Draft total maximum daily load evaluation for Buffalo Creek in the Oconee River basin (zinc)

DRAFT
Total Maximum Daily Load Evaluation for
Buffalo Creek in the
Oconee River Basin
(Zinc)
Submitted to: The U.S. Environmental Protection Agency
Region 4 Atlanta, Georgia
Submitted by: The Georgia Department of Natural Resources
Environmental Protection Division Atlanta, Georgia

June 2001

Total Maximum Daily Load Evaluation Buffalo Creek (Zinc)

June 2001

Table of Contents

Section

Page

1.0 INTRODUCTION.........................................................................................................................1 1.1 Background...........................................................................................................................1 1.2 Watershed Description..........................................................................................................1 1.3 Water Quality Standard.........................................................................................................1

2.0 WATER QUALITY ASSESSMENT ...............................................................................................4

3.0 SOURCE ASSESSMENT ............................................................................................................5

4.0 TMDL DEVELOPMENT APPROACH ..........................................................................................6 4.1 Steady-State Approach.........................................................................................................6 4.2 Critical Conditions .................................................................................................................6

5.0 ALLOCATION.............................................................................................................................8 5.1 Total Maximum Daily Load ....................................................................................................8 5.2 Waste Load Allocations.........................................................................................................8 5.3 Load Allocations....................................................................................................................9 5.4 TMDL Results .......................................................................................................................9 5.5 Seasonal Variation................................................................................................................9 5.6 Margin of Safety....................................................................................................................9

6.0 POINT AND NONPOINT SOURCE APPROACHES....................................................................11

7.0 PUBLIC PARTICIPATION..........................................................................................................12 REFERENCES

Georgia Environmental Protection Division

Atlanta, Georgia

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Total Maximum Daily Load Evaluation Buffalo Creek (Zinc)

June 2001

1.0 INTRODUCTION
1.1 Background
The State of Georgia assesses its water bodies for compliance with water quality standards criteria established for their designated uses as required by the Federal Clean Water Act (CWA). Assessed water bodies are placed into three categories; supporting, partially supporting, or not supporting their designated uses depending on water quality assessment results. These water bodies are found on Georgia's 305(b) list as required by that section of the CWA that defines the assessment process, and are published in Water Quality in Georgia every two years.
Some of the 305(b) partially and not supporting water bodies are also assigned to Georgia's 303(d) list, also named after that section of the CWA. Water bodies on the 303(d) list are required to have a Total Maximum Daily Load (TMDL) established for the water quality constituent(s) in violation of the water quality standard. The TMDL process establishes the allowable loading of pollutants or other quantifiable parameters for a water body based on the relationship between pollution sources and in-stream water quality conditions. This allows water quality based controls to be developed to reduce pollution and restore and maintain water quality.
The State of Georgia has identified 10 miles of Buffalo Creek, from Keg Creek to its confluence with the Oconee River, in the Oconee River basin as not supporting its designated uses for the parameter zinc. In addition, this same segment of Buffalo Creek is listed as not supporting its designated uses for pH. The water use classification for Buffalo Creek is Fishing.
1.2 Watershed Description
The Buffalo Creek watershed is located in the Oconee River basin in central Georgia in Washington County (see Figure 1). The watershed is part of the Coastal Plain Red Uplands Ecoregion. It is in the Southern Coastal Plain Soil Province. Buffalo Creek originates in Hancock County and flows south into Washington County.
Upstream of the confluence of Buffalo Creek and the Oconee River, the stream flows through areas that are predominantly forest with many abandoned and active kaolin mines. There is also a significant urban area around the City of Sandersville and some agricultural land. The stream flows through wetland areas and becomes very slow and wide with a swampy streambed for most of the listed segment. The size of the watershed is estimated to be 290 square miles.
The 1-day, 10-year minimum (1Q10) statistical flow value at the Highway 272 Bridge near Oconee, Georgia, is approximately 23 cubic feet per second (cfs). In addition, the 7-day, 10-year minimum (7Q10) statistical flow value is approximately 26 cfs.
1.3 Water Quality Standard
The water use classification for Buffalo Creek is fishing. The fishing classification, as stated in Georgia's Rules and Regulations for Water Quality Control Chapter 391-3-6-.03(6)(c), is established to protect the "Propagation of Fish, Shellfish, Game and Other Aquatic Life; secondary contact recreation in and on the water; or for any other use requiring water of a lower quality."

