ILLINOIS POLLUTION CONTROL BOARD

September

8,

1988

IN THE MATTER OF:

)

JOINT PETITION OF THE CITY OF

)

DIXON AND THE ILLINOIS

)

PCB 87—71

ENVIRONMENTAL PROTECTION

AGENCY FOR EXCEPTION TO THE

COMBINED SEWER OVERFLOW

REGULATIONS

OPINION AND ORDER OF THE BOARD

(by R.C. Flemal):

This matter comes before the Board on the May 28,

19871

joint petition of the City of Dixon

(“Dixon”)

and the Illinois

Environmental Protection Agency (“Agency”)

for exception

to

35

Ill.

Adm.

Code 306.305

(a) and

(b)

to relieve Dixon from the

requirement

to construct

and operate certain combined sewer

overflow

(“CSO”) transport

and treatment facilities.

Hearing was

held

in Dixon on August

7,

1987.

For the reasons described below,

the Board

finds

that

Petitioners have made the showings requisite for granting the

relief requested.

The relief will accordingly be granted,

subject to conditions

as stipulated

to by Petitioners and

consistent with the Board’s

rules

and regulations.

CSO REGULATIONS

The Board’s CSO regulations are contained

in 35

Ill. Adm.

Code Subtitle

C,

Chapter

I, Part 306.

They were amended

in R81—

17,

51 PCB 383, March 24,

1983.

Sections pertinent

to the

instant matter are Sections 306.305 and 306.3&l(a)~

Section

306.305 provides

as follows:

All combined sewer overflows and treatment plant bypasses

shall be given sufficient

treatment

to prevent pollution,

or

the violation of applicable water standards unless an

exception has been granted by the Board pursuant

to Subpart

D.

1 Dixon sought an extension of

the filing date for its CSO

exception

until July

1,

1987,

in PCB 85—217.

This was granted

by

the Board by Order

of June

5,

1986,

70 PCB

108.

92—35

---

—2—

Sufficient treatment shall consist of the following:

a)

All dry weather flows,

and the first flush

of storm

flows as determined

by the Agency, shall meet the

applicable effluent standards;

and

b)

Additional

flows,

as determined by the Agency but not

less

than ten times average dry weather flow for the

design year,

shall

receive a minimum of primary

treatment and disinfection with adequate retention time;

and

C)

Flows

in excess of those described

in subsection

(b)

shall

be treated,

in whole

or

in part,

to the extent

necessary to prevent accumulations of sludge deposits,

floating debris and solids

in accordance with 35 Ill.

Adm. Code 302.203,

and to prevent depression of oxygen

levels;

or

d)

Compliance with

a treatment program authorized

by the

Board

in an exception granted pursuant

to Subpart D.

Subpart D allows

the discharger

to file

a petition for

an

exception either singly,

or jointly with the Agency as Dixon has

done.

A joint petition may seek an exception based

on minimal

discharge impact as provided

in Section 306.361(a):

An exception justification based upon minimal discharge

impact shall include,

as

a minimum,

an evaluation of

receiving stream ratios,

known stream uses,

accessibility to

stream and side land use activities

(residential,

commercial,

agricultural,

industrial,

recreational),

frequency and extent of overflow events,

inspections

of

unnatural bottom deposits,

odors,

unnatural floating

material

or color,

stream morphology and results of limited

Stream chemical analyses.

Pursuant

to 306.361(a) Dixon and

the Agency assert that

oyerflows

from its combined storm and sanitary sewer system have

minimal impact on the water quality and do not restrict the use

of the Rock River

(the receiving stream).

Accordingly, they

contend that the approximately $2,344,000 expenditure

(R.

at

18)

which would be necessary

to come into compliance via fully

Separating

the Dixon sewer system

is not justified.

FACILITIES

Dixon

is

located on north and south banks of

the Rock River

in the northeast part of Lee County,

Illinois.

The City

is

~rimari1y residential

in nature,

although there are

a number

of

light

industries and commercial establishments.

The 1980

population was 15,170.

92—36

---

—3—

Dixon owns and operates

a municipal sewerage system, which

includes

a collection

system,

sewage pumping stations, and

a 3.84

million gallons per day (“MGD”),

average dry weather

flow,

activated sludge wastewater treatment plant

(“WWTP”).

The

collection service area covers approximately 2,250 acres

(3.5

sq.

mi.)

