ILLINOIS ENVIRONMENTAL PROTECTION AGENCY

September

11, 2003

City OfLincoln, IL

)

)

Petitioner,

)

)

v.

)

)

IEPA-03-00l

ILLINOIS ENVIRONMENTAL PROTECTION

)

AGENCY,

)

(Provisional Variance- Water)

)

Respondent.

)

).

Re:

Provisional Variance From

35

Ill. Adm.

Code 302.2 12 For Ammonia Nitrogen,

304.120(b) For CBOD5, And 304.141(a) For Suspended Solids

NPDES Permit # 1L0029564

Dear Mr. Eaton:

The Agency has completed its technical review of the aftached provisional variance

request submifted by the City ofLincoln on September 2,

2003.

Based on the re~~iew,

the

Agency GRANTS the requested provisional variance subject to

specific conditions set

forth below for a period of45 days.

The City of Lincoln seeks a provisional variance to allow yard piping modifications

around the aeration basins and tertiary filters as part ofa major upgrade at its wastewater

treatment plant.

Units that will remain in

operation during the term ofthe provisional

variance include: primary clarifiers; trickling filter; secondary clarifiers; excess flow

clarifier; excess flow chlorine tank; and effluent flow measurement/sampling facilities.

Upon completion ofimprovements, the wastewater treatment facility will be equipped to

comply with more stringent effluent limitations for ammonia nitrogen.

In addition, the

current design average flow will be increased

from 3.35 millions gallons per day (MGD)

to4.19MGD.

The Agency’s review ofthe requested provisional variance has concluded the following:

1.

The environmental impact from the proposed activity should be minimal;

2.

No other reasonable alternative appears available;

3.

No public water supplies should be

effected;

4,

No federal regulations will preclude the granting ofthis request; and

---

5.

The City will face an arbitrary and unreasonable hardship if the request is

not granted.

The Agency hereby GRANTS the City of Lincoln a provisional variance from 35 Ill.

Adm.

Code 302.212 for ammonia nitrogen, from 35 Ill. Adm.

Code 304.120(b) for

CBOD5, and from 304.14 1(a) for total suspended solids

for a period of 45 days beginning

September

15,

2003 subject to the following specific conditions:

A.

During the variance period, the City’s effluent shall meet the monthly

average concentrations of40 mg/l

for CBOD5, 50 mg/i fortotal

suspended

solids, and

15 mg/I for ammonia nitrogen.

B.

The City shall notify Roger Calloway ofthe Agency by telephone at

217/782-9720 when construction starts and again when construction ‘is

completed.

Written confirmation ofeach notice shall be sent within five

days to the following address:

Illinois Environmental Protection Agency

Bureau of Water

—

Water Pollution Control

Attention:

Roger Callaway

1021

North Grand Avenue East, MC #19

P.O.

Box 19276

Springfield, Illinois 62794-9276

C.

The City shall sign a certificate of acceptance ofthis provisional variance

and forward that certificate to Roger Callaway at the address indicated

above withinten days ofthe date ofthis order.

The certification should

take the following form:

I (We)

,hereby accept and agree to be

bound by all terms and conditions of the provisional variance

granted by the Agency in

_____________

dated

Petitioner

Authorized Agent

Title

Date

---

D.

The City shall continue to monitor and maintain compliance with all other

parameters and conditions specified in its National Pollutant Elimination

Permit No. IL 0029564.

Enclosure

CC:

IPCB, Clerk•

Joseph B.

Svoboda

ChiefLegal

Counsel

---

September

1,

2003

ENVIRONMENTAL

MANAGEMENT

CORPORATION

150 WEST

KICKAPOO

LINCOLN, IL 62656

(217) 732-4030

By

this submittal,

the

City

of Lincoln,

IL is

submitting

an Application for Provisional

Variances

for

the

Wastewater

Treatment Facility.

