Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001



## TOTAL MAXIMUM DAILY LOAD (TMDL)

**For**

**Total Mercury in Fish Tissue Residue**

**In the Middle & Lower Savannah River Watershed** 

**For Segments Clarks Hill Lake Dam to Stevens Creek Dam**  **Stevens Creek Dam to US Highway 78/278 US Highway 78/278 to Johnsons La**  **nding Johnsons Landing to Brier Creek**  **Brier Creek to the Tide Gate**Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

i 

## TOTAL MAXIMUM DAILY LOAD (TMDL) **Total Mercury in Fish Tissue Residue**
**In the Middle & Lower Savannah River Watershed**  Under the authority of Section 30 3(d) of the Clean Water Act, 33 U.S.C. 1251 et seq ., as amended by the Water Quality Act of 1987, P.L. 100

- 4, the U.S. Environmental Protection Agency is hereby establishing a TMDL for total mercury for the protection of public health associated with the c onsumption of fish taken from the following segments of the Savannah River in Georgia: Clarks Hill Lake Dam to Stevens Creek Dam Stevens Creek Dam to US Highway 78/278 US Highway 78/278 to Johnsons Landing Johnsons Landing to Brier Creek Brier Creek to the Tide Gate **The calculated allowable load of mercury that may come into the identified segments of the Savannah River without exceeding the applicable water quality standard of 2.8 nanograms per**  **liter is 32.8 kilograms per year.** EPA interpreted the State o f Georgia’s narrative water quality standard for toxic substances for the protection of public health to determine the applicable water quality standard. Based on a current estimated loading of 58.8 kilograms per year, an estimated 44% reduction in mercur y loading is needed for the identified sections of the Savannah River to meet the applicable water quality standard of 2.8 nanograms per liter. It is estimated that reductions in air deposition of mercury will result in a 38% to 48% reduction in mercury l oading to the Savannah River. Twenty

- nine (29) facilities permitted by the State of Georgia under the National Pollutant Discharge Elimination System Program are provided wasteload allocations in this TMDL. This TMDL shall become effective immediately, and is incorporated into the Continuing Planning Process for the State of Georgia under Sections 303(d)(2) and 303(e) of the Clean Water Act.

Signed this _________ day of___________, 2001.

_____________________________ Beverly H. Baniste

r, Director Water Management DivisionTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

ii **Table of Contents** 1. Executive Summary

................................ ................................ ................................ ................... 1

2. Introduction

................................ ................................ ................................ .............................. 5

3. Phased Approach to the TMDL

................................ ................................ ................................ 7

3.1. Phased Approach to Atmospheric Sources

................................ ................................ ........ 8

3.2. Phased Appr oach to Water Point Sources

................................ ................................ ......... 9

4. Problem Definition

................................ ................................ ................................ ................... 12

4.1. Health Effects of Mercury

................................ ................................ ................................ 13

5. Applicable Water Quality Standard

................................ ................................ ......................... 14

6. Background

................................ ................................ ................................ ............................ 19

6.1. Mercury Cycling

................................ ................................ ................................ ............. 22

6.2. Source Assessment

................................ ................................ ................................ ......... 26

6.2.1. Sources of Mercury

................................ ................................ ............................... 27

6.2.2. Water Point Sources

................................ ................................ .............................. 28

6.3. RELMAP Mercury Deposition Rates

................................ ................................ .............. 29

6.4. Available Monitoring Data

................................ ................................ ............................... 31

6.4.1. EPA Region 4 Data

................................ ................................ ................................ 32Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

iii 6.4.2. Water Column Data

................................ ................................ ............................... 34

6.4.3. Sediment Data

................................ ................................ ................................ ....... 35

6.4.4. Watershed Soil Data

................................ ................................ .............................. 36

6.4.5. Fish Tissue Data

................................ ................................ ................................ ..... 37

7. Model Development

................................ ................................ ................................ ................ 40

7.1. Watershed Hydrologic and Sediment Loading Model

................................ ....................... 40

7.2. Water Quality Fate and Transport Model

................................ ................................ ........ 41

8. Total Maximum Daily Load (TMDL)

................................ ................................ ....................... 42

8.1. Critical Condition Determination

................................ ................................ ...................... 42

8.2. Seasonal Variation

................................ ................................ ................................ .......... 43

8.3. Margin of Safety

................................ ................................ ................................ ............. 44

9. TMDL Development

................................ ................................ ................................ ............... 45

9.1. Model Results

................................ ................................ ................................ ................. 45

9.1.1. Nonpoint Source

................................ ................................ ................................ .... 46

9.1.2. Water Quality Model

................................ ................................ ............................. 48

9.2. TM DL Determination

................................ ................................ ................................ ...... 55

10. Allocation of Loads

................................ ................................ ................................ ............. 56Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

iv 10.1. Atmospheric Reductions

................................ ................................ .............................. 57

10.2. Allocation to NPDES Point Sources

................................ ................................ ............ 60

10.3. State and Federal Responsibility

................................ ................................ .................. 69

11. Assumptions with Respect to Loadings from South Carolina

................................ ................. 70

12. Appendix A

................................ ................................ ................................ ........................ 72

13. References

................................ ................................ ................................ .......................... 75Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

v **Table of Figures**

Figure 1 BAF vs. Length Fish Collection from Savannah Basin

................................ ......................... 18

Figure 2 Savannah Watersheds

................................ ................................ ................................ ........ 20

Figure 3 Savannah Watershed Delineation

................................ ................................ ....................... 21

Figure 4 Savannah Watershed Landuses

................................ ................................ .......................... 22

Figure 5 Mercury Cycling i n the Aquatic Environment

................................ ................................ ...... 26

Figure 6 Mercury Dry Deposition Rates as Reported in the Mercury Report to Congress

................. 30

Figure 7 Mer

cury Wet Deposition Rates as Reported in the Mercury Report to Congress

................. 31

Figure 8 Savannah Watershed Water Column Sample Locations

................................ ...................... 33

Figure 9 Savannah Watershed Fish Collection Locations

................................ ................................ .. 34

Figure 10 Model Predictions versus Observed Data for the Savannah River for Drought Conditions

.. 52

Figure 11 Model Predictions versus Observed Data for Total Mercury in the Sediments during Low Flow

................................ ................................ ................................ ................................ ............... 53

Figure 12 Model Predictions versus Observed Data for t he Savannah River for Annual Average Flow 5 4

Figure 13 Model Predictions versus Observed Data for Total Mercury in the Sediments Annual Average
Flow

................................ ................................ ................................ ................................ ....... 55Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

vi **Table o f Tables** 

Table 1 Georgia Department of Natural Resources Fish Consumption Guideline

............................... 12

Table 2 Fish Tissue Analysis

................................ ................................ ................................ ............ 19

Table 3 Summaries of Mercury Emissions in the RGM Airshed during the Baseline Period (1994

- 1996) 28

Table 4 Water Column Mercury Concentrations

................................ ................................ .............. 35

Table 5 Sediment Mercury Concentrations

................................ ................................ ...................... 36

Table 6 Mercury Concentrations in Soils from Surround Watershed

................................ ................. 36

Table 7 Fish Tissue Mercury Data

................................ ................................ ................................ ... 37

Table 8 Annual Average Total Mercury Load

................................ ................................ .................. 47

Table 9 Specified and Calculated Reaction Rates and Coefficients

................................ .................... 49

Table 10 Flows, Depths, Velocities and Volumes used in WASP Model

................................ .......... 50

Table 11 NPDES Permitted Facilities and Assigned Wasteload Allocation at 2.8 ng/l

....................... 62Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

1 

## 1. Executive Summary

The U.S. Environmental Protection Agency (EPA) Region 4 is establishing this Total Maximum Daily Load (TM DL) for total mercury in the middle/lower Savannah River Basin for the 5 contiguous segments of the Savannah River from the Clarks Hill Lake Dam to the Tide Gate. The segments are as follows:

• Clarks Hill Lake Dam to Stevens Creek Dam

• Stevens Creek Dam to US Highway 78/278

• US Highway 78/278 to Johnsons Landing

• Johnsons Landing to Brier Creek

• Brier Creek to the Tide Gate

Four of these segments are listed on the State of Georgia’s 2000 Section 303(d) list of impaired waters because mercury in certain speci es of fish tissue exceeds the the Georgia Department of Natural Resources (GDNR) Fish Consumption Guidelines State’s guidelines. The fifth segment, Johnsons Landing to Brier Creek, was inadvertently omitted from the State of Georgia’s 2000 Section 303(d) list. This segment is impaired based on GDNR Fish Consumption Guidelines, and the Georgia Environmental Protection Division intends to include this segment on the State’s 2002 Section 303(d) List (personal communication, Mork Winn, February 27, 2001). Th erefore, this TMDL identifies the allowable annual load of total mercury for the middle/lower Savannah River from Clarks Hill Dam to the Tide Gate that will result in attainment of the applicable water quality standard, and the unrestricted use of these se gments for fish consumption.

This TMDL satisfies a consent decree obligation established in Sierra Club, et. al. v. EPA Civil Action, 1:
94

- CV

- 2501

- MHS. The State of Georgia requested EPA to develop this TMDL for the impairedTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

2 segments of the Savannah Riv er, and as such, EPA is establishing this TMDL for Georgia for the 5 segments of the Savannah River. Although the mid

- line of the Savannah River serves as the east

- west boundary between the states of Georgia and South Carolina, the TMDL does not provide w asteload allocations to South Carolina NPDES facilities. This TMDL reflects assumptions that concentrations of mercury in the South Carolina portion of the Savannah River will meet the applicable Georgia water quality
standards at the South Carolina

- Georg ia border.

EPA originally proposed this TMDL for total mercury for the middle and lower Savannah River between Clarks Hill Dam and the Tide Gate on February 8, 2000. In response to significant comments received during the public comment period, the TMDL was revised and re

- proposed on December 8, 2000. This public comment period closed on January 22, 2001. By establishing this TMDL at this time, EPA is satisfying a court

- order to finalize this TMDL by February 28, 2001. This TMDL is being established in phases with this TMDL document representing the first phase of the process. EPA expects to develop a revised TMDL for mercury for the middle/lower Savannah River in 2004. EPA believes that a phased approach is appropriate for this TMDL because informatio n on the actual contributions of mercury to the Savannah River from both point and nonpoint sources will be much better characterized in the future.

In order for this TMDL to be developed, the applicable water quality standard must be determined. The State of Georgia does not have a numeric water quality standard for the protection of public health from total mercury. EPA determined that Georgia’s numeric water quality standard for protection of aquatic life, 12 nanograms per liter (ng/l), is not prot ective of human health. Based on site

- specific field data from the middle/lower Savannah River, ambient concentrations of total mercury in the water column are well below 12 ng/l yet concentrations of mercury in fish tissue exceed levels protective of pub lic health. Therefore, EPA does not regard the State’s aquatic life criterion as the applicable water quality standard for this TMDL. Instead, EPA has derived a numeric interpretation of the State of Georgia’s narrative water quality standard
for toxic su

bstances (Chapter 391

- 3

- 6

- .03 Section (5)(e)) using EPA’s Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health (EPA 2000). Using recommended nationalTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

3 values, and site

- specific data collected in the middle/lower Savanna h River Basin, EPA interpreted Georgia’s water quality standard and has determined that the applicable water quality standard for total mercury in the ambient water of the Savannah River Basin is 2.8 ng/l (parts per trillion). At this concentration, or be low, fish tissue residue concentrations of mercury will not exceed 0.4 mg/kg, which is protective of the general population from the consumption of freshwater fish. This interpretation of Georgia’s water quality standard was based on site

- specific data ga thered for the Savannah River in 2000 specifically for the purpose of this TMDL. It does not apply to any other water in the State of Georgia. In addition, in any future TMDLs for Savannah River, it is possible that EPA may revise this interpretation
bas ed on new site

- specific data collected at that time.

During the time that this TMDL was proposed and was in public review between December 8, 2000, and January 22, 2001, EPA issued federal criterion recommendations for methylmercury on December 30,
2000. (See Water Quality Criteria for Protection of Human Health: Methylmercury, EPA

- 823

- F

- 01

- 001.) This document recommends 0.3 mg/kg as a fish tissue residue concentration for protection of human health.
Since EPA was under court order to finalize this TMD L by February 28, 2001, EPA had insufficient time to consider the new federal criterion recommendations in the establishment of this TMDL. Therefore, EPA may reconsider this TMDL at some future date (prior to 2004) in order to consider the new federal cri terion guidance in the context of this waterbody. It should be noted, however, that today’s TMDL protects the designated uses and achieves the applicable water quality standard as interpreted by EPA. In order to assure protection, EPA made conservative a ssumptions in this TMDL in the derivation of the applicable water quality standard, particularly relating to the bioaccumulation factor (BAF). EPA assumed that all 17.5 grams per day of fish consumed are of largemouth bass, which as a trophic level 4 fish , bioaccumulates mercury at comparatively high rates. (This means that consumers of these fish will be exposed to more mercury than would be the case if they consumed lower trophic level fish species.) The resulting water quality standard as interpreted by EPA appears to be as protective as the numeric value EPA would have derived using the recommended assumptions in the Human Health Methodology (a “weighted” BAF ratherTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

4 than a trophic level 4 BAF; a general population consumption rate of 17.5 grams per d ay; a methylmercury reference dose of 0.0001 mg/k/day; and a relative source contribution dose of 0.00027 mg/kg/day). This conclusion depends on the appropriate “weighted BAF” value, which will be considered in any future
revision of this TMDL.

Computeriz ed modeling techniques have been employed in the development of this TMDL. The loading of mercury from the watershed into the Savannah River was simulated using a Watershed Characterization System (WCS) model developed by EPA Region 4 (USEPA, Region 4, 20 01). The WCS provides a simplified simulation of precipitation

- driven runoff and sediment delivery. Solids load from runoff is used to estimate pollutant delivery to the River from the watershed. The water quality model known as WASP5 (Ambrose, et al., 1993) is used to simulate mercury fate and transport in the Savannah River. WASP5 is a general dynamic mass balance framework for modeling contaminant fate and trans port in surface waters.

EPA evaluated the current loading conditions and calculated the water column concentration using the modeling approach described in this document. **The calculated allowable load of mercury that can come into the Savannah River without exceeding the applicable water quality standard**  **as interpreted by EPA**  **of 2.8 ng/l is 32.8 kilograms/year.**  Because this assessment indicates that 99% of the loading of mercury is from atmospheric sources, 99% of the allowable load will be assigned to the load allocation, and 1% of the available load will be assigned to the wasteload allocat ion. Therefore, the Load
Allocation and Wasteload Allocation for the middle/lower Savannah River are:

Load Allocation (atmospheric sources) = 0.99 (32.8) = 32.5 kilograms/year

Wasteload Allocation (NPDES sources) = 0.01 (32.8) = 0.3 kilograms/year

The estimated current loading of mercury to the Savannah River from the surrounding watershed is 58.8 kilograms/year. This load was determined by adding the predicted mercury load for each of the subwatersheds taking into account delivery times and volatilizat ion that occurs in the tributaries. TheTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

5 difference between the estimated current mercury load (58.8 kg/year) and the calculated allowable load (32.8 kg/year) is 26 kilograms/year. Since 32.8 kg/year is 56% of the estimated current loading of mercury, it is estimated that a 44% reduction in total mercury loading is needed for the middle/lower Savannah River to achieve a water column concentration of 2.8 ng/l.

An analysis conducted by the EPA Region 4 Air Program concludes that an estimated 38% to 48%
redu ction in mercury deposition to the Savannah Watershed can be achieved by 2010. EPA expects these reductions to be achieved through full implementation of the current Clean Air Act (CAA) Section 112 Maximum Achievable Control Technology (MACT) requirements , Section 111 New Stationary Source Standards, and Section 129 Solid Waste Combustion requirements at sources within the local airshed. (USEPA, 2000)

This TMDL assigns a cumulative wasteload allocation (WLA) to all NPDES point sources of 0.3 kilograms
per year. This TMDL assumes that this cumulative WLA will be accomplished through the imposition of numeric water quality

- based permit limits or through the implementation of mercury minimization plans at appropriate NPDES facilities. The wasteload allocati on options for NPDES permitted facilities are
described in Section 10

.


## 2. Introduction

The U.S. Environmental Protection Agency (EPA) Region 4 is establishing this Total Maximum Daily Load (TMDL) for total mercury for the middle /lower Savannah River from the Clarks Hill Lake Dam to the Tide Gate. The segments are as follows:

• Clarks Hill Lake Dam to Stevens Creek Dam

• Stevens Creek Dam to US Highway 78/278

• US Highway 78/278 to Johnsons LandingTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

6 • Johnsons Landing to Brier Creek

• Br ier Creek to the Tide Gate

Four of these segments are listed on the State of Georgia’s 2000 Section 303(d) list of impaired waters because mercury in certain species of fish tissue exceeds the the Georgia Department of Natural Resources (GDNR) Fish Consump tion Guidelines State’s guidelines. The fifth segment, Johnsons Landing to Brier Creek, was inadvertently omitted from the State of Georgia’s 2000 Section 303(d) list. This segment is impaired based on GDNR Fish Consumption Guidelines, and the Georgia En vironmental Protection Division intends to include this segment on the State’s 2002 Section 303(d) List (personal communication, Mork Winn, February 27, 2001).

TMDLs are required for waters on a state’s Section 303(d) list by Section 303(d) of the Clean W ater Act (CWA) and the associated regulations at 40 CFR Part 130. A TMDL establishes the maximum amount of a pollutant a waterbody can assimilate without exceeding the applicable water quality standard. The TMDL allocates the total allowable pollutant loa d to individual sources or categories of pollution sources through wasteload allocations (WLAs) for point sources regulated by the National Pollutant Discharge Elimination System (NPDES) program and through load allocations (LAs) for all other sources. Th e WLAs and LAs in the TMDL provide a basis for states to reduce pollution from both point and nonpoint sources that will lead to restoration of the quality of the impaired waterbody. The purpose of this TMDL is to identify the allowable load of mercury th at will result in attainment of the applicable water quality standard as interpreted by EPA , and the unrestricted use of the identified segments for fish consumption.

This TMDL satisfies a consent decree obligation established in Sierra Club, et. al. v. EPA, Civil Action: 94

- CV

- 2501

- MHS. The Consent Decree requires TMDLs to be developed for all waters on Georgia’s current Section 303 (d) list consistent with the schedule established by Georgia for its rotating basin management approach. The State of Ge orgia requested EPA to develop this TMDL, and as such, EPA is establishing this TMDL for Georgia for the 5 segments of the Savannah River. Although the mid

- line of theTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

7 Savannah River serves as the east

- west boundary between the states of Georgia and Sout h Carolina, the TMDL does not provide wasteload allocations to South Carolina NPDES facilities. This TMDL reflects assumptions that concentrations of mercury in the South Carolina portion of the Savannah River will meet the applicable Georgia water qualit y standards as interpreted by EPA at the South Carolina

- Georgia
border.

On February 8, 2000, EPA originally proposed this TMDL for total mercury for the segments of the Savannah River listed on the State of Georgia’s 1998 Section 303(d) List. During the p ublic comment period on that proposed TMDL which closed April 10, 2000, EPA received extensive and significant comments on the TMDL. As a result, EPA obtained an extension of the schedule to finalize the TMDL from June 7, 2000 to February 28, 2001. This TMDL satisfies the court

- ordered commitment.



## 3. Phased Approach to the TMDL

EPA recognizes that it may be appropriate to revise this TMDL based on information gathered and analyses performed after February 2001. With such possible revisions in mind, this TM DL is characterized as a phased TMDL. In a phased TMDL, EPA or the state uses the best information available at the time to establish the TMDL at levels necessary to implement applicable water quality standards and to make the allocations to the polluti

on sources. However, the phased TMDL approach recognizes that additional data and information may be necessary to validate the assumptions of the TMDL and to provide greater certainty that the TMDL will achieve the applicable water quality standard. Thus, the Phase 1 TMDL identifies data and information to be collected after the first phase TMDL is established that would then be assessed and would form the basis for a Phase 2 TMDL. The Phase 2 TMDL may revise the needed load reductions or
the allocation of

the allowable load or both. EPA intends to gather new information and perform new analyses so as to produce a revised or Phase 2 TMDL for mercury for the identified segments of the Savannah River, if necessary, in 2004. The phased approach is appropria te for this TMDL because information on the actual contributions of mercury to the Savannah River from both point and nonpointTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

8 sources will be much better characterized in the future.



### 3.1. Phased Approach to Atmospheric Sources
The impairment of the Savannah River by mercury is largely due to the deposition of mercury from the atmosphere. This TMDL estimates that approximately 99 percent of the pollutant loads to the River come from the atmosphere ( Table 8 ). An analysis of atmosphe ric deposition to the Savannah River watershed is included in this TMDL as Appendix A. Mercury is emitted into the atmosphere by a large number of different sources. The mercury that reaches the Savannah River watershed comes from nearby sources (local s ources) as well as sources much farther away, both within the United States (national sources) and outside of the United States (international sources). Only a small part, approximately 1 percent, of the mercury loading into the Savannah River is due to d ischarges from water point sources (e.g., pipes) into the
Savannah River or its tributaries.

In Appendix A, EPA has made its best attempt to characterize the air sources of mercury to the watershed, given the time available to the Agency for establishing the TMDL. The analysis of deposition of mercury from the atmosphere to the Savannah watershed depends heavily on modeling conducted for the Mercury Study Report to Congress (EPA, 1997). This Study was based on the Regional Lagrangian Model of Air
Polluti on (RELMAP) modeling, which has several areas of uncertainty, and assumptions that could affect the level of reductions projected by the analysis. Many of these uncertainties are not unique to the analysis of atmospheric deposition prepared for the Savann ah River Mercury TMDL. Some of these uncertainties include the estimates of the amount of the chemical form or species of mercury emitted by each source category; the projected level of reductions from each source category subject to the Clean Air Act (CAA ) Section 129 or 111 or MACT; the definition of local sources contributing deposition to the watershed; the contribution from global sources; and other aspects of the modeling. While it is not possible to quantify the net effect of these factors, EPA belie ves the assumptions made to address these uncertainties are reasonable
and consistent with the state

- of

- the art mercury modeling available at the time this TMDL was prepared andTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

9 that the agency has reasonable assurance that needed air reductions will be ac hieved. Nonetheless, it is important to point out that, because of these uncertainties, the anticipated 38% to 48% reductions in atmospheric deposition reported in this TMDL are an estimate only.

EPA expects that emissions of mercury from air sources (a nd consequently deposition of mercury to the Savannah River) will continue to be reduced during the first phase of this TMDL through implementation of the CAA’s MACT and Section 129 and Section 111 regulations. In addition, EPA expects reductions in
the a ir emissions of mercury may be achieved through implementation of voluntary programs. At the same time, EPA is considering additional regulatory actions under the CAA that may result in further reductions of mercury emissions from air sources. EPA is also undertaking new computer modeling that will allow a better characterization of sources contributing to the deposition of mercury and, therefore, more certainty regarding the extent of mercury reductions that can be achieved in a watershed from air sources . By 2004, when EPA expects to revise the TMDL, this additional modeling information and estimates of additional future reductions will be available, allowing EPA to validate the assumptions and verify the anticipated reductions in loadings and revise the TMDL accordingly.



### 3.2. Phased Approach to Water Point Sources
At this time, there is relatively little data on the actual loading of mercury from NPDES point sources in the
basin. Because, until recently, EPA’s published method for the analysis of mercury w as not sensitive enough to measure mercury at low trace level concentrations, most NPDES facilities have not detected mercury during their required priority pollutant monitoring. EPA assumes, however, that all facilities discharge some mercury into the Ri ver with their effluent because mercury is pervasive in the environment and is present in rainwater.

Recently, in 1998, EPA adopted a new analytical procedure that detects mercury at low trace level concentrations (0.5 nanograms/liter) (See EPA Method 16 31, Revision B, 40 C.F.R. 136.3(a)). A sampling by EPA of a small subset of the NPDES dischargers in Georgia in the Savannah River Basin usingTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

10 the trace level Method 1631 analytical technique verifies EPA’s assumption that all facilities are discharging

s ome mercury. As NPDES permits are reissued, dischargers will be required to use the version of Method 1631 then in effect for analyzing mercury. (Georgia Rules and Regulations for Water Quality Control, Chapter 391

- 3

- 6

- .06). Therefore, in the Phase 2 TM DL, data on the concentration of mercury in point source discharges using the more sensitive analytical technique will be available to characterize the actual loading of mercury into the Savannah River. This will allow EPA, as appropriate, to refine waste load allocations provided in the TMDL.

Other circumstances may also influence the wasteload allocations that are established in the second phase of this TMDL. As an example, EPA issued criterion guidance for methylmercury on December 30, 2000. ( See Water Quality Criteria for Protection of Human Health: Methylmercury, EPA

- 823

- F

- 01

- 001.) This new guidance was issued after this TMDL was proposed on December 8, 2000, and is not incorporated into the development of this TMDL. However, the Federal Register not ice announcing the availability of the new methylmercury criterion guidance explains that EPA expects the states to use the federal criterion as guidance in updating their water quality standards. EPA expects states to adopt a new or revised water quality criterion for methylmercury at levels necessary to protect human health. The State of Georgia will be undertaking a review of their water quality standards within the next 3 years; therefore, EPA anticipates that by 2004 Georgia will have adopted a numeri c human health criterion for methylmercury. The revised 2004 TMDL will be based on the State’s numeric human health criterion for mercury, if such criterion exists,
rather than on EPA’s interpretation of the State’s narrative water quality standard for to xic substances as was done in this Phase 1 TMDL (See Section 5 ).

Because the impairment of the Savannah River by mercury is due predominantly to air deposition, the complete elimination or significant reduction of mercury from water point source discharges would produce little benefit in the quality of the Savannah River. In addition, the elimination or significant reduction of mercury would likely be expensive and possibly technically infeasible for point sources to implement. Since many of the NPDES facilities in the basin affected by this TMDL are municipal wastewater treatment plantsTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

11 that are funded through the taxpayers, EPA chooses to move cautiously before implementing wasteload allocations that may cause significant eco nomic hardship in a situation where, as here, EPA expects most of the needed mercury reductions to be achieved through Clean Air Act reductions in mercury emissions from air sources. In this Phase 1 TMDL, EPA expects point source loadings of mercury will be reduced primarily through mercury minimization programs developed and implemented by some point sources.

In summary, during implementation of the Phase 1 TMDL, EPA expects the following activities to occur:

• 29 NPDES facilities will monitor for mercur y and characterize it in their influent and effluent for mercury using the more sensitive analytical technique (the version of Method 1631 then in effect). These facilities consist of 15 municipal facilities, and 14 industrial facilities. (See Section 10 .2.)

• Where appropriate, NPDES point sources will develop and implement mercury minimization plans;

• Air point sources will continue to reduce emissions of mercury through implementation of the Clean Air Act Section 112 MACT requirements and Section 129 Soli d Waste Combustion requirements;

• EPA and the regulated community will improve the mercury air emissions inventory;

• EPA will refine and revise the mercury air deposition modeling to better characterize sources of mercury; and

• EPA and the states will collect additional ambient data on mercury concentrations in water,
sediment and fish.

• EPA expects Georgia to adopt a numeric water quality criterion for methylmercury for the protection of human health that is based on EPA’s recent criteria guidance, either as p ublished or as
modified to reflect site

- specific conditions, or that are based on other scientifically defensible methods. (See 40 C.F.R. 131.11(b))Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

12 EPA intends to use the data and information collected and developed during the next four years to revise the Phase 1 TMDL, as necessary, to assure that EPA’s interpretation of the State’s applicable water quality standard is appropriate, and that the allowable load will be achieved by implementation of the TMDL.
EPA’s intention to revise the TMDL is consiste nt with the State of Georgia’s Rotating Basin Management Program (RBMP) schedule. Under Georgia’s current RBMP schedule, NPDES permits in the Savannah River Basin will be reissued in 2005. Therefore, EPA intends to revise the TMDL one year prior to
reissu ance of permits in the Savannah River Basin.



## 4. Problem Definition

The water segments in the Savannah River Basin for which this proposed TMDL is being established are listed on the State of Georgia’s 2000 Section 303(d) list except Johnsons Landing to Brie r Creek (Johnsons Creek to Brier Creek is impaired and will be listed on the State’s 303(d) List, See Section 2 ). The waters were listed (and Johnsons Landing to Brier Creek will be listed) because mercury in the tissue of sev eral species of fish exceeds the Fish Consumption Guidelines (FCG) established by the State of Georgia. (See Georgia Department of Natural Resources, 2000.) The Fish Consumption Guidelines establish limits on the
amount of fish that should be consumed ove r a given time frame (a week or a month) in order to protect
human health.

The Georgia Department of Natural Resources (DNR) uses a risk

- based approach to determine how often contaminated fish may be consumed at different levels of fish tissue contaminat ion assuming a consumption rate of approximately 32.5 grams per day. Table 1 provides the frequency of consumption for three different levels of fish tissue contamination with mercury.

**Table 1**  **Georgia Department of Natural Resource s Fish Consumption Guideline** 

Mercury Fish Tissue Threshold (mg/kg) Frequency of Consumption 0.23 Once a WeekTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

13 0.70 Once a Month 2.3 Do Not Eat If fish tissue contains 0.23 mg/kg (parts per million) or more mercury, the State’s FCG indicates that the fi sh should not be consumed more than once a week. If fish tissue contains 0.70 mg/kg (parts per million) or more mercury, the State’s FCG indicates the fish should not be consumed more than once a month, and if the fish tissue contains 2.30 mg/kg (parts pe r million) or greater of mercury, the State issues a “Do Not Eat” guideline.

The following FCG are in place for the segments of the Savannah River covered by this TMDL: 1) Columbia County

- 1 meal per week for largemouth bass and spotted sucker, 2) Rich mond/Burke Counties

- 1 meal per week for largemouth bass, 3) Screven County

- 1 meal per week for largemouth bass, 4) Effingham County

- 1 meal per month for largemouth bass, 5) Fort Howard

- 1 meal per week for white catfish and 1 meal per month for larg emouth bass and bowfin, 6) Chatham County

- 1 meal per week for largemouth bass, and 7) Tidal Gate

- 1 meal per week for white catfish.



### 4.1. Health Effects of Mercury
The State of Georgia’s fish consumption guideline program is designed to protect consumers in Georgia from the health effects of mercury consumed through fish in the diet. Human exposure to inorganic mercury in large amounts can cause a variety of health effects. The two organ systems most likely affected by methylmercury are the central nervou s system and the kidney. However, the most significant concerns regarding chronic exposure to low concentrations of methylmercury in fish are for neurological effects in the developing fetus and children.

EPA recently issued national advisory concerning risks to children and to pregnant or nursing women associated with mercury in freshwater fish caught by their friends and family. (See EPA Consumption Advisory: Advice for Women and Children on Non

- commercial Fish Caught by Friends and Family, EPA

823

- F

- 01

- 004, January 2001.) The groups most vulnerable to the effects of mercury pollution include:Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

14 women who are pregnant or may become pregnant, nursing mothers, and young children. To protect against the risks of mercury in fish caught in freshwaters, EPA i s recommending that these groups limit fish consumption to one meal per week for adults (6 ounces of cooked fish, 8 ounces uncooked fish) and one meal per week for young children (2 ounces cooked fish or 3 ounces uncooked fish). The National Academy of Sc iences confirms that methylmercury is a potent toxin and concludes that the babies of women who consume large amounts of fish when pregnant are at greater risk for changes in their nervous system that can affect their ability to learn. (NAS, Toxicological Effects of Methylmercury, July 2000) EPA is issuing this advice for women who are pregnant or may become pregnant, nursing mothers, and young children to raise awareness of the potential harm that high levels of methylmercury in fish can cause to a baby or child’s developing brain and nervous system. This advice provides guidance on the amount of fish caught by friends and family that these groups can eat to keep methylmercury from reaching harmful levels.

