Memorandum

Date:	November 29,2022

To:	Administrative Record - Sac and Fox Meskwaki Nation WWTF and PWTF

Cc:	Project File

From:	Gerald H. Memming

RE:	Waste Load Allocations - Sac and Fox Meskwaki Mechanical WWTF Outfall 00 land Public Water Treatment Facility Outfall 003

Waste load allocations (WLAs) and permit limits were calculated for ammonia for the above referenced WWTF and for total residual
chlorine (TRC) for the Public Water Treatment Facility (PWTF). Below are the assumptions used in the calculations and the
resulting limits.

Receiving Stream Flows

Outfall 001: Mechanical Treatment Facility - Treated Effluent

Flow data from Richland Creek, USGS gage 05451900 located near Haven, was used to estimate the flow of the unnamed tributary
(locally known as Onion Creek), which the facility discharges to. The area for the Richland Creek watershed is 56.1 square miles.
USGS gage 05451900 lias 73-year flow record collected from 1949 to the present. The Onion Creek watershed is 5.51 square miles.
Therefore, their watershed ration is 0.0982 (5.51/56.1). For the calculated acute and chronic low flow values for Onion Creek, refer
to the table below.

Season

Onion Creek

30Q10 (cfs)

7Q10 (cfs)

1Q10 (cfs)

Spring

0.3949

0.1882

0.1304

Summer

0.0895

0.0386

0.0230

Winter

0.0527

0.0326

0.0186

There is potential recreational use and/or fishing in Onion Creek.

Outfall 003: Public Water Treatment Facility - Backwash Wastewater

Flow data from the Iowa River at Marshalltown, USGS gage 05451500, and Timber Creek near Marshalltown, USGS gage
05451700, were added together and then multiplied the flow with an area ration (1880/1650). The drainage area of the Iowa River
above Outfall 003 is 1880 square miles and above USGS gage 05451500 is 1532 square miles. The drainage area above USGS gage
005451700 on Timber Creek is 118 square miles. For the calculated acute and chronic low flow values for the Iowa River, refer to
the table below. To be protective of downstream users, a mixing zone equivalent to IDNR's was used to develop the WLAs for total
residual chlorine (TRC). Based on a November 11,2020 of Iowa Wasteload Allocation (WLA) Procedure, the zone of initial dilution
(ZID) is limited to 2.5% of the 1Q10, and the chronic mixing zone is limited to 25% of the 7Q10.

Season

Iowa River

30Q10 (cfs)

7Q10 (cfs)

1Q10 (cfs)

Early Life Stages Present
(March 1 - September 30)

89.57

64.56

56.19

Early Life Stages Absent
(October 1 - Februaiy 28 [29]

53.72

42.31

39.54

Water Quality Standards

Outfall 001: Mechanical Treatment Facility - Treated Effluent

The facility located within tribal boundaries discharges to Onion Creek that does not have a designated use classification. To be
protective of the Clean Water Act 101(a) goals acute and chronic water quality criteria will apply. EPA used its 1999 Update of
Ambient Water Quality Criteria for Ammonia to evaluate protection of aquatic life. An evaluation of downstream state water quality
standards, namely the Iowa Department of Natural Resources (IDNR) Water Quality Standards, Chapter 61, of the Iowa
Administrative Code, was also conducted to ensure discharges from the Facility would not cause an exceedance of those state criteria.
Early Life Stages present criteria apply March through September, and Early Life Stages absent criteria apply October through
Februaiy. Because the effluent flow is greater than the stream flow during the critical time, rapid and complete mix is assumed. All
stream flow at the point of discharge will be considered for dilution. Water quality criteria is based on pH and temperature values of
the receiving stream flow.	-1 -


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Outfall 003: Drinking Water Treatment Facility - Backwash Wastewater

In order to protect downstream users, EPA used IDNR's Total Residual Chlorine (TRC) criteria to determine the need for Water
Quality-based Effluent Limits (WQBEL) for TRC. The TRC criteria are 19 |ig/L acute and 11 |ig/L chronic. Raw well water is
currently being used to backflush the dual media filters. If the facility uses potable finished water containing chlorine to backflush the
filters, monitoring for TRC with limitations will be required. The PWTF is required to maintain a chlorine residual of 1.3 mg/L in the
finished water.