Georgia Environmental Protection Division

Atlanta, Georgia

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Total Maximum Daily Load Evaluation Buffalo Creek (Zinc)

June 2001

Georgia Environmental Protection Division

Atlanta, Georgia

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Total Maximum Daily Load Evaluation Buffalo Creek (Zinc)

June 2001

Chapter 391-3-6-.03(5)(e)(ii) of Georgia's Rules and Regulations establishes criteria for metals which applies to all waters in the State. The established chronic criterion and acute criterion for dissolved zinc are as follows:

acute criteria for dissolved zinc = (e(0.8473[ln(hardness)] + 0.8604))(0.978) g/L chronic criteria for dissolved zinc = (e(0.8473[ln(hardness)] + 0.7614))(0.986) g/L

The hardness used in the above equations is expressed as mg/L as CaCO3. The minimum hardness allowed for use in these equations shall not be less than 25 mg/L as CaCO3, and the maximum shall not be greater than 400 mg/L as CaCO3.
This regulation requires that instream concentrations of dissolved zinc shall not exceed the acute criteria indicated above under 1Q10 or higher stream flow conditions and shall not exceed the chronic criteria indicated above under 7Q10 or higher stream flow conditions.
In accordance with Georgia Rules and Regulations for Water Quality Control 391-3-6-.03(5)(e)(ii), guidance found in EPA's "Guidance Document of Dynamic Modeling and Translators August 1993" may be used to determine the relationship between the total recoverable concentration of a metal and the dissolved form of a metal. The metals translator is determined using default linear partition coefficient values found in an EPA document entitled, "Technical Guidance Manual for Performing Waste Load Allocations Book II: Streams and Rivers."
In addition, Georgia Regulation 391-3-6-.06(4)(d)5.(ii)(b)(2) allows methods from this EPA guidance document to be used to translate dissolved criteria concentrations into total recoverable permit limits. Metals effluent permit limitations are required to be expressed as total recoverable metal per 40 CFR 122.45(c). Therefore, the TMDL will be expressed as both the total maximum daily load of total recoverable zinc that will be protective of the dissolved zinc chronic criterion and the total maximum daily load of total recoverable zinc that will be protective of the dissolved zinc acute criterion.

Georgia Environmental Protection Division

Atlanta, Georgia

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Total Maximum Daily Load Evaluation Buffalo Creek (Zinc)

June 2001

2.0 WATER QUALITY ASSESSMENT
The listing of Buffalo Creek for zinc resulted from the assessment of water quality data that were collected at State Road 272 near Oconee, Georgia. Two water quality samples were collected, one in 1999 and one in 2000. The data is provided in Table 1.
The translator formulas are presented in Section 4.1 of this TMDL. The calculated translator is a function of the instream TSS. The average TSS from this trend monitoring station in 1999 was 16 mg/L.
Table 1. Zinc Data Collected From Buffalo Creek

Date 11/16/99

Measured Total
Recoverable Zinc
Concentration ( g/L)
61

Calculated Translator
(Total Recoverabl
e to Dissolved)
3.8

9/14/00

400

3.8

Assumed Dissolved
Zinc Concentration
( g/L)

Calculated Total
Hardness (mg/L as CaCO3)

Acute Criterion
( g/L)

16

49

62

104

74

88

Chronic Criterion
( g/L)
57 81

Georgia Environmental Protection Division

Atlanta, Georgia

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Total Maximum Daily Load Evaluation Buffalo Creek (Zinc)

June 2001

3.0 SOURCE ASSESSMENT
A source assessment characterizes the known and suspected sources of zinc in the watershed for use in a water quality model and the development of the TMDL. The sources of zinc in this watershed are both point sources and nonpoint sources. Both will be addressed in this TMDL.
There are several point source discharges in this watershed. The point sources that discharge to Buffalo Creek are authorized to discharge through the Georgia National Pollutant Discharge Elimination System (NPDES) program. In accordance with the NPDES program, these facilities have periodically taken samples of their discharges and some have analyzed for the parameter zinc. Others have not tested for zinc because of the type of discharge.
The area has many kaolin mines and several associated industries. The Sandersville WWTP is the only major municipal point source discharger in the watershed. It treats both municipal and industrial wastewater using an activated sludge system with a design capacity of 1.7 million gallons per day (MGD). The City of Sanderville and Thiele Kaolin Company are the only two facilities with permits that currently have zinc limitations. The permit limits are provided in Table 2.
Table 2. Zinc Data Collected From NPDES dischargers to Buffalo Creek