The

provisional variance

is intended to

allow the

City to

make

required yard

piping

modifications

around

the

existing

Aeration

Basins

and

Tertiaiy

Clariflers

in

conjunction with the

Wastewater

Treatment System Improvements

Project. The City

intends

to begin

the

modifications

on or about

September

15,

2003.

The

intent ofthe project is

more fully described

in the

attached

Application

for Provisional

Variances.

Enclosed please

find

the following

documents

associated with the City’s Application for Provisional

Variances:

1.

Application for Provisional

Variance

2.

AttachmentA

—

Basis ofDesign

3.

Attachment B

—

Process Flow Schematic

4.

Attachment C

—

Facility Plan

5.

Attachment D

-

Two (2) Copies

Two (2) Copies

Two (2) Copies

Two (2) Copies

Two (2) Copies

The

City

of Lincoln

requests

that

the Agency

issue a Provisional Variance

to the NPDES

permit for

the

referenced project.

If you

have

any

questions

regarding

this

request, please

do

not

hesitate to

contact our consultant

for the project, Joseph Pisula, at Donohue & Associates, Inc. at

217-352-9990.

Please forward a

copy of the variance response documents to

Donohue at the following

office:

115

North Neil

Street,

Suite 213,

Champaign,

IL

Very tmly yours,

.~

ii~~~J3

~

Grant

Eaton

WWTF

Facility Operator

SEP

0

2

2003

Illinois Environmental Protection Agency

Division

ofWater Pollution Control

P. 0.

Box

19276

MC #19

Springfield,

illinois

62706

Attention:

Roger

Callaway

Re:

City

ofLincoln, IL

NPDES Permit #

1L0029564

Dear

Roger:

Cc:

Donohue & Associates,

Inc.

---

I

Provisional Variance Application

for the

City ofLincoln, Illinois

NPDES Permit No. 1L0029564

September, 2003

L

Applicable Regulations (35

III. Adm. Code 180.202-b-i)

By this Provisional Variance Application, the City of Lincoln formally

requests that

the illinois

EPA

grant

the City

temporary relief from the

CBOD5,

suspended solids,

and

ammonia nitrogen

discharge standards

for the plant as

defined in

35

ill.

Adm. Code 302.

The currentNPDES permit

for

the

facility

stipulates

that

the following

averages

for

CBOD5

and

suspended

solids

to

not

exceed:

Parameter

CBOD5

Suspended Solids

Monthly Average

‘20 mg/!

25 mgfl

Weekly Average

40 mg/I

45 mg/l

The

current NPDES

permit

for

the facility

stipulates

that

the following

averages

for

ammonia

nitrogen to not exceed:

.

I

Under

this

variance,

it

is

proposed

that

during

the

variance

period,

the

monthly

average

for

CBOD5 and suspended solids in

Revised

Revised

Parameter

CBOD5

Suspended

Solids

I Monthly Average

I

40 mg/I

I

50 mg/l

Under

this

variance,

it

is

proposed

that

during

the

variance period,

the

monthly

average

for

ammonia nitrogen in the plant effluent be revised to not exceed the following:

City of Lincoln, illinois

Wastewater TreatmentSystem Improvements

Donohue #10479

4

Monthly Average

3.4 mg/i

5.2

mg/I

Daily Maximum

7.3 mg/I

10.3

mg/I

Monthly Average

15 mg/l

—1—

---

II.

Project

Description

(35 III. Adm.

Code 180.202-b-2)

The City ofLincoln is located in Logan County

approximately

35 miles northwest of Springfield,

illinois.

Lincoln’s

2000 population

was

15,369

persons

based

on

US

Census

data. The project

consists

of an expansion

to

the

City’s

wastewater

plant from its

current flow capacity of 3.35

million gallons per day

(MGD) to

a 4.19 MGD capacity.

Currently the plant receives

an

annual

average of 3.6 MGD of flow. The plant

upgrade is also being implemented in

order to

comply

with more

stringent IEPA

effluent discharge

limits

for ammonia nitrogen that

were imposed in

November 2001. The project will have a useful life of 20 years.

