MEMORANDUM 

TO: Bill Swietlik, EPA 

FROM: Joanna Kind, ERG 

DATE: April 19, 2013 

SUBJECT: Literature Review – Impacts of Coal Pile Runoff and Leachate (DCN 

SE02153) 

1.0 INTRODUCTION

 ERG is providing technical support to the U.S. Environmental Protection Agency (EPA) 

for development of revised effluent limitations guidelines and standards (effluent guidelines) for 

the Steam Electric Power Generating Industry. In support of the development of revised effluent 

guidelines, ERG conducted a literature review regarding the environmental impact of identified 

pollutants of concern. As part of this review, ERG examined the pollutants contained in coal pile 

runoff and coal pile leachate, as well as the impacts on flora, fauna, and ground water from these 

waste streams. 

Approximately 50 percent of facilities in the steam electric industry are coal-fired plants. 

At these plants, the coal is unloaded from trains, barges, and/or trucks in a designated area and 

conveyed to an outdoor storage area, referred to as the coal pile. Power plants generally store 

between 25 and 40 days worth of coal in the coal pile, which can amount to over 500,000 tons of 

coal being stored at the plant. 

As rainwater and melting snow comes in direct contact with coal piles, constituents that 

are native to coal are transferred to the water. Wastewater originating from coal piles can reach 

nearby water resources in two ways: 1) seeping from coal piles and traveling along the surface of 

the ground prior to reaching surface waters (known as coal pile runoff); and 2) flowing through 

the coal pile and directly entering the groundwater system (known as coal pile leachate). The 

quantity of coal pile runoff and leachate depends upon the amount of precipitation, the physical 

location and layout of the coal pile, and the extent to which water infiltrates the ground 

underneath the coal pile. Coal pile runoff is usually collected in a runoff pond during or 

immediately after times of rainfall. 

 This memo highlights the literature ERG identified related to coal pