ILLINOIS POLLUTION CONTROL BOARD

March

26,

1975

CITY OF MOUNT VERNON,

Petitioner,

v.

)

PCB 74—489

ENV~.JNMENTAL PROTECTION AGENCY,

Respondent.

OPINION AND ORDER OF THE BOARD

(by Mr. Dumeile):

The City of Mount Vernon

(“Petitioner”)

filed a variance

petition on December 27,

1974.

The Illinois Environmental

Protection Agency

(“Agency”)

filed

a Recommendation to grant

the variance on February

6,

1975.

No hearing was held.

Petitioner operates a secondary sewage treatment facility

located in Jefferson County.

Petitioner’s sewage treatment

plant discharges

to Casey Fork,

approximately 7-1/4 miles

upstream from where Casey Fork enters Rend Lake.

Rend Lake

discharges into the Big Muddy River which is a tributary of

the Mississippi River.

Petitioner’s

sewage treatment plant has an average

influent of 1.86 million gallons per day

(mgd).

Petitioner

states that its present plant produces an effluent with the

following average values:

Average BOD5

4.2 mg/l

Suspended Solids

22.3 mg/l

Ammonia nitrogen

5.4 mg/i

(as nitrogen)

Phosphorus

8.1 mg/I

Because Casey Creek has a 7—day 10—year low flow of zero,

Petitioner’s effluent must not cause

a violation of the 0.05

mg/i of phosphorus requirement of Rule 203(c)

at the entrance

to Rend Lake and the 1.5 mg/l ammonia nitrogen standard of

Rule

203(f)

of the Water Pollution Regulations.

Rule 404(f)

provides that for discharges

to streams with less than 1:1

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dilution that the effluent shall not exceed 4 mg/i of BOD~

and

5 mg/i of suspended solids.

Petitioner has requested

a

variance from the above three provisions.

Petitioner is in the process of upgrading its existing

sewage treatment facility and has obtained both

a Step I and

Step

II Federal Assistance Grant to help pay the cost of

drawing up final plans and specifications for the proposed

upgrading.

Petitioner has a construction grant priority of

116.

On December 19, 1974 Petitioner was issued a National

Pollutant Discharge Elimination System

(NPDES) Permit by the

United States Government.

Petitioner states that its proposed

treatment plant is tentatively scheduled for completion in

January of 1977.

Petitioner’s NPDES Permit requires completion

of construction by June 30, 1977 and attainment of full

operation by July 30,

1977.

The Agency estimates that the

treatment system should be in operation by October

1,

1977.

Petitioner estimates that following completion of the proposed

treatment plant it will discharge an effluent with the

following characteristics:

Average Dry Weather Flow

3.8 mgd

Average BOD5

10 ppm

Average Suspended Solids

12 ppm

NH3

(Ammonia Nitrogen)

1.5 ppm

Phosphorus

0.05 ppm

Although estimating compliance with the phosphorus

requirement of Rule 203(b), Petitioner states that there is

no evidence that removal of phosphorus down to the requirement

set forth in the Rule is technically feasible.

The Agency

points out that Petitioner’s NPDES Permit sets forth final

standards of

4 mg/i for BOD5 and S mg/i for suspended solids.

The Agency states that Petitioner may discharge 10 mg/i of

BOD5 and 12 mg/i of suspended solids only if granted

a

“Pfeffer exemption”

under Rule 404 (f) (ii).

The Agency

questions whether Petitioner will ever be capable of consistently

discharging an effluent with a phosphorus concentration of

no more than 0.05 mg/i and therefore recommends that Petitioner

be granted a variance from Rule 404 (f) (ii) (A)

,

(D),

and

(E)

as they pertain to obtaining a phosphorus concentration of

0.05 mg/i.

The Agency~srecommendation is conditioned on

the instaliation by Petitioner of best available nutrient

removal facilities as soon as possible in conjunction with

the proposed upgrading of Petitioner’s sewage treatment

plant.

Petitioner alleges that to require compliance with the

three rules would impose an arbitrary and unreasonable

hardship during the period it is proceeding to complete its

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222

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updated sewage treatment plant.

Petitioner alleges that the

use of chemical precipitation to enhance its effluent quality

is not feasible because it would overload Petitioner’s

existing sludge digesters.

Petitioner further alleges that

satisfactory land is not available for spray irrigation and

that soils found in the area are shallow silts, underladen

by tight clays and hardpan with the result that spray irrigation

could cause surface runoff with no appreciable water quality

benefits.

Petitioner states that transportation of its

effluent to a watershed other than that of Rend Lake would

require transporting the waste a distance of 17 miles east

to the Skillet Fork watershed into a low flow stream.

Petitioner states that the dissolved oxygen cpntent of Casey

Creek is substantially higher downstream from its discharge

than upstream and that even considering the dissolved oxygen

sag due to carbonaceous and nitrogenous oxygen demand, that

the downstream level of dissolved oxygen does not approach a

critical level.