The project consists

of general construction

work,

including the following

additional facilities:

activated sludge

aeration basins, a secondary clarifier

tank, sludge dewatering equipment

and its

building,

and a

new

preliminary

treatment

facility.

Modifications

to

the

existing wastewater

facilities

are

proposed

to

include

code-related

improvements

to

the

existing

buildings

and

tankage, plus associated electrical, mechanical, structural, piping ventilating, and instrumentation

and control systems

upgrades.

The Lincoln Wastewater Treatment Facility discharges to the Salt Creek. The Salt Creek has a 7-

day,

10-year low flow of 33.3

cfs

(21.52 MGD)

upstream of the plant discharge

as

indicated by

data provided by the illinois State Water Survey.

Ill..

Quantity & Types of Materials

(35 III. Adm. Code i80.202-b-3)

Not Applicable

IV.

Quantity & Types Emissions

(35 lii. Adm.

Code 180.202-b-4)

The

Project

involves

modifying

the

process

piping

around

the

existing

Aeration Basins

and

Tertiary Clarifiers. Additionally the Tertiary Clarifier Flow Splitter Structure (Structure 506) will

be

modified

to

bring

it

into

compliance

with

current environmental

regulations

The

General

Contractor

(Femily

Dickerson)

on

the Project anticipates that

the

Aeration Basins

and Tertiary

Clarifiers

will

need

to

be

bypassed for

22

working days

(30 calendar

days)

to

complete the

required piping modifications. Modifications

to the Tertiary Clarifi~r

Flow

Splitter Structure will

be completed

during the

same time that the piping modifications

are being made.

It

is expected

that

the

concentration

of

CBOD5,

suspended

solids,

and

ammonia

in

the

plant’s

effluent

will

increase

during

the

project,

due

to

bypassing

flows

around

the

Aeration

Basins

and

Tertiary

Clarifiers.

As

the calculations

in

Attachment “A”

indicate,

it expected that the Trickling Filter

and Primary

Clarification

will

achieve

61

removal of the BOD

in

the

raw influent

wastewater.

Effluent

CBOD5

concentrations

are

estimated

at

40

mg/i

based

on

an

assumed

influent

CBOD5

concentration of 118

mg/i.

Effluent

suspended

solids

concentrations

are

estimated

at

50

mg/I

based

on

an

assumed

suspended solids concentration of 170 mg/l

into the trickling filter’s

secondary clarifiers.

City of Lincoln, illinois

Wastewater Treatment System Improvements

Donohue#10479

-2-

---

Bypassing the

activated

sludge process will result in

the loss of the

nitrification process

in the

Aeration

Basins.

The

1935

era

trickling filters

were

not designed for nitrification

and

will not

reduce the

influent

ammonia concentrations. Based

on

the

significant impacts

to

the

facility’s

nitrification

process

effluent

ammonia

nitrogen concentrations

are estimated at 15

mg/I based on

an assumed influent ammonia nitrogen concentration of 15 ingfl.

V.

Drinking Water Regulations Variance

(35 III. Adm.

Code i80.202-b-5)

The

Project involves

improvements

to

the

City’s

Wastewater

Treatment

System.

No

project

-

activities

are

related

to

the

City’s

public

water

supply.

Therefore

this

portion

of the

Illinois

Administrative

Code is not applicable to this project.

VI.

Assessment of Adverse Environmental Impacts,

(35 Ill. Adm.

Code 180.202-b-6)

The

modifications

to

the

yard

piping

around

the

Aerations

Basins

and

modifications

to

the

Tertiary

Clarifier

Splitter Box

(Structure 506)

are

expected to

take place around September

15,

2003, during dry weather conditions.

During these times

it expected

that the influent flows

and

loadings

should be

below

the

original

design

loadings of the plant.

With the

existing Primary

Clarifiers,

Trickling

Filter,

and

Secondary

Ciarifiers

in

operation,

the

project

construction

sequencing attempts to minimize impacts on the facility’s treatment process.

