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D

CITY

OF

ROCK

ISLAND.

Petitioncr,

lv.

ILI"INOIS

ENVIRONMENTAL

PROTECTION ACENCY,

)

)

)

)

pcB

e8-r64

)

(VARTANCE)

)

)

)

t

Respondent.

)

A M EN

pEp

PErl[[oNlJOR

!'ARIAJIC

E

The

City

of

Rock Island

("City"),

through

itu

nltorneys,

hercby

petitions

the Board for

n

variance

from

35

lll.

Adrn. Code

$

306.305

(d)

arrd an

exccption

approved

thereunder

by

the

Board on

May

9, 1986

("Exception")

to

the

cxtent

the

rule

as

rnodilied by the Exception

requircs

that thc

City

operate its

nrain trciltnlcnt

plant

at n nraxinnrnr

florv

level ot' l6 nrillion

gallons

lrer

day

("MCD").

ulgKgBgglg

On Decenrbcr

26, 19E5,

the

City nnd

the lllinois Environnrcntal

Prolrction Agcncv

("lllinois

trPA")

filed

n

Joint

Petition

for

Exccption seekirrg

rclief

ftour

the

requircntents of

.15

fll,

Adln.

Code

$

306.305

(a)

and

(b)

to

construct

and

operatc

ccrlain contbined

servcr

overtlorv

("CSO")

transport

and

trcatment

facilities.

(lixhibit

l). On l\,lav

9,

1986. the lllinois

Pollution

Control Board

("Boarel")

granted

the

City and

lllinois

EPA's

Joint

Petition

lbr Exccplion.

(Exhibit

2). The

City

requests a

variance

becau$e Condition

Lb.

of

the Exception

is interprcted

by

the

ltlinois

EPA

as

requiring the City's

nrain trentment

plant

1"Plant")

to have

n

l6 MCD

design ntaximum flow

("DMF")

level,

rvhen its

actual

DMF

lcvcl

is l2 MGD,

t

a

3

a

O

o

o

c

---

More

specifically,

the

Board

in Condition

t.b.

required

the City to

implentent

all

mortifications

to its

server

systenr as

iderrtified

in

Paragraphs

14.

l5

and

16 of the Joint

Petiticut

for Exception

in

rvhich tire City

agreed

to

perfonn

nrodifications

in order

to

obtain the

lllinois

EPA's

supporr

for the Joint

Petition.

At

Paragraph

l5

of the

Jnint

Petition,

the

rtodifications

were describe{

as

"lhe

construction

of head

rvorks intprcvenrents

to

allou'

operatiott

ot'tlie

trcatmcnt

plant

at tlre

design

nraxinruur

florv

level of

lfi ntillion

gallons

a

dny."

1'he

16

tvlGf)

figure

was clerived

l'rom a

1982 report of the

City's

tlren

consultant

rvhich

rvas

introduced

bctbre

the

Board as

Exhibit

2 of

the

CSO

Exception

ltearing

(PCB-85'214).

Recentty,

the

City

learned

that

even

rvith

the

past

inlprovements and

thc

itttprovetttents

compteted

since

that

tinrc,

the DMF

is actually

l2

MCD

rather ihfln

l6 MGD,

solely because

cf

un{ersiecd clarifiers.

Thc

lenrainder

of the

treatment

units are

capable

of treating the

DN4F ol'

l6 MGD. Accordingly,

the City

rcqucsts

a

variflncs to address

this

nristake

tvhile it

rlto\,cs

lbnvard

to design and

constnrct

additional

secottdary

clarilictrtion

vrlrich

rvill

allorv tlre

Platrt

to

treat

a

DMF of

l6 MGD.

I N FOR$ATIOM

L RqOg I

REM

ENTS.

A.

Stat-enrer,..

of8elieU.$-|04.121(a))

The

City

secks

suclr

relief as

nray tre necessary

to allorv

it

the

ncccssary

tintc

to

construct

nrodi{icatiorrs

to the

Plant

to

increase the

DMF from l2 MCD to

l(r MGD

rvhilc

rcrnairting

in

conrpliance

during

design

and

construction

period

rvith

thc

Exception

previ<luslv

approved by tlte

Board

to

the

nrle

governing

the treatmenl

of overflorvs

and

bypasses.

'l'he

rule

govcrning

the

lrealnrent

of

overllorvs and bypasscs

is set l'ortr'

at

35 lll. Adrtr.

Code

$

306.305

rvhiclr

provides:

---

a

O

o

o

o

o

c

o

o

o

All cornbined

sewer

overflows

and

treattnent

plant

bypasses

shall

be

given

sufiicient

treatment

to

prevent

pollution, or the

violation

of

applicable

water

quality

standards

unless

an

exception

has been

granted

by the

Board

pursuant to Subpart

D.

Suffrcient

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)

Additionalflows,

as determined'-!-,y

the

Agency

but

not

less than

ten times

the average

dry

weather

flow for the design

year,

slull

receive a

minimum of

primary

treatment

and disinfbction

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

ofoxygen

levels; or

d)

Compliance

with

a treatment

program

authorized

by

the

Board

in

an exception

granted

pursuant

to Subpart

D.

On May

9, 1986, the

Board

granted

llie

City aird

Agency's

Joint Petition

fbr an Exception

pursuant

to

35 lll. Adm. Code

$

306.305

(o)

from the

requirements

to construct and

operate

certain CSO

transport

and

treatment

facilities.

The Illinois

EPA interprcts one of the conditions

of

the

Exception as

requiring that

the

Plant handle

a

DMF of

l6 MGD.

The

City

retained Fluff&

HuE

Inc.

("Huff')

to

study the

Plant due

to

problems

attempting

to treat

l6

MGD.

Huffrecently

discovered

that

the

actual

DI\,IF of the

Plant is

currently

l2 MGD.

(Exhibit 3

at

page

4).

The City

has

embarked

upon an expeditious

program

to design

and

construct

improvements

to the

Plant

to

increase the

DMF from

l2 MGD

to

l6

MGD.

These modifications

include

an additional

finai

clarifier,

digester refirrbishnrent,

aeration

basin

improvements

and

various

piping

modifications.

Attached

as

Exhibit

4

is a

compliance

program

schedule

to

carry out this

work

which

is cun'ently

estimated

to

cost

$2,500,000.00.

o

---

o

i-his

discovery

leaves

the City

two alternative

courses of

action:

(

I

)

request

that

the

I 6

O

MGD

referenced

in

the Exception

be

permanently

corrected

to the

actual

DMl.'

level

of

l2

MGD

or

(2)

request

a

variance

to allow

the tirne necessary

to design

and

construct

modifications

to the

Plant

to enable

it

to treat a DMF

of l6

MGD.

The

City has

elected

to expend

the

adclitiona!

o

resources

to

design and

constn

,'t

the modifications

necessary

to

treat a DMF

of l6 MGD.

Therefore,

the City

requests

the

preseni ,

. ec€

to enable

the City

to remain in

compliance

wirh

O

the

Exception

to the CSO regulations

during

the

design

and

construction

period.

fhe

schedule

attached

as Exhibit

4 is

contir,gent

upon

the Illinois

EPA's

tirnety review

of

the construction

perndt

application

and

issuance

of the necessary

construction permit.

it

also

o

assumed

that

a construction

bid

may

be timely

awarded.

The

City requests

that

a variance

be

granted

until November

l,

2001

which is

one

month

after the

estimated

project

completion

date.

O

B.

Descrjption

of Business

and

Area Affected (8

104.121(b))

The

City

is

a

municipality

located

in northwestern

Iliinois

on

the

Mississippi

and Rock

O

Rivers,

186

miles

west of

Chicago. The

City owns

and

operates

its own

server

system

and

treatment

plants.

The

City is

served

by

two sewage

treatment plants,

but

only

the main

treatment

plant

is rhe

subject

of this

Amended

Petition

for

Variance.

o

c.

Mate

lo4.l2l(c))

The Plant

has

an

8

MGD

design

average

flow

capacity

and 12

MGD

DMF

capacity.

It

a

con.rsts of

two

parallel grit

removal

chambers, 8 primary

settling

tanks,

a complete

rnix

activated

sludge

process,

two

secondary

clarifiers

and chlorinating

facilities.

Treatecl

effluent

is

clischarged

into the

Mississippi

River. Flows

in

excess

of the maximum

amount

that

can be practicaily

treated

D

are bypassed

and

discharged

through

Outfall 001A

to

the Mississippi

River.

D

---

D.

Materials Discharged

({

104.121(d))

The Exception

previously

granted

by the

Board

covered the

main

treatment

plant

bypass

00lA

which discharges

combined sewer

overflow.

E.

Present

Failure

(6

104. l2l

(e))

The

variance

requested is somewhat

unusual

in

that the City already obtained an

Exception

to the requirements

of

35 Ill.

Adm. Code

$

306.305(a)

and

(b)

on

May 9, 1986. The

present

dilemma

stems from

the erroneous description in

the

May 1982

Combined Sewer

Overflow

Study by

the

City's

prior

consultant that

the

DMF fcr

the

Plant

was l6 MGD. The l6

MGD

figure was mentioned in

Paragraph l5

of the Joint Petition for Exception

which

was

thereafter

adopted by reference

as a condition

to the Board's

Order

granting

the Exception.

This

error

has

been

further

perpetuated

by the inclusion

of

the l6 MGD figure

in

the City's NPDES

permit

as the basis for calculation

of loading limitations.

If the 1982

Combined

Sewer Overflow

Study had

contained the

correct DMF

of 12 MGD,

that figure would

have been

adopted

as

a

condition

to the CSO

relief

granted

to the City

and this Amended Petition

for

Variance

rvould

be

unnecessary. The

City is moving forward

to design

and

construct

modifrcations

to

its

Plant

which

will

allow

it

to treat

a

DMF

of

16

MGD.

The

City cannot

presently

treat flows

in excess

of l2 MGD

without

suffering

solids

washout

which

will

lead to

the loss of biological

treatnlent

capabilities.

As

a consequence,

the

City cannot meet

the

eflluent lirnitatior's

contained in

its NPDES pernrit

while

directing

l6 MGD

through

the

plant.

Accordingly,

the City limits flow

to

approximately

l2 MGD

by using

the

CSO

Outfall 00lA to

discharge volumes in

excess of l2

MGD.

F.

Compllgnce

Plan

(8

104. l2l

(f))

---

t

c

o

o

o

The

City

is

already

proceeding to

design

and

construct

modifications

to

its Plant

which

will

allow

it to treat

a

DMF

of

16 IvIGD.

These

improvenients

include

an

additional

final clarifier,

cligester

refurbishmen-t,

ael'ation

basin

improvements

and

various

piping

modifications.

Exhibit

4

is

a

compliance

program

schedule

to carry

out this

work

which

is currently

estimated

to

cost

$2,500,000.00.

With the

eombination

of

the

new sludge

d.ewatering

equipment

installed

in early

t997 ardthe

proposed modifications

to

the

Plant,

the

City will

be able

to treat

a

DMF

of up

io

16

MGD.

G.

Environmental

Impact

(ti

104.121(g))

The

granting

of

the

requested

relief

will

have

no adverse

impact

upon

the environilent.

lf

the correct

DMF

of

l2

MGD

had been

included

in

the

May

1982

Combined

Sewer

Overflow

Study

rather

than

the

l6

MGD

figure, it

would

have

been adopted

as a

condition

by the

Board

and

incorporated

into

the City's

NPDES

permit. Moreover,

based

on two

stream

impact studies,

the

Bcrard

found

in

its

May

9,

1986

Order

granting

the

Exception

that

the

CSOs

from bypass

00lA

produce

minimal

impacts

on the

Mississippi

fuver.

The

l6 MGD designation

error

does not

affect

the

validity

of the

conclusion

that

the

bypass

produces minimal environmeutal

impacts

sirtce

the

May

1982 Combined

Sewer

Overflow

Study

was

based upon actual

overflorv

monitoring and

sampling

data,

and

the

Huff study

was

based upon

analyses

of sediment

and stream

samples.

The

conciusions

of

these

studies

remain applicable

today

because the

studies

evaluated

the

impact

of

the

Plant

as

it actually

existed,

not based

upon

the

mistaken characterization.

H.

Past Cornptiance

Efiorts

(Q 104' 121(h))

The City

constructed

all

modifications

to the

sewer

system

required as conditions to the

Exception

consisiing

of

improvements

to

ttre

screening

system,

flow diversion by increasing weir

o

---

)

elevations

and

interceptor

chamt,er

modificltions.

Further,

the

City

cornpleted

the

installation

of

I

new sludge

dewatering

equipment

in early

1997'

I.

Compliance

Alternativp{$i-Q4-12(il)

The only

compliance

alternative

for the

City

is to

seek

permallent corrections

to

the

t

Exception

and

the

City's

NPDES

permit

to

reflect the

actual

l2

MGD

present DMF

of the

Plant

J.

Interim

Measures

(Q

104'.i21(j))

O

As discussed

above,

the

Roard

has

previously

found

th.ai

the

CSOs

frorn

bypass

00 i A

produce rninimal

environmental

impacts

on

the

Mississippi

River.

Accordingly,

there

is no

^

adverse

environmental

impa:

I

to

minimize.

Furtherntore,

the

City

cannot

treat

peak flor-l.5 eu"t

12

o

MGD during

the

interim

and

comply

with

the

effluent

limitations

in

its

NPDES

perrnit.

K.

Stateinent

of

Hardship

(8 l04.l2l(k))

O

The

erroneous

description

in the

Combined

Sewer

Overflow

Study

that

the

DIVIF

oithe

plant

was

16

MGD

was unfortunately

referenced

by

the

Board

as a

part

of

the

Exception

and

O

thereafter

made a

condition

of

the

City's

NPDES

permit.

Upon

discoverinp;

this

error,

the

City

has no

way

of

increasin;

the DMF

from

l2

MGD

to

l6lv'iGD

without undertaking

the design

and

construction

of the

modifications

cescribed

above

in Section

F.

Without

the

requested

variance,

t

the

City

will

be

in apparent

violation

of the

Exception

granted

unrler

35

lll.

Adm. Code

$

306.305(d)

as

interprcted

by

tire

Illinois

EPA

a:rd as

included

in

its NPDES

permit

until

completion

of

the

modificatiorrs.

Thus, the

City

rvould

be

subject

to the

requiretnents

cf

35 lll.

o

Adm.

Code

$

306.305(a)

and

(b)

to

construci

and

operate

cettain

CSO

transport

and

treatnlent

ihcilities

which

were

estimated

in

1985 to

cost

$54.9

rnillion

in capital

costs

and

$6.9

million in

3

annualoperatirig

costs.

(Exhibil

2

at

page 7).

o

---

L.

Consistencv

r.,ith Federal

LaW

The

Board

may

grant

the

relief

requested

consistent

with

federai

law. The

g;anting

of a

variance

woulC

not

violats

airy of

the

provisions

of

the Clean

Water

Aci, 33

U.S.C.

{$

l25l

to

l1]87.

Assrrming

the

Board

g!'ants

this variance,

the

City will

seek a

rnodifrcation

of

its

NPDES

pelmit

to

correctly list

a

DMF

of l2 MGD

and calculate mass loadings

on

ihis correct D\ lF tevel

urrtil such time

as these improv(.;'nents

are cornpleted.

I

M.

Waiver of Hearing

The

City hereby

requests

a hearing

iir

this

matter.

-

N.

Affrdavit

D

The

affidavit

of Mr. Robert

T. Hawes,

the

Direcror

of

Public

Works

for

the Citv. is

attacired

as Exhibi: 5 in

support of

the material

facts

asserted in

this

amended

petition.

)

coNCLUsIoI.

The

City requests

this variance

to correct

an error which

was originally

contained

in

a

N4ay

1982 Combined

Sewer Overflow

Study

which stated

that

the DMF of

the

City's Plant

was l6

)

I\4GD. The

actual

present

DMF

of the

City's Plant

was

and

is l2 MGD.

Unfoilunaiely,

this error

was

adopted

by reference

as

a condition

to the May

9, 1986

Order

by the

Board

granting

arr

)

Exception

to

35 Ill.

Adm.

Code

$

306 305(a)

and

(b)

and thereall:: included

in

the City's

NpDF

permii.

The Board previously

found

that

CSOs from

the Plant produced

rninimal

environmental

impact on

the MississippiRiver.

Nevertheless,

the

City

is

proceeding

to

implement

improvemenis

I

to its Plant including

an additional final

clarifier,

new

digestcr

and various piping

nrotlifications

which

wili

enable

the

Plant

to treat

a DMF

up

to 16 MGD.

Accordingly,

the

Board

should grant

)

the requested

variance

based

upon the

arbitrary

and unreasonable

hardship

which

yrould

he

---

imposed upon

the City

if it w'ere

not

able to

avail

itself of the

May

9, 1986

Exception due

to

the

l6 MGD error

and to

provide

the

basis to

modi$ the

City's NPDES

permit in

the

interim.

iilithout

the relief

granted

in the

Exception, the

City would arguably

be subject

to

the

requirements

of

35 lll.

Adm. Code

$

306.305(a) and

(b)

to

construct

and

operate

certain CSO

transport

and

treatment

facilities which

were

estimated

in

1985 to cost

$54.9

million

in capital

costs and

$6.9

million

in

annual

operating

cosis.

WHEREFORE,

the

City respectfully

requests that

the

Board

grant

the

variance

relief

requested

in

this

petition.

Roy

M. Harsch

Thomas A. Iramilton

G,\RDNER.

CARTON

& DOUGLAS

O

321 North

Clark Street

Suite

3400

Chicago,

Illinois

60610

t

,

o

a

o

Respectfu

lly submitted,

CITY OF

R

o

---

a

I

o

o

a

a

o

o

o

a

O

o

---

I

lil

=l

61.1

rll

a.l

uil

-_t

la: I

hl

al

l-l

l:l

it

I

h

a.

li

ff

n

Hi

4

a..

BEFORE

THE

ILLINOIS

POLLUTIOH

COHTROL

EOARO

I!

ry-E

NTATTER

0F

THE

.JOINT

PETTTION

)

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TtE-ciil

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)

sEyER

ovERFLot{

REGULATIoNs

t

PC8

85-

PETIIION

FOR

EXqEPTIOH

H01{

cOr'lE

the

ci

ty

of

Roe

k

Isr

and

(',cf

ty

"

)

,

Rock

Is.rand

county,

11

r i

noi

s,

by

its

cfty

lilanager,

J.

Neil

Nielsen

and

the

I'l'tinois

Environmental

protection

Agency

("Agency"),

by

its

Hanager

of Environmenar

prograns,

Roger

A.

Kanerva,

pursuant

to

35

I'll.

A&.

Code

306.353,

and

respectfully

requests

that

the

I1'linois

Po]'lution

contror

Board grant

an

exception

to 35

Iil.

Adm.

code

305'305(a)

and

(b)

to.rerieve

the

city

of

the

requirement

to

construct

and

0perate

certain

combined

seHer

overf.tow

(uCSO,,)

transport

and

treatrient

facilities'

The

Petitioners

submit

that

because

existing

overf'lows

from

the

city

of

Rock

island

haye

minimal

impact

on

the

water

quarity

of

the

r'rississippi

River

and

do

not

restrict

strearn

use,

the

constru.ction

of

the

requfred

csO

facirities,

estimated

to

cost

in

excess

of

$55

miilion,

vou.!d

be

unreasonabie.