The purpose of this TMDL is to establish the accept able loading of mercury from all sources, such that mercury levels in the middle/lower Savannah River will not exceed the applicable water quality standard as interpreted by EPA

for protection of public health. If concentrations in the River can be reduce d to the applicable water quality standard as interpreted by EPA (expressed in terms of ambient water column concentrations), fish tissue levels of mercury will decrease over time. Eventually, fish tissue levels of mercury should become low enough that co nsumers may eat unlimited quantities of fish from the River
without fear of health effects.



## 5. Applicable Water Quality Standard

TMDLs are established at levels necessary to attain and maintain the applicable narrative and numerical water quality standards. (See 40 CFR Section 130.7(c)(1).) The State of Georgia’s Rules and Regulations for Water Quality Control do not include a numerical water quality standard for human health for total mercury. The only mercury criterion provided in State regulations is 12 ng/l for protection of aquatic life from total mercury. EPA recognizes that the derivation of a human health criterion for mercury is moreTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

15 complex than most metals because of the methylation of mercury that occurs in the aquatic environment. (See Ambient Water Quality Criteria for Mercury Document, EPA, 1986) Like the current criteria guidance, the 1986 criterion document recommends that fish tissue be analyzed to determine whether the concentration of methylmercury exceeds the level necessary to protect human health. The document acknowledges that a 12 ng/l aquatic life criterion, while protecting the health of the fish themselves, may not prevent the unacceptable bioaccumulation of mercury in fish tissue, which would adversely affect the health
of human s consuming the fish.

EPA collected site

- specific data on ambient mercury in the water column and fish tissue from the Savannah River which indicate the 12 ng/l aquatic life criterion is not protective of human health. In July 2000, EPA collected sample s of ambient water at 10 locations in the mainstem and 6 locations in tributaries to the Savannah River from below Clarks Hill Dam to the Tide Gate. Total mercury concentrations in the water ranged from 0.27 ng/l to 9.50 ng/l. These concentrations of merc ury are well below the State’s 12 ng/l aquatic life criterion. However, the average fish tissue residue concentration from 13 of the 16 sampling locations exceeds 0.23 mg/kg. Thus, at water concentrations below 12 ng/l (significantly below in most
instan ces), fish tissue is accumulating mercury at levels above the State’s Fish Consumption Guidelines indicating that a water concentration of 12 ng/l is not protective of human health.

Since the State lacks a numeric water quality criterion for the protecti on of human health, EPA has interpreted the State’s narrative water quality standard for toxic substances (Chapter 391

- 3

- 6

- .03 Section (5)(e)) to identify a water concentration sufficient to protect the human health designated use. In order to
use the bes t available, sound science in interpreting this narrative, EPA used the Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health (EPA 2000) to derive the applicable water quality standard for this TMDL. This standard as interpreted by EPA is the maximum concentration of mercury that can be present in the water column without causing a fish tissue residue concentration that poses adverse health effects.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

16 Using EPA’s Methodology for Deriving Ambient Water Quality Criteria fo r the Protection of Human Health (referred to as EPA’s Human Health Methodology), EPA determined that a 0.4 mg/kg fish tissue residue value will protect the general population from the adverse health effects of mercury due to the consumption
of freshwater fish. To interpret Georgia’s Water Quality Standards, EPA assumed that the general population consumes 17.5 grams per day of large mouth bass, a trophic level 4 fish. EPA is using 0.4 mg/kg in fish tissue as the appropriate “end point” upon which to bas e the interpretation of the applicable water quality standard.

To calculate the maximum water column concentration that will not allow mercury to bioaccumulate in fish tissue to above 0.4 mg/kg, the EPA Human Health Methodology is again applied. The met hodology is expressed below:

) * * ( ) * * Re ( Hg FractionMe BAF nRate Consumptio rsion UnitsConve BodyWeight e ferenceDos WQS =

where:
WQS = EPA’s Interpretation of Georgia’s Water Quality Standard Reference Dose = 0.0001 mg/kg/day MeHg Body Weight = 70 kg Units Conversion = 1.0E6 Consumption Rate = 0.0175 kg/day Fish • Bioaccum ulation Factor = 4,000,000 as measured in the Savannah Watershed Fraction of the Total Mercury as Methylmercury = 0.0353 as measured in the Savannah Watershed

In the calculation, the Region used the recommended national values for most of the factors in t he Human Health Methodology, including the reference dose of 0.0001

- mg/k/day methylmercury; a standard average

• The fish intake value of 17.5 g/day (general adult population) was taken from EPA’s 2000 Revisions to the Methodology for Deriving Am

bient Water Quality Criteria for the Protection of Human Health (65 FR 66444

- 66482 (11/3/200)).Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

17 adult body weight of 70 kg; and the consumption rate for the general population of 17.5 grams per day. (Note that a recent report by the Nationa l Academy of Sciences confirms that methylmercury is a potent toxin, and concludes that EPA’s reference dose of 0.0001 mg/kg/day is appropriate (See NAS, Toxicological Effects of Methylmercury, July 2000)). For the other factors in the calculation,
bioa ccumulation and fraction methylmercury, EPA collected site

- specific data from the Savannah River Basin in August and September of 2000. (The site

- specific data is presented in Section 6.4 .) From this
site

- specific data, EPA d etermined a representative BAF value to be 4,000,000 and a median measured percentage methylmercury of 3.53%. Using recommended national values, and factors calculated from site

specific data, EPA interpreted Georgia’s water quality standard and has deter mined that the applicable water quality standard for total mercury in the ambient water of the middle and lower Savannah River Basin is 2.8 ng/l (parts per trillion). This water quality standard, when fully achieved, will prevent the unacceptable
bioaccum ulation of mercury in fish from all segments of the middle/lower Savannah River. This interpretation of Georgia’s water quality standard was based on site

- specific data gathered for the Savannah River in 2000 specifically for the purpose of this TMDL. It does not apply to any other water in the State of Georgia. In addition, in any future TMDLs for Savannah River, it is possible that EPA may revise this interpretation based on new site

- specific data collected at that time.

In determining the applicable water quality standard as interpreted by EPA , it was necessary to determine a representative bioaccumulation factor (BAF) as discussed above. It is common to have a large range in BAFs calculated from field data collected within the same river system. Figure 1 illustrates the range of BAFs calculated for all the fish sampled by EPA in August and September of 2000. The BAFs range from less than 1 million to over 18 million. An appropriate BAF for interpreting Georgia’s Water Qu ality Standards was selected from the central tendency of the measured data for a fish 315 millimeter (mm) in length. (See Figure 1 ) EPA is assuming a 305

- 315 mm fish is representative of the size and age of fish that
is most li kely to be consumed and also represents the minimum length requirement for the fisherman to keep. A representative BAF for a 315 mm fish in the Savannah River Basin is 4,000,000.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

18 Length vs. BAF

0 2000000 4000000 6000000 8000000 10000000 12000000 14000000 16000000 18000000 20000000

150 250 350 450 550 650 750 LengthBAF Bowfin Chain Pickerel Grass Pickerel Large Mouth Bass Striper All Fish Linear (All Fish)

**Figure 1**  **BAF vs. Leng th Fish Collection from Savannah Basin** 

**Furthermore, to support the selection of the 4,000,000 BAF value, the individual fish for each segment/tributary were analyzed to determine a central tendency BAF that would be protective of the fish species and popul**  **ation that this TMDL is being developed to protect. Data collected for the sections of the river and tributaries were analyzed**  **and compared statistically.**

Table 2 provides the average BAFs determined for each tributary and segm ent of the Savannah River Basin for which data was collected. This analysis shows that an acceptable BAF would be between 3,255,807 and 4,604,485. Using this analysis and regression method shown in Figure 1 , the selection of 4,0 00,000 provides a reasonable estimate of the BAF to be used in the Human Health Methodology calculation.

The site

- specific data used to develop the applicable water quality standard was obtained during a one

- time sampling event in the summer of 2000. EPA intends to revisit its interpretation of Georgia’s water quality standard in Phase 2 when more data is available for total mercury in the water column over a longer time period and environmental conditions.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

19 **Table 2**  **Fish Tissue Anal ysis** 

**River/Tributary Segment Average**  **Fish Tissue**  **(ppm) Water**  **Column Total**  **Hg (ng/L)**  **Water Column**  **MeHg (ng/L)**  **Fraction**

**MeHg Average** 

**BAF** Savannah River

- Below Clark's Hill Dam 0.251 0.27 0.02 0.078 11,710,280 Savannah River

- Below Horse Creek 0.074 0. 68 0.10 0.141 768,229 Savannah River

- Below Butler Creek 0.316 1.19 0.16 0.131 2,026,871 Savannah River

- Below Upper Three Run 0.181 3.27 0.07 0.020 2,744,723 Savannah River

- Below Lower Three Run 0.180 9.50 0.06 0.006 3,142,770 Savannah River

- Below Brier

Creek 0.415 2.80 0.09 0.032 4,703,913 Savannah River

- Clyo, USGS Gage 0.633 3.28 0.09 0.027 7,271,958 Savannah River

- Below Ebenezer Creek 0.665 3.44 0.08 0.022 8,698,953 Savannah River

- Tide Gate (Freshwater) 0.407 4.44 0.09 0.021 4,319,872 Savannah Riv er

- Tide Gate (Estuary) 0.389 4.09 0.06 0.015 6,321,951 Horse Creek 0.264 6.16 0.24 0.039 1,096,266 Butler Creek 0.305 2.14 0.39 0.182 780,769 Upper Three Runs Creek 0.783 5.82 0.16 0.027 4,896,829 Lower Three Runs Creek 1.085 2.43 0.13 0.051 8,676,761 Brier Creek 0.493 2.15 0.11 0.050 4,562,963 Ebenezer Creek 1.269 3.34 0.65 0.195 1,948,651 Average 0.482 3.44 0.15 0.065 4,604,485 Median 0.398 3.28 0.10 0.035 4,441,418 Average (Mean) River 0.351 3.30 0.08 0.049 5,170,952 Median River 0.352 3.28 0.0 8 0.024 4,511,893 Average (Mean) Tributary 0.700 3.67 0.28 0.091 3,660,373 Median Tributary 0.638 2.89 0.20 0.051 3,255,807 

## 6. Background

The middle & lower Savannah River watershed is located in eastern Georgia. The entire drainage area ofTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

20 the Savannah w atershed (USGS Hydrologic Unit Code (HUC) 3060106, 3060108, 3060109) is approximately 9318 square kilometers. The Savannah watershed is presented in Figure 2

.

**Figure 2**  **Savannah Watersheds**
To develop the TMDL, EPA divided the Savannah watershed into 31 subwatersheds ( Figure 3 ) that represent all of the major tributaries to the Savannah River. This TMDL presents a total mercury load for
each of these subwatersheds in order to dete rmine the impact of atmospheric deposition on the Savannah
River.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

21 **Figure 3**  **Savannah Watershed Delineation**
The watershed contains several different types of land uses. The landuses for the Savannah River watershed are given in Figure 4 . Different landuses collect and distribute mercury at different rates as a
function of runoff and erosion.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

22 **Figure 4**  **Savannah Watershed Landuses**



### 6.1. Mercury Cycling
Mercury chemistry in the environmen t is quite complex and is not totally understood. Mercury has the properties of a metal (including persistence due to its inability to be broken down), but also has some properties of a hydrophobic organic chemical due to its ability to be methylated thro ugh a bacterial process. Methylmercury is easily taken up by organisms, and will bioaccumulate. It is effectively transferred through the food web, magnifying at each trophic level. This can result in high levels of mercury in organisms high on
the foo d chain, despite nearly immeasurable quantities of mercury in the water column. In fish, mercury is not usually found in levels high enough to cause the fish to exhibit signs of toxicity, but the mercury in sportTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

23 fish can present a potential health risk t o humans.

Figure 5 provides a schematic of mercury cycling in the aquatic environment. The boxes represent stores of mercury, while the arrows illustrate the various fluxes that control mercury cycling in the environment. The

to p of the diagram summarizes the various forms of mercury that may be loaded into a waterbody. It is important to recognize that mercury exists in a variety of forms, including elemental mercury (Hg (0)), ionic mercury (Hg (I) & Hg (II)), and compounds in which mercury is joined to an organic molecule. In the schematic, Hg (I) is ignored, as Hg (II) generally predominates in aquatic systems. Mercuric sulfide (HgS or cinnabar) is a compound formed from Hg (II), but is shown separately, as it is the predomi nant natural ore. Organic forms of mercury include methylmercury (CH3Hg or “MeHg”), and also other organic forms, including natural forms such as dimethylmercury and man

- made compounds such as organic mercury pesticides.

In the aquatic mercury cycle it is critical to consider the distribution of mercury load between the various forms. The major forms reaching the water from the watershed can have different behavior:

• Mercuric sulfide (HgS), can be washed into the water as a result of weathering of natural cinnabar outcroppings. HgS has low solubility under typical environmental conditions and would be expected to settle out to the bottom sediments. However, under aerobic conditions Hg (II) may be liberated by a bacteria

- mediated oxidation of the sulfide i on. This Hg (II) would then be more bioavailable and would be available for methylation. Alternatively, under anaerobic conditions, HgS may be formed from Hg (II).

• Methylmercury (MeHg) is found in rainfall and may be found in small amounts in mine tailin gs or sediments. It is more soluble than HgS and has a strong affinity for lipids in biotic tissues.

• Elemental mercury (Hg (0)), may remain in mine tailings, as has been noted in tailings piles from recent gold mining in Brazil. Elemental mercury tends t o volatilize into the atmosphere, though someTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

24 can be oxidized to Hg (II).

• Other mercury compounds contain and may easily release ionic Hg (II). Such compounds are found in the fine residue left at abandoned mine sites where mercury was used to extract gol d or silver from pulverized rock.

Dimethylmercury is ignored in the schematic because this species seems to occur in measurable quantities only in marine waters. Organic mercury pesticides also have been ignored in this TMDL study since such pesticides ar

e not currently used in this country and past use is probably insignificant.

Mercury and methylmercury form strong complexes with organic substances (including humic acids) and strongly sorb onto soils and sediments. Once sorbed to organic matter, inverte brates can ingest mercury. Some of the sorbed mercury will settle to the bottom, and if buried deep enough, mercury in the bottom sediments will become unavailable to cycle. Burial in bottom sediments can be an important route of removal of mercury from the aquatic environment.

Methylation and demethylation play an important role in determing how mercury will accumulate through the food web. A biological process that appears to involve sulfate

- reducing bacteria may result in methylated Hg (II). Rates of biological methylation of mercury can be affected by a number of factors. Methylation can occur in water, sediment and soil solution under anaerobic conditions and to a lesser extent under aerobic conditions. In water, methylation occurs mainly at the sediment

- water interface and at the oxic

anoxic boundary within the water column. The rate of methylation is affected by the concentration of available Hg (II) (which can be affected by the concentration of certain ions and ligands), the microbial

concen tration, pH, temperature, redox potential, and the presence of other chemical processes. Methylation rates appear to increase at lower pH. Bacteria also cause demethylation of mercury.

Note in Figure 5 that both Hg (II) and meth ylmercury (MeHg) sorb to algae and detritus, but only the methylmercury is assumed to be passed up to the next trophic level. Invertebrates eat algae and detritus,Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

25 thereby accumulating any MeHg that has sorbed to these constituents. Fish eating the inver tebrates and either growing into larger fish (which have been shown to have higher body burdens of mercury) or eaten by larger fish will then bioaccumulate mercury. At each trophic level, a bioaccumulation factor must be assumed to represent the magnifica tion of mercury that occurs as one moves up the food chain.