Ammonia

Outfall 001: Mechanical Treatment Facility - Treated Effluent

There is reasonable potential for the facility to exceed water quality criteria for ammonia. Below are the assumptions and equations
used in the calculation of reasonable potential. It was assumed there was no in-stream ammonia decay and the facility average daily
discharge flows for each season was used in the calculations. Current background ammonia concentrations were obtained from the
Iowa Department of Natural Resources, Water Quality Monitoring and Assessment Section, on October 31, 2022.

The following equation was used in the calculation of the Waste Load Allocations (WLAs) for this facility:

WLA = WOS * (stream flow + discharge flow) - (background concentration * stream flow)

discharge flow

The calculated permit limits are based on the chronic waste load allocation for the periods March through May and June through
September and the acute waste load allocation for the period October through February.

Since pH and temperature are the "drivers" that determine acute and chronic water quality criteria, EPA has decided to split the Early
Life Stage present period into a spring period (March - May) and a summer period (June - September).

Proposed Calculated Permit Limits

Spring Season (Early Life Stages Present) March through May
Daily Maximum Limit - 4.07 mg/L
Monthly Average Limit -1.71 mg/L

Summer Season (Early Life Stages Present) - June through September
Daily Maximum Limit - 3.25 mg/L
Monthly Average Limit -1.62 mg/L

Winter Season (Early Life Stages Absent) - October through February
Daily Maximum Limit - 6.09 mg/L
Monthly Average Limit - 3.04 mg/L

Existing Permit Limits

Spring Season (Early Life Stages Present) March through May
Daily Maximum Limit - 5.85 mg/L
Monthly Average Limit - 2.71 mg/L

Summer Season (Early Life Stages Present) - June through September
Daily Maximum Limit -4.13 mg/L
Monthly Average Limit -1.80 mg/L

Winter Season (Early Life Stages Absent) - October through February
Daily Maximum Limit - 5.92 mg/L
Monthly Average Limit - 2.26 mg/L

See Ammonia Waste load Allocation Setup Sheet below for further detail.

See Wasteload Allocation Development Sheets below for further detail.

See Reasonable Potential Development Sheet below for further detail.

Methods based on Technical Support Document for Water Quality-based Toxics Control (EPA/505/2-90-001 PB91 127415, March
1991).

-2-


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AMMONIA WASTELOAD ALLOCATION SETUP SHEET









Prepared by Gerald H. Memming on November 23.2022



















Facility Name

Sac and Fox Meskwaki Nation - Outfall 001











Permit Number

LA.0073750











Pollutant

Ammonia











Seasons in Permit Limits

Spring

Summer

Winter













Months in Season

Mar-May

June-Sept

Oct-Febr













Stream Flovr (cfs) Acute - Onion Creek

0.1304

0.0230

0.0186



Used area ratio between USGS gage stations and EPA s DFLOW Model

Stream Flow (cfs) Chronic - Onion Creek

0.3949

0.0895

0.0527



Used area ratio between USGS gage

stations and EPA's DFLOW Model

Effluent Discharge (MGD)

0.28985

0.2342

0.1839



Used Average Monthly Discharge Flow of Facility

Background concentration (mg/L) Acute

0.06

0.02

0.034



Data provided by IDNR. Iowa WLA Procedure. November 11.

2020

Background concentration (mgL) Chronic

0.06

0.02

0.034



Data provided by IDNR. Iowa WLA Procedure. November 11,

2020

Stream pH

8.2

8.225

8.2



Data provided by IDNR. Iowa WLA Procedure. November 11.

2020

Stream Temperature :C

8.6

21.85

4.68



Data provided by IDNR. Iowa WLA Procedure. November 11.