In

support

of

this

request,

petltioners

state

as

follows:

l'

The

totai

popuration

of

Rock

Isrand

is

45,g52,

per

u.s.

census

(1980)'

The

city

is'located

in

Northwestern

illinois

on

the

l,tississippi

and

Rock

Rivers,

186

miles

r,est

of

chicago.

The

cfty

owns

and

operates

its

own

seyer

interceptor

systern

and

treatment

piant.

2.

thr

l'!ty

is

see,L.ing

relief

from

Section

306.305(a)

and

(U)

which

requlres

,

1!',ruct

co,?rbi,ned

seHer

overfror

transport

capacity,

pumping,

gr.it

remo

"';

.

'je,

primary

settring,

disinfection

and

upgrade

of

existinc

---

'(

(,,^

facl

I

f

ties

to

trp,r

{

not

surmarlze

and

granted,

ten

ffmes

the

and

city's

dry

treat

the

xeather

an

cost

csO

additional

faciritfes

of

flow.

those

The

e.{cess

required

whieh

folloring

stonn

wi,

facilitfes.

be

paragr6pl5

f.l

ow

required

consisting

The

of

if

studies

the

an

of

exception

petition

first

and

flush

xi,l1

is

;::;:Tions

which

showed

existins

cso,s

have

only

minimal

impact

are

,hich

the

cip.j:,ii:::::';t"phs

or

this

petition.

The

cs'

racirrties

existing

detair.

and

A

description

propased

treahent

of

the

.peration

is

an

included.

exception

and

control

perfor

is

granted

Equipnent

are

described

both

for

in

exfsting

facill

exceptfon

is

presented.

ties

is

described'

Fina''y,

the

rerrofirilr]c€

justi

fication

of

the

for

city's

gran*ng

an

CSq

FACILITIES

REQUIRED

8Y

T}IE

RULES

dry

comprete

for

Exhibits

with

weaiher

relief

3'

35

Irl'

treatnent

A

Ihe

is

and

frow

Adn.

city

not

B,

rourd

granted.

pp.

code

has

for

73_lE6).

receive

determined

the

306.305(a)

first

An

primary

additional

The

frush

prerinrinary

and.(b).

City

sedimentation

of

is

ten

storm

present.ly

(For

cost

(.l0)

frows

a

estiinates

times

detaired

and

provfded

required

disinfection.

the

expranarorr

for

average

this

to

canprianee

providerequest

design

It

5€€

::ll,:l::

:j:l;,:T.:;::

,.:'.'ow

srouRd,

covered,

off*rine

storase

treatmnt

treatnent

bvpasses'

of

plant,

These

flrst

and

storage

flush.

vould

facirities

alion

Ld.

at

for

l4t.

wouro

total

occurrence

oo.r.,.

capture

of

,;;,",::r:_tl:::

and

overfloyJs

ntegration

or

p)ant

with

the

main

subsequent

secondary

to

allow

4.

attainment

The

ful

I

,

cotnpliance

of.,,,-^-.

proposal

,

would

upgrade

the

'-

sF,'qse

Ene

main

treatrEnt

piant

an

d

hyd

raur

i.

.u

p..

i

;.

T;j-";:,:'::1T:",T

t

rea

tmen

r

p

r

an

t

c

ompo

ne

n

t

s

lion

for

flows

over

and

---

.&:,{l

lj rtl

,i

if

ijl

:I

-l;1

i{i:

l

.t'N:

E:

r:

.t

'!.:

.ii:i

:.1

i:

*'i

tt ti

:-fri

tf.:

:-! i

a.'al:

)1.':

1s*

above

those

either

captured

or

taken

through

the

main

treatment

plarit

would

be

provided'

The

proposal

invo'lves

an

optimum

cofibination

of

upgrading

the

nain

treatnent

plant

for

seconda.rT

treatrnent

of the

captured

flow

and

primary

treatmnt

and

di

sinfection

through

sedimentatf

on.

IId.

at

149,

f igure

47.

A1

r

flows

greater

than

the

capacity

of

the

main prant,

storage

and

primary

treatmnt

facil

ities

are

discharged

rithout

treatmnt.

The

cost

of

tiie

.least

expensive

full

comp'liance

alternative

l,as

est{mated

in

19g2

to

be

15.z

mil.lion

dollars'

and

the

annual

operation

and

maintenance

costs

Here

estimated

to

be

3.7

mil'llon

do]lars.

id.

at

lg1.

Later

figures,

as

set

forti

in Exhibit

A,

would

change

the

respective

costs

of

the

project

to

$5q.9

mi.llion

in

capital

costs

and

$5.9

milrion

in

operating

costs,

if

treatment

based

upon

totar

suspended

sol

ids

(Tss)

was

rcquired.

The

amounts

rcurd

be

sr

ightry

.rower

if

treatnent

based

upon

biological

oxygcn

demand

(gOO)

ras

required.

It

is

assumed

that

these

cost

estimates

wourd

be

revised

upwards

significantly

if

a{'usted

for

the

cument

value

of

the

dollar.

OHTROL

EQUIPI,{ENT

5'

Rock

Isrand,

rike

most

order

cities

in

the

lridrest,

originalry

c.nstructed

combined

se'ers

to

convey

both

n'nic.ipal

sewage

and

stonnxater.

Through

the

years,

the

city

has

embarked

upon

a

se'er

separation

progran

which

has

left

only'l7x

of

the

system

still

combined.

There

are

five

combined

sewer

overf'lows

and

one

treatnent

prant

bypass..which

discharge

po.rutants

into

the

l,tissi

ssippl

R{ver.

6.

The

C{ty

of

Rock

Island

is

served

by

only

the

main

treatnent

plant

is

the

subject

plant's

seryice

area

is

delineated

in

Figure

treatnent

plant

serues

an

area

of

5,600

acres,

i7t

or

g70

acres

of.rhich

are

two

sewage

treatrent

plants,

but

of

this

joint

peiltion.

The

main

2

of

Exhibit

A.

The

main

---

1i

served

by

combined

sexers.

These

areas

are

shown in

Exhibii

A,

Figure

3.

Tne

sewer systm

ls

conposed

of

approximately

170 mi'les

of

sewer.

pipe

sizes

range from

flve

lnch,

to

ni.ne

feet

by

eight

feet

outfal'l

at

the main p.lant.

shallow sehers

lie

at

a

depth

of three feet,

whi'le

the

deepesi

are

from

thirty-five

to

forty

feet

below

the

ground.

The

average

depth

of

the

sewers

is

betvien

efght

and

ten

feet.

The

system

uses

tuo

ma;'or

interceptor

sewers

the "north

slope"

and

"south

s'lope."

7.. The

north

srope

interceptor

is

a

ninety-six

inch

sewer

with

a fur.l

pipe

capacity

of

204

mgd.

The

souilr

slcpe

interceptor

is

a

seventy-two

inch

setler

rith

a

ful1 pipe

capacity

of 135.8

ngd.

The

main

treatmnt

plant

has

an

8

mgd

design

average

flow

capacifl

and

a'15

mgd

design

maximum

f1m

capacity.

tt

consists

of

two

para'Her

grit

removar

chambers,

eight primary

settring

tanks,

the

complete

mix

activated

sludge

process,

tlo

secondary

crar{fiers,

and chlorination

facilities.

tt

was

designed

to

treat

a

BoD

loading

of 62,s00

PE.

Treated

effluent

is

discharged

into

the

r,rississippi

River.

sTR4lt

IHPACT

A}{

t-YsEs

8'

Two

stream

impact

analyses

were

perforined.

The

nrost

recent

(Exhibit

C),

performed

by

James

E.

Huff,

p.E.,

on behalf.

of

Rock

Is.land,

assessed

the

effect

of

eso

on bottom

sediments.

'

Mr.

Huff

assessed

stream

impact

throuqh

independent

sampling

of

the

bottcm

sediments

and

by

anarysis

of

previous

sampling

data

col'lected

by

the

Agency

in,iu1y,

l9g4

and

by

l,lissman,

Stanely

in

May,

1985'

Id.

at'1.

All

samp'les

were

subjected

to

chemical

ana'lysis

as

well

as

physicat

irg"".ion.

campl:s

nere

anaryzed

for

'read,

zinc,

oii

and

grease,

volatj'le

I

solids,

arrd

toiai

so1ids.

In

addltion,

the

samples

were

ranked

blind

by

three

individuars

for

odor

intensity.

The

Huff

study

found

that

the

discharge

from

the

Rock

isrand

outfail

structure

has..rr.rt.d

io

u

---

I imi

tecl

area

al

ong

the

near

shore

of

the

ri

ver

wi

th

er

evated

po.l

.rutant

levels.

Id.

at

5.

Th{s

area

is

approximatery

five

hundred

feet

in

rength

by

fifty

feet

ln

rfdth"

Ihe

leve'ls

of

pollutants

are

all

below

the

nean

values

the I'llinois

Environrnntal

Protection

Agency

found

in

its

survey

of

sediments

rithin

one

mjre

of

wastewater

treatmnt

p'rant

outfails,

with

the

exception

of

zinc'

Id'

at

Appendix'

A]'l

zinc

values

Here

within

one

standard

deviation

of

the

Illinofs

Envlronmentaj protection

Agency,s

rEaR

value.

There

is

no

sedlmentatlon

belon

the

c50's,

where

the

river

bottcrn

consists

of

soiid

rock.

:

Thus,

there

is

minimar

impact

in

t,e

receivrng

stream

frcrn

the

city,s

cs's.

9'

A

study

was

arso performed

by

r,{issman,

stanrey

&

Associates,

on

beharf

of

the

city

in

rgg2

to

determine

the

frequency,

magnitude

and

rrnpact

of

the

combined

sewer

overfrows

into

the

Mississippi

River.

Exhibit

g,

$s5-g

ana

10'

The

study

invo'lved'l)

npnitoring

the

combined

sewer

overflows

in

the

system,2)

determining

the quantiv

and

qua'rity

of

the

sewer

system

overflows,

and

3)

assessing

the

impact

of

the

overflows

on

the

Mississippi

River.

The

stu(y

concruded

that

arthough

the

city

is

not

neeting

appricabre

effluent

limitations

because

of

the poilutant

overf'row,

the

impact

of

the

overf.roH

on

the

Mississippi

River

is

minimal.

:

10'

The

study

was

conducted

using

historicar

records

as

we.t.r

as

a

fie.rd

investigatfon

which

consisted

of

monitoring

the

five

cso

aischarg.

poinar.no

the

treatrent

p'rant

bypass,

recording

r3.jnfar'r

data

and pnysicariy

inspecting

the

receivlng

streams.

In

order

to

quant.ify

the

volumes

and

rates

of

flow

discharging

frcm

ure

sewer

system,

six

portabre

continuousry

recording

flow

meters

vere

instalred

at

the

cso.rocations

to

measune

overfror{s

to

the

Misslsslppi

River'

In

addition,

Rustrak

event

recorders

were

connected

to

the

se'en

storil

pumps

at

the

Main

l'{unicipal

sewage

Treatnent

prant

to

continuously

---

I

record the

length

of

time

each punp

operated

during

plant

bypassing

caused

by

storm events.

To

quantify

the

quality

of

flq}r

being

discharged

frcm

the

cso

system during

storm

eYents,

two

portable,

automatic

samp'lers

Here

installed

and malntained

at

tvo'tocations

Hithin

the

system.

overflow

samples

from

five

typica'l

storm

events

at

each

location

were

collected

at

preselected

time

intervals

to

provide

baiic

data

on

effluent

water

quality.

These

samples

were

analyzed

for

the

following

constituents,

'l

)

biologicai

oxygen

demand

(u800,,1,

2)

chemicar

oxygen

demand

("c'D'),

3)

suspended

so'rids,

4)

tota.r

dissorved

solids'

5)

armonia

nitrogen,

6)

phosphorus,

and

7)

reaa.

The

impact

of

the

overf'ows

frcm

the

five

cso

discharge

points

ud

the

main

treatrBnt

prant

outfall

rcre

assessed

through

physical

investigation.

11.

The

comprexity

of

Rock

Isrand's

combined

sewer

systsn

requrred

the

use

of

a

mathematical

nndel

to

project

the

overf'tow

quantities

assoclated

with

the

various

storm

conditions.

The

simplied

storm{ater

management

model

ss}/H}l

developed

by

USEPA

was

used

to

get

a reasonable

picture

of

the

characteristics

of

the

overflor*s

that

occur

from

Rock

Island,s

seler

system.

SSHIfi

was

used

initia'l'!y

to

describe

.the

basic

rainfal.l,/overflow

relationshfps

for.the

study

area

based

on

the

entire

period

of

rainf.a.ll

records

available

(2g

years).

The

model

was

cajibrated

using

data

obtained

from

the

twenty

storm

and

overf.low

events

monitored

during

the

field

investjg.ation.

In

Hareh,

19g0,

the

City

began

to

rnnitor

and

sampre

the

five.or."irow

locations

on

the

r,,rississippi

continuousry

for

twenty-one (2r)

weeks.

The purpose

of

the

monitorlng

and

sanpl.{ng

progran'xas

to

co]lect

basic

data

on

the

overfrow

quantity

and

quar

ity

frsn

the

cso

to

the

r,li

ssi

ssippi

furing

storm

evenrs.

Any

probrms

found

rcre

corrected

irrnediatery

pursuant

to

a

weekry

maintenance

program.

overflol

quantity

was

anaryzed

in reration

to

rainfail

for

arl

oi

the

cso

---

(.

rcni tored

si

tes-

Linear

regressions

of

ralnfal

I

versus

total

overf'l

ow

were

deve'loped

for

the

entire

system.

Linear

regression

was

also

used

to

determine

peak

rates

of

cmbrned

sewer

overfrows.

gased

upon

this

mode.r

,

it

t,as

determlned

that

820

m{l'lion gallons

per

year

of

combined

sewer

flo,.,

is

being

discharged

to

the

r'flssissippi

River

from csO.

Id.

at

ii

and

36-37.

1?'

First

flush

analysis

was

performed

by

tabulating

significant

rainfa.ll

events

whlch

were

f'lcw

recorded

between

Harch

lSth

and

A.rgust

g,

19g0.

These

events were

monitored

at

tr+o

overf'lor

'tocations.

The

first

'location

indicated.

a

need for

ccmplete

first

flush

treatnrent

of'12.2

million

gallons

based

on

TSs

and

5.6

million

gallons

based

on

g00;

the

second,

5.3

million

gallons

TSS

and

3.9

milllon gailons

900.

The

detailed

anaiysis

can

be

found

in

Exhibrt

B"

'During

the

.|03

annual

overf'low

stonn

events,

the

esilmated

total

annual

mass

load{ngs

h€re

cqnputed

to

be 610,000

pounds

of

BOD

and

4,500,000

pounds

of

suspended

solids

from

a'li

cso's.

0ver.gG

of

these

mass

loadings

are

discharged

at

the

main

treatnBnt

plai:t

through plant

bypass.

Exhibit

B,

page

67.

Because

of

the

size

of

the

Hississippi

River

and

its

high

flows,

it

has

considerable

assimi'lative

capacity

to handle

a

substantial

anount

of

poliutant

mass'loading.

Based

upon

this

capacity,

csO

plurre

test

results

and

the

Illinois

Environmenta'l

Protection

Agenc-v's

oHn.

l,liss'!ssippi

test

results

(see,

!{ater

Qua'lity

l'lanagement

Easin

Plan

for

the

Mississippi

Nor.th

River

Basin

and

the

Mississippi

North

central

River

Basir/lg75),

it

rras

concluded

tiat

tlre

city's

c50

irnpact

rs

mrnimar.

The

mean

dairy

flov

of

the

l,rississippi

is

31'085

mgd"

The

ten

year,

seven

day

row

frow

i:

g,900

mgd.

r}e

csg

overfrow

event

based

on

a

one

year

frequency

sto.n

event

i+ould

discharge

52.7

mgd

to

the

Rlver

whlch

is

insignificant

when

compared

to

the

ten

year,

seven

day

iow

fiol

and

the

mean

daily

f'roi

of

the

River

noted

above.

Furthermore,

because

---

of

background

concentrations

in

the

lijsslssipp{,

reduction

in

the

csO

po{nts

vould

general]y

not affect

rlver

water qualfty

downstream.

Thus,

"the

Rock

Isiand CSQ's

by themselves

have

a

effect

on

the l'lfssiss{ppi

River

*ater

quality.,,

see,

Exhibii

JOI}{T

IGREB'IEHT

mass

loadings

6g

upstream or

negl

igibl

e

A,

page

'176.

'13'

0n

September

26,1985,

the

Agency

issued

a

letter

iExhibit 0) to

ure

clty

agreeing

tl

support

this

ioint

petition.

The

clty

in

turn

agreed

to

ccmply

rith

certain

stipulated

cond'itions

set forth

in

that

letter.

The

city

has

agreed'to

fully

comply

wit}r

the

listed

conditions

as

an

alternative

to

maklng the

npdifrcations

to

its

system

descrlbed

in paragraphs

3

and 4

above.

'14.

By

complying

vith

the

conditions

of Exhibit

D,

the

cig

wilj

be

abie

to

avoid

constructing

the

above-described

csO

treatmnt

facilfti'es

whlch

would

have a maximm

capital

cost

of

$54.9

mi1'lion,

and

maximum

operating

costs

of.

$6'9

million peryear.

The

modifications

which

the

city

wil'l

now

make

if

thls

exception

is

granted

are

described

fn

detail

fn Exhibit

E.

l5'

These

rpdifications

essentially

involve

the

construction

of

head

works

improvements

to

allow

operation

of

the

treatment plant

at

the

design

maximum

flow

level

.of

sixteen

million gal'lons

a''day.and

to

construct

improvements

to the

north

slope

interceptor

systen

to

assure

that

maximum

availab]e

transport

capacity

wiil

be

uti'rized

prior

to

bypassing.

The

city

will

also

implement

a

one

year

shore'rine,i'ispection

program

and

improve

operat{on

and

ma{ntenance

practices

at the

treatmnt plant

so

tJrat

sludge

and

debrls

are

not

xashed

out

frcrn

the

wet

we]]s

into

the

river.

16'

The

rpdifications

will

conslst

of

I

)

improvements

to

rJle

screenlng

systen

at

a

project-e<l

cost

of

$75,000,

Z)

flm

diversion

by

increaslng

weir

elevations

at

a cost

of

33,000,and

3)

interceptor

charnber

npdlficatior,

.a.

cost

of

$23,000.

The

totar

cost

cf

these

modifrcations

wourd

be

$.r0r,000.

---

17'

There

is

a

minimar

impact

upon

the

ifissrssippi

River

frora

Rock

Island's

exlstlng

ecmbrned

se*er

overfrws

and

there

shou.rd

be

even

Jess

impact

as

a

result

of

the

iointly

proposed

inodliications

to

the

treatrnent

systems.