Typically, almost all of the mercury found in fish (greater than 95%) is in the methylmercury form. Studies have shown that fish body burdens of mercury increase with increasing size or age of th e fish, with no signs of leveling off.

Although it is important to identify sources of mercury to the waterbody, there may be fluxes of mercury within the waterbody that would continue nearly unabated for some time even if all the sources in the
watershed and waterbody were eliminated. In other words, compartments within the watershed and waterbody store significant amounts of mercury, and this mercury can continue to cycle through the system even without an ongoing source of mercury. The most important store of mercury is likely the river sediments and the surrounding swamps and marshes. The mercury in these pools may cause exposure to biota by being:

• Resuspended into the water column, where it is ingested or adsorbs to organisms that are later ingested

.

• Methylated by bacteria. The methylmercury tends to attach to organic matter, which may be ingested by invertebrates and thereby introduced to the food web. It is methylmercury that poses the real threat to biota due to its strong tendency to accumulate in biota and magnify up the food
chain.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

26 **Figure 5**  **Mercury Cycling in the Aquatic Environment**



### 6.2. Source Assessment
A TMDL evaluation examines the known potential sources of the pollutant in the watershed, including point

sources, non

point sources, and background levels. For the purpose of this TMDL, facilities permitted under the National Pollutant Discharge Elimination System (NPDES) Program are considered point sources. Similarly, for the purpose of this TMDL air sources of mercury identified in the Mercury Report to Congress (EPA, 1997) which are located in the watershed and within a 100

- kilometer boundary around the watershed, referred to as the local airshed are treated as nonpoint sources. All other air sources, outside
the loc al airshed, are considered background sources of mercury. The source assessment serves as the basis for development of a model, and as the basis for the allocation of the total allowable load.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

27 **6.2.1. Sources of Mercury** 

It is estimated that approximately 99% of t he mercury loading to the watershed is from atmospheric deposition (See Table 8 Annual Average Total Mercury Load ). Mercury is deposited to the watershed as wet deposition (dissolved in rain) and as dry deposition of gaseous and particulate forms of mercury. For a more inclusive discussion of the air analysis performed as part of this TMDL, see Appendix A. Mercury deposited in the watershed comes from sources within the local airshed, from national sources located beyond the loc al airshed, and from international sources far away. Reactive gaseous mercury (RGM) is the dominant form of mercury in both rainfall and most dry deposition processes, and most of the RGM emitted from man made sources is deposited relatively quickly. Ther efore, the analysis of air point sources focuses on sources located in the local airshed, and on their emissions of RGM to the air. For the purposes of this TMDL, the sources within the local airshed are treated as the nonpoint sources of mercury. Those sources outside the local airshed are considered to be part of the background load of mercury since identification of the distant sources that contribute mercury to the watershed was not accomplished for this Phase 1 TMDL.

The emissions inventory files prepared for the Mercury Report to Congress (EPA, 1997) identify stationary point sources of mercury in Georgia and South Carolina within the local airshed. Table 3 identifies these stationary sources of mercury deposition and th eir estimated contribution in 1995 of RGM, the form of mercury that is most likely to deposit within the local airshed, including the Savannah River watershed.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

28 **Table 3**  **Summaries of Mercury Emissions in the RGM Airshed during the Baseline Period (1994** 

**- 1996)** 

**Source Category No. of** 

**Sources Total Hg** 

**Emissions Baseline**  **Period (kg/yr)**  **% of**

**Total Hg % of** 

**Total Hg that is**  **RGM Total RGM** 

**Emissions Baseline**  **% of**

**Total RGM** 

MedWIs 36 963 25.65 73 703 39.93 Power Plants 17 866 23.08 30 260 1 4.76 Chlor

- alkali 1 597 15.92 30 179 10.18 MuniWCs 3 589 15.69 60 353 20.08 Res/Ind Boilers 80 477 12.70 30 143 8.12 Pulp and Paper 12 121 3.23 30 36 2.06 Portland Cement 3 113 3.01 10 70 3.95 Sew Sludge Incin 6 26 0.69 60 16 0.88 HazWIs 2 1 0.03 8

- 95 <1 0.02 Total 160 3753 100.00 1760 100.00

**6.2.2. Water Point Sources** 

Facilities covered by the National Pollutant Discharge Elimination System (NPDES) program are considered in this TMDL to be point sources of mercury within the Savannah watershed. There a re approximately 80 NPDES facilities in Georgia discharging effluent to the Savannah River and its tributaries. (See Appendix B for a list of these facilities.) Because of the pervasive nature of mercury, and its presence in rainwater, it is assumed that all NPDES facilities discharge some mercury to the River. Because, until recently, EPA’s published method for the analysis of mercury was not sensitive enough to measure mercury at low trace level concentrations, most NPDES facilities have not detected me rcury during priority pollutant monitoring. Therefore, most facilities do not have permit limits for mercury in their NPDES permits since they have not demonstrated “reasonable potential” for mercury in their effluent. This TMDL will address only those f

acilities that have the potential to discharge mercury above 2.8 ng/l (the applicable water quality
standard as interpreted by EPA ) and that may be adding mercury to their effluent above that in their present source water (See Section 10.2 ).Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

29 In 1999, EPA published a new analytical detection method for mercury that can reliably measure the chemical down to 0.5 ng/l ( 64 CFR 30417 ). Using this more sensitive analytical procedure and related field sampling protocols, EPA sampled a small cross section of the NPDES facilities in Georgia in the watershed (22 out of approximately 80 facilities). This limited sampling study confirmed EPA’s suspicion that all NPDES facilities are discharging some concentration of mercury. Half of the f acilities sampled (11 out of 22) are discharging mercury at a concentration below the water quality standard as interpreted by
EPA of 2.8 ng/l, and the other half are discharging above this concentration. Based on the limited data from
this one

- time sampl

ing event, EPA is estimating that NPDES point sources contribute approximately 1% of the current total load of mercury to the River.



### 6.3. RELMAP Mercury Deposition Rates
As part of the Mercury Report to Congress, a national airshed model (RELMAP) was applied to the continental United States. This model provides a distribution of both wet and dry deposition of mercury as function of air emissions and global sources. Figure 6 and Figure 7 illustrate the dry and wet deposition rates for the Savannah River watershed as derived by RELMAP. The RELMAP model was based upon the existing emissions inventory (1995 and 1996) and did not include some foreign airsheds (e.g., Mexico).Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

30 **Figure 6**  **Mercury Dry Deposition Rates as Reported in the Mercury Report to Congress**Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

31 **Figure 7**  **Mercury Wet Deposition Rates as Reported in the Mercury Report to Congress**



### 6.4. Available Monitori n g Data
The States of Georgia and South Carolina have routinely collected fish from the Savannah River for fish tissue analysis. Because mercury may bioaccumulate in fish tissue to mg/kg levels (parts per million), analytical procedures have been capable of detecting mercury at these levels. Therefore , data is available from the states for 1988 to 1998 on fish tissue from the Savannah River. These data indicate fish tissue, on average; exceed the State’s Fish Consumption Guidelines in the water segments covered by this TMDL. In addition, EPA conducte d a field sampling study in August and September of 2000 that included fish

- tissue sampling and analysis. These data are available below in Section 6.4.4.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

32 The states have also collected and analyzed ambient water concentration samples for total mercury. As explained above in Section 6.2.2, the analytical method for mercury used in the recent past has a detection limit of 200 ng/l, which is not sensitive enough to detect mercury at the low concentrations typically found in ambient surface water (rivers, cr eeks, and estuaries.) Therefore, laboratory results from samples of surface water collected by the states during their routine surface water monitoring programs typically have indicated

a non

- detect for mercury. Therefore, there is little ambient surfac e water mercury data available from the states. EPA’s sampling study of the listed segments of the Savannah River in August and September of 2000 (EPA, November 2000) included water samples from 16 locations within the watershed. Samples were analyzed us ing EPA Method 1631, which has a detection limit of 0.5 ng/l. The results are presented
below at Section 6.4.2.

**6.4.1. EPA Region 4 Data** 

EPA Region 4 sampled the Savannah River watershed in August and September of 2000. Since even low
concentrations of mercu

ry in water can lead to significant accumulation of mercury in fish tissue, EPA sampled the Savannah River using the most sensitive sampling and analytical techniques. The samples were collected using the “clean hands” method (EPA, November 2000), and ana lyzed using the ultra

- trace level analytical technique, EPA Method 1631 (USEPA, 1999). EPA adopted this method in June of 1999 for mercury in water for data gathering and compliance monitoring under the Clean Water Act and Safe Drinking Water Act. This method can reliably measure mercury to 0.5 ng/l (parts per trillion).

The purpose of this data collection effort was to collect data needed for the development of this mercury TMDL. The sample locations for the water column are illustrated in Figure 8 . Water column, sediment and soil samples (taken adjacent to the water column samples outside the flood plain) were taken from 10 locations in the mainstem and 6 locations in tributaries throughout the middle and lower Savannah Rive r watershed.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

33 **Figure 8**  **Savannah Watershed Water Column Sample Locations**
Sample locations for the fish collection are illustrated in Figure 9 . The 16 collection sites are located throughout the mainstem

and tributaries in the middle and lower Savannah Basins. The fish collection consisted of 5 fish per sampling location, with the species of interest being largemouth bass. Largemouth bass were targeted because the State of Georgia’s Fish Consumption Gui deline is established to protect consumers from the consumption of largemouth bass. When 5 largemouth bass were not obtainable, other fish (Bowfin, Chain Pickerel, Grass Pickerel) were substituted.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

34 **Figure 9**  **Savannah Watershed Fis h Collection Locations** 
The following sections provide the results of the field sampling for mercury.

**6.4.2. Water Column Data** 

Water column samples were taken to determine the ambient concentration of mercury in the water column using Method 1631, an ultra

- trace l evel clean sampling and analytical technique with a quantification level of 0.5 ng/l. The water column samples were analyzed for both total mercury and methylmercury. Because methylmercury is the primary form of mercury taken up in the food chain, it was important to quantify the fraction of the total mercury in the methyl form. Table 4 provides the measured mercury concentrations in
the water column in mainstem and tributaries in the Middle/Lower Savannah watershed.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

35 **Table 4**  **Water Column Mercury Concentrations**

**ID Station**  **Total Hg (ng/l)**  **MeHg**

**(ng/l) Percent**  **MeHg** M

- 0 Savannah River

- Below Clark's Hill Dam 0.27 0.02 7.8 M

- 1 Savannah River

- Below Horse Creek 0.68 0.10 14.1 M

- 2 Savannah River

- Below Butler Cr

eek 1.19 0.16 13.1 M

- 3 Savannah River

- Below Upper Three Runs Creek 3.27 0.07 2.0 M

- 4 Savannah River

- Below Lower Three Runs Creek 9.50 0.06 0.6 M

- 4 Savannah River

- Below Lower Three Runs Creek(Filtered) 1.47 0.07 4.4 M

- 5 Savannah River

- Below Brier Creek 2.80 0.09 3.2 M

- 6 Savannah River

- Clyo, USGS Gage 3.28 0.09 2.7 M

- 7 Savannah River

- Below Ebenezer Creek 3.44 0.08 2.2 M

- 8a Savannah River

- Tide Gate (Freshwater) 4.44 0.09 2.1 M

- 8a Savannah River

- Tide Gate (Freshwater) (Filtered) 1.00 0.03 3.2 M

- 8b Sava nnah River

- Tide Gate (Estuary) 4.09 0.06 1.5 T

- 1 Horse Creek 6.16 0.24 3.9 T

- 2 Butler Creek 2.14 0.39 18.2 T

- 3 Upper Three Runs Creek 5.82 0.16 2.7 T

- 4 Lower Three Runs Creek 2.43 0.13 5.1 T

- 5 Brier Creek 2.15 0.11 5.0 T

- 6 Ebenezer Creek 3.34 0.65 19 .5

**6.4.3. Sediment Data** 

Samples of river and tributary sediments were gathered at the same locations as the water samples to determine the amount of mercury associated with the sediments and porewater. This data provides important information that can be used t o parameterize the water quality model by providing evidence of the effects of mercury in the sediments on the total mercury water column concentration.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

36 **Table 5**  **Sediment Mercury Concentrations**

**ID Station**  **Total Hg (ng/g)**  **MeHg (ng/g**  **) Percent**  **MeHg** M

- 0 Savannah River

- Below Clark's Hill Dam 2.69 0.02 0.6 M

- 1 Savannah River

- Below Horse Creek 10.16 0.00 0.0 M

- 2 Savannah River

- Below Butler Creek 3.09 0.00 0.1 M

- 3 Savannah River

- Below Upper Three Runs Creek 3.18 0.01 0.3 M

- 4 Savannah R

iver

- Below Lower Three Runs Creek 2.98 0.00 0.1 M

- 5 Savannah River

- Below Brier Creek 10.08 0.01 0.1 M

- 6 Savannah River

- Clyo, USGS Gage 2.53 0.12 4.7 M

- 7 Savannah River

- Below Ebenezer Creek 83.36 0.56 0.7 T

- 1 Horse Creek 19.56 0.03 0.2 T

- 2 Butler Creek 14.02 0.02 0.1 T

- 3 Upper Three Runs Creek 3.08 0.00 0.1 T

- 4 Lower Three Runs Creek 3.13 0.00 0.1 T

- 5 Brier Creek 3.43 0.00 0.1 T

- 6 Ebenezer Creek 143.23 0.34 0.2

**6.4.4. Watershed Soil Data** 

Soil samples were collected from the surrounding watershed where the other samples were taken. EPA collected the soil samples to be used in the calibration of the watershed model. Table 6 provides the mercury concentrations associated with soils collected during the summer of 2000.

**Table 6**  **Mercury Concentrations in Soils from Surround Watershed**

Station Percent Dry Wt. Total Hg

(ng/g) Dry Weight MeHg

(ng/g) Dry Weight

Savannah River

- Below Clark's Hill Dam 75.7 78.6 0.04 Savannah River

- Below Butler Creek 79.1 33.1 0.03 S avannah River

- Below Upper Three Runs Creek 82.5 22.7 0.05 Savannah River

- Below Lower Three Runs Creek 82.9 56.8 0.00 Savannah River

- Below Brier Creek 90.8 43.6 0.26 Savannah River

- Clyo, USGS Gage 78.1 71.8 0.95 Savannah River

- Below Ebenezer Creek 94.5 33.9 0.01 Butler Creek 97 43.8 0.06Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

37 Horse Creek 82.6 43.6 0.01 Upper Three Runs Creek 82.5 56.4 0.01 Lower Three Runs Creek 66.1 137.7 0.54 Brier Creek 84 26.3 0.32 Ebenezer Creek 91.7 28.1 0.11
**6.4.5. Fish Tissue Data** 

Samples of fish were taken from the S avannah River and tributaries within the same area as the water column and sediment samples. Trophic level four fish (largemouth bass) were targeted in the collection because they represent a major portion of the fish size that is caught and kept by angle rs and consumed as a source of food, and because Georgia’s Fish Consumption Guideline is based on the protection of public health from the consumption of largemouth bass. Trophic level four fish also represent the upper end of the
food chain where the bio magnification of mercury would be the highest. The fish fillets obtained during EPA’s sampling effort were analyzed for total mercury. Table 7 provides the individual fish data. The fish tissue mercury concentration was used to determine the appropriate interpretation of Georgia’s water quality standard for use in the TMDL.

