) Where the adjacent land use to water body segments would
discourage primary contact activities; or
4) Whether the water bodies are being used for primary contact
activities. The permittee shall make inquiries of local
residents, land owners, or local law enforcement officials.
The permittee shall also make a list of all downstream access
areas and contact custodians to determine the uses and
water-based activities of the water body segment in question.
b) The permittee shall conduct surveys necessary to determine whether
any affected waters which flow through or adjacent to parks or
residential areas have the potential to attract the public and
create a risk of incidental or accidental contact. Such water
bodies are protected by the seasonal fecal coliform standard of 35
Ill. Adm. Code 302.209(a) unless the permittee can demonstrate
that access is limited by such impediments as fences or steep
banks.
c) The Agency shall review the information provided by the permittee
and determine whether it is accurate and complete in accordance
with the requirements of this Section.
SUBPART C: FECAL COLIFORM DIE-OFF MODEL
<BSection 378.301 Die-off Equation>>
a) The permittee shall model the die-off of fecal coliform from its
discharge using the first-order die-off equation provided in
Appendix A of this Part. Appendix B of this Part provides
step-by-step guidance for the application of this equation.
Appendices C through E of this Part provide further assistance in
the application of the equation.
b) The die-off equation predicts levels of fecal coliform at points
downstream from the fecal coliform source. The equation includes
variables to reflect upstream levels of fecal coliform, changes in
dilution and travel time, and other stream-specific parameters.
c) In modeling the effects of its discharge, the permittee shall
collect additional stream-specific information as necessary to
demonstrate compliance with fecal coliform water quality
standards. The amount of field data necessary to utilize the
equation as specified in Appendix B of this Part will depend on
the proximity of the source to protected waters and the nature of
the receiving waters. Additional field data collected will
produce more accurate prediction of downstream levels of fecal
coliform.
<BSection 378.302 Cumulative Effects of Multiple Sources>>
a) When modeling fecal coliform die-off, the permittee must account
for contributions of additional downstream sources. Requests for
exemption will be denied when die-off modeling indicates that the
combined effect of multiple sources will lead to fecal coliform
water quality violations of 35 Ill. Adm. Code 302.209 or 302.306.
b) In reviewing any request for exemption, the Agency shall
re-examine previously modified NPDES permits when modeling
indicates that there is a potential for fecal coliform water
quality violations of 35 Ill. Adm. Code 302.209 or 302.306 due to
the combined effects of:
1) the source's modified fecal coliform limits;
2) the permittee's modified fecal coliform limits; and
3) any new source.
<BSection 378.APPENDIX A First Order Die-off Equation>>
The first order die-off equation provides a method of estimating fecal
coliform die-off in a receiving water as a function of time:
N(t) = [N(u)/(1+1/d) + N(o)/(1)] x e (-k t)
Definition and discussion of terms:
N(t) is the predicted concentration of fecal coliform at travel time t
downstream; units = #/100 ml.
N(u) is the fecal coliform concentration upstream of the source being
modeled; units = #/100 ml.
This term will often be negligible relative to the contribution of the
source.
N(o) is the fecal coliform concentration in the effluent of the
source;
units = #/100 ml.
d is the ratio of the receiving water discharge directly upstream of
the
source to the discharge of the source; no units.
k is the first order die-off rate constant; units = 1/hours. The
value of
k can vary as a function of receiving water characteristics, including
temperature, exposure to sunlight, and turbidity.
t is the travel time to the point of interest below the source; units
= hours.
e = 2.718
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<BSection 378.APPENDIX B Application of the Die-off Equation>>
a) Sketch the receiving stream and the progression of higher order
streams it flows into, up to and including the major river basin.
Major river basins are listed in Appendix C. Also identify on
your sketch:
1) Smaller streams which are tributary to the receiving water
below the point of discharge.
2) All point source dischargers.
3) All public and food processing water supply intakes.