Grantlng

the

requested

exceptlon

wou.ld

provide

a

cost

savings

of

over

$55

milflon

from

the

cost

of

Rock

Isrand,s

ccmplrance

rith

the

express

terms

of

the

rule.

The

grant

of

this

petiilon

is

absoluteiy.essential

because

Rock

Island

does

not

have

the

economic

base

to

afford

such

a

staggering

sum.

I{HEREFoRE,

petitioners,

Ilrinois

Environmentar

protection

Agency

and

the

city

of

Rrck

Is'land

respectfully

request

thht

the

i'llinois

pollution

contror

Board

hold

public

hearings

upon

this petition,

and

that

the

petition

for

an

exception

to

the

cqnbined

ser{er

overflow

treatrent

regulations

be

granted.

Respectful

ly

submi

tted,

CITY

OF

ROCK

'ISLIIID

ILLIHOIS

ENVIRONIIENTAL

PROTECTIOH

AGEIICY

TF:

sdlsp/30Ssen

-l

2

8y:

---

I

I

I

a

o

o

3

o

o

o

a

---

t

I

1,,.

)

3'

I

1

i

D:,1

S.

I

1rl

6

o

p

E

Di

I

I

!

I

aq

I

!

E

a;

(

ILLINOIS

POLLUTION

CONTROL

BOARD

Hay 9

'

1986

IN

TIiE HATTER

OF:

I

)

THE

JOINT

PETITION

OF

THE

CITY

)

OF

RCCK ISLAND

AND

THE

ILLINOIS )

ENVIRONMENTAL PROTECTION

AGENCY

)

FOR

EXCEPTION TO THE

COHBINED

)

SEHER

OVERFLOI.I

RECULATIO}IS

)

PCB 85-214

HR.

ROY H.{RSCH APPEARED

ON

BEHALF

OF

THE CITY

OF ROCK

ISLAND

HR. THOI{AS DAVIS

APPEARED

ON

BEHALF

OF

THE ENVIRONMENTAL

PROTECTION

ACENCY

OPINION

AND ORDER

0P THE

BOARD

(by

R.

C.

F1ema1):

,

This

maEter

comes

before

the

Board

upon

a

joint

petition

for

a combined

sener overflol

(CSO)

except,ion

filed

pursuant

to

35

I11. Adm.

Code,

SubtitLe

C, Chapt,er f,

Fart

306,

Subpart

D,

by

the City

ofsRock Island

("Rock

Island")

and

the fllinois

Environmental' Protect,ion

Agency

("Agencyn).

PeEit,ioners

specifically

requesl

exception from

35

I11"

Adm.

Code

305.305(a)

and

306.305

(b

)

.

The

Board

conduct,ed a

public

hearing

in Rock

Island

on

Harch

3,

1985.

In

additio.l

Lo testimony.

presented

by

the

Joint

Petit,ioners,

testinony

in support

of the requested

relief rras

presented

by

ils.

Emily Srnith,

chairperson

of

the

Rock

Tsland

Facilities

Seudy Jury

of

Experts.

Ttre Jury of Experts

eonsists

of

thirEeen citizens,

represenEing a cross-section

of

comraunity

interests, vho

have

folloved

the progress

of all phases

of the

CSO program

for several

years.

GSO.

.RECUtATI.ONS

The

CSO regulations

are contained

in

35

I11.

Adm"

Code,

Subtitle

C, Chapter I,

Par., 305.

They

yere

amended

in

R8I-17, 51

PCB

383,

Harch

24, 1983.

Section 306.305 provides

as

folLovrs:

A11 combined sever overflo,*s

and

treatmen|:

plant

bypasses shalL

be

givdn

sufficient

treatment

to

DrevenE

pollution, or

the

violation

of

applicable

water

standards unless

an

except_iori

has been

granted

by the

Board pursuant

to

Subpart,

D.

59425

---

't

.l

-r!

.r,!:

.E

!::.

O,T.

-?--

(.

.;.

6

t+

:ii

Sufficient

treatment

shall

consist,

elf

the

folloving:

a)

fl0ws

A11

dry

as

veat,trer

determined

flons,

by

the

and

Agency,

the

first

sha11

flush

,"ni

of

tr,"

st,orro

.

applicable

effluent,

sEsndard!;

and

_

b)

reEenlion

pr:'mary

no.

f::_:!:.

AddiEional

less

fgsipn

tre6tment,

than

time;

flonsr

ten

yearr

and

6s

Limes

:nd

delermined

sha11

disinfect,ion

to

receive

average

by

vith

dry

a

the

minimum

veather

Agency

adeguiie

of

buE

flow

c)

neces:ary

deposirs'

shall

Fiovs

be

in

treated,

excess

!9

froicing_debris

prevent

of

in

those

vhole

accumulations

described

and

o,

in part,

of

in

sludee

subsection

Eo

the

exE,enE

(b)

depress

wich

35

ion

r1r.

of

Adm.-code

oxyrr,en

leve1s

3o2.2o3.

;

oi

"oiia"-li-iIEJra"r,."

and

r"

pi"""ir-

d)

Compliance-rviEh

rhe

Board

in an

a

exception

treat,ment,

grintEa

program

pur"""nu-;;-

authcri

ze,3

by

,

SubparE

D.

I

minimal

except,ion

rsland

subparE

has

ciischarge

eirher

done.

D

a*ovs

sing1y,.

I

impact

Joinc

the

ai

or

peiitiol

discharger

provided

joinriy

qay

viitr-ilr"

in

to

.""t-un

section

fir.e

agln"t;-;;

a

exception

petit,ion

305"3Gr(a):

nl"t.for

based

an

on

rece:i.ving,

accessibility

impact.shall

An

(residential,

exception

stream

justification

include'

commerciaf,

to

rat,ios,

sEream

as

and

-a

known

minimumi

based

side

stieam

upon

land

an

use

minimal

uses,

evalua.ion

acti.rities

discharge

of

recrearional)

inspecr,ions

of

,

,rnnacurai.

frequency

dnd

Uottor'-J"fo.i.c.

"gii""fl"fur,

extdnt

or

ou"iFior-IJrr,.",industrial,

,

-;;;;;

and

unnatural

results

floaeing

oE

timitea

material

stream

or

colbrr_stream

morphology

,-'=.

Rock

inpact"

lsland

showing

and

pursuint,

the

Agency

to

believe

Secrion

t!:y

30'6.SSfi"j

"r.t"ri."ir-rn"ir""!.t""'!q"g

maile

the

"minimal

suPPoRT.

pocuMENIS

r

Exhibir

in

sit,uation,

support

Rock

2

(rereienced

rsland

of

the

the'petition,

reports

has

undertaken

as

of

Exhibir

r*hich

rtre

have

severar

g-in"Ji,ini'I"t.irionl.

principal.

been-"uoritt"d

studies

anong

of

these

its

"i*ili::

as

exhibics

is

cSO

Thisthe

::

AugusE

l::yT"n.

sE,udies

I

t

19E3

a

is

response

augmenEed

(

Ex. r;

supplement

riierencJa

by

rrro

oLher

-to

ar-r,.rriiii,:

the

Mir!i;;;

iEFA'r""i.r-i"....-ori"o

i=i'

lirnr"y

Joine

&

Associaces

pecirion)

r

:.:;1

s*l

;'r!l

69-426

---

6s

P'E'

Exhibir

A

fourLh.maj_or

c

in

ioinr

docunient

puf

il'io;t-;;;

submitted

-;;";;r"";

as

Exhibit

by

James

3

(referenced

E.

Hurr,

record

'

and

before

dears.

the

vieh-cso-;;i:,cEs

Board

arso-

contains

on

3tricm

several

boE.om

exhibits

sedinre

si:bniE,t,ed

irs.

The

il":;fiE:tt'

or

part'i.cur"r-ilieccs

or

rhe

tesiimony

presenrer

ac

qACKcROIJNg.

own

includes

Erearmenr,

Hississippi

(

-

r9B0

sysEem

The

c"ns'r")

approxirnarerv

city

planrs,

of

and

.

servers

of

.is

no"t

Rock

rhe

r-ocaJ;;-;;'noirtr""i"ri

and

ni""rll

Main

rsla'ia,

izo-iir"r-"F-;;;;r!.-

vasle

Rock

rhi"h

treatment

rsia;;

has

a

plants.

;;n"

population

iirinois

rr

and

arso

The

operares

on

inllu<:es

of

systemrhe

46.g62

iEscvo.

-iiain

the

the

joinr

Hain

piant

peEi'ion.

and

iBs

Th;-H;ii

iriU.iury

pi""e

seser

and

i.

rn=-iournr".i-iiliil-..o,ry

sysEen

are

the

subiect,

of

r.ncercepror

Slope

Interceptor,.

seyers,

the

Norrh

si"t;

iit"ii"p.or

"iir"a

by

and

Ewo

Ehe

majoi

sourh

underEook

originally

serving

sewage

As

and

abour

with

a

construcred

sr,ormwat,er.

s5.9

many

2,930

:rillion

older

combiiea

eities

Betneen

piolt"r

in

1970

serr"r"

Ec

the

separaE,e

,nJ-rgib

Hidvest,,

io

JJr,rr.y

combined

Rock

Rock

both

rsrand

JsLand

municipaJ^

severs

commercial

combined.

section

Hain

triburarv

Plarrt

of

ro

rhe

areas

The

(R'.

the

ciry

comb:--.,.a-"r"u"

at-.10).--et-irusent

-of

Hain

Ehe

""r""'oFo;[;

(Ex.

planr'ibio"Je-Eii66'"ll""r

ro),

and

are

;,5oor;:;;;

.ori""pon-J

r.ocated

approxinately

in-the

vi.rh

rriburary

ncrth-cent,ral

remainsL7z

irr""piiriip"r

oE

ro

the

rhe

area

separaLion

vould

be

mosr

"orruni[y

difiicuic'r"i

ii,..-ii"ilur.