**Table 7**  **Fish Tissue Mercury Data**

**Location Type**  **Total Length (mm)**  **Wt. lbs. Total Hg (Wet** 

**Weight) (mg/kg)** Below Clark's Hill Dam LMB 5 10 3.79 0.40 Below Clark's Hill Dam LMB 337 1.13 0.12 Below Clark's Hill Dam LMB 328 1.16 0.26 Below Clark's Hill Dam LMB 305 0.77 0.15 Below Clark's Hill Dam LMB 319 0.94 0.32 Horse Creek LMB 340 1.22 0.12 Horse Creek LMB 331 1.20 0.29 Horse Creek LMB 310 0.86 0.14 Horse Creek LMB 270 0.56 0.30 Horse Creek LMB 316 0.94 0.48 Below Horse Creek LMB 329 1.12 0.10 Below Horse Creek LMB 261 0.57 0.07Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

38 **Location Type**  **Total Length (mm)**  **Wt. lbs. Total Hg (Wet** 

**Weight) (mg/kg)** Below Horse Creek LMB 255 0.47 0.08 Below Horse Creek LMB 218 0.33 0.05 Butler Creek GP 219 0.17 0. 19 Butler Creek GP 170 0.08 0.45 Butler Creek GP 220 0.18 0.33 Butler Creek LMB 232 0.38 0.25 Below Butler Creek LMB 460 3.13 0.52 Below Butler Creek LMB 310 0.87 0.24 Below Butler Creek LMB 288 0.61 0.59 Below Butler Creek LMB 282 0.79 0.10 Below Butler Creek LMB 275 0.59 0.13 Upper Three Runs Creek Bowfin 585 4.21 1.04 Upper Three Runs Creek Bowfin 589 3.92 0.64 Upper Three Runs Creek Bowfin 567 3.72 0.54 Upper Three Runs Creek Bowfin 603 3.91 1.19 Upper Three Runs Creek Bowfin 505 2.67 0.50 Below Upper Three Runs Creek LMB 322 0.91 0.16 Below Upper Three Runs Creek LMB 340 1.03 0.22 Below Upper Three Runs Creek LMB 280 0.58 0.09 Below Upper Three Runs Creek LMB 304 0.78 0.28 Below Upper Three Runs Creek LMB 284 0.61 0.16 Lower Three Run s Creek Bowfin 624 5.12 1.36 Lower Three Runs Creek Bowfin 570 3.61 1.14 Lower Three Runs Creek Bowfin 509 2.45 0.76 Lower Three Runs Creek Bowfin 588 3.38 1.22 Lower Three Runs Creek Bowfin 540 3.01 0.95 Below Lower Three Runs Creek LMB 302 0.76 0.10 Below Lower Three Runs Creek LMB 401 1.90 0.34 Below Lower Three Runs Creek LMB 294 0.70 0.15 Below Lower Three Runs Creek LMB 355 1.41 0.22 Below Lower Three Runs Creek LMB 273 0.57 0.08 Brier Creek LMB 290 0.59 0.48 Brier Creek LMB 263 0.47 0.78Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

39 **Location Type**  **Total Length (mm)**  **Wt. lbs. Total Hg (Wet** 

**Weight) (mg/kg)** Brier Creek LMB 255 0.47 0.71 Brier Creek LMB 235 0.37 0.23 Brier Creek LMB 214 0.25 0.27 Below Brier Creek LMB 302 0.76 1.04 Below Brier Creek LMB 401 1.90 0.33 Below Brier Creek LMB 294 0.70 0.34 Below Brier Creek LMB 355 1.41 0.14 Below Brier Cre ek LMB 273 0.57 0.23 Clyo, USGS Gage LMB 477 3.98 1.44 Clyo, USGS Gage LMB 301 0.83 0.36 Clyo, USGS Gage LMB 310 0.71 0.51 Clyo, USGS Gage LMB 295 0.65 0.50 Clyo, USGS Gage LMB 295 0.69 0.36 Ebenezer Creek Bowfin 654 2.32 1.02 Ebenezer Creek Bowfin 545 2.30 2.17 Ebenezer Creek Chain Pickerel 415 0.98 1.25 Ebenezer Creek Chain Pickerel 365 0.59 0.82 Ebenezer Creek LMB 285 0.64 1.08 Below Ebenezer Creek LMB 325 0.91 0.25 Below Ebenezer Creek LMB 272 0.56 0.41 Below Ebenezer Creek LMB 275 0.51 0.4 0 Below Ebenezer Creek LMB 465 3.00 1.07 Below Ebenezer Creek LMB 500 3.94 1.19 Tide Gate (Freshwater) Bowfin 570 3.96 0.19 Tide Gate (Freshwater) Bowfin 570 3.94 0.68 Tide Gate (Freshwater) Bowfin 572 3.94 0.97 Tide Gate (Freshwater) LMB 260 0.45 0. 19 Tide Gate (Freshwater) LMB 280 0.61 0.21 Tide Gate (Freshwater) LMB 250 0.42 0.20 Tide Gate (Estuary) Striper 490 2.98 0.34 Tide Gate (Estuary) Striper 530 3.71 0.35 Tide Gate (Estuary) Striper 540 3.94 0.34 Tide Gate (Estuary) Striper 340 3.29 0. 39Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

40 **Location Type**  **Total Length (mm)**  **Wt. lbs. Total Hg (Wet** 

**Weight) (mg/kg)** Tide Gate (Estuary) Striper 505 3.10 0.54



## 7. Model Development

The link between the fish tissue residue concentration and the identified sources of mercury is the basis for the development of the TMDL. The linkage is defined as the cause and effect rel ationship between the selected indicators, the fish tissue residue concentration and identified sources. This provides the basis for estimating the total assimilative capacity of the river and any needed load reductions. In developing this TMDL, EPA combi

ned models of watershed loading of mercury with a model of mercury cycling and
bioaccumulation in the water. This enables a translation between the end

- point for the TMDL (expressed as a fish tissue residue concentration of mercury) and the mercury loads to the water. The loading capacity of the River for mercury is then determined by the linkage analysis as a mercury

- loading rate that is consistent with meeting the end

- point fish tissue residue concentration.



### 7.1. Watershed Hydrologic and Sediment Loading Mod el
An analysis of watershed loading could be conducted at various levels of complexity, ranging from a simplistic gross estimate to a dynamic model that captures the detailed runoff from the watershed to the receiving waterbody. The limited amount of data available for the Savannah River watershed prevented EPA from using a detailed dynamic watershed runoff model, which needs a great deal of data for calibration. Instead, EPA determined the mercury contributions to the Savannah River from the surrounding watershed and atmospheric components based on an annual mass balance of mercury in water and sediment loading from the watershed.

Watershed

- scale loading of mercury in water and sediment was simulated using the WatershedTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

41 Characterization System (WCS) (USE PA, 2001). The complexity of this loading function model falls between that of a detailed simulation model, which attempts a mechanistic, time

- dependent representation of pollutant load generation and transport, and simple export coefficient models, which do not represent temporal variability. The WCS provides a mechanistic, simplified simulation of precipitation

- driven runoff and sediment delivery, yet is intended to be applicable without calibration. Solids load from runoff can then
be used to estimate

pollutant delivery to the receiving waterbody from the watershed. This estimate is based on mercury concentrations in wet and dry deposition, which is processed by soils in the watershed and ultimately delivered to the receiving waterbody by runoff, eros ion and direct deposition (EPA, November 2000)



### 7.2. Water Quality Fate and Transport Model
Water Quality Analysis Simulation Program (WASP5) (Ambrose, et al., 1993) was chosen to simulate mercury fate in the Savannah River. WASP5 is a general dynamic mass bala nce framework for modeling
contaminant fate and trans port in surface waters. Based on the flex i ble com partment modeling approach, WASP can be applied in one, two, or three dimensions with advective and dispersive transport between discrete physical

compartments, or segments. A body of water is represented in WASP as a series of discrete computational elements or segments. Environ mental proper

ties and chemical concentra tions are modeled as spatially constant within seg ments. Each variable is a

dvected and dispersed among water segments, and exchanged with surficial benthic segments by diffusive mixing. Sorbed or particulate fractions may settle through water column segments and deposit to or erode from surficial benthic seg ments. Within
the b ed, dissolved vari

ables may migrate downward or upward through percola tion and pore water diffusion. Sorbed variables may migrate downward or upward through net sedimenta tion or erosion.

Two WASP models are provided with WASP5. The toxics WASP model , TOXI5, combines a kinetic structure adapted from EXAMS2 with the WASP5 transport struc ture and simple sediment balance algorithms to predict dissolved and sorbed chemical concentrations in the bed and overlying waters.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

42 TOXI5 simulates the transport and transformation of one to three chemicals and one to three types of particulate material. The three chemicals may be independent, such as isomers of PCB, or they may be linked with reaction yields, such as a parent com pound

- daughter product sequence. Ea ch chemical exists as a neutral compound and up to four ionic species. The neutral and ionic species can exist in five phases: dissolved, sorbed to dis solved organic carbon (DOC), and sorbed to each of the three types of solids. Local equilibrium is as sumed so that the distribution of the chemi cal between each of the species and phases is defined by distribution or partition coeffi cients. The model, then, is composed of up to six systems, three
chemi cal and three solids, for which the general WASP5 mass balance equation is solved.

The WASP model was parameterized to simulate the fate and transport of mercury for the development of this TMDL. Site specific and literature values were used to predict water column concentrations as a
function of flow.



## 8. T otal Maximum Daily Load (TMDL)

The TMDL is the total amount of a pollutant that can be assimilated by the receiving waterbody without exceeding the applicable water quality standard, in this case, a numeric interpretation of the State of Georgia’s narrativ e water quality standard for toxic substances of 2.8 nanograms per liter (ng/l) . This TMDL determines the maximum load of total mercury that can enter the Savannah River watershed within a year without exceeding 2.8

- ng/l total mercury in the water column . (See Section 5 for a discussion of EPA’s interpretation of Georgia’s water quality standard for this TMDL.)



### 8.1. Critical Condition Determination
The average annual flow and average annual loading represents the critical condition s for this TMDL. Average annual flow and average annual loading are appropriate for several reasons. First, EPA’s human health methodology, which has been used to derive an appropriate numeric interpretation of Georgia’s narrative water quality standard for toxic substances for this TMDL, assumes that health effects due toTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

43 mercury occur as a result of long

- term exposure to mercury in fish tissue through consumption of contaminated fish. The bioaccumulation of methylmercury in fish tissue is a long

- term, multi

- year, process. In fact, the applicable water quality standard as interpreted by EPA in this TMDL is based upon a largemouth bass of 315 millimeters in length, which represents a 3 to 5 year old bass. Therefore, the annual average load is more appro priate than a daily load for representing the long

- term processes of bioaccumulation in fish tissue that are associated with the potential for health effects. Second, the State applies their human health criteria at a flow equivalent to the annual averag e flow (Georgia Rules and Regulations for Water Quality Control, Chapter 391

- 3

- 6

- .03(5)(e)(iv) which requires the application of average annual load in the TMDL.



### 8.2. Seasonal Variation
Mercury is expected to fluctuate based on the amount and distribution of r ainfall, and variable emissions from local and distant atmospheric sources. Since wet deposition is greatest in the spring and winter seasons, loadings of mercury are highest during these seasons. However, these seasonal impacts or other
short

- term varia bility in loadings are damped out by the biotic response of bioaccumulation, which as discussed above, is a long

- term process. Therefore, seasonal variations are not important in this TMDL, which is expressed as an average annual load.

Methylation of merc ury is expected to be highest during the summer because high temperatures and static hydrologic conditions result in hypoxic and/or conditions that promote methylation, and since predator feeding activity is also high during the summer, mercury bioaccumula tion is expected to be greatest during the summer. However, based on the refractory nature of mercury, seasonal changes in body burden would be expected to be slight. Inherent variability of mercury concentrations between individual fish of the same
and/or different size categories is expected to be greater than seasonal variability.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

44 

### 8.3. Margin of Safety
A Margin of Safety (MOS) is a required component of a TMDL that accounts for the uncertainty about the relationship between the pollutant loads and the quality of the receiving waterbody. The MOS is typically incorporated into the conservative assumptions used to develop the TMDL. A MOS is incorporated into this TMDL in a variety of ways. These include:

• Selecting the highest predicted water column concentrat ion of mercury in the entire stretch of river to determine the load reduction needed to achieve Georgia’s water quality standard. This approach conservatively assumes that fish are exposed to the highest water column concentration and
accounts for uncerta

inties associated with identifying the precise locations where the fish take in
mercury.

• Calculating BAFs from only trophic level four fish. This approach conservatively assumes that the public consumes only largemouth bass. This may be an over

- estimate of amount of mercury to which the public is exposed through fish consumption because the typical diet of fish from other trophic levels that do not bioaccumulate mercury to the same degree as trophic level four fish. However, this assumption contributes t o the TMDL’s margin of safety because it accounts for uncertainties associated with precise fish diet. It also protects members of the public that consume fish from different trophic levels, but at a rate higher than the 17.5 g/day fish consumption rate

e mployed for this TMDL.

• Assigning a 1% load reduction to point sources. While EPA believes that such reductions, considered together with reductions from air sources, are necessary to achieve water quality standards, EPA also recognizes that future studies of mercury emissions from air sources may indicate that water quality standard can be achieved solely by controlling air sources. By assigning a 1% load reduction to point sources, EPA accounts for the possibility that air source reductions
are insuffici

ent. Thus, in addition to reflecting what EPA believes today are necessary loadTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

45 reductions from point sources, the 1% reduction helps account for EPA’s lack of precise knowledge concerning the relationship between the effects of Clean Air Act controls and water quality.

• Incorporating a number of conservative assumptions in deriving the estimate of anticipated reductions in emissions to the air. These are described in the Analysis of Atmospheric Deposition of Mercury to the Savannah River Watershed (2000). In addition, the resulting estimate does not take into account reductions resulting from voluntary control measures or new regulations. Therefore, reductions from air sources may possible be greater than presently estimated.



## 9. TMDL Development

In order to establish the maximum annual average load of mercury that be assimilated by the Savannah River and achieve the appropriate water quality standard, interpreted by EPA to be 2.8 ng/l, the watershed loadings of mercury to the River must be integrated with the fate and transport of mercury in the River. As discussed above (Section 8.1.), annual average loads and average annual flows are used as the basis for assessing the current loadings of mercury to the River and to assess the future load reductions of m ercury needed to achieve the applicable water quality standard.