Also

important to

note is that illinois EPA has indicated that the

Salt

Creek is not listed on the

303(d) list as

a protected water ofthe State of Illinois.

Therefore, it is not expected at this time

that any Total Maximum Daily Load (TMDL) limitations will be put in place for this stream.

VII.

Hardship Statement

(35 III. Adm. Code i80.202-b-7)

The Project involves yard piping modifications

around the existing Aeration Basins and Tertiary

Clarifiers. Additionally,

the existing Tertiary

Clarifier Flow Splitter Structure will be modified to

bring it into compliance

with current environmental regulations. The yard piping and flow splitter

modifications

are

estimated

by

the

General

Contractor’ (Femily-Dickerson)

to

take 22

working

days (30 calendar days) to complete.

During this time, the facility’s capacity to remove CBOD5,

suspended solids, and ammonia nitrogen will be reduced.

A detailed construction sequencing

schedule was provided

as

part of the

construction documents

for the Project. The construction sequencing schedule required that the Contractor provide bypass

pumping from the Aeration Basins to the Secondary

Clarifiers while the Secondary ClarifierFlow

Splitter (Structure 506) was out of service. The modifications

to the Flow Splitter are

required to

bring

the

structure

in

compliance

with

current

environmental

regulations.

Modifications

to

the

Splitter Structure are

structural in nature and require all flow to the structure to

be shut-off while

the modifications are completed.

The

General Contractor

(Femily

Dickerson) for the project has expressed

concerns regarding the

ability to complete the required yard piping modifications

while the Aeration Basins and Tertiary

City of Lincoln,

Illinois

Wastewater Treatment System Improvements

Donohue#10479

---

Clarifiers

remain in

operation.

Femily

Dickerson has

stated

that they believe

it is

necessary to

bypass flows

around the entire activated sludge

process while the yard piping

modifications

are

completed. Presently there is no way to isolate the pipes and these pipes must

remain

in service

‘for the

Activated Sludge Process

to operate.

Thus, bypass

pumping

around the Tertiary Clarifier

Flow

Splitter

Box

will not

facilitate the

required yard

piping

improvements necessary for

the

project.

The provision oftemporary wastewater treatment facilities to replace that capacity would place a

severe

hardship

on

the

City.

Such

facilities

could

include

a

temporary

package

wastewater

treatment

plant or the trucking of the City’s wastewater to another wastewater treatment facility.

The cost ofthose options could easily exceed the City’s annual budget for operating the facility.

Therefore, the Implementation ofthese temporary treatment methods is considered not financially

feasible.

VIII.

Description

(35

IH. Adm. Code 180.202-b-8)

A.

Compliance Procedures

To ensure that proper treatment of the wastewater occurs during the project,

the Contractor will

be required to follow the work sequence detailed in the Project Documents.

The Activated Sludge

Process Facilities will be taken out of operation to make the modifications to it for a period of

22

working days (30 calendar days) in conjunction with the Improvements Project.

All plant

flows

up

to 6.3-MGD

will treated utilizing the existing

Primary Clarifiers, Trickling

Filter, Secondary

Clarifiers,

Excess

Flow

Clarifier,

Excess

Flow

Chlorine

Contact

Tank,

and

Effluent

Flow

Measurement/Sampling

Facilities.

The

Aeration

Basins,

Tertiary

Clarifier

Flow

Splitter

and

Tertiary

Clarifiers

will

be

taken

out

of

operation

to

facilitate the

yard

piping

modifications

necessary for these

structures in

conjunction with the Improvements Project.

Wastewater flows

in

excess of

6.3

MGD

would

be

captured

and

treated

by

the

existing Excess

Flow

Facilities.

Doing

this

will ensure

that the

facility’s

treatment process continues

to

operate

effectively

and

environmental impacts are

minimized.

B.

Timetable

The

Contractor has been

directed

to complete the modifications

to the yard piping

and Tertiary

Clarifier

Flow

Splitter

(Structure

506)

within

22

working

days

(30

calendar

days)

after

commencing work on those modifications.