NPDES Discharger
Sandersville WWTP GA0032051 Thiele Kaolin GA0002453

Permit Design
Flow MGD
1.7
4.0

Permitted Total Recoverable Zinc Concentration ( g/L)
111.4

Calculated Translator (Total Recoverable To
Dissolved)
3.8

62.3

3.8

Assumed Dissolved Zinc Concentration
( g/L)
29
16

In addition to permitted discharges to the watershed, there are also permitted sludge application sites in the watershed. Atmospheric deposition of zinc in the watershed could add a quantifiable load of zinc, but it is not well understood at this time.

It is unknown whether any nonpoint sources potentially cause or contribute to excursions of the water quality standard for zinc. There is no data available which indicates any specific nonpoint source of zinc.

Georgia Environmental Protection Division

Atlanta, Georgia

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Total Maximum Daily Load Evaluation Buffalo Creek (Zinc)

June 2001

4.0 TMDL DEVELOPMENT APPROACH
An important component of TMDL development is to establish relationships between source loadings and in-stream water quality. In this section, the numerical modeling techniques used to develop the TMDL are discussed.
4.1 Steady-State Approach
Steady-state models are applied for "critical" environmental conditions that represent extremely low assimilative capacity. For effluent-dominated riverine systems critical environmental conditions correspond to low flows. The assumption behind steady-state modeling is that effluent concentrations that protect water quality during critical conditions will be protective for the large majority of environmental conditions that occur. A mass balance equation is used in section 5.3 to model the critical conditions. and calculate zinc allocations. The allowable zinc concentration in Buffalo Creek will be used to calculate the allocations in order to protect the stream.
4.2 Critical Conditions
The critical flow conditions for this TMDL occurs when the ratio of effluent to stream flow is the greatest. For protection of the chronic criteria, this flow condition occurs when the Sandersville WWTP and Thiele Kaolin are discharging at their design capacity and the stream is flowing at 7Q10 conditions. For protection of the acute criteria, this flow condition occurs when the Sandersville WWTP and Thiele Kaolin are discharging at their design capacity and the stream is flowing at 1Q10 conditions. It is assumed that these will be the critical periods for aquatic life. Table 3 provides the critical flow data.
Table 3. Critical Flow Conditions for Buffalo Creek

Source of Flow Thiele Kaolin WTF Sandersville WWTP Buffalo Creek (during 7Q10 conditions) Buffalo Creek (during 1Q10 conditions)

Flow value (MGD/ cfs)
4.0/6.2
1.7/2.6
17/26
15/23

The hardness of the receiving waters is also a critical condition in calculating the dissolved fraction of zinc in the Creek. A lower hardness results in a higher proportion being in the dissolved form resulting in more conservative criterion. Based on the available data for Buffalo Creek (i.e., 49 mg/L and 74 mg/L as CaCO3), the hardness value used for critical conditions is 49 mg/L. This hardness value corresponds to a dissolved zinc chronic criterion of 57 g/L and a dissolved zinc acute criterion of 62 g/L.
Consistent with the suggestions in the EPA guidance document referenced in Georgia's water quality standards for metals, the translator for converting total recoverable zinc concentrations to dissolved zinc concentrations will be expressed as follows:
A translator may be established using the methods documented in EPA's "Technical Guidance Manual for Performing Waste Load Allocations Book II: Streams and Rivers". The partition coefficient for zinc found in the EPA's Technical Guidance Manual is expressed as:
Kd = Kpo x TSSa

Georgia Environmental Protection Division

Atlanta, Georgia

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Total Maximum Daily Load Evaluation Buffalo Creek (Zinc)

June 2001

where

Kd = partition coefficient for zinc in L/kg Kpo = 1.25 x 106 TSS = total suspended solids concentration in mg/L
a = -0.7038

It is important to note that the authors of EPA's Technical Guidance Manual derived the above po' coefficient and the `a' exponent based on the statistical analysis of 2253 data
records collected from rivers and streams distributed throughout the United States.