2020

% mixing (0-1) Acute

1

1

1



Used complete mixing zone value





% mixing (0-1) Chronic

1

1

1



Used complete mixing zone value





Ammonia WQS Acute

5.72

5.47

5.72



Table 3a. IDNR Chapter 61. Water Quality Standards



Ammonia WQS Chronic

0.92

1.078

2.91



Tables 3b and3c. IDNR Chapter 61. Water Quality Standards



Is this a Controlled Discharge Lagoon? (y/n]

n

n

n













Salmonic Present? (y/n)

n

n

n













Early Life Stages Present? (y/n)

y

y

n























Ammonia Wasteload Allocation Development Sheets
1. Spring Season (March - May)

Facility Name- Sac and Fox Meskwaki Nation - Outfall 001
Permit Number- IA0073750	Pollutant:

11/18/2022

Ammonia

Multipliers

3.11

MDL

1 31

AML

0.32

LTAa

078

LTAc

monitoring samples
CV

Design flow MGD=
rt Used

12
0.6
0.42

12

WLA = WQSVstream flow + discharge flow) - (background cc

discharge flow

LTAa = WLA acute " LTAa multiplier
LTAc = WLA chronic * LTAc multiplier
AML mg/L = the smaller LTA (LTAa or LTAc) * AML multiplier
DML mg/L = the smaller LTA (LTAa or LTAc) * DML multiplier
AML lbs/day = AML mg/L ' discharge flow * 8 34
DML lbs/day = DML mg/L * discharge flow * 8 34

Acute WLA Chronic WLA LTAa LTAc

Concentration limits

Mass limits

AML mg/L

MDL mg/L

AML #/d

DML m

Spring (March-May)

7.363

1.678

2 364

1 308

1.710

4.073

5 989

14 266























































Input data for Limits calculator

Seasons in Permit Limits	Spring

Months in Season	March-May

Stream Flow (cfs) Acute	0 1304

Stream Flow (cfs) Chronic	0.3949

Effluent Discharge (MGD)	0 28985

Background concentration (mg/L) Acute	0.06

Background concentration (mg/L) Chronic	0 06

Stream pH	8 2

Stream Temperature °C	8 6

% mixing (0-1) Acute	1

% mixing (0-1) Chronic	1

WQS Acute*	5 72

was Chronic*	0 92

Salmonid Present? (yM)	n

Early Life Stages Present? (y/n)	y

'* Calculated Ammonia Water Quality Criteria are based on EPA's 1999 Ammonia Criteria Update

3-


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2. Summer Season 0une - September)

Facility Name- Sac and Fox Meskwaki Nation - Outfall 001
Permit Number- IAQ073750	Pollutant

11/18/2022

Ammonia

Multipliers

3.11

MDL

1 55

AML

0 32

LTAa

078

LTAc

monitoring samples

12

CV

0.6

Design flow MGD-

0.42

n Used

4

WLA = WQS'istream flow + discharge flow) - (background cc

discharge flow

LTAa = Wl-A acute * LTAa multiplier
LTAc = WLA chronic * LTAc multiplier
AML mg^L = the smaller LTA (LTAa or LTAc) * AML multiplier
DML mg/L = the smaller LTA (LTAa or LTAc) * DML multiplier
AML lbs/day = AML mg/L' discharge flow * 8 34
DML lbs/day = DML mg/L' discharge flow' 8 34

Acute WLA Chronic WLA LTAa LTAc

Concentration limits

Mass limits

AML mg/L

MDL mg/L

AMLWd

DML #/d

Summef (June-Sept)

5815

1 339

1 887

1 045

1 622

3 254

5.681

11 397























































Input data for Limits calculator

Seasons In Permit Limits	Summer

Months in Season	June-Sept

Stream Flow (cfs) Acute	0 0230

Stream Flow (cfs) Chronic	0 0895

Effluent Discharge (MGD)	0 23420

Background concentration (mg/L) Acute	0 02

Background concentration (mg/L) Chronic	0 02

Stream pH	8 2

Stream Temperature °C	21 85

% mixing (0-1) Acute	1

% mixing (0-1) Chronic	1

WQS Acute*	5.47

WQS Chronic'	1.078

Salmonid Present? (y/n)
Early Life Stages Present? (y/n)