### 9.1. Model Results
Both the Watershed Characterization System (WCS) nonpoint source runoff model and the receiving waterbody model (WASP5) are used to determine the maximum load of mercury that can occur and not exceed the applicable water quality standard of 2.8 ng/l as interpreted by EPA . This section provides detailed information on how the models are applied, how the watershed and waterbody are broken down into segments (computational boxes) an d how the mercury is transported throughout the watershed.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

46 **9.1.1. Nonpoint Source** 

The main driving force for the WCS mercury model is the input of the appropriate wet and dry deposition rates for mercury. The wet and dry deposition rates that were used in the WCS model were derived from the RELMAP air deposition model results reported in the Mercury Report to Congress. The RELMAP predictions for both wet and dry deposition were converted to a GIS coverage ( Figure 6 and Figure 7 ) to provide a spatially variable deposition rate for the watershed. The WCS model was used to calculate the total load of mercury entering the mainstem portion of the Savannah River from the sub basins d elineated in Figure 3 . The predicted annual loads are given in Table 8 . For each of the sub basins, the total load is presented in mg/yr, and the percentage of the contribution of mercur y from soil/erosion, runoff, direct deposition and impervious soil are presented. The watershed model was calibrated to match the soil
concentrations that were measured in the field.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

47 **Table 8**  **Annual Average Total Mercury Load**

**Sub Wa tershed**  **Area**

**(ha) Total Load** 

**mg/yr Load/ha**  **% Impr**

**Soil %**  **Sediment %** 

**Runoff % Direct** 

**Dep %**  **NPDES** Kiokee 32836.2 1669435.968 17.84 11.77 65.95 13.57 8.71 0 Little Kiokee 10088.81 331540.4058 11.05 31.17 23.49 34.63 10.7 0 Horse 42746.97 5147562.706 41.76 48.53 7.95 35.83 7.68 0 Butler 25390.8 3334875.266 49.68 66.84 7.04 14.13 11.98 0.01 Hollow 29416.43 2526441.021 29.43 37.81 33.08 22.42 6.69 0 Upper Three Runs 56241.64 3329200.071 22.57 58.61 11.55 27.76 2.09 0 Fourmile 8710.13 3595104.186 14.92 60.6 8 1.25 32.14 5.93 0 Lower Three Runs 46814.15 363748.1273 19.34 34.16 23.6 34.85 19.89 0 Brier Creek, SC 6666.03 2997886.561 22.05 30.02 36.68 29.28 4.02 0 Watchcall 8565.4 440622.7377 19.56 22.18 38.29 34.33 5.19 0 Boggygut 12453.06 513979.5685 15 17. 29 47.96 25.32 9.42 0 Newberry 10942.14 566475.2132 18.24 30.34 35.14 20.52 14 0 Steel 18310.91 793120.762 12.03 42.15 1.43 45.59 37.34 0 Beaverdam 12445.57 630715.4352 17.83 41.31 18.39 23.24 16.96 0.1 Sweetwater 15726.24 1025257.81 21.55 18.38 34.82 29.49 17.3 0 Rocky 17327.97 1190980.475 22.3 10.02 51.67 21.94 16.37 0 King 7684.87 483180.7 22.22 12.57 20.19 23.28 43.96 0 McDaniel 7389.59 369119.15 17.92 15.7 15.71 22.93 45.66 0 Dry 10533.89 835142.4918 25.97 19.63 40.85 30.46 9.06 0 Buck 24444.0 6 1448923.275 20.02 16.76 35.24 26.26 21.73 0 Utchee 42722.19 3836027.353 33.56 57.18 9.71 12.67 20.42 0.02 Spirit 36322.28 1933472.456 19.07 43.43 18.67 21.09 16.39 0.68 McBean 28999.99 2996561.842 15.72 24.1 38.67 25.45 11.78 0 Boggy 18934.66 99364 0.7169 17.21 21.83 30.71 40.29 7.17 0 Jackson 15552.96 945151.025 20.75 17.3 35.21 21.92 25.57 0 Cypress 23982.3 942136.3707 13.05 22.65 32.07 33.37 11.91 0 Ebenezer 60100.2 1995424.682 11 21.56 24.35 38.82 15.26 0.01 Pipemaker 52092.53 3482463.854 25. 96 32.44 2.04 8.72 56.39 1 Lockner 7001.55 209844.6119 10.33 42.03 11.97 38.36 6.88 0.75 Sand 22305.24 618689.0742 9.54 33.85 17.55 34.7 13.9 1.53 Brier Creek, GA 219195.9 9230475.848 10.92 31.01 25.68 36.62 6.68 0Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

48 **9.1.2. Water Quality Model** 

The WASP5 toxic c

hemical program TOXI5 was set up to simulate mercury in the mainstem of the Savannah River. The segments identified in Section 1 comprise the mainstem of the Savannah River for the purposes of this analysis. The mainstem of the river was divided into 31 reaches. Each reach was further divided into 2 vertical compartments representing surface water and surficial sediment. The 2 centimeters (cm) deep surficial sediment layer actively exchanges silt and clay

- sized solids as we ll as chemicals within the water column. In addition, this layer is the site for active microbial transformation reactions. Sediment

water column diffusion coefficients were set at 10 - 5 cm 2 /sec. Two classes of solids, sand and silt, were
simulated. San

d makes up most of the benthic sediment compartments, which have a dry bulk density of 0.5 g/ml. Given a particle density of 2.7 g/ml, the sediment porosity is about 0.8 and the bulk density is 1.3 g/ml. Silt is found both suspended in the water column a nd in the sediment. These simulations assumed that 10 mg/L of silt enters the mainstem from the subwatersheds, settling out at an assumed velocity of 0.3 m/day. Silt in the surficial sediment compartments is assumed to resuspend at a velocity of 0.006 m/ day, giving a concentration of about 0.005 g/ml, or about 1% of the surficial sediment. The exchanging silt carries sorbed mercury between the water column and surficial sediment. Mercury was simulated as 3 components B

elemental mercury, Hg 0 ; inorganic divalent mercury, Hg(II); and monomethyl mercury, MeHg. Hg(II) and MeHg partition to solids and dissolved organic carbon (DOC). These are represented as equilibrium reactions governed by specified partition coefficients. The three mercury components are also subject to several transformation reactions, including oxidation of Hg 0 in the water column, reduction and methylation of Hg(II) in the water column and sediment layer, and demethylation of MeHg in the water column and sediment layer. These are repr esented as first

- order reactions governed by specified rate constants. Reduction and demethylation are driven by sunlight, and the specified surface rate constants are averaged through the water column assuming a light extinction coefficient (here, 0.5 m - 1 ). In addition to these transformations, Hg 0 is subject to volatile loss from the water column. This reaction is governed by a transfer rate calculated from velocity and depth, and by Henry’s Law constant, which was set to 7.1 H 10 - 3Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

49 L

- atm/mole

- K. Unde r average flow conditions, velocity ranges from 0.2 to 0.3 m/sec, while depth ranges from 0.37 to 0.69 m. The specified and calculated reaction coefficients used here are summarized in Table
9

.

**Table 9**  **Spe cified and Calculated Reaction Rates and Coefficients**  **Component Reaction**  **Compartment Coefficient Value** 

Volatilization Water 1.0

- 3.9 day - 1 (calc) Hg0 Oxidation Water 0.0001 day - 1 Reduction Water 0.010 day - 1 (surface) 0.074

- 0.090 (calc) Met hylation Water 0.0001 day - 1 Methylation Sediment 0.00002 day - 1 Partitioning to silt Water, Sediment 4 x 10 5 L/kg Partitioning to sand Water, Sediment 1 x 10 4 L/kg Hg(II)

Partitioning to DOC Water, Sediment 2 x 10 4 L/kg

Demethylation to Hg(II) Water Sediment 0.0001 day - 1 0.00002 day

- 1 Demethylation to Hg0 Water (Photolysis) 0.1 day - 1 (surface) 0.074

- 0.090 (calc) Partitioning to silt Water, Sediment 4 x 10 5 L/kg Partitioning to sand Water, Sediment 1 x 10 3 L/kg MeHg

Partitioning to DOC Water, Se diment 2 x 10 5 L/kg Two separate simulations of mercury in the Savannah River were run representing average flow and drought flow conditions. The average flow simulation was run for 30 years, so that steady

- state conditions are
achieved in the water and surficial sediment. Drought flow conditions were run for 180 days using the
average

- flow concentrations as initial conditions. Volumes, depths, and velocities were obtained from the EPDRIV1 hydrodynamic model currently being applied to Savannah River in support of work being conducted by Georgia EPD.

The flows, depths, velocities, and volumes used for average and drought conditions are summarized in Table
10

.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

50 **Table 10**  **Flows, Depths, Velocities and Volumes used in WASP Model** 

River Mile Segment Volume (m) Depth (m) Velocity (m/sec) Tributary Flow (cms) 213 1 2916469 2.33 0.43 Headwater 273.49 203 2 2427977.4 2.52 0.53 197 3 3737187.3 3.50 0.68 193 4 5808927.7 6.96 0.27 190 5 6741527 7.53 0.28 Horse Creek 4.50 186 6 4740424.8 7.44 0.38 182 7 3374938.1 7.20 0.37 179 8 2684006.2 5.87 0.61 Butler Creek 0.85 175 9 4041461.1 6.20 0.69 Spirit Creek/Bear Island 2.15

169 10 3085140.2 5.74 0.75 Hollow Creek 2.41 164 11 3806153.5 6.98 0.65 0.00 159 12 3738075.5 5.84 0.65 McBean, Boggy Gut, Newberry 2.83

154 13 2841953.7 6.71 0.66 Upper Three Runs 3.77 150 14 5921744 5.79 0.66 Fourmile Creek 1.10 142 15 7914561.9 5.70 0.65 Beaverdam, Steel Creek 3.34

133 16 9761070 5.57 0.81 Sweetwater, Lower Thr ee Runs 3.99

116 17 6340925.8 5.63 0.70 Brier Creek, SC 1.81 107 18 7804913.5 5.96 0.65 Savannah Watch Call 2.04

96 19 5184161.4 6.95 0.72 Brier Creek, GA 25.57 89 20 3849710.4 7.51 0.67 0.00 84 21 3905226.2 7.21 0.70 Savannah Dry Branch 4.90

79 22 3989054.6 7.20 0.67 0.00 74 23 4086191.3 7.03 0.66 0.00 69 24 3918680.3 7.15 0.73 Boggy Branch 4.39 64 25 4858331.9 7.56 0.61 0.00 59 26 4767405.5 7.70 0.61 0.00 54 27 5109182.5 7.85 0.56 0.00 49 28 4910985.4 7.94 0.55 0.00 44 29 3656800.3 7.8 4 0.76 Ebenzer, Lockners, Abercorn 12.46

39 30 8558710.5 6.36 0.94 0.00 29 31 10107590 5.73 1.45 0.00 The WCS model calculates mercury loadings to each reach. These values are specified as constant Hg(II) and MeHg loadings for each surface water comp artment. Loadings for average flow conditions reflect bothTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

51 wet and dry deposition throughout the watershed, followed by runoff and erosion to the tributary stream network. Loadings for drought flow conditions include only dry de position (11 ìg/m 2

- yr) directly to water surfaces. These loadings to the tributary network are subject to reduction and volatilization losses in transport to the mainstem. Under drought flow conditions, these losses could be very significant due to the
l ong travel times. Average reduction factors were calculated for each tributary inflow using a reduction rate constant of 0.1 day - 1 along with that subwatershed’s flow, water surface area, and assumed depth:

T k / ) e - (1 = factor reduction r T k

- r max

max • •

where k r is the reduction r ate constant in day - 1 and T

max is the travel time for the tributary in days. The travel time is calculated as the total tributary surface area times its average depth divided by its average flow.

Figure 10 compares the model pr edictions versus what was measured in the field summer of 2000. Because of the severe drought condition in Georgia prior to and during the sample collection, the only loading source of mercury to the watershed was direct deposition on the water. This mod eling exercise was done to aid in the parameterization and calibration of the water quality model.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

52 Low Flow Water Column Total Mercury Concentrations

0 1 2 3 4 5 6 7 8 9 10

0 50 100 150 200 250 River Mileng/l Total Hg Measured

**Figure 10**  **Model Predictions versus Observed Data for the Savannah River for Drought Conditions**
Figure 11 provides a comparison of model predicted mercury sediment concentrations versus what was
measured in the field.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

53 Low Flow Total Mercury Concentration in Sediments

0 5 10 15 20 25 30

0 50 100 150 200 250 River Mileug/kg Predicted Observed Trib sediments

**Figure 11**  **Model Predictions versus Observed Data for Total M ercury in the Sediments during Low Flow** 
Figure 12 provides the predicted water column concentrations under annual average load and flow for the Savannah River. The highest predicted water column concentration is used in the TMDL calculation to determine the maximum annual average load that could occur and still achieve the applicable water quality
standard as interpreted by EPA

.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

54 Average Annual Flow Water Column Total Mercury Concentrations

0 1 2 3 4 5 6 7 8 9 10

0 50 100 150 200 250 River Mileng/l Total Hg Observed

**Figure 12**  **Model Predictions versus Observed Dat a for the Savannah River for Annual Average Flow** 
Figure 13 provides a comparison of model predicted mercury sediment concentrations versus what was measured in the field under annual average flow conditions.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

55 Total Mercury Concentration in Sediments Annual Average Flow

0 2 4 6 8 10 12 14

0 50 100 150 200 250 River Mileug/kg Predicted Observed

**Figure 13**  **Model Predictions versus Observed Data for Total Mercury in the Sediments Annual Average Flow**



### 9.2. TMDL Determination
To determine the total maximum load that can come into the Savannah River without exceeding the appl icable water quality standard of 2.8 ng/l as interpreted by EPA , the current loading conditions are evaluated and the water column concentration in the River is determined using the modeling approach described above. This allows the development of a relat ionship between mercury loading and water column mercury concentrations in the River. Using this developed relationship, the total maximum load can be determined. Because the water column mercury concentration response is linear with respect to changes i n load, a proportion can be developed to calculate the total maximum mercury load from the watershed that would achieve the derived water quality standard of 2.8 ng/l as interpreted by EPA . The TMDL is calculated as given below:Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

56 Load

TMDL WQS Load Average Annual Current ion

Concentrat Segment Highest

. .

wh ere: Highest Segment Concentration = 5.0 ng/l Current Annual Average Load to the Savannah River = 58.8 kilograms/year Water Quality Standard = 2.8 ng/l as interpreted by EPA **The TMDL Load is calculated as 32.8 kilograms/year total mercury**

.


## 10. Allocation of Lo ads

In a TMDL assessment, the total allowable load is divided and allocated to the various pollutant sources. This allocation is provided as a Load Allocation (LA) to the nonpoint sources, defined in this TMDL as the
air sources within the 100

- kilometer b oundary of the watershed, and as a Wasteload Allocation (WLA) to the point

- source facilities in Georgia with a NPDES permit. The difference between the current load and the allowable load is the amount of pollutant reduction the sources need to achieve in order for the waterbody to ultimately achieve the applicable water quality standard of 2.8 ng/l as interpreted by EPA

. **The calculated allowable load of mercury that can come into the Savannah River without exceeding the applicable water quality standard o**  **f 2.8 ng/l as interpreted by EPA**  **is 32.8 kilograms/year.**  Because this assessment indicates that 99% of the loading of mercury is from atmospheric sources, 99% of the allowable load will be assigned to the load allocation, and 1% of the available load will be assigned to the wasteload allocation. Therefore, the Load Allocation and Wasteload Allocation for the
middle/lower Savannah River are:

Load Allocation (atmospheric sources) = 0.99 (32.8) = 32.5 kilograms/year

Wasteload Allocation (NPDES sources) = 0 .01 (32.8) = 0.3 kilograms/yearTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

57 The estimated current loading of mercury to the Savannah River from the surrounding watershed is 58.8 kilograms/year. This load was determined by adding the predicted mercury load for each of the subwatersheds taking into ac count delivery times and volatilization that occurs in the tributaries. The difference between the estimated current mercury load (58.8 kg/year) and the calculated allowable load (32.8 kg/year) is 26 kilograms/year. Since 32.8 kg/year is 56% of the estim ated current loading of mercury, it is estimated that a 44% reduction in total mercury loading is needed for the middle/lower Savannah River to achieve a water column concentration of 2.8 ng/l.



### 10.1. Atmospheric Reductions
EPA estimates that approximately 99% o f current mercury loadings to the River are from atmospheric deposition; therefore, significant reductions in atmospheric deposition will be necessary if the applicable water quality standard as interpreted by EPA of 2.8 ng/l is to be attained. Based on t he total allowable load of 32.8 kilograms per year, a 44% reduction of mercury loading is needed to achieve the applicable water quality standard as interpreted by EPA . An analysis conducted by the EPA Region 4 Air Program (Appendix A) concludes that an e stimated 38% to 48% reduction in mercury deposition to the Savannah River watershed can be achieved by 2010. This conclusion was derived using the following methodology:

• The analysis used the results of national atmospheric mercury deposition modeling don e for EPA’s
1997 Mercury Study Report to Congress (referred to as The Mercury Study ) to estimate the level of mercury deposited to the Savannah River watershed during the baseline period (1994

- 1996) from local sources (those in the watershed or within 100 km of the watershed), plus national and global sources. The analysis presumes that local sources primarily contribute to the loading by deposition of reactive gaseous mercury (RGM, divalent mercury gas), while national sources (i.e.,
at a distance >100 km

) contribute particle bound mercury, and global sources contribute gaseous elemental mercury.