The partitioning of zinc between solid and dissolved phases can be determined as a function of the partition coefficient for zinc and the concentration of solids in the water column. This
function is expressed as:

Ct/Cd = 1 + Kd x TSS x (10-6 kg/mg)
where Ct = total zinc concentration in g/L Cd = dissolved zinc concentration in g/L
Instream TSS data is available for Buffalo Creek. The average total suspended solids (TSS) for 1999, from this trend monitoring station is 16 mg/L. Applying this value to the above relationship, the expected ratio of total zinc to dissolved zinc (i.e. the translation factor) is 3.8.

Georgia Environmental Protection Division

Atlanta, Georgia

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Total Maximum Daily Load Evaluation Buffalo Creek (Zinc)

June 2001

5.0 ALLOCATION
5.1 Total Maximum Daily Load
A TMDL is the sum of the individual WLAs for point sources and load allocations (LA) for nonpoint sources and natural background (40 CFR 130.2). The sum of these components may not result in an exceedence of water quality standards for that water body. To protect against exceedences, the TMDL must also include a margin of safety (MOS), either implicitly or explicitly, that accounts for the uncertainty in the relationship between pollutant loads and the water quality response of the receiving water body. Conceptually, a TMDL can be expressed as follows:

TMDL = WLAs + LAs + MOS
The TMDL is the total amount of pollutant that can be assimilated by the receiving water body while maintaining water quality standards. For pollutants such as metals, TMDLs are expressed on a mass loading basis (e.g., pounds per day). In accordance with 40 CFR Part 130.2(i), "TMDLs can be expressed in terms of ... mass per time, toxicity, or other appropriate measure."
5.2 Waste Load Allocations

As is stated in Section 4.1 of this report, the dissolved zinc chronic criterion is equal to 57 g/l and the dissolved zinc acute criterion is equal to 62 g/L for the established critical conditions. Using a translation factor equal to 3.8, the allowable instream total recoverable concentrations are 217 g/L and 226 g/L, to protect against chronic and acute effects of zinc, respectively.
The WLAs for this TMDL, are for the loading to Buffalo Creek. Each facility's waste load allocation is calculated using the effluent design flow and the critical low flow. These facilities do not discharge into Buffalo Creek, but discharge to tributaries upstream in this watershed that are effluent dominated. The wasteload allocations require the effluent concentration from each point source not exceed the allowable instream total dissolved and total recoverable chronic and acute concentrations at the end of pipe with no dilution. The waste load allocation is the sum of the allowable loadings from the individual point sources. The allowable point source loadings are calculated by multiplying the allowable effluent concentrations by the effluent design flow (see Table 4).
These total recoverable concentrations are higher than the current zinc limits for the permitted facilities. The current permit limits were based on limits without a translator. Any permits in this watershed will need to meet this wasteload allocation, as well as any more stringent limitations required for the specific receiving waters.

Facility

Permitted Limit

Sandersville WWTP
Thiele Kaolin Company

0.40 kg/day 1.68 kg/day

5.3 Load Allocations

Georgia Environmental Protection Division Atlanta, Georgia

Table 4. Wasteload Allocation

Total Dissolved Zinc

Chronic

Acute

Total Recoverable Zinc

Chronic

Acute

0.37 kg/day 0.86 kg/day

0.40 kg/day 1.40 kg/day 0.94 kg/day 3.29 kg/day

1.45 kg/day 3.42 kg/day

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Total Maximum Daily Load Evaluation Buffalo Creek (Zinc)

June 2001

There are currently no known zinc contributions to Buffalo Creek from nonpoint sources. The allowable
zinc concentration in Buffalo Creek (217 g/L and 226 g/L, to protect against chronic and acute effects of zinc, respectively) will be used with the wasteload allocation data to calculate the load allocations (see Table 5).

In the event that nonpoint source contributions of zinc were present, it is extremely unlikely that the WLA would need to be different than what has been established in Section 5.2 of this report, because the WLA requires that the effluent from each facility must itself be protective of the water quality criteria. Considering this information, the load allocation is established so that is protective of the standard.

5.4 TMDL Results This TMDL can be summarized as follows:

Table 5. TMDL

Parameter
Total Dissolved
Zinc Total Dissolved Zinc

Criteria Chronic Acute

WLA 1.23 kg/day

LA

MOS

2.44 kg/day Implicit

TMDL 3.67 kg/day

1.34 kg/day 2.18 kg/day Implicit 3.52 kg/day

Total Recoverable
Zinc Total Recoverable Zinc

Chronic Acute

4.69 kg/day 9.31 kg/day Implicit 14.0 kg/day 4.87 kg/day 7.93 kg/day Implicit 12.8 kg/day

5.5 Seasonal Variation

The low flow critical conditions incorporated in this TMDL are assumed to represent the most critical design conditions and to provide year-round protection of water quality.