(Ex.

1,

p.

2), approximately 85

of which

is served by

separate sewers and 15

by combined sewers

(Petition at 2).

Generally,

the combined sewer

service areas

are

located

in the

older, more fully developed residential—commercial areas of

the

central portion

of the City.

Sewage

flows on the north

and south

sides of the Rock River

are collected

in separate interceptors which run parallel

to the

river,

and conveyed

to the

WWTP

which

is located on the west side

of the City.

Interceptors have the capacity for transporting

from 3.lx

to 9x average dry weather

flow

(Ex.

9 at 3—4),

and the

WWTP has

the capability of providing at least primary treatment

for all loads

received.

There are presently nine CSOs listed on Dixon’s NPDES permit

(R.

at

14), identif~edrespectively as outfalls 002 through 005

and 007 through 011

.

An additional,

non—permitted outfall

located on the Swissville Interceptor near Palmyra Avenue has

also been recognized

(R.

at

16).

There are thus

a total of

ten

CSO outfalls, each

of which is located along

and discharges into

the Rock River.

Of the ten known CSO outfalls,

it

is contended by

Petitioners that only five remain active

or potentially active

CR.

at

14).

Inactivation has been caused by sewer separation

activities undertaken

to date.

The five active or potentially

active CSOs,

and the side of the Rock River

from which they

discharge,

are:

003

Madison Avenue

(South)

007

Hennepin Avenue

(North)

009

Ottawa Avenue (North)

010

Dement Avenue

(North)

011

Assembly Place

(North)

Two of

the active CSOs,

010 and 011, discharge

to the Rock

River

above

the Dixon Dam,

a hydroelectric structure.

The

remaining three discharge below the Dam.

2 The NPDES permit also lists various other overflow points,

including bypasses at the WWTP (Ex.

1 at 1).

Other overflow

points include an emergency high—level overflow

(006)

located at

a major sewage pump station

(Reynoldswood Station);

it

is

designed

to activate only under emergency circumstances at the

station

(Ex.

8 at

2;

R.

at

62).

92—37

---

—4—

Land use

in the area tributary to CSOs 003 and 007

is

predominately commercial;

land use

in the areas tributary to CSOs

009,

010,

and

Oil

is predominately residential

(Ex.

1

at

4).

In

all five basins land

is fully developed and no additional growth

is projected

(Id.).

Additionally, there are

no known industrial

or

other users tributary

to the CSO overflows which could cause

discharge

of toxic

or hazardous materials

into the CSO system

(Ex.

1

at

7).

PRESENT CSO SITUATION

Integral

to an understanding of

the present CSO situation in

Dixon

is awareness

of

a major change

in the nature of the CSO

discharges which occurred

in 1985.

Gathering of data on the

Dixon CSO was begun

as early as preparation of

the 1977 Dixon

Facilities Plan.

In spite of

the fact that these data indicated

that even small rainfall events were capable

of triggering CSO

discharges at the majority of

active outfall points,

Dixon

believed that the impact

of the CSOs on the Rock River was

sufficiently minimal such that

a CSO exception could

be

justified.

Accordingly, Dixon

began preparation

of

a three—phase

CSO exception study.

Phase

I

of

this study was submitted

to the

Agency in January 1985, Phase II was submitted

to the Agency in

Augu~t1985,

and Phase III was submitted

to the Agency

in October

1985

However,

coincident with

the preparation of the CSO

exception studies, Dixon discovered that the two interceptors

were clogged with debris

to as much

as 1/2

to 3/4 of

their

diameters

(R.

at 12).

When this debris was cleaned out

in

1985,

a dramatic decrease

in the number of CSO events was

immediately

recognized.

So rare did CSO events become that Dixon was able

to

record only

a single small event

(Ex.

7,

p.

2)

during the

remainder

of 1985 and prior

to January 1,

1986,

deadline

for

submission to the Board of CSO exception petitions.

It was

furthermore apparent that the CSO discharge quantity and ~uality

which had existed prior

to cleaning of

the interceptors no longer

prevailed.

For this reason Dixon sought an extension of the

filing deadline for their CSO exception to allow them to better

document the CSO impact under

the new, clean—interceptor regime;

the extension was granted

by Board Order

of June

5, 1986

(70 PCB

108).

Illustrative

of the change

in the CSO condition occasioned

by the interceptor cleaning

is the status of CSO 007.