' Calculated Ammonia Water Quality Criteria are based on EPA's 1999 Ammonia Criteria Update


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3. Winter Season (October - February)

Facility Name- Sac and Fox Meskwaki Nation - Outfall 001
Permit Number- IA0073750	Pollutant

11/18/2022

Ammonia

Multipliers

3 11

MDL

1 55

AML

0 32

LTAa

0.78

LTAc

monitoring samples

12

CV

0.6

Design Row MGD=

042

n Used

4

WLA- WQS'(stream flow + discharge flow! • (background <

discharge flow

LTAa = WLA acute * LTAa multiplier
LTAc = WLA chronic * LTAc multiplier
AML mg/L - the smaller LTA (LTAa or LTAc) * AML multiplier
~ML mg/L = the smaller LTA (LTAa or LTAc) * DML multiplier
AML lbs/day = AML mg/L * discharge flow * 8 34
DML lbs/day = DML mg/L * discharge flow * 8.34

Acute WLA Chronic WLA LTAa LTAc

Concentration limits

Mass limits

AML mg/L

MDL mg/L

AML #/d

dml m

Winter (Oct-F«br)

6 091

3442

1 956

2 686

3 036

6091

10 635

21 336























































Input data for Limits calculator

Seasons In Permit Limits	Winter

Months in Season	Oct-Febr

Stream Flow (cfs) Acute	0 0186

Stream Flow (cfs) Chronic	0 0527

Effluent Discharge (MGD)	0 1839

Background concentration (mg/L) Acute	0 034

Background concentration (mg/L) Chronic	0 034

Stream pH	8 2

Stream Temperature °C	4 68

% mixing (0-1) Acute	1

% mixing (0-1) Chronic	1

WQS Acute-	5 72

WQS Chronic*	2 91

Salmonid Present? (y/n)
Early Life Stages Present? (y/n)

'* Calculated Ammonia Water Quality Criteria are based on EPA's 1999 Ammonia Criteria Update.

Ammonia Reasonable Potential Development Sheet

Reasonable Potential Development for Water Quality Based Effluent Limitations













Facility Name-

Sac and Fox Meskwaki Nation WWTF - Outfall 001

Date:

11/28/2022





NPDES Permit Number-

IA0073750







































































Outfall 001

Undesignated Tributary to Iowa River (Onion Creek)

Pollutant: Ammonia



























Spring

Summer

Winter















Acute

Chronic

Acute

Chronic

Acute

Chronic













Stream Flow (cfs)

Effluent Discharge (MGD)

0.1304
0.28985

0.3949
0.28985

0.0230
0.2342

0.0895
0.2342

0.0186
0.1839

0.0527
0.1839

Reasonable Potential Multiplying Factors (@ 99% & 99%)



Number of
Observations

CV



Background concentration (mg/L)

0.06

0.060

0.020

0.020

0.034

0.034



0.2

0.4

0.6

0.8

1



Water Quality Standard

5.72

0.92

5.47

1.078

5.72

2.91

1

2.5

6

13.2

26.5

48.3



% mixing (0-1)

1.0

1.0

1.0

1.0

1.0

1.0

2

2

4

7.4

12.7

20.2



CV (0.6 is recommended)

0.6

0.6

0.6

0.6

0.6

0.6

3

1.9

3.3

5.6

8.9

13.4



Number of monitored data

5

5

9

9

8

8

4

1.7

2.9

4.7

7.2

10.3



Maximum Observed value

1.83

1.83

1.50

1.50

6.90

6.90

5

1.7

2.7

4.2

6.2

8.6



Multiplier from table

4.2

4.2

3.2

3.2

3.3

3.3

6

1.6

2.5

3.8

5.5

7.5



Predicted max effluent concentration

7.686

7686

4.800

4.800

22.770

22.770

7

1.6

2.4

3.6

5

6.7



Down Stream Concentration

5.970

4.119

4.515

3.855

21.377

19.222

8

1.5

2.3

3.3

4.6

6.1



Reasonable Potential?