5.6 Margin of Safety
The MOS is a required component of TMDL development. As specified by section 303(d) of the CWA, the margin of safety must account for any lack of knowledge concerning the relationship between effluent limitations and water quality. There are two basic methods for incorporating the MOS: 1) implicitly incorporate the MOS using conservative model assumptions to develop allocations; or 2) explicitly specify a portion of the TMDL as the MOS and use the remainder for allocations.

The MOS was implicitly incorporated into the TMDL for Buffalo Creek through the use of critical conditions established in section 4.1 of this report. Through the use of low flow conditions, the lowest of available hardness values, and the methods used to develop the translators, the margin of safety for this TMDL adequately accounts for the lack of knowledge concerning the relationship between effluent limitations and water quality.

Georgia Environmental Protection Division

Atlanta, Georgia

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Total Maximum Daily Load Evaluation Buffalo Creek (Zinc)

June 2001

6.0 POINT AND NONPOINT SOURCE APPROACHES
An allocation to an individual point source discharger does not automatically result in a permit limit or a monitoring requirement. Through its NPDES permitting process, Georgia will determine whether each of the permitted dischargers to the Buffalo Creek watershed has a reasonable potential of discharging zinc levels equal to or greater than the allocated load. The results of this reasonable potential analysis will determine the specific type of requirements in an individual facility's NPDES permit. As part of its analysis, the EPD will use its EPA-approved 1995 NPDES Reasonable Potential Procedures to determine whether monitoring requirements or effluent limitations are necessary.
If effluent limitations are determined to be necessary for any or all of these facilities, they should be established in accordance with Georgia Rules and Regulations for Water Quality Control, Section 391-36-.06(4)(d)5.(ii)(b)(2). This regulation establishes that to protect against chronic effects, an effluent limitation should be imposed as a monthly average limit. To protect against acute effects, an effluent limitation should be imposed as a daily maximum limit. Additionally, if effluent limitations or monitoring requirements are determined through a reasonable potential analysis to be necessary for any or all of these facilities, it is recommended that concentration limits or concentration monitoring requirements should be imposed in addition to any loading limits or monitoring requirements.

Georgia Environmental Protection Division

Atlanta, Georgia

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Total Maximum Daily Load Evaluation Buffalo Creek (Zinc)

June 2001

7.0 PUBLIC PARTICIPATION
A thirty-day public notice will be provided for this TMDL. During this time the availability of the TMDL will be public noticed, a copy of the TMDL will be provided as requested, and the public will be invited to provide comments on the TMDL.

Georgia Environmental Protection Division

Atlanta, Georgia

11

Total Maximum Daily Load Evaluation Buffalo Creek (Zinc)

REFERENCES

June 2001

GAEPD, NPDES Reasonable Potential Procedures. Atlanta, GA. January 1995.
GAEPD, Rules and Regulations For Water Quality Control, Chapter 391-3-6, June 2001, Georgia Department of Natural Resources, Environmental Protection Division.
USEPA. Technical Guidance Manual for Performing Waste Load Allocations: Book II Streams and Rivers - Chapter 3 Toxic Substances. U.S. Environmental Protection Agency, Office of Water, Regulations and Standards, Monitoring and Data Support Division, Washington, D.C. June 1984.
USEPA. 1991a. Technical Support Document for Water Quality based Toxics Control. U.S. Environmental Protection Agency, Office of Water, Washington, DC. EPA-505/2-90-001, April 1991.
USEPA. 1991b. Guidance for Water Quality based Decisions: The TMDL Process. U.S. Environmental Protection Agency, Office of Water, Washington, DC. EPA-440/4-91-001, April 1991.
USEPA. Appendix J of Water Quality Standards Handbook: Second Edition (i.e., "Guidance Document on Dynamic Modeling and Translators August 1993"). U.S. Environmental Protection Agency, Office of Water, Washington, D.C. EPA/823/B-94-005a. August 1994.
USEPA, 1998. Better Assessment Science Integrating Point and Nonpoint Sources (BASINS), Version 2.0 User's Manual, U.S. Environmental Protection Agency, Office of Water, Washington D.C.

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Atlanta, Georgia

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