It is expected that the modifications will begin around

September

15, 2003.

VIII.

(35 III. Adm. Code 180.202-b-9)

Alternative

methods of compliance

include

a

temporary

package

wastewater treatment

plant or

the trucking of the City’s

wastewater to another wastewater treatment facility.

The cost of those

City of Lincoln, Illinois

Wastewater Treatment System Improvements

Donohue#10479

4..

---

options could

easily exceed

the

City’s

annual budget for operating

the

facility.

Therefore,

the

implementation of these alternative methods ofcompliance is considered not fmancially feasible.

IX.

Variance Duration (35 III. Adm.

Code 180.202-b-i 0)

The City ofLincoln

formally

requests that the ProvisionalVariance be issued for a duration of45

consecutive calendar days.

X.

Previous Variances (35

III. Adm.

Code 180.202-b-il)

The

City

of

Lincoln

has

not

requested,

nor has

received

any

provisional

variances

for

its

wastewater system within the previous calendar year.

Xl.

Status of Current Permit (35 III. Adm.

Code

180.202-b-i2)

The

City’s

Wastewater

Treatment

Facility

is

currently

operating

under

NPDES

Permit

No.

1L0029564,

which was made effective on

October

1, 2001.

That permit remains in

effect until

September

30, 2006.

City of Lincoln,

Illinois

Wastewater TreatmentSystem Improvements

Donohue#10479

-5-

---

ATTACHMENT “A”

Basis

ofDesign

Current Conditions

and

Facilities

Client:

Environmental Management

Corporation

Project:

Wastewater Treatment and Sewer System

Improvements

-

Variance Permit

Donohue Project No.

10479

Revised:

May 29,

2003

Task:

& Facilities

1996-98 Population Equivalent

of plant,

based on BOO

=

1996-98

Population Equivalent of plant, based on SS

=

1996-99 Design Avg.

Flow

=

1996-99 Maximum

Monthly Flow

=

Maximum Weekly

Flow

=

Maximum

Daily Flow

=

Design

Peak Hourly Flow

=

1996-99 BOO load at avg day

=

1996-99 SS

load at avg day

=

1996-99 NH3-N

load at avg. day

=

Est.

1996-99 Avg

Daily TKN

load

=

Est.

1996-99 Avg.

Daily Phos.

load

=

1996-98

Max

Daily BODload

=

1996-98 Max.

Daily SS

load

=

Max

Daily

NH3-N

load

=

Est.

1996-98 Max.

Daily TKN

load

=

Est.

1996-98 Max.

Daily Phos.

load

=

MGD (same as

listed on NPDES permit)

MGD

MGD

MGD (Pump Capacity)

MGD (Pump Capacity)

lb CBOD/day

lb SS/day

lb NH3-N/day

lb TKN/day

lb P/day

lb CBOD/day

lb SS/day

lb NH3-N/day

lb TKN/day

lb

P/day

RESULTING

DESIGN AVG,

RAW

INFLUENT CONCENTRATIONS

118

‘

mg/I

BOD

170

mg/ISS

15

mg/I NH3-N

10

n.~~/l

P

II.

First analyze capabilities of Blo-roughing side of Treatment Processes~

NOTE:

Plant upgrade

in

1977 routes

75

of the flow through Bio-roughing

stage first before discharge into Act.

Sludge

System

Al.

Flow and

loading

split into

Raw Sewage Pumps

inside

“Pump & Service

Bldg’

10479.315

Final Variance Basis of Design.xls

Percentage of split to blo-roughing side

=

I.

Raw Wastewater

A.

Compile Present Day Flows and

loads

19,412

23,730

3.35

4.19

5.03

6.30

6.30

3,300

4,746

428

570

279

6,635

11,729

871

1,162

647

p.