yes

yes

no

yes

yes

yes

9

1.5

2.2

3.2

4.3

5.7

















10

1.4

2.2

3

4.1

5.3

















11

1.4

2.1

2.9

3.9

5

















12

1.4

2

2.8

3.7

4.7

















13

1.4

2

2.7

3.6

4.5



Effluent concentration = Max Observed * Multiplier

14

1.4

2

2.6

3.4

4.3





15

1.4

1.9

2.5

3.3

4.1



Down Stream Concentration =

16

1.4

1.9

2.5

3.2

4



(Effluent Discharae * Effluent concentration) + (Background concentration * Stream Flow)

17

1.4

1.9

2.5

3.1

3.8



(Effluent Discharge + Stream Flow)

18

1.4

1.9

2.4

3

3.7







19

1.4

1.8

2.4

3

3.6



NOTE: Data entree from April 2018 through June 2022





20

1.3

1.8

2.3

2.9

3.5

















>20

Use HighestValue



















-5-


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Total Residual Chlorine (TRC)

Outfall 003: Public Water Treatment Facility - Backwash Wastewater Effluent

See Total Residual Chlorine (TRC) Wasteload Allocation Setup Sheet below for further detail.

See Wasteload Allocation Development Sheet below for further detail.

Methods based on Technical Support Document for Water Quality-based Toxics Control (EPA/505/2-90-001 PB91 127415,
March 1991).

TOTAL RESIDUAL CHLORINE WLA SETUP SHEET

Prepared by	Memtraiif cnXroofcer Zis 1121

Fz:ilitv

i2z z.r.6 Ten I

Irik" -ak: I'atior. - C strati C

u *



Permit

:acc~5~5C



?s'\hzznt

Total Chlcrins l.TFvC'



SeatQE.1 in Permit Liruif:

Pfi;=nt

Atifctt?







Month; jti

Mar-:~pt

Cct-Febr







Mrs am Fie-- - I"-a

55. :s

i> 5-





Unz arsa iziic s*r..V'S*n fagrs sratscm aid E?A 5 DFLO'.V Icd* i

^i'42U"51 Fie"' Ufz' Chi'Cili; - FLj'--ci"

6-.56

¦i2 51





Usid aria ia:ic U:G:i ?a?i stations and EPA ; DFLO'-V Modit

E::r.iiiit Dlsikarf- :)-IGD.

C.1555

C-L.555





Ussd A'-'srafs Mcntb-y Diiiharf- flc— c-f Fa_ui:y

Backn-c^rtd tcncs-ntrancn [tv.z L. Ar:;i



C





Difaul: Ea:k=rrr^nd

Background iznc^r.traticu: nil L . Cnrcni;



c





Default Barkirs^ni

5'rimi rH

8.21

S.2





Background "ibsi prc-'idid by ID>7R. lo-va. *.VLA Prcisd-jirs. 2C2C

iWizsii :C

16-1"

-iS





Barkit'C'snd ~'ab~ yrevji-d by ID1CF.. ?rcc~chi'i. 2C2C

:rviL'iinz 'C-l;

C.025

C.E25





ID".-TF. rnbiin? rcn* vahii. Ic"-a v.lA Pre ir-d^ri. Nov. 2C'22

:: rnt-ntr:? Clii'Cf.:;

C

C.25





ID"-?. n;i>;inf r;r.i vak>~. Io-"a vTLA Pro:* isr-. 2-cv. 2C2C

Xcri itrar-cnia WQI- A:u:i

c.c;s

c.c;s





IDIvF. Qualify arars intrTia

sjiin'-cnii Chrcni:

c-c;:

" c*'





ID Is?.IVarii Quality rhtoni:

Zi this, i L crtEicUri Disdiarp Liiccr." ;y n

tt

n







Prii-sf.!:? fyn'

V

n







Early Lif= ikapi Pi-iisrj" :.y r.'

y

n








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TRC Wasteload Allocation Development Sheets
1. Early Life Stages Present (March - September)

Facility Name-

Sac and Fox Meskwaki - Outfall 003

11/21/2022

Permit Number-

IA0073750



Pollutant:

Total Residual Chlorine (TRC)

Multipliers



WLA = WQS'fstream flow + discharoe flow) - fbackaround concentration * stream flow)

3.114

MDL



discharge flow

1.552

AML



LTAa = WLA acute * LTAa multiplier

0 321

LTAa



LTAc = WLA chronic * LTAc multiplier

0.527

LTAc



AML mg/L = the smaller LTA (LTAa or LTAc) * AML multiplier

monitoring samples



0



DML mg/L = the smarter LTA (LTAa or LTAc) * DML multiplier

CV



0,6



AML lbs/day = AML mg/L * discharge flow * 8.34

Design flow MGD=



28



DML lbs/day = DML mg/L ' discharge flow * 8.34

n Used



4





Acute WLA Chronic WLA LTAa LTAc

Concentration limits

Mass limits

AML mg/L

MDL mg/L

AML #/d

DML m

Present (March-Sept)

0.130

0 748

0.042

0.394

0.065

0.130

1.510

3.030























































Input data for Limits calculator

Seasons in Permit Limits	Present

Months in Season	March-Sept

Stream Flow (cfs) Acute	56.19

Stream Flow (cfs) Chronic	64.56

Effluent Discharge (MGD)	0.1555

Background concentration (mg/L) Acute	0

Background concentration {mg/L) Chronto	0

Stream pH	8.21

Stream T emperature °C	16.17

% mixing (0-1) Acute	0.025

% mixing (0-1) Chronic	0.25

WQS Acute*	0.019

WQS Chronic*	0.011

Satmonid Present? (y/n)	y

Early Life Stages Present? (y/n)	y

2. Early Life Stages Absent (October - February)

Facility Name- Sac and Fox Meskwaki - Outfall 003
Permit Number- IA0073750	Pollutant:

11/21/2022
Total Residual Chlorine (TRC)

Multipliers

3.114

MDL

1.552

AML

0.321

LTAa

0.527

LTAc

monitoring samples

0

CV

0.6

Design flow MGD=

28

n Used

4

WLA = WQS*(stream flow + discharge flow) - (background concentration * stream flow)

discharge flow

LTAa = WLA acute * LTAa multiplier
LTAc = WLA chronic * LTAc multiplier
AML mg/L = the smaller LTA (LTAa or LTAc)" AML multiplier
DML mg/L = the smaller LTA (LTAa or LTAc) * DML multiplier
AML lbs/day = AML mg/L * discharge flow * 8.34
DML lbs/day = DML mg/L * discharge flow * 8.34

Acute WLA Chronic WLA LTAa LTAc

Concentration limits

Mass limits

AML mg/L

MDL mg/L

AML #/d

DML m

Absent (Oct-Sept)

0.097

0.494

0.031

0.260

0.048

0.097

1 128

2.263























































Input data for Limits calculator

Seasons in Permit Limits	Absent

Months in Season	Oct-Sept

Stream Flow (cfs) Acute	39.54

Stream Flow (cfs) Chronic	42.31

Effluent Discharge (MGD)	0.1555

Background concentration (mg/L) Acute	0

Background concentration (mg/L) Chronic	0

Stream pH	8.20

Stream Temperature °C	4.68

% mixing (0-1) Acute	0.025

% mixing (0-1) Chronic	0.25

WQS Acute*	0.019

WQS Chronic*	0.011

Salmonid Present? (y/n)	n

Early Life Stages Present? (y/n)	n


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