C378.

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

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.

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.

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

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.

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.

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.

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

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.

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.

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

@R+R

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.

@R+R

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)

@R+R

V = <P1.49>> R(2/3)(h) S(1/2)

Q = <P1.49>> AR(2/3)(h)S(1/2)

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.

@R+R

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.