This

outfall was historically the most active

of the CSOs, with

The three phases

of

the CSO exception study are Exhibits

1,

3,

and 5,

respectively,

in the

instant record.

92—38

---

—5—

discharges occurring

for 92

of rainfall

events

(Ex.

3

at

2).

Subsequent

to cleaning,

there have been only a

few isolated

discharge events,

and rainfalls as large

as 1.6 inches

in

6 hours

have failed

to cause

overflows (Id.).

From mid—1985 through the time of filing of the instant

petition, Dixon gathered data on their new CSO condition.

These

are incorporated into a revised Phase III report, which was

submitted

to the Agency in Februa~y1987

and supplemented by

submissions

in April and May 1987

At the time of hearing

it was discovered that the outfall

point for CSO

003

(Madison Avenue

—

South) had been incorrectly

identified

in the previous studies.

Dixon accordingly undertook

further studies directed toward clarifying the CSO situation at

003.

Results of this work, plus reports on the general progress

of

the CSO control program, were filed with the Board

on December

3, 1987 (“Status Report”)

and August

4,

1988

(“Final

Submission”).

Inflow

and infiltration, other

than as caused by flood

backflow from the Rock River, has not been

a significant problem

for the Dixon sewer

system

(R. at 42—44).

Upland

infiltration

is

limited because most

of the City’s sewer

lines are above the

watertable

CR.

at 42).

DOCUMENTATION OF MINIMAL IMPACT

Section 306.361(a)

requires that Petitioners seeking a CSO

exception on

the basis of minimal discharge impact,

as

is the

case here, make a number

of showings.

Pursuant thereto,

Petitioners provide the following information and observations.

Receiving Stream Ratios

Petitioners assert that the flow of the Rock River provides

substantial dilution potential for its CSO discharges.

The

drainage area of the Rock River

at Dixon

is approximately

8,600

square miles

(Ex.

1 at

3)

and the average flow

is approximately

3,000 MGD

(R.

at 18).

The average discharge contrasts with the

most recently estimated CSO discharge for the one—year storm of

approximately 0.13 million gallons (Final Submission, Attachment,

Letter

of June

28,

1988).

The revised Phase

III study and its April and May supplement

are Exhibits

7,

8,

and 9,

respectively,

in the instant record.

92—39

---

—6—

Known Stream Uses

The primary use

of the Rock River

in the vicinity of Dixon

is for water

sports,

including boating,

water

skiing,

and fishing

(Ex.

1 at

5;

Ex.

3 at

1).

Dixon also characterizes the area

below the Dixon Dam as “one of the top fishing spots

in northern

Illinois for game fish species”

(Ex.

3

at 1).

It further notes

that the “excellent quality of sport fishing”

is

a verification

that even under past CSO regimes Dixon’s CSOs “have had

an

insignificant effect on the Rock River

in

the City of Dixon”

(Id.).

There are no public beaches on the Rock River

in or

immediately downstream from Dixon,

and the Rock River

is not

utilized downstream for any potable water supply system

(Ex.

1

at

5).

Accessibility to Stream Side Land Use Activities

Most of

the north

shore of the Rock River through Dixon

is

bordered by a strip park

(R.

at

68).

However, under normal river

conditions

the park

is separated from the river by

a vertical

river bank and rip—rap which does not allow ready access from the

park into the river

or

to the river’s edge

(R.

at 69—70).

Swimming and launching of boats does not occur within the

vicinity of any of

the CSO outfalls

(Id.).

The single active CSO outfall on the south shore, 003,

occurs

in

a mainly industrial

area.

Shoals along the bank allow

access

to the river’s edge,

and are frequented by fishermen.

Frequency and Extent of Overflow Events

Early studies

of the Dixon CSO situation had suggested that

overflow events were relatively

frequent.

However,

subsequent

to

the 1985 cleaning

of the interceptors,

data from which realistic

estimates

of the frequency of CSO events could be made beáame

difficult to obtain.

In part this reflected a real decrease

in

the frequency of events.

However, data collection was also

exacerbated by several abnormally dry periods,

as during the

summer months

of

1988.

Four minor events were recorded during

the period May 1986 through October 1986,

the smallest

of which

was triggered by

a rainfall

of 0.5 inches in one hour.

The

record indicates only two events

in 1987, occurring on November

1

and November 16

(Status Report, Attachments, Letters

of November

9 and 17).