• The total RGM emitted from local sources was estimated for the baseline period from the emissionsTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

58 data files used to conduct The Mercury Study modeling. Local so urces include categories such as hospital and medical waste incinerators, municipal waste incinerators, electric utility plants, a chlor

alkali chlorine production facility, and industrial and residential boilers.

• Future RGM emissions for 2010 from local s ources were estimated using projected population growth as an indicator of growth in emissions over time, along with calculated reductions in mercury emissions due to MACT and Waste Combustion controls. Then an estimate of RGM deposition to
the watershed w

as calculated for 2010 as proportional to local emissions.

• Combining the RGM value with an estimate of proportional national and global source contributions in 2010 developed the sum total deposition of mercury to the watershed in 2010. Comparison of
the total value emitted in 1995/1996 with the total value calculated for emissions in 2010 indicates that a 38% to 48% reduction of mercury deposition is probable over the approximately 15 years from the baseline to 2010, based on currently promulgated standar ds in the Clean Air Act (MACT and Section 129.)

EPA expects these reductions to be achieved through full implementation of currently promulgated Clean Air Act (CAA) requirements under Section 112(d) Maximum Achievable Control Technology (MACT)
and Section 129 Solid Waste Combustion, and Section 111 New Stationary Sources, at sources within the local airshed and nationally. The local airshed is defined in this TMDL to be the area within the watershed
and a 100

- kilometer boundary around the watershed. Addi tional reductions may be realized after further implementation of these requirements and other Clean Air Act sections.

The analysis conducted by the EPA Region 4 Air Program in Appendix A provides reasonable assurance that reductions needed in mercury load ing can be achieved by reductions in mercury emissions from air
sources within the local airshed and nationwide. There are, however, uncertainties in the air deposition analysis that should be recognized and are explained in Appendix A. Some of these unc ertainties include the estimates of the amount of the chemical form or species of mercury emitted by each source category; theTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

59 projected level of reductions from each source category subject to Section 129 or MACT regulations; the
definition of local sourc es contributing deposition to the watershed, the contribution from global sources, and other aspects of the modeling. While it is not possible to quantify the net effect of these factors, EPA believes the assumptions made to address these uncertainties are reasonable and consistent with the state

of

- the art mercury modeling available at the time this TMDL was prepared, and that the Agency has reasonable assurance that needed air reductions will be achieved notwithstanding these uncertainties. It is anticip ated, however, that additional data and information collected during implementation of this Phase 1 TMDL will allow a more certain analysis of attainable air reductions to be accomplished in the Phase 2
TMDL . EPA will determine at that time whether it is appropriate to revise the load allocation, or the wasteload allocation, to assure that the applicable water quality standard as interpreted by EPA will be
achieved.

Future additional reductions in air deposition of mercury, beyond that presented in Appendi x A, may occur through the implementation of voluntary programs as well as new CAA regulatory actions being considered by EPA. This TMDL does not currently depend on any additional future reductions beyond those identified in Appendix A. While it is not possible at this time to quantify these anticipated mercury reductions, an estimate of such quantification will be more likely during the Phase 2 TMDL. In December 2000, EPA announced that it intends to begin developing a regulation under CAA Section 112 to limit mercury
emissions from coal

- fired power plants. A proposal is expected in late 2003 and a final regulation at the end of 2004. As a group, these plants are the largest remaining source of mercury emissions in the United States. It is too early to estimate the reductions in mercury emissions that may result from regulation of electric utilities. In the meantime, we expect to see reduced emissions of mercury from this sector as a number of regulations are implemented to control SO 2 and NO x , since some control technologies used to limit these pollutants collaterally reduce mercury emissions as well. A review of regulatory and related initiatives to reduce mercury emissions is provided in Appendix A. At this time, the overall, or relative percent , reduction in mercury emissions that may be realized in the future from the variety of activitiesTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

60 underway or proposed is uncertain, and estimating such reductions is not appropriate for this TMDL. However, EPA is committed to continuing to track emission s of mercury and evaluate additional ways to reduce releases of mercury to the environment.



### 10.2. Allocation to NPDES Point Sources
This TMDL estimates that approximately 1% of the current loadings of mercury to the River are from NPDES point sources. For a dis cussion of EPA’s basis for this estimate, see Section 8.2.2. At this time, one NPDES point source in Georgia has a permit to discharge mercury to the Savannah River. This facility is the Olin Corporation located in Augusta (NPDES Permit Number GA0003719) . The TMDL also identifies 28 other NPDES point sources in Georgia for a wasteload allocation in this TMDL that Georgia and EPA believe have the potential to discharge significant amounts of mercury in their effluent. Twenty

four of these facilities have been identified because of their volume of flow (greater than 1 million gallons per day) or based on limited effluent data or the fact that they were rated as “major industrial” facilities by the State of Georgia. In making such “major industrial” facility determinations, Georgia takes into account factors such as toxic pollutant potential, public health impacts, and impacts on water quality. Another 4 facilities, considered to be “minor municipal” or “minor industrial” facilities, are also identified in t he TMDL for a wasteload allocation. Data collected by EPA at these facilities in August 2000, indicate mercury concentrations in the facility’s effluent above the applicable water quality standard as interpreted by EPA of 2.8 ng/l. EPA believes it is rea sonable to assume that mercury is present in the discharge of these 29 NPDES permittees because of the persistent nature of mercury, and its pervasive presence in the environment, including rainwater. Table 11 (below) provides the list of NPDES facilities in Georgia that are provided a wasteload allocation in this TMDL.

There are approximately 50 other NPDES permitted facilities in Georgia located within the watershed. (See Appendix B for a list of all NPDES facilities in the watershed of the middle and l ower Savannah River Basin provided to EPA by the Georgia Environmental Protection Division.) The TMDL does not provide aTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

61 specific wasteload allocation to these facilities since they discharge less than 1 million gallons per day, or are
considered “minor in dustrial” facilities. EPA assumes that these facilities are discharging mercury in
concentrations below the 2.8

- ng/l applicable water quality standard as interpreted by EPA, or are not adding concentrations of mercury above that in their source water. Th ese facilities have a smaller flow rate (compared to the facilities identified above), and they are considered by the State of Georgia to be “minor municipal” or “minor industrial” facilities based on the factors set forth above (a “minor municipal” facili ty has flow less than 1 million gallons pre day). As the new more sensitive EPA Method 1631 mercury analytical procedure is implemented in the NPDES program these “minor” facilities must verify through monitoring whether or not they are significant contri butors of mercury (State of Georgia Rules and Regulations for Water Quality Control, April 2000, Chapter 391

- 3

- 6

- .06, and January 1995 Reasonable Potential Procedures). EPA can consider this information in the revision of the TMDL in 2004, and will
estab lish a wasteload allocation for any facilities for which data demonstrates mercury is present in their effluent at levels above the amount present in their source water.

In order to achieve the water quality standard as interpreted by EPA for mercury in th e Savannah River, EPA has assigned to all NPDES point sources in the basin a cumulative wasteload allocation of 0.3 kg/year. For each of the 29 facilities identified as potential significant contributors of mercury, EPA is providing a specific wasteload a llocation (WLA). This WLA is expressed in two different forms. The first is described as Option A below, and the second is described as Option B. The NPDES permitting authority is authorized by this TMDL to apply either option to the NPDES point sources affected by this TMDL. In the context of this TMDL, EPA believes it is reasonable to offer this choice to the permitting authority for the following reasons. First, based on EPA’s analysis, either wasteload allocation option, in the aggregate, is expect ed to result in point source mercury loadings less than the cumulative wasteload allocation. Second, EPA believes this flexibility is the best way of ensuring that the necessary load reductions are achieved without causing significant social and economic disruption. EPA recognizes that NPDES point sources contribute only a small share of the total mercury contributions to the Savannah River. However, EPA alsoTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

62 recognizes that mercury is a highly dangerous pollutant that can bioaccumulate in fish tissue at levels harmful
to human health. Therefore, EPA has determined, as a matter of policy, that NDPES point sources known to discharge mercury at levels above the amount present in their source water should reduce their loadings of mercury using appropriate, cost

- effective mercury minimization measure in order to ensure that the total point source discharges are at a level equal to or less than the cumulative wasteload allocation specified in this TMDL. The point sources’ WLA will be applied to the increment of mercury in their discharge that is above the amount of mercury in their source water. For further discussion of the legal and policy rationale underlying these wasteload allocations, see the Response to Comments. EPA recommends that the permitting aut hority make this choice between Option A and Option B in consultation with the affected discharger because EPA is not able to make the case

- by

- case judgments in this TMDL that EPA believes are appropriate.

Option A: Criteria end

- of

- pipe

Under Option A, t

he wasteload allocation is equivalent to applying Georgia’s water quality standard as interpreted by EPA to the discharger’s effluent at the outfall point. For this TMDL, EPA has interpreted Georgia’s water quality standard to be 2.8 ng/l. Therefore, und er this option, the wasteload allocation for each NPDES point source identified in this TMDL would be the product of multiplying 2.8 ng/l by the permitted or design flow rate of each identified NPDES point source. The result would be the maximum
mass load ing of mercury from that point source. The sum of these individual wasteload allocations is 0.001 kg/year, which is significantly less than the 0.3 kg/year cumulative wasteload allocation provided to all NPDES facilities. Under Option A, the individual was teload allocations for each NPDES point source affected by this TMDL are provided in Table 11

.

**Table 11**  **NPDES Permitted Facilities and Assigned Wasteload Allocation at 2.8 ng/l**
Major Municipal NPDES ID MGD Kg/Yr Augusta

–

Butler Creek GA0037621 46.1 1.78E

- 04 Columbia County

–

Crawford Creek GA0031984 1.5 5.81E

- 06 Columbia County

–

Reed Creek GA0031992 4.6 1.78E

- 05Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

63 Columbia County

–

Little River GA0047775 1.5 5.81E

- 06 Garden City WPCP GA0031038 2 7.74E

- 0 6 Richmond County

–

Spirit Creek GA0047147 2.24 8.67E

- 06 Savannah Crossroads (proposed facility) GA0038326 1.2 4.64E

- 06 Savannah

- President Street GA0025348 27 1.04E

- 04 Savannah

- Wilshire/Windsor GA0020443 4.5 1.74E

- 05 Savannah Travis Field GA0020427 1 3.87E

- 06 Sylvania WPCP GA0021385 1 3.87E

- 06 Tybee Island GA0020061 1 3.87E

- 06 Waynesboro GA0020231 2 7.74E

- 06

Major Industrial/Federal DSM Chemicals Augusta Inc GA0002160 3.765 1.46E

- 05 Fort James GA0046973 18 6.97E

- 05 Georgia Power Vogtle GA0 026786 7.2 2.79E

- 05 International Paper Company GA0002801 58.6 2.27E

- 04 Kemira GA0003646 23 8.90E

- 05 PCS Nitrogen Fertilizer L.P. GA0002071 1.152 4.46E

- 06 PCS Nitrogen Fertilizer LP GA0002356 0.362 1.40E

- 06 Savannah Electric Effingham GA0003883 108 4. 18E

- 04 Stone Container GA0002798 4.86 1.88E

- 05 Union Camp Corporation GA0001988 28.09 1.09E

- 04 USA Fort Gordon GA0003484 1.921 7.43E

- 06 USA Hunter AFB STP GA0027588 0.544 2.11E

- 06

Significant Municipal Minors DHR Gracewood School Rec WPCP GA004727 9 0.5 1.94E

- 06 DHR Gracewood Hospital GA0022161 0.003 1.16E

- 08

Significant Industrial Minors Olin Corporation Augusta GA0003719 1.246 4.82E

- 06 Citgo Asphault GA0004332 0.054 2.09E

- 07 Option B: Mercury characterization or minimization

Under Option B, the individual wasteload allocations are equivalent to the level of mercury in a point source’s effluent after implementation, when appropriate, of cost

- effective and appropriate mercury
minimization measures. EPA assumes that feasible/achievable mercu ry load reductions resulting from the mercury minimization efforts will, as a cumulative amount of all 29 facilities, result in a total loading of less than 0.3 kg/year. This assumption is based on information indicating wastewater treatment plants, which account for about 50% of the affected facilities, can attain significant mercury reductions through source reduction efforts. The effectiveness of mercury minimization efforts at industrial facilities is highly facility

specific; however, significant redu ctions may be attained through product substitution and other measuresTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

64 (See Mercury Report to Congress, 1997, Section 4, and Overview of Pollution Prevention Approaches at POTW’s, EPA 1999). If the cumulative effects of mercury minimization planning effor ts are shown during the Phase 2 TMDL evaluation in 2004 not to be less than the cumulative 0.3 kg/yr wasteload allocation, EPA will provide a specific wasteload allocation to each facility to assure that the cumulative wasteload
allocation will be attained

. Option B has a variety of different components that apply depending on whether the point source currently has a water quality

- based effluent limitation for mercury in its NPDES permit. Affected NPDES permits would need to incorporate permit conditions o r limitations as follows in order to be consistent with the assumptions of this TMDL. See 40 C.F.R. § 122.44(d)(1)(vii)(B).

For the NPDES facility in Georgia with a current permit limit for mercury (Olin Corporation, NPDES Permit Number GA0003719), this T MDL assumes that the permit will include:

• a numeric water quality

- based effluent limitation for mercury that is identical to its current water quality

- based limit for mercury;

• a requirement to monitor for mercury using the version of EPA Method 1631 then i n effect;

• a requirement to expeditiously develop a mercury minimization plan;

• a requirement to implement appropriate cost

- effective mercury minimization measures identified through mercury minimization planning; and

• following completion of the mercury mi nimization plan, a numeric effluent limitation for mercury will be established in the permit that reflects the achievable level of mercury in the discharger’s effluent upon implementation of appropriate, cost

- effective minimization measures.

For NPDES faci

lities in Georgia identified in Table 11 (except for Olin Corporation, NPDES Permit Number GA0003719) this TMDL assumes that the permits will includes:Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

65 • a requirement to characterize the effluent using the version of EPA Method 16 31 then in effect in order to quantify the amount of mercury present in the influent and effluent, if any;

• a requirement to develop a mercury minimization plan if the monitoring data shows mercury is present in their effluent at levels greater than in thei r influent or source water, and the effluent concentration exceeds 2.8 ng/l).

• a requirement to implement appropriate cost

- effective mercury minimization measures identified through mercury minimization planning if the monitoring data shows that an increa sed amount of mercury is present in the final effluent (as described above).

While this TMDL assumes that the State of Georgia, as the permitting authority, will determine the necessary elements of a mercury characterization/ minimization study plan, E PA would expect the plan(s) to have elements similar to the following: (1) influent/effluent monitoring with sufficient frequency to determine variability and to identify if an increased amount of mercury is present. If the facility’s discharge is shown t o result in an increased amount of mercury, the plan should also include the following additional elements: (2) the identification and evaluation of current and potential mercury sources; (3) monitoring to confirm current/potential sources of mercury; (3) the identification of potential methods for reducing/eliminating mercury, including housekeeping practices, material substitution, process modifications, materials recovery, spill control & collection, waste recycling, pretreatment, public education, labor atory practices, and disposal practices, and the evaluation of the feasibility of implementation; (4) implementation of cost

- effective and appropriate minimization measures identified in the plan; and (5) monitoring to verify the results of waste
minimizat ion efforts. In addition, EPA expects the permit to establish a reasonable schedule for the implementation of each element and to require appropriate progress reports.

This TMDL accords the permitting authority a certain amount of discretion in incorporat ing these wasteload allocations into NPDES permits. The permitting authority is free to determine the appropriate frequency,
duration and location of monitoring associated with the mercury characterization component of theTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

66 wasteload allocation. The permi tting authority also has the discretion to determine the level of oversight in connection with the development of mercury minimization plans and the discharger’s choice of appropriate,

cost

- effective measures to implement. EPA believes that each of these decisions is heavily fact

- dependant and that the permitting authority is in a better position than EPA to make them.