1)

vireie

"-ip"inir"

(R.

at

11).

:,: :"il"oiil"ii

::'o;;::g'i::";:1":;";n:'il":;.$:11_

:! ::

crr.rres

:

ou.fal1s

002-006

are

overfrovs

from

the

NorthrreatmenE

plan.i

{i !: i:

'slough-,

"'ffiq".

a

high-velociEy

i:'ssl

1,BBil,

i

j;::li;n"*i:;jir_i!'r',

Hi

s

s

i s

s i pp

i

"iJ"-"r,unne1

.of

th*

H?t

reaches

of

sylvirn

vhich

has

beln

developld-"-I-""'u"e-',,sy

eot

located

upstream

from'tf,"-CS6

discharges

(R.

"'iil:::i3:lrll"ii"n.

at

59).

-3-

and

Pro

Sf

d.

.

P.l,a.n..f

o=r".pOTl.l

.a,nd.

**l

".pgr

t,

'

Ir

pr

""

"*

repLr.

^--r-

y.

.Ex:cepE.ion

.r.:'1epr.agn

oa

da

E,eo

t,e

sepEembeE

x. );

referenced-E

*n

r,.s

.

.f

or

.

..Ioi

n.E.

:-n

Jo:_nE

retit,ion).

These

s

illld*":

consider,

8n:eng

orher

ff5li#;.0:;:::::':1,::^:la.

l::t-

i;i.;;";:;;;:

;x;3p:l!"I"0

:::i: T: ::.

"

y.i

ji

T:_c

ha

ra

c

r

e

r:_

f.i

i"

i'

iF

";

i

i

",iI

;"

"::;;::i

T:::i:;:l:'

"?"

:;:'l:: : ::; :F:i;;";";;'

;i;";;:';":il

:;"lr

cso",

"

no

River.

ii;;;:'""E

or

rhe

impacr,

of

ehe

cverf

lov-s

on

.iI.ii.:]r:;u;;:

59427

---

-4-

voods

vhich

range

in

viaet,-"p

lo

rso-y";;";-;;

rracs

t

and/or

river

sLage

in.-"r-zr-aj."

i5at.ionn11v

-,,^*

tl:nl1ng-in.p8rE

on

ourfalls

The

has

Hississippi

recriit,ional

River

in

t_he

reach

of

the-cso-and.the

bypass

smail

boating

use

is

"""

5gi.il;;*";-uii.ri..t,ing

(R.

at,

22)

t

vater

rs

no.

skiing

addressed

does

in

occur,

the

"rt"t""i.rized

t""orJ

but

the

amount

as

"heavyn

of

lwimming

(R.

at

nhich

29).

occurs

sorne

ne6rest'

supply

Sylvan

is

slough,

dorvnsiream

at

Huscat'ine'

is

also-r"JJ-iJ,

known

ro"ul-rpproximat,eLy

rvithdraval

-inl"'"t"igi.

commerciar

0f vate.-

barge

'fr"

25

io,

miles

,i,,r"rr

public

rraffic.

doynstream.

but

vater

nor

The

DOCUHENT.ATIOry.

OF.

.

XINIHAL

.

LHP.ACT

i:

lil:::l

ff::;:'inlli"ilt;::.':,'li-'::i:t.I_.f

;o

Il;;"91.':;

:":',.i;:' l:::r'ir

!l:.csos.

and

bypass

"i"!

li'5i"in3"l"lill;i;,

J

i, i

i

ol

F

"iii,

f I,l"

5: : ;, i

j

:

;,

:;

"

i.,

i

"

"!

lj_

itr

;';";

:

"':

lil

:::.:

"1,

t;;

if

,ol:t]:.i:l li 3 il:_ :!' ?lll''

ilna'"i!i,,!li

".il:'r:;;:

""

5i

"n

I ll'lli

::I

I"i'. I:::"T:

tL

::I';l

"-iii.

eil

i;,

";::;"

l.lii,

t:;:i":

(

day

sever

f1ov

acEivated

chlorinarion

removal

("mgd')

aapaciry.

The

vith

chambers,

Hain

sludge.processl

a

design

fu1l

frciiiri""l'

Treatn

_rire

pipe

eight

average-iio"

ltoirf;-si"o"

-nt

primary

plant

il!

two

prunr

secondary

consists

capacity

r"t"i."iror:i"

set.iing

h;'"

of

;;-!

clarirrersr

and

g"nt:,

tvo

million

a

para11e1

a

ro

the

ninery_six

mgd

afld

complete

gal.tons

maximum

grit

inch

nrix

per

(

""p""i[y

oE

z}a-;;;:

exeeplron'

As

condiEicns

Rock

rsland

associaEed

vich

granEing

of

the

requested

"gr"""

to undercake-certain

rnodificat,ions

design

s10pe

r-mprovements

!:_:!:

rnEercepEor

maximum

lyr!**.

to

level

al'r-ow

T9r"

of

operaEion

irioiJ!

ii-rii

rhe

and

oi

consir""t,ion

the

improvemen!s

t,reaimenc

of

to

plant

head

the

at

vorksNorth

the

'o

deLailed

esE,imated

s3'0c0'

chamber

modificaEions

increase

a!

capacity

an

est,imaEed

modificat,i.ons

in

The

in

vi11

cost

Exhibir

elevations

I

agreed-

consise

be..

oi

installacLon

utiliz"a-prio,

StOtrOOb.

5.'

co

;;";;""'E;aE

ai-ui:'.lrirated

oi-ri)-irprovemenEs

of-Jr""i"r".-;.;;:-rI'in

inpiovlmencs

Ttre

coit

t,o

:.oprovement,s

rnEximum

of

overf

Ehus

S75,006,'tZ)

cose

1oH

aggregate

av'ilab1e

Eo

of-

evenE,s.

the.

are

s23,ooo,

estimaEed

screening

further

interceitorto

transport,

The

I

ani

tot,al

cosr,

svsEem.

(3)

of

l.li?l?111r

.lnuch

6r

rr.,"-rl"a5"rj

access.

;:::"::

rhe

levee

is

occupi;-;;-iffi,iiiilli'i"ll

l!"ri;li::

Harch

to

August

of

lgBOr

'iI'

an

overFlov

:: : I : : :i,

;lg"::

I t'

;t

;;

";;;

"

"31'!:;';i:1"'!lll"::"9,.:"0

E!o"i'!?

i

iff

: .

o"i'ili"

o;l:"

cons

i.s

t,ed

Progrsm

:l-En"

:;ff

i;::l,"F,3i"ill:::'*:-

::-:l: :i,.-iii"r'"'i"

From

;il:I";ffi"t1::.

net'ers

r

moniloring

oF-ti.-i;;;E;

qua1ity,andphysica1i.".,o..F;'^nnFrL^c:...

d,,a1.iF;,

rranE

punps

:_,

direcr,ed

_.

physical

l!led-discharge

discharge

inspecEio"

co"o"irJri

t,o

or

outfaLl.OOii,

in"-ii"I'330

ooii:

points

nith

of

time

the

Hain

sampling

of

vater

points.

d

ischarge

69128

---

number

program'

an

uEiLized,

average

Dat,a

and

simplified

elong

from

ye6ri.r!"_esr,imar,ion

volumes-

Ehe

virh

of

L9g0

srorm

hiscoii"":.

overflow

monitoring.and

waier

event,s

rras

uun.g"runi-lrJa"r

,!ini.ri-;;;;,

done

t,haE

sampling

uriliii"g-cilrliiJJ.".

could

ro.esrimaEe

progran

be

(ssLtHH).

expect,ed

Has

-

rhe

in

analysis

froro

each

indicat,es

discharge

the

point-f"r-year

foli;ring

nur6er

(Ex.

11):

and

volumes

of

events

This

OU.TFALL

-oE.rr

002

003

004

005

005

-5-

NUHBER

OF..EVENTS

-TO-r-

15

24

50

40

50

VOLUHE

d'n*/vea.r)

-Ts1T-

L2.5

7.6

10.

3

79.

3

9.6

d

averase

These

approximat,ely

i

s charge

data

year.

.pp'oI1Tu

indicate

700

Sini.tarly,

million

g:

that

ri'

i zo'-ii

bypass

Eh"

iiiion,

rri"l

five

oolA

from

ot,he,

;;iig

can

103

be

;J

iSO.-"";

evenEs

expected

;;'ilF"illo

durine

to

discharge

the

."

-i,rrrng

per

nould

implemented

:u

event's

year

ue

rlducla

if

per

.he

(R.

vear

aC'43)improvements

uy'l'riz-;r;";n"

(R.-

ae

36-7).

as

agreed

number

Th5

r20

to

of

by

iiiiron

events

petitioners

decreased

ga110n

.3pproxima

are

fieure

io

Ee

40

ly

I:tr::: :f"rl:_l?!^ii.-riion

sallons

diseharged

ar

oorA

is

::;;;;:,::?3.'::

i*ol::1:::i: : ;i;:il .'

il:'T;u;;

"';"

::il"i

:,

::l:l'H::i::"::

::: I?j: it;;i-iil:=i;,,

jgrll':i:'3:::':il:;

i :'

:

:. i: : : ::,F; : _

"

: :^ I :,:

".:.

I

-

i

ni

"-i

g

r,'

",1

i,

i

i

i

=

is

esrinaced

Ehar

d

;

i.

i il

1.,

i

!