4) Water body reaches wherein primary contact activities are
feasible or known to be engaged.
b) Sources which discharge directly to receiving waters which are
obviously suitable for primary contact use and therefore applying
for a seasonal exemption only, do not need to assess downstream
primary contact potential or use. Sources which are applying for
a year-round exemption must carefully assess such potential or use
for the entire affected reach of the undisinfected discharge.
c) Subdivide downstream waters into segments where discharge and
stream cross-sectional area are relatively uniform. Segments will
typically begin at confluences with other streams. Number the
segments and identify each on the above sketch. Where available
note stream mile numbers established by U.S. Geological Survey
(see Appendix C) for the receiving stream.
d) Establish discharge rates for each segment. If no discharge data
is available, the equations developed by the Illinois State Water
Survey (Appendix C) may be used. For waters protected to 200
fecal coliform per 100 ml, the median discharge (50% recurrence
frequency) shall be utilized. For waters protected to 2000 fecal
coliform per 100 ml, calculate discharges for the 10%, 30%, 50%,
70%, and 90% recurrence frequencies.
e) Derive average velocities for all necessary recurrence frequencies
in each segment. In the absence of field measurements, velocity
is best estimated through the use of the Manning equation
(Appendix D). For some situations, equations developed by the
Illinois State Water Survey (Appendix C) may suffice; however,
these equations tend to over-estimate velocity, so it may be
beneficial for a discharger to go to a more detailed analysis.
f) Assess the average concentration of fecal coliform directly
upstream of the source (N(u)) and for all significant tributaries
listed in Part A. Data from Agency ambient monitoring stations
may be useful in some instances.
g) Assess the concentration of fecal coliforms in the effluent prior
to disinfection (N(o)). An average over at least 3 months is
preferable, but a minimum of 4 samples in 30 days will be
acceptable. A conservative value of 400,000 fecal coliform per
100 ml may be utilized when effluent specific data is not
available.
h) Determine the appropriate die-off rate constant (k). Available
literature values for k range from 0.01/hour to greater than
1.00/hour. In the absence of stream-specific data, the following
values may be used: 0.06/hour for the months May thru October,
and 0.03/hour for the months November thru April. Stream
assessments are preferred and may be necessary to demonstrate
compliance. (See Appendix E).
i) Calculate fecal coliform levels at intervals downstream using the
design average flow for the source, for all necessary recurrence
frequencies and values of k. Incorporate the contributions of
additional downstream sources as necessary. Compare the results
to the required levels of protection. (These levels are 200/100
ml for primary contact and 2000/100 ml for water supplies).
j) In cases where the predicted level approximates the required level
of protection, the Agency will require additional stream-specific
information. Such information may include, but is not limited to:
1) Die-off studies to determine k.
2) Dye tracer studies to determine V.
3) Stream surveying to determine Q.
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<BSection 378.APPENDIX C Discharge and Travel Time Estimation>>
The Illinois State Water Survey, in a publication entitled, "Hydraulic
Geometry of Illinois Streams," (by J.B. Stall and Y.S. Fok, WRC Research
Report 15, 1968) provides a method of predicting discharge and average
stream velocity in stream basins as a function of drainage area. The
equations are listed below. Where an equation is not listed for the basin
of interest, the statewide composite equations may be used. Drainage areas
can be obtained from the U.S. Geological Survey report entitled "River
Mileages and Drainage Areas for Illinois Streams - Volumes 1 and 2," (by R.
W. Healy, Water Resources Investigation 79-110 and 79-111, 1979).
Hydraulic Geometry Equations for Illinois River Basins
Description of Units
Q = discharge in cubic feet per second (cfs)
V = average velocity in feet per second (fps)
A(d) = drainage area in square miles
F = frequency in percent of days, as a decimal
1n denotes that all logarithms are natural logarithms to the base
e = 2.718
Statewide Composite Equations
1n Q = 1.176 - 5.22 F + 0.984 1n A(d) (cfs)
1n V = 0.103 - 1.81 F + 0.158 1n A(d) (fps)
Rock River