As discussed below, this TMDL assumes that point sources will not be authorized to discharge mercury above current effluent levels. Optio n B is predicated on the judgment that the 0.3 mg/year cumulative wasteload allocation will be achieved by applying waste minimization measures to current point source effluent conditions. Allowing an increase in current effluent loadings of mercury could undercut the assumptions upon which this TMDL is based unless the permitting authority can demonstrate that any such increase is offset by decreases of mercury from other point source(s) so that the cumulative wasteload allocation of 0.3 kg/year is not ex ceeded.

EPA recognizes that the State of Georgia's regulations authorize compliance schedules for water quality

based effluent limitations and conditions once those requirements are imposed in NPDES permits. See Rules and Regulations for Water Quality Con trol, Chapter 391

- 3

- 6

- .06(10). Under these regulations, the Director of EPD is authorized to establish as a compliance deadline the date that he or she determines to be “the shortest reasonable period of time necessary to achieve such compliance, but in n o case later that an applicable statutory deadline.” Because there is no applicable statutory deadline relating to the achievement
of these WLA

- based limitations, point sources affected by this TMDL may be eligible for compliance schedules under this prov

ision of Georgia's regulations. This TMDL assumes that the permitting authority will establish the shortest reasonable period of time for compliance with permit limitations and conditions
based on this TMDL. This TMDL also recognizes, however, that the p ermitting authority is in the best position to determine the timing of mercury characterization and the compliance schedules for developing and implementing mercury minimization plans.

Regarding the compliance schedules in permits to meet permit limitati ons and conditions based on Option B,Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

67 EPA makes the following observations. First, EPA believes that a point source with a flow of under 5 million gallons per day can develop a detailed mercury minimization plan within three to six months after the

mercur y characterization phase is completed and it has been determined that a minimization plan is requires. Point sources with a larger flow could develop a plan within about six to 12 months. Second, prompt characterization of the point sources’ mercury disc harges will assist EPA in determining whether it is necessary to revise the TMDL in the near future. Any unnecessary delay in obtaining this information could interfere with that effort. Third, with respect to implementation of appropriate, cost

- effectiv e mercury minimization measures, EPA believes that the permitting authority is in the best position to determine what constitutes “the shortest reasonable period of time for compliance.” EPA recognizes that the implementation of mercury minimization measu res can take several years, especially when they involve small, diffuse sources discharging mercury to Publicly Owned Treatment Works (POTWs).

Other Assumptions Incorporated into this TMDL

. The wasteload allocation component of this TMDL reflects the follo wing additional assumptions:

• The permitting authority may write permit conditions that allow the discharge of mercury at levels equal to the amount of mercury in the facility’s intake water (from the Savannah River or its tributaries), stormwater, and/or w ater drawn from the public water supply. If the permitting authority determines that mercury is present in the final effluent at levels above that level present in the influent, the permitting authority will establish permit limits consistent either Optio n A or Option B of this WLA. The permitting authority also should consider whether any increased mercury concentration in such discharges present potential for violation of an applicable acute standard for mercury, and include appropriate limits to protec t against such violations.

• No NPDES point source will be authorized to increase its mass loadings of mercury above levels reflected in current water quality

- based effluent limitations or current effluent quality, whichever is lower (in the case of facilit ies with such limitations) or current effluent quality (in the case of facilitiesTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

68 subject to mercury characterization requirements).

• The permitting authority will establish the shortest reasonable period of time for compliance with permit limitations and conditions based on this TMDL.

• The State of Georgia will require those facilities rated as “minor municipal” and “minor industrial” facilities to monitor for mercury using the version of EPA Method 1631 then in effect to verify whether or not they have a added mercury. (State of Georgia Rules and Regulations for Water Quality Control, April 2000, Chapter 391

- 3

- 6

- .06, and January 1995 Reasonable Potential Procedures)

. This TMDL incorporates wasteload load allocations in the form of Option B only because each of the following factors is present:

• this TMDL addresses mercury, which EPA believes is best handled at these levels through waste minimization rather than through end

- of

- pipe treatment;

• the NPDES point sources, in the aggregate contribute only 1% of the total current mercury loadings to the Savannah River;

• EPA has reasonable assurance that implementation of pollution controls required under current law will result in reductions sufficient to achieve the load allocation of 32.5 kg/year assigned to air sources, thus authorizing a cumulative wasteload allocation of 0.3 kg/year.

• if the Savannah River were currently attaining water quality standards, mercury discharges from the identified NPDES point sources at levels equivalent to the cumulative wasteload allocation of 0.3 kg/year would not cause or contribute to an exceedance of applicable water quality standards for
mercury as interpreted by EPA in the River; and

• the recent adoption of EPA Method 1631 Revision B makes it difficult for EPA to state withTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

69 c ertainty how many of the point sources identified in this TMDL actually discharge a net addition of mercury at levels exceeding 2.8 ng/l. Under these circumstances, waste characterization is a reasonable first step.



### 10.3. State and Federal Responsibility

EPA in tends to undertake the following responsibilities under this TMDL:

1. Review “major” NPDES permits and other identified “minor” NPDES permits for facilities located in the watershed of the segments of the Savannah River that are covered by this Phase 1 TMDL;

2. Take the lead on further characterization of air sources; and

3. Take the lead on revising the TMDL.

EPA expects Georgia to undertake the following responsibilities:

1. Identify the “major” NPDES facilities affected by this TMDL;

2. Identify other NPDES “minor” facilities affected by this TMDL which have the potential for a significant concentration of mercury in their effluent;

3. Modify the NPDES permits for the facilities identified in 1 and 2 above to reflect the conditions as
identified in Section 10.2 .;

4. Determine the frequency and duration of the mercury characterization to be undertaken by the facilities identified in 1 and 2 above;

5. Determine the due date and objectives for the mercury minimization plan to be developed by the
fac ilities in 1 and 2 above that are shown to be discharging mercury in excess of 2.8 nanograms/liter through the mercury characterization effort in 4 above;Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

70 6. Review the mercury minimization plans and determine the plan’s acceptability as identified in 5
abo ve;

7. Assure that mercury minimization plans are implemented as expeditiously as practicable; and

8. Adopt numeric water quality criteria for mercury for protection of public health in accordance with 40 C.F.R. §131.11(b).



## 11. Assumptions with Respect to Loadings f rom South Carolina

This TMDL reflects EPA’s assumption that concentrations of mercury in the South Carolina portion of the Savannah River will meet the applicable Georgia water quality standards at the South Carolina

- Georgia border. The water quality stan dard that applies to this TMDL is Georgia’s narrative water quality criterion for toxics, which provides that Georgia waters shall be free from toxic substances in amounts harmful to humans. EPA has interpreted that standard as 2.8 ng/l. As a technical m atter, meeting Georgia’s standard at the border is important because there is no hydrological difference between the South Carolina and Georgia portions of the Savannah River. Moreover, the fish travel freely across the border; they may be exposed to merc ury in South Carolina, but be consumed by individuals in Georgia. Therefore, an important assumption of this TMDL is that concentrations of mercury at the Georgia/South Carolina border will not exceed 2.8 ng/l.

EPA believes that this assumption is reaso nable because the TMDL already takes into account substantial
reductions from South Carolina air sources located within the Savannah River watershed and within a 100 km radius of the watershed. The TMDL’s gross load allocation to air sources also already accounts for emissions that EPA expects to remain from South Carolina air sources after application of air pollution controls. In addition, with respect to NPDES point sources in South Carolina, EPA believes that loadings
from South Carolina can meet Geor gia’s water quality standard as interpreted by EPA for mercury at theTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

71 border if South Carolina employs either of the two

- wasteload allocation approaches discussed above for Georgia NPDES point sources. This TMDL expressly assumes that limitations on South Carolina point sources that reflect either approach will meet the requirements of 40 C.F.R. § 122.4(d), which states that South Carolina may not issue an NPDES permit unless it includes conditions that ensure compliance with Georgia’s water quality standa rds. For a discussion of the bases for EPA’s assumption, see the Response
to Comments.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

72 

### 12. 

## Appendix A

Appendix

- A Savannah River Hg TMDL.PDFTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

73 Appendix B

–List of NPDES Facilities in Middle/Lower Sav annah Basin
Facility NPDES Permit # County A&M Products Inc. GA0036811 Jefferson Air Liquid America GA0046230 Chatham Albion Kaolin Company GA0002470 Richmond Atlantic Wood Ind. GA0047783 Chatham Augusta Butler Creek GA0037621 Richmond Budget Inn Sav

annah GA0034096 Chatham Central of Georgia R/R GA0002381 Chatham Citgo Asphalt Refining Co. GA0004332 Chatham Coastal Water & Sewer Co. GA02

- 234 Effingham Columbia Co. Crawford GA0031984 Columbia Columbia Co. Detention Center GA02

- 002 Columbia Columb ia Co. Health Dept. GA0049735 Columbia Columbia Co. Little River GA0047775 Columbia Columbia Co. Reed GA0031992 Columbia Crawford Eastside WPCP GA0033693 Oglethorpe CSR Aggregates Richmond GA0037231 Richmond Dearing LAS GA02

- 007 McDuffie DHR Gracewoo d Hospital GA0022161 Richmond DHR Gracewood Sch. WPCP GA0047279 Columbia DIT SRA#112/I

- 75 Visitor GA0033278 Chatham DIT Sylvania Welcome Stat GA0030287 Screven DOT Rest Areas #62 & #63 GA0047325 Columbia DSM Chemicals Augusta, Inc. GA0002160 Richmond E.M. Industries Inc. GA0034355 Chatham ECC International Wrens GA0048101 Jefferson Effingham Elem School GA0046990 Effingham Engelhard Corp Chatham GA0048330 Chatham Fort James Company GA0046973 Effingham GAF Corporation Savannah Plant GA0003841 Chat ham Garden City WPCP GA0031038 Chatham Georgia Pacific Corp. GA0047007 Chatham Georgia Pacific Gypsum GA0001961 Chatham Georgia Power Vogtle GA0026786 Burke Grovetown LAS GA02

- 222 Columbia Gulfstream Aerospace Corp GA0003255 Chatham Harlem WPCP GA00 20389 Columbia Hephzibah WPCP GA0049433 Richmond Hercules GA0026867 Chatham Herty Foundation Savannah GA0002402 Chatham Hiltonia LAS GA02

- 033 Screven Intermarine USA GA0003671 Chatham International Paper Co. GA0037711 Burke International Paper Co. GA0002801 Richmond Kemira GA0003646 Chatham King Division of Spartan Mills GA0004049 Richmond Martin Marietta Aggr. GA0002909 Richmond Martin Marietta Matl Inc GA0037346 ColumbiaTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

74 Olin Corporation Augusta GA0003719 Richmond PCS Nitrogen Fertilizer LP GA0002071 Richmond PCS Nitrogen Fertilizer LP GA0002356 Chatham Peridot Chemicals GA0002925 Richmond Pooler/Bloomingdale Req GA0047066 Chatham Richmond Co Spirit Cr. GA0047147 Richmond Rincon GA0046442 Effingham Sardis WPCP GA0020893 Burke Savannah Elec Effingham GA0003883 Effingham Savannah Elec Riverside GA0003751 Chatham Savannah Elec Wentworth GA0003816 Chatham Savannah Electric & Power Co GA0047708 Chatham Savannah President St GA0025348 Chatham Savannah Sugar Refinery GA0003611 Chatham Sa vannah Travis Field GA0020427 Chatham Savannah Wilshire/Windsor GA0020443 Chatham Savannah Yacht Club GA0033189 Chatham Solutia Inc GA0002178 Richmond South Carolina Electric GA0003786 Richmon Southern Aggregates Columbia GA0036790 Columbia Southern States Phosphorous & Fert GA0002437 Chatham Springfield GA0020770 Effingham Stone Container Corp GA0002798 Chatham Sylvania Yarns Systems Inc WQ

- IP

- 047 Screven Thermal Ceramics Inc GA0002488 Richmond Thiel Kaolin Hobbs GA0032981 Warrant Tybee Island GA0020061 Chatham Union Camp Corporation GA0001988 Chatham USA Ft. Gordon GA0003484 Richmond USA Hunter AFB STP GA0027588 Chatham Waynesboro WPCP GA0020231 Burke Wrens WPCP GA0021857 JeffersonTotal Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

75 

## 13. References

Ambrose Jr R.B., Wool, T.A., and Martin J.L . (1993) WASP%, A Hydrodynamic and Water Quality Model

–

Model Theory, User’s Manual, and Programmer’s Guide

. U.S. Environmental Protection Agency. Environmental Research Laboratory, Athens, Georgia. EPA/600/3

- 87/039. Balogh, S. and L. Liang. 1995. Mer cury pathways in municipal wastewater treatment plants. Water Air and Soil Pollution 80: 1181

- 1190. Bodaly, R.A., J.W.M. Rudd, and R.J. Flett. 1998. Effect of urban sewage treatment on total and methyl mercury concentrations in effluents. Biogeochemistr y 40: 279

- 291. Dvonch, J.T., J.R. Graney, G.J. Keeler, and R.K. Stevens. 1999. Use of Elemental Tracers to Source Apportion Mercury in South Florida Precipitation. Environ. Sci.Technol. 1999, 33 , 4522

- 4527. Georgia Department of Natural Resources. 2000. Guidelines for Eating Fish from Georgia Waters. Mugan, T. J.. 1996. Quantification of total mercury discharges from publicly owned treatment works to Wisconsin surface waters. Water Environment Research 68(2): 229

- 234.
Tsiros, I.X. and Ambrose, R.B., 1998. Environmental Screening Modeling of Mercury in the Upper Everglades of South Florida. Journal of Environmental Science and Health, A33(4), 497

- 525. USEPA. 1997. Capsule Report. Aqueous Mercury Treatment. EPA/625/R

- 97/004

USEPA. 2000. EPA’s 200 0 Revisions to the Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health (65 FR 66444

- 66482) (11/3/200) USEPA. Office of Research and Development. Technology Transfer. Washington, DC. USEPA. 1997. Mercury Study Repor t to Congress. EPA

- 452/R

- 97

- 003. Office of Air Quality, Planning and Standards. Office of Research and Development. Washington, DC. USEPA. 1998. Better Assessment Science Integrating Point and Nonpoint Sources, BASINS, Version 2.0 User’ s Manua l. U.S. Envi ronmental Protection Agency, Office of Water, Washington, D.C.

USEPA. 1986. Quality Criteria for Water 1986. U.S. Environmental Protection Agency, Office of Water, Washington, D.C.Total Maximum Daily Load for Total Mercury in the Middle/Lower Savannah River, GA February 28, 2001

76 USEPA. Region 4. 2000. Savannah River Mercury TMDL Data Report. U.S. Env ironmental Protection Agency, Region 4, Atlanta, Georgia. USEPA. Region 4. 2001. Watershed Characterization System

–User’s Manual. U.S. Environmental Protection Agency, Region 4, Atlanta, Georgia. USEPA, 2000. Water Quality Criteria for Protection of Human Health: Methylmercury, USEPA. 1999. Method 1631. Mercury in water by oxidation, purge and trap, and cold vapor atomic fluorescence spectrometry. USEPA, Office of Water, Office of Science and Technology, Washington, D.C. USEPA, 2001. Consumptio n Advisory: Advice for Women & children on Non

- commercial Fish Caught by Family and Friends. USEPA. 1996. Method 1669. Sampling ambient water for trace metals at EPA water quality criteria levels. USEPA, Office of Water, Washington, D.C.

USEPA. 1998. Method 1630. Methyl mercury in water by distillation, aqueous methylation, purge and trap, and cold vapor atomic fluorescence spectrometry. USEPA, Office of Water, Office of Science and Technology, Washington, D.C Western Lake Superior Sanitary District. Blueprint for Mercury Elimination. World Wide Web URL: http://www.wlssd.duluth.mn.us. Accessed on 2001 February 12.