"uori

i7i

of

rE

from

seperated

slorm

r"r"i"

aR.

t,he

700

srillion

gallons

d;;i;""

ei

73).

outfsll

separared

'

similarry,

0olA

srorm

are

se'er

some

apparently

of

svstlm

the

trigtAi"a-uv'InFirer"rion

103

t"Ef,"r

annuar-

;ll;_!i-}or,

Even.s

estimated

inro

for

rhe

and

are

the

afixed

sanibary

combined

to

sever

sever

vet

veils

systen

syst-em

vhich

(Ex.

(R.

at

receive

19i.

55,

6r-7ri.

flow

from

Ttre

both

pumps

"ri"t"iiiig

the

aE

stormobre

oe

-nr.-rriiing

vel1s

ou!fa11.

causes

The

the

recird'i"

pumps

to

activate

and

drain

the

we1ls

of

these

via

yet,

t,he

evenrs

are

relared

ro

simple

"n"i""r

as

Eo

vhat

percencage

of

the

103

vear

0o1A

poinr'

these

Ehe

'/elrs

(R.

(R-

could

iE

ar

ar

is

ro

consr'irur'"

E1)

49-50).

surmised

f ill.

r

_aDd

and

rui*i--ii"th"

i.t

iha..-i"rirltlii8n-i".

disct,"ig".upproxiroarei

;in"-rujority;

"rp-yiit

;""ora

;i

oilir,5=r"r

;;"-purnping

it

Iiro:lrible

i,

y'

,9-

indicared

r;-!o-lirll"

rvetls.

evenrs

iur"I"u"ing

rhar,

Ar

ar

one

p.,

"r"ir.,ii-"ur,*titJr"-"ipio*irnarely

half

of

ii, r'li,ilE"i

i, I*;,::"

t:J;"

j:

l;;iit:tT:iili'.

"

en,ed',

",

i

i,"o

ny

0014

vhich

vere

occasioned

by

flov

ro

rhe

rr"rr.tnifl_of

bypasses

at

the

planE's

16

mgd

aesign-maiiium

rto,

(R.

*.'l;ii:t

exceeding

I

,l

+t

69429

---

fn

comparing

the volumes

of

the

CSOs

to E,he

flov

in

the

receiving stream,

Petitioners

not,e

thaE

the

mean

daily

discharge

of the

Hississippi

River

at

Rock

rsl-and

is

31,085

msd,

and

ehac

t'he

ten-year seven-day

1ov

flow

is

8r900

mgd

(pecitlonr

par.

12).

rn

contrast,,

an

overfloy

event,

of a

5ne-year

rrequlncy

vould

discharge ebout,

52.7

million gallons

(petirion,

p"r,

iZ>.

Thus,

if

the one-year

recurrence

inEerval

discharg"

reie

to occur

at

the Eime of average

flow

in

the

Hississippi,

iI

vould

be

subjecc

to a

receiving

retio

of

590:1;

if it'occurred

at,

E,he

time

mixing

of the

raEio

ten-year

of

169:1.

seven-day

Low

flon it,

vouLd

be

subjeeg

to

I

chemical

anal-yses

of

the

cso

discharges

as

conducted

in 19BO

included

the following

parameters:

biochernical

oxygen

dernand

(TSS)

(BoD),

r

chemical

t,otaJ.

dissolved

oxygen

demand

solids

(TDS),

(coD),

total

anihonia

s,,r"peniEd

nitrogen,

solids-

phosphorous,

c50s in

combinaEion

and

leed.

make

volunre

an average-annual

analysis

indicat,ed

cont,ribuEion

Ehai

the

or

0.6

six

million poyngl

of BOD

and 4"5

million pounds

df rss

ro

rhe

Hississippi

River.

Over 802

of

these Loneribucions

are

discharged

from

at the

Hain Plane

via 0o1A

due

to

the

larger

volumeo

PetiEioners

(R.

at,37).

number

conclude

tGiven-Ehe-high

of event,s:

that-nthe

:nq_pollutant

f16r+s

Rock

of

rsLand

rhe

loadings

Hissilsiopi

csos

by'thernselves

at

that

Rivel,-

loine

lt"-u".e.negLigib1e

(Pec,itionr

par.

12;

ef

Ex.

fecE

2,

on

p.

the_lrississippi

17il.

River

vater

qua1it.y"

a----

In a

more recent,

study

(tl,rif

Scudy, Ex.

3),

assessmenE

yas

made

of the impact

of

Hain PlanE

outfalr

00:[A'

on

bottom

sediments..

.

Ttre

assessment

v/as

undert,aken

tirrough

independent

sampling

of the boBtom

sediments

and

by analysil'of previoui

s.ampling

data

collected

by

rhe

Agency

i1_.fuly 1984,

lnd

by

Hissman,

-st.anl-ey

&

Associat,es

in-Hay

,

1995.

-

subjected

to chemical

analysis

as

ve11

a!'-physically'irr"p""i"a.

A11

samples

iere

sampLes

were

analyzed

for

1ead,

zinc,

oil

ini

grease,

voratile

blind

solids,

by

and

three

total

individuals

solids.

rn

for

addiEion,

odor

inEensiEy.

the

sailpres

,ere

rantea

perspect,ive-t,o

hundred

elevated_po1lutanr,

resulted

Ttre

feet,

Huff

in a

in

limit,ed

Scudy

the

lengrh

1evels.

leve1s

found

area

!V

of

that

fifef

along

Ttria_area

pollutants

discharges

feer

the

near

in

is

yiitir.

as

approximately

shore

f_rom

found,

the

To

of

ulre

p;;"i;;-

bypass

tirl

comparea

rivei-wltnii";-

cSo

has

of

the

bot,tom

observed

sedimenE,s

levels

collect,ed

to

those

iecordeg

from

sices

i"

doinst,ream

?

general

eg"""y"'5t"ay

5r

treatment

plants

(Ex.

16).

rn

rhe

case

of csO oolA

"Lr"s"

values

of observed

constitulents

are

belov

the

mear

values

"ii--"rfi-

found

-6-

'I'here

is

no sedimentaLion

belov

the

CSOs,

vhere

Ehe river

boEtom

consisEs

i

five North

of solid

Slope

Intercept,or

rocK.

69-t30

---

,":

-7-

by

the

Agency in

the

general

survey of

sedirnent

collecEed

vithin

one

mile

of

vastewat.er

trealment,

planc outfa1ls.

'On

this

basis,

Huff

concludes

t,hat. t,he

nimpact,

from

the

exist,ing

Rock

Island

combined sewer

overflovs

on

the Hississippi

River is

not,

discernible

based

upon

these

sediment,

results

in the

zone

of

impact,"

(R.

at

84).

To

further assure

that

Ehe

CSOs

have

minimal environmental

impacti

Rock Island has

agreed,

as a'condition

t,o granEing.of

the

except,ionr

to

implement, a

one-year shoreline

inspection

program.

fttis program

is

inEended

to

quanEify and document Ehe

amount,

of

debris atE,ributable

to the CSOs

(R"

aE. 16).

EC

ON

OM.I.

C.

.T{AR

D SF: I

P

Rock Island has determined preliminary cost, estimates

for

fulL

compliance

vith

SecEion 306.305(a) and

305.305(b).

Under

t,hese rules Rock f sland

rvould

be

required

to

provide

complete

treat,ment

for the first

flush

of st,orm

flovs.-

An additional

gen

t,imes

Ehe

average design

dry veat,her

flov

nould

require

primary

sedimentat,ion

and disinfection.

The

Petitioners

believe

that,

these reguiremenEs

vould

necessitate,

as

the

least expensive

opeion, thetprovision of belov ground, covered, off-1ine

sEorage

faciLiEies to capture

and reduce

the occurrence

of

overfloys or

plane

bypasses.

These sEorage

faciLiEies

vould

operate

in

int,egraeion

vith

the main

EreaE,ment pLant, and

vould

a1lov

for

total capt,ure

and

subseguent

segondary

treatment

of the

firsE

flush. Addieionally,

full compliance

rrould

require

upgrading

the

Hain

Plant,

to a11on attainmenE

of

current

design

standards

for

treat,ment plant

componenls and

hydraulic

capaciEy

(Petitionr

paf.

4)

;

In aggregat,e

the

fuI1 compliance

alEernative vas

estimated

in

1982

to cosc 525.2 miLlion,

and

the

annual operation

and

maintenan'ce costs

nere

estimated

to

'be

53.7 nillion

(Ex.

2,

p.

181).

Later

figures,

as

seE

forth

in

Exhibits 1

and

12,

raise

these

figures Eo a toial of S54.9

grillion

in capital

cost,s

and

S5.9 million

in operating

costs

under

the

assunpEion

th6E

toeal

suspended solids lonErol-vould

aLso be required.

Ttre

latter

amounts

rrould

be "slightly

lover

if treatnent,

based

upon

biological

(sic)

oxygen demand

(BOD)

vas required"

(Pltition,

par.4).

At hearing Hr. Roberu

T.

Hayes,

City Engineer

of Rock

Island, further testified that t.he

cost of full compliance

is

esEimated to be S54,330,000, and

if

Lhese

cosLs

verl

spread

over

a

20 yeat

period at an interesE

rate oE

87,

the uveragi

reside:rt,ia1 sever use

charge

would

increase from

53

charge

vouLd

increase from

S37.2L

Lo

5103.90

per

quarter.

'

I

4;,

df"

69-t3l

---

-8-

"='""

rUD

..'...-

t

DeCembef

5,

OR.DER

{

DI.S

CUSSI€N

.

OF.

OR.DER

305.305(a)'

3s

111'

The

Adm'

Board

as

code

determines

it

relates

306'361t"1-itrac

th6t

ro

iirst

petiEioners

exceprion

frulh

oi

have

ro-3!"iii.'iii]'Loa"

shoyn pursuanE

to

receiving

agreed

excepEion.