1

-

1

---

ATTACHMENT “A”

Basis of Design

Current

Conditions

and

Facilities

Bio-roughing side Current Design iwg. i-low

=

.s.35

MGD

Design

Maximum Monthly Flow

=

4.19

MGD

Maximum Weekly Flow

=

5.03

MGD

Maximum Daily Flow

=

6.30

MGD (Pump Capacity)

Design Peak Hr.

Q to

bio-roughing side

=

6.30

MGD (Pump Capacity)

Peak instantaneous Flow

=

0.00

0

BOO load to bio-rough side at Design

Avg

Flow

=

3,300

lb CBOD/day

SS

load to bio-rough side at Design Avg Flow

=

4,746

lb SS/day

NH3-N

load to bio-rough side

at Design Avg.

Flow

=

428

lb NH3~N/day

BOD load that bypasses bio-rough side at Design Avg Flow

=

0

lb CBOD/day

SS

load

that

bypasses

bio-rough side at Design Avg Flow

=

0

lb SS/day

NH3-N load that bypasses

bio-rough side at Design Avg

Flow

=

0

lb NH3-N/day

BOO load

to bio~roughside at Max.

Daily Flow

=

6,635

lb CBOD/day

SS

load to bio-rough

side at Max.

Daily Flow

=

11,729

lb SS/day

NH3-N load

to bio-rough side

at Max.

Daily Flow

=

871

lb NH3-N/day

BOD that bypasses

bio-rough side at Max.

Daily Flow

=

0

lb CBOO/day

SS that bypasses bio-rough side at Max.

Daily Flow

=

0

lb SS/day

NH3-N that bypasses bio-rough side

at Max.

Daily Flow

=

0

lb NH3-N/day

A-2.

PumpIng Capacity In Pump and Service

Building

Pump #1

=

556

gpm

Pump #2

=

1,042

gpm

Pump #3

=

1,389

gpm

Pump #4

=

1,389

gpm

Pump totalcapacity

=

4,375

gpm

(with no units out ofservice)

6.3

MGD

Pump firm capacity

2985.92

gpm

(with largest unit out ofservice)

4.3

MGD

B-i.

Compute BOD reduction

in Primary

Clarifiers at max. permitted

Design Avg. Flow

BOO load

to bio-rough side at Design

Avg

Flow

=

3,300

lb CBOD/day

Avg Flow to

Primary Clarifiers

=

3.35

MGE~

Total

primaryclarifier surface area

=

2,080

SF

SSR at Design Avg.

Flow

=

1,611

gpd/SF

CBOD removal

in

Primary Clarifiers at Design Avg.

Flow

=

26

from

chart

-

EPA Stds. App.

E,

Fig.

2

BOD

load out of Primaries at max.

permitted

Avg. 0

=

2,442

lb CBOD/day

B-2.

Compute BOO reduction in Primary

Clariflers at Max.

Daily Flow

10479.315

Final Variance Basis of Design.xls

‘

p.

1

-

2

---

El

=

Wi

=

V=

F=

No. of trickling filter units

Each trickling filter’s diameter

Surface area of one trickling filter unit

Total surface area of both trickling filter units

lb CBOD/day

gpd

SF

gpd/SF

from

chart-

IEPA Stds. App. E,

Fig. 2

lb CBOD/day

ATTACHMENT

“A”

Basis ofDesign

Curreni Conilitions

andFacilities

BOO load to bio-rough

side at ~ax. uaily i-low

=

b,635

Peak Hour Flow to

Primary Clarifiers

=

6,300,000

Total

primary clarifier surface area

=

2,080

SSR at Max. Daily Flow

=

3,029

CBOD removal in Primary Clarifiers at Max.

Daily Flow

=

20.0

BOO load out of Primaries at Max.

Daily Q

=

5,308

C-i.