1n Q = 0.24 - 3.50 F + 1.03 1n A(d)
1n V = 0.20 - 1.50 F + 0.13 1n A(d)
Galena River
1n Q = 0.13 - 2.27 F + 0.96 1n A(d)
1n V =-0.06 - 0.81 F + 0.06 1n A(d)
Fox River
1n Q =-0.24 - 3.33 F + 1.13 1n A(d)
1n V = 0.11 - 1.39 F + 0.16 1n A(d)
Mackinaw River
1n Q = 1.39 - 7.52 F + 1.00 1n A(d)
1n V = 0.38 - 2.26 F + 0.09 1n A(d)
Henderson Creek
1n Q = 1.44 - 5.00 F + 0.89 1n A(d)
1n V = 0.58 - 1.76 F + 0.01 1n A(d)
Spoon River
1n Q = 0.86 - 4.82 F + 1.00 1n A(d)
1n V = 0.52 - 1.63 F + 0.08 1n A(d)
LaMoine River
1n Q = 1.03 - 5.60 F + 0.92 1n A(d)
1n V =-0.13 - 1.16 F + 0.11 1n A(d)
Sny River
1n Q =-2.27 - 5.87 F + 1.63 1n A(d)
1n V =-1.29 - 1.06 F + 0.39 1n A(d)
Sangamon River
1n Q = 0.65 - 4.93 F + 1.03 1n A(d)
1n V =-1.01 - 0.95 F + 0.26 1n A(d)
Des Plaines River
1n Q = 1.78 - 4.98 F + 0.90 1n A(d)
1n V = 0.26 - 1.31 F + 0.08 1n A(d)
Kankakee River
1n Q = 1.41 - 5.12 F + 0.96 1n A(d)
1n V =-0.38 - 1.19 F + 0.17 1n A(d)
Vermilion River (Illinois River Basin)
1n Q = 0.97 - 6.28 F + 1.01 1n A(d)
1n V =-0.20 - 2.19 F + 0.17 1n A(d)
Kaskaskia River
1n Q = 0.95 - 5.88 F + 1.02 1n A(d)
1n V =-0.26 - 1.28 F + 0.14 1n A(d)
Vermilion River (Wabash River Basin)
1n Q = 1.11 - 4.96 F + 0.98 1n A(d)
1n V =-0.81 - 2.20 F + 0.29 1n A(d)
Embarras River
1n Q = 0.04 - 5.61 F + 1.17 1n A(d)
1n V =-0.92 - 1.62 F + 0.26 1n A(d)
Little Wabash River
1n Q = 1.91 - 7.90 F + 0.96 1n A(d)
1n V =-1.38 - 1.18 F + 0.30 1n A(d)
Big Muddy River
1n Q = 1.26 - 8.50 F + 1.09 1n A(d)
1n V =-0.75 - 1.47 F + 0.18 1n A(d)
Big Bay Creek
1n Q = 1.48 - 7.90 F + 1.05 1n A(d)
1n V =-0.53 - 0.41 F + 0.14 1n A(d)
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<BSection 378.APPENDIX D Manning Equation>>
V = <P1.49>> R(2/3)(h) S(1/2)
n
Q = <P1.49>> AR(2/3)(h)S(1/2)
n
where: Q is the discharge in cfs.
V is the average velocity in fps.
A is the cross-sectional area of the stream in square feet.
R(h) is the hydraulic radius of the stream in feet, as
determined by the cross-sectional area (A) divided by the
wetted perimeter.
S is the slope of the stream in decimal form.
n is the Manning coefficient.
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<BSection 378.APPENDIX E Field Assessment of Die-off Rate Constant>>
Assessing the fecal coliform die-off rate constant (k) below a source is a
fairly straight-forward process. It is important, however, that sampling
be conducted under appropriate conditions. The following guidelines should
be observed in planning and conducting the necessary field work.
a) Assessment of k must be conducted on an undisinfected effluent.
b) Assessment of k for warm months (May thru October) should be
conducted when water temperature is at least 20 C. For cold
months (November thru April), water temperature should be less
than 10 C.
c) Stream discharge and effluent discharge must be relatively steady.
Precipitation events within the past 24 hours or during sampling
should be avoided. The dilution ratio should be such that initial
fecal coliform levels will be well above background levels.
Stream velocity should average 0.2 feet per second at the minimum.
d) Fecal coliform levels in the undisinfected effluent, upstream
(dilution) waters, and significant downstream tributaries and
sources should be assessed for several days prior to conducting
the k study. Extreme variability in these levels should be
avoided if possible.
e) At least 5 downstream sampling stations must be established. The
first station should be the closest point where it is likely that
the effluent has completely mixed with the stream. Other sites
should be selected with regard to location of downstream
tributaries and fecal coliform sources and convenience of access,
and should be representative of typical stream reaches. A typical
example might include stations at 1, 3, 5, 10, 15 and 25 miles
downstream of the source.
f) Stream discharge should be measured at each station. Information
necessary to calculate travel time between sites must also be
collected (this is typically done via the Manning equation, see
Appendix D).
g) Samples should be collected during the daylight hours in one day
if at all possible. Agency protocol for fecal coliform sampling
requires that samples be iced immediately and transported to a
laboratory for analysis within 6 hours.
h) Resources permitting, it is preferred that at least 2 warm weather
and 2 cold weather studies be conducted. Values of k should be
calculated using the die-off equation for each stream reach. An
overall average for each study should also be computed.
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