The Agency states that Petitioner

is operating its

sewage treatment plant as efficiently as possible and that

no greater pollutant removal can be achieved without the

addition of more treatment facilities.

The Agency recommends

that the Board not require such interim treatment facilities

because the time required to design and install them would

be roughly equivalent

to the time required to carry out

Petitioner’s proposed upgrading

of its sewage treatment

plant.

The Board finds that Petitioner would suffer an arbitrary

and unreasonable hardship if required to adhieve compliance

immediately with Rule 203(c),

203(f),

and 404(f).

However,

Petitioner does discharge a significant amount of phosphorus

to Rend Lake based upon

a materials balance.

Petitioner

states that the average phosphorus concentration

in Rend

Lake,

based upon a water quality value of 0.08 ppm is 63,968

pounds.

Converting Petitioner’s average effluent phosphorus

value of 8.1 ppm to

a yearly value results in an estimated

contribution of 45,891 pounds.

The Agency calculated that

Petitioner’s discharge amounted to 126 pounds of phosphorus

per day as compared to the 83.9 pounds of phosphorus contained

in Casey Fork upstream from Petitioner’s discharge.

TheAgency states that Petitioner’s discharge of phosphorus

could be the source of additional algal growth in Rend Lake.

However, the Agency believes that the additionl algal growth

has little immediate adverse environmental effect,

but that

continued addition of decomposable plant growth could shorten

the life of the Lake.

The Board agrees with the Agency

concern over future additional discharges of phosphorus to

16—223

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lakes or reservoirs.

This was the reason for the adoption

by the Board of Rule 203(c).

The Board therefore will

condition the grant of this variance upon requirement to add

nutrient removal facilities in conjunction with the proposed

upgrading.

In addition,

any extension of this variance will

have

to contain

a more detailed evaluation

of methods of

compliance with the phosphorus requirements of Rule 203(c)

or alternative means of discharges such as land application

or diversion from the Rend Lake watershed.

The record in this case

is not wholly satisfactory.

Little is said by either party as to the extent of algae

blooms,

if any,

on Rend Lake.

The 0.05 mg/l phosphorus

level of Rule

205(c) may not necessarily be an effluent

standard, but is

a stream standard at

the confluence with

Rend Lake.

If significant amounts of phosphorus

“drop out”

in the 7-1/4 mile length of Casey Fork then a higher amount

of phosphorus could perhaps be discharged by Mount Vernon.

But no data are given on this point.

Lastly, the state of dissolved oxygen levels in the

hypolimnion

(if one exists)

in Rend Lake are not given.

If,

in fact,

algae growth on Rend Lake

is significant, then the

Board should be told what effects this algae growth is

having upon dissolved oxygen levels.

Also it is not wholly

correct to compare the suspended phosphorus

in Rend Lake’s

waters with incoming loads.

In Lake Erie, more than 95

of

incoming phosphorus

“disappears1’ presumably

to sediments.

What is significant

is the rate of increase of phosphorus

in

the water.

Rend Lake is shallow and wind currents may

suspend sediment,

thus giving apparently high phosphorus

levels.

But is this phosphorus

in a form that will support

algae growth?

In future or similar proceedings,

these

questions must be answered.

Because Petitioner

is required to obtain an NPDES

Permit, the Board may grant Petitioner

a variance for up to

a five year period.

The Board has determined that Petitioner

should be granted a variance until July 1,

1977 because of

legal deadlines.

This Opinion constitutes the Board’s findings of fact

and conclusions of law.

ORDER

The Pollution Control Board hereby grants the City of

Mount Vernon

a variance from January

1,

1975

to July

1,

1977

from Rules 203(c),

203(f)

as pertains to ammonia nitrogen,

Rule 404(f)

as pertains to BODç and suspended solids, and

Rule 404(f) (ii) (A),

(D), and

(~)

as pertains to phosphorus

16—224

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subject to the following conditions:

1.

Petitioner keep abreast of developments

in phosphorus

removal technology and shall report quarterly to the Agency;

2.

Petitioner apply advanced phosphorus removal

techniques as

such techniques become practicable;

3.

Petitioner continue to pursue its present program

of upgrading its sewage treatment plant including nutrient

removal facilities;

4.

Petitioner maintain and operate

its sewage treatment

plant in the manner that will maximize the quality of effluent;

5.

Petitioner apply for and obtain all necessary

permits.

6.

Effluent limits

(on a monthly average)

shall not

exceed:

Average SOD5

4.2 mg/l

Suspended Solids

22.3 mg/l

Ammonia Nitrogen

5.4 mg/l

(as nitrogen)

Phosphorus

8.1 mg/l

IT IS SO ORDERED.

I, Christan L. Moffett,

Clerk of the Illinois Pollution

Control Board, hereby certify the above Opinion and Order

wer~adopted on the

I~(~’~

day of March, 1975 by a vote of

__________.

C ristan L. Moffe

t,

Illinois Pollution Co

1 Board