Several events were also recorded

in early 1988

(Final Report).

In most of the 1986

to 1988 events less than the

full five active CSOs experienced

actual overflow.

The most recent estimate

of first flush capture for the one—

year storm

(Final Submission,

Letter Attachment dated June

28,

1988)

indicates that the Dixon sewer

system captures and conveys

92—40

---

—7—

to the WWTP approximately 78

of the first flush BOD5 load and

92

of the first flush TSS load.

This estimate

is based on the

physical configuration of the system as of May,

1988.

Accordingly,

it does not reflect

a decrease

in the extent of CSO

overflows expected

to follow from increasing weir heights at the

remaining active CSOs or from reconstruction of

the 003 outfall.

Inspections of Outfalls

(Bottom Deposits, Odors,

etc.)

Phase II of the Dixon CSO Study

(Ex.

3)

contains results of

field

inspection, including detailed sketches and photographs, of

all ten permitted CSO outfalls.

The study indicates

that near—

shore bottom deposits range

from rock,

to sand and gravel,

to

sand and gravel mantl~dby thin silt deposits.

Rock and/or

coarse rock fragments prevail

at the high velocity locations

immediately downstream from the Dixon

Darn.

Gravel,

sand,

and

silt—mantled coarse deposits prevail upstream

from the Dam and

downstream beyond

the high—velocity zone.

The same study also observes that no sludge or sanitary

debris was found at any of

the ten permitted outfall points.

An

exception to this circumstance was subsequently discovered

at

outfall 003 (Final Submission at 1—2).

Reconstruction of outfall

003 has subsequently occurred,

and Joint Petitioners contend that

the problem has been resolved

(Id.).

An Agency inspection

conducted

in August 1987 has also concluded that there are no

problems at any of the other outfalls

(Id.;

Status Report,

Attachment, August 13,

1987 Agency Reconnaissance Survey Report).

Stream Morphology

The Rock River

in the vicinity of Dixon

is characterized as

a shallow,

fast—flowing, high—discharge stream

(Ex.

3 at

1).

The

fall caused

by the Dixon Dam provides for added aeration of

the

stream,

even under very low stream discharges

(Id.).

Stream Chemical Analyses

Dixon provides

results of water quality monitoring at U.S.

Geological Survey water quality stations located on the Rock

River

above and below Dixon

(Ex.

7, Attachment Exhibits Ill—A and

Ill—By.

These indicate generally good water quality both

upstream and downstream from Dixon.

CSO MODIFICATION PROGRAM

Joint Petitioners’

contention that the Dixon CSOs have

minimal

impact on the Rock River notwithstanding,

Dixon has

agreed

to undertake

a program to further reduce CSO impacts.

92—41

---

—8—

Dixon agrees

to plug those CSO discharges which are no

longer active.

At present,

these can be identified

to

include

002

(which

is already plugged),

004,

005,

008 and the recently—

discovered unpermitted outfall north of Palmyra Avenue.

Dixon

is justifiably reluctant to plug the remaining five

CSOs at the present time, even though

two

of them (009 and 011)

are characterized

as minor bypasses

(R.

at 14), due

to threat

of

sewer backups into basements during very severe rainfall events

CR.

at

17).

Dixon

is agreeable, however,

to raising the weirs

which divert flows

to each

of these CSOs (Id.).

This action

is

expected

to significantly reduce both the number

and extent of

CSO events

(R.

at 31—32).

Dixon also agrees

to provide a backup system at

the

WWTP.

Absent this system,

a power

failure at

the plant necessitates

bypassing

raw sewage

(R.

at 26—8).

Although

this system

improvement

is independently required pursuant

to

the Clean Water

Act,

its implementation will also provide CSO benefits

(R.

at

28)

Another provision of

the Dixon

system improvement program

consists of providing backflow prevention and manhole seals for

floods up

to the 100—year flood

(R.

at 29).

This provision is

expected

to have significant impact on the CSO situation because

it will restrict storm water

and river water from entering the

sewer

system,

and hence preserve capacity for conveyance

of

combined sewer discharges

to the WWTP

(R.

at 30—31).

A major

facet of Dixon’s CSO program is continued

inspection

of

its interceptor sewers,

and cleaning of them as

necessary

(R.

at

33—35).

This

is an essential element

of the program, given

the significant evidence that the past high frequency CSO

discharge events was related

to clogged interceptors.

Dixon has for the past several years practiced

a program of

street sweeping on

a regular basis,

a program

it characterizes as

its “accelerated street cleaning program”

(R.

at 39—41).

Dixon

commits to continuing this program.

Finally,

Dixon commits

to a continued policy of separating

combined sewers when street improvement projects are undertaken

CR.

at 35, 37—8).

CONCLIJSION

The Board determines that Petitioners have shown pursuant

to

35

Ill.

Adm. Code 306.361(a)

that exception to 35

Ill. Adm. Code

306.305(a),

as

it relates

to first flush

of storm flows,

and

to

35

Ill.

Adm. Code 306.305(b) would produce minimal

impact on the

receiving stream.

Accordingly,

the Board will grant the

92—42

---

—9—

exception.

The Board

further

will accept

the conditions as

proposed by Joint Petitioners

in

their Petition and

as modified

at hearing

(R.

at 19—20,

23;

Ex.

10 at 8—9).

Some of the system improvements offered by Dixon had been

completed

at the time of hearing

(R.

at

24);

others have been

completed subsequently (Status Report; Final Submission).

The

Board further notes

that Dixon has committed

to completion of all

improvements by July 1,

1988,

a date now in

the past.

Although

the record does not explicitly show that Dixon has met this

deadline,

the Board will accept Dixon’s commitment

to the

deadline at

face value,

and condition the grant of exception

accordingly.

ORDER

The City of Dixon

is

hereby granted an exception from 35

Ill. Adm. Code 306.305

(a)

as

it relates

to first flush

of storm

flows and from 35 Ill.

Adm. Code 306.305(b)

for combined sewer

overflows,

to

the Rock River,

subject to the following

conditions:

1.

The City shall complete the following improvements by

July 1,

1988:

a.

Installation of standby power system at the WWTP,

providing backflow prevention systems at vulnerable

CSOs,

and installation of sealed manhole frames as

specified

in the City’s approved Municipal Compliance

Plan and NPDES permit.

b.

The City shall permanently inactivate

the following

combined sewer

overflows:

1.

College Avenue

(already blocked)

(002)

2.

South Galena Avenue

(G04)

3.

South Ottawa Avenue

(005)

4.

North Galena Avenue

(008)

5.

Unreported non—active overflow on

Swissville Interceptor,

just north

of Palmyra Avenue.

c.

The City shall

raise overflow weirs or dams to the

maximum extent practicable, without causing basement

backups at the following locations:

1.

South Madison Avenue

(003)

2.

North Hennepin Avenue

(007)

3.

North Ottawa Avenue

(009)

4.

North Dement Avenue

(010)

5.

Assembly Place

(011)

92—43

---

—10—

2.

The City shall inspect interceptor sewers annually and

clean

these sewers as necessary.

3.

The City shall continue the present accelerated street

cleaning operations in the combined sewer areas.

4.

The City shall continue

its past practices of separating

combined sewers during Street improvement projects,

as

funding

is available, until the City’s goal

of complete

separation is achieved.

5.

The City shall submit to the Agency by January 31st

of

each year

a report summarizing

all

sewer system

inspection and maintenance performed during the

preceeding year.

The report

for

the year 1988 shall

summarize efforts

to raise overflow weirs and plug

outfalls.

6.

This grant of exception does not preclude the Agency from

exercising

its authority

to require as

a permit condition

a CSO monitoring program sufficient

to assess compliance

with this exception and any other Board regulations and

other controls,

if needed,

for compliance,

including

compliance with water quality standards.

7.

This grant

of exception

is not to be construed

as

affecting the enforceability of any provisions

of this

exception,

other Board regulations,

or the Environmental

Protection Act.

Section 41 of

the Environmental Protection Act,

Ill.

Rev.

Stat.

1985 ch.

111 1/2 par.

1041, provides for appeal of final

Orders of the Board within

35 days.

The Rules of the Supreme

Court of Illinois establish filing requirements.

IT

IS SO ORDERED.

I, Dorothy M. Gunn,

Clerk of

the Illinois Pollution Control

Board, hereby certify that the abo e Opinion and Order was

adopted

on the

~

day of

___________________,

1988, by

a

voteof

7~

.

Dorothy

M. q4nn, Clerk

Illinois Pollution Control Board

92—44