35

r11"

Lo

Adm.

by

st,ream.

The

Petit,ioners.

code

Board

3oo.3o5(u!

Accordingly,

furrhir-rvirl

voura

the.Aoaia-riii

n1oa.,""-rinirnal

acee;;

lfr;'condiEicns

"ror,

grant

flows,

inpacr

Bhe

as

and

on

!o

Lhe

'?re

relief

eEf

support

luenr,

is

of

E,reaE,menE.

Board

rest,ricted-gnry

this

notes

peEirion

of

that

CSbs,

is

to'those

the

pr"ii""t.e-;r-;f,;-assumpEion

Agency

subst,antive

has

emphasized

requirements

that

rhar

itsfor

r,he

"nd

this

standards

condiEionr

(R.

at

aod

94)

has

.

not

Roct

obJecred

istana

not

_appeais-io

to-ief

Li

i.i.

i"f-frori

trare

*"i"r--qJ"iir.v

been

avare,,of

-rn"

Environrnenrai

notes

t,h8t

up

t,o

proe."c'ion

t,he

present,

et"nIi

ti,r",

ni"

the

in.ricaieJ_that

United

StatesBoard

only

i.self

variance

grEnced

!i."..

non-permanenr,

consistenr

niEh

)

rerieE

Ehe

rr6r"iieil-q"rii.;

clean

l{at,er'eci

('see

st,andards

documenL

can

be

il.+!l;1 .'f::.::^l:ryIr, 1n_ !i1cus-,

i"n"-*iir,

u5sir;,

-;;;;;

ocrober

(

3;.l3ller!li:.1.'q'mlnt

is

pari

or

eire

recoia-"F,^"'lo"il'lt;::"i;:

i;qlliii"-

of

grderr

thae

the

rhis

e*clpcion

as

DroDosed

issue

is

es

by

cEz?,

granted.

p"iiiioners,

ir,"Ei

.':"

fang"ate-iaencirying

;iii-i;;r;r"."i;;o

Ehe

if;"u""'

s

+q'6uaEc

rsencLEylng

Ehe

scoPe

I

condiEions:

as

3s

from

such

111.

1.

the

provision

iam.

The

treatment

code

city

re'dtes

of

30E:ao;(;i,-;;bj";;-;;tie-iorrowing

requirenenis

Rock

to

rsland

first

or

is-hereby

rrustr-or--"torro

gs

rrr.

iar.

granted

code

frorrs,

an

306.sbltal,

exceDtion

and

from

a'

0O1A,

outfalls

such

excep!1.n-ghal!

as

idenrified

002,

003,.004,

in'Ehi;'proceeairtl-

be

O05r

limited

and

to

OOe-"ii";;

combined

--

;;;:""-r".

sevrer

b.

proceeding.paragraphs

modificaeions

The

CiEy

of

14,

Rock

t,o

15,

i.s

Island

and

sever

16

sha11

of-

lyst;;

Lhe

implemenE

periri."-ii-iii"

as

identified

all

in

'

c

'

15

shoreliie

Ttre

of

city

rhe

of

perition

inspection

Rock

rsland

i.n'tli"-fr."l"orng.

progran

sha1l

desrribed

irnplement

in

theparagrpah

a

.___

from

cS.

exercisins_its

?:.

monitoriilg

Ti:

grant

program

aut,horiiy-to

of

excepticn

sufiicient,'eo

require

does.not

assess

al

preclude

a

permit

comptiance

.he

condition

Aeencv

vith

a)

69432

---

-9-

!!t= _glg"pEion

and any

oEher Board

regulat,ions, including

Section

306.305(c);

and b)

other controls

if needed

for

complianEe,

.

including

compliance vith

rlat,er qualit,y

standards.

3.

This

granE

of

except,ion

is noE to be const,rued

as

affeeEing

the enforceabiliE,y

of

any

provisions

of this

excepEion,

ot,her Board

regulat,ions,

or

the

Act.

4:

Within

fort,y-five

days

of

the daEe

of this Order,

.the

City

shaL1

execute

a

Certificction

of

AccepEance

and

Agreernent to

be

bound

to

aL1

terms

and conditions

of

the

excepE,ion granEed.

The

Certificacion

shal1

be

submitEed Eo

the Agency

at

22QO

Churchill Road, Springfield,

fllinois

,

62706.

The

forty-five

day

period

shall

be

held

in

ebeyance during any period

thaE

this

matter is

being

appealed.

The form of said certification

shall

be as

follovs:

'

,,,CERTIFTCATION

.

,

I,

(1.1e

)

'

:......

having

read

the

Order of Ehe l1ffi"'ie6'ffiTE-rd,

in Fcn

85-214,

dared

Hay

9,

1985,

undersEand

and accbpE the saiC

Order,

realizing thaE

such aceept,aRce

renders

e11

terrns

and

condit,ions

thereto binding and

enforceable.

Pe

E

it,

io.ner

tsy:

Authorized Agent

'IitIe

Date

IT IS

SO

ORDERED.

Board

Hembers Joan Anderson

and

Jacob

D.

Dunelle

concurred.

I, Dorot,hy H. Gunn,

I1linois

PolluEion

Ccntrol

Board,

hereby

cerEify Eha

adooted

on the

....'.':

by

a

voEe

oE

..'

@...-

.

uunnr

er

Pollution

Control

Board

69.{33

---

I

I

D

D

D

---

o

t

o

o

o

a

PRELIMINARY

ENGINEERING

REPORT

for

TI{E

IIPGRADE

OF

THE

ROCK

ISLA}ID

WASTETVATER

TREATMENT

PLA}IT

Decemb

er

t997

by

James

E.

Hufi

F.E.

O

\/

.

/\\/

#ffi##1n4

r^tc'

7

i

;;'d;i;i&"'

fi#€oNsulrANrs

---

o

o

o

o

o

-

o

o

a

o

TASLE

OF

CONTENTS

I. INTRODUCTION

2.

DSSTING

CAPACITY

AI.IALYSIS

2.1

Cnit

Chamber

2.2

P

imary

Sedimentation

Page

....i

2.3

Aeration

Tad6

2.4

Secondary

Clarifiers

.........3

.....4

2.5

Sludge

Digestion

Capacity

.

..

3. PROPOSED

UPGRADING

.

3.1

Addidonal

Sccondary

Clarifier

3.3

Sludge

Digestion

4.

PRELIMINARY

COST

ESTTMATE

FiGURE

l:

ROCK

ISLAI.ID

..,""....4

.........6

i.? Iti-.rt'

Sedimgntatiou

Modifications

...7

......9

SCHEI4ATIC

LIST

OFT'ICURES

Hgs?T{c

*ASTE*ATER

TREAT[4Et'ir

plA]rr

LISTOFTABLES

TABLE

t:

*ASTE*ATERTREATMENTIJ'GRADEcosrEs.Ir]rATE

LIST

OFAPPENIDICES

APPENDD(

A:

SUPPORTING

CALCULATIONS

APPENDD(B:

pRoposEDsrretAiofi;ilwrNc

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D

.1.

TNTRODUCTTON

The city

of

Rock

Island's

wastewater

Treabent

plant

was

last

upgraded

in

the

early

1970,s.

Th:

teatrnent plant

was

designcd

to

process

g.0

MGD

on avenrge,

with

a peak

flow

of

16.0

MGD.

The

treabxeut

process

includes

grit

removal,

primary

sedimentation,

activated

sludge,

and

seasonal

processed

disinfectioa'

through

secondary

trro

anaersbic

sludge

is

sludge

cr:rrently

digesters,

wasted

then

to

tbe

dewatered

pridary

q.

sed.imentation

r sand

drying

beds

basins.

or

a

sludge

new

belt

is

filter

press'

Excess

flows,

uot

processed

ti'ougb

tbe

trca@ent

pran!

are p,,mped

around

the

plant

and

combine

with

the

teaueEt

plant

effluent

prior

to

discharge

into

the

Mississippi

River.

Figure

I

is a

simplified

flow

schematic

of

the

teatnentprocess.

During

wet

weather

cvents,

sludge

wash

out

from

the

secondary

clarifiers

bas

beeu

e4perienced

To

ninimize

this

sludge

wash

oul

the

Ciry

has

hjstorically t;rni1g4

tle

flow

tbroggh

tbe

plant

to

Ieveis

below

the

design

ma'ximun

flow

@I@

of 15

MGD.

In

essence,

the

plant

is

not

currentry

capabre

ofprocessing

l6

MGD

without

significant

sludge

washouts

from

tbe

secondary

clarifiers.

Fluf

&

Hus

Inc'

was

rctaiued

by

Rock

Island

to

review

the

design

capacity

of

cach

unit

operation.

From

this

evaluation,

several

significant

upg:adedmodifications

are proposed

herein.

In

additio4

a

prelimina'y

cost

estimate

is

provided

to

sewe

as

the

basis

forproceeding

with

upgading

the

prant.

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2.

F\'ISTT{G

CAPAC--

.AgA.LIil,r

As

the

existing

teabrent

plant

was

designed

in

1g70,

the

engineers

likely

r:sed

the

,,Recomme'ded

is

standards

existiag

Engineers'

Standards

utilized

Design

herein

is

for

or

the

Scwage

"Ten

Average

appropriate

versu's

-

states

worls"

the

Flow

1968

guide

stan&rds,"

(DAF)

by

Edition,

the

for

Great

checkiug

or

Design

as

which

Lakes

it

is

capacities.

Mo<imum

was

referred

-

upper

most

Mississi.opi

to

It

FIow

likely

shourd

in

the

(DMF)

utilized

industy.

be

River

noted

is

dr:ring

proposed,

Board

that

As

the

the

no

of

acrual

tbe

change

state