Flows and

loadings

into Trickling Filters at Daily Average Flow

As per 35

III. Adm.

Code 370.900-h-2,

use NRC formula on page 706 of WEF MOP 8(1992)

Nat’l Research Council (NRC) formula:

P=

R/O

=

BOD load outof Primaries at max. permitted Avg. 0

=

Wi

=

El

=

lOO#(l+O.OO85x(Wl#VF)°~5)

percent

BOO removal efficiency

BOD

loading into trickling filter, ppd

volume ofIF media, acre-ft

number of passes of the organic mat’l

=

(1+R/Q) ÷

(1+(1-P)

x

R/Q~

weighting factor, 0.9 for military TF plants

recirculation ratio (recirc ~

+

plant flow Q)

2,442

lb CBOO/day

2,442

lb CBOD/day

V

=

media area x media depth

=

=

135

feet

=

14,314

SF

=

14,314

SF

0.33

acres

5.00

feet

1.64

acre-feet

0.9

1.20

recirc cap.

is 3.0 MGD when plant ADF

is

2.5 MGD

Depth of each trickling filter’s

media

=

V

(volume of TF media)

=

P=

lR/Q

=

10479.315

Final

Variance Basis of Design.xls

p.

1-3

---

ATTACHMENT “A”

Basis ofDesign

Current Condit~onsandFaciliti9

~

El

=

69.7

percent BOO removal in trickling filters

REALITY CHECK

Compute applied

BOO load per volume of media

=

W

+

(VF)

847

lb

BOO per day per acre-ft

34.12

lb BOO per 1000 cu-ft

BOO load out of Secondary Clarifiers at Design

Avg. Q

=

739 lb CBOD per day

26

mg/I CBOD

C-2.

Flows

and loadings into Trickling Filters at Max.

Daily Flow

As per 35

Ill. Adm. Code 370.900-h-2,

use NRC formula

onpage 706 of WEF MOP 8(1992)

Nat’l Research Council

(NRC) formula:

El

=

lOO÷(l÷O.OO85x(Wl.z~VF)°~5)

El

=

percent BOD removal efficiency

Wi

=

BOD loading into tricklingfilter, ppd

V

=

volume of TF

media, acre-ft

F

=

number of passes of the organic

mat’I

=

(l÷R/O)

+

(i+(l-P)

x

RJQ~

P

=

weighting factor, 0.9for militaryIF plants

R/O

=

recirculation ratio

(recirc 0÷

plant flow 0)

BOO load out of Primaries at Max.

Daily Q

=

5,308

lb CBOD/day

Wi

=

5,308

lb CBOD/day

V

=

media area x media depth

No

of trickling filter units

=

~

Each trickling

filter’s diameter

=

135

feet

Surface

area of one trickling filter unit

=

14,314

SF

Total surface area of both trickling filter units

=

14,314

SF

0.33

acres

Depth of each trickling filter’s

media

=

5.00

feet

V

(volume of TF

media)

=

1.64

acre-feet

Pr

0,9!,

R/Q=

1.20

Fr

1.75

10479.3 15

Final

Variance Basis of Design.xls

p.

1

4

---

ATTACHMENT

“A”

Basis ofDesign

=

.

.

.61.0

percent BOD removal in trickling filters

Current Concutions andFacilities

BOO load out of Secondary Clarifiers at Max.

Daily Q

=

2,071

lb CBOD per day

39

mg/i

CBOD

C-3.

Flow and

loading Into Secondary Ciarifiers

No. of Secondary Clarifiers

=

2

Secondary Clarifier #1’s diameter

=

40

feet

Surface area of Secondary Clarifier

#1

=

1,257

SF

Percent of total

=

39

Secondary Clarifier #2’s diameter

=

50

feet

Surface area of Secondary Clarifier #2

=

1,963

SF

Percent of total

=

61

Total Secondary Clarifier surface

area

=

3,220

SF

Average Flow to Secondary Clarifiers

=

3,350,000.00

gpd

Existing Surface

Settling Rate (SSR)

=

1,040

gpd/SF

Design Peak

Hr. 0 to bio-roughing side

6.30

MOD

6,300,000

gpd

Existing

Surface Settling

Rate (SSR)

=

1,956

gpd/SF

10479.315

Final Variance Basis

of Design.xls

p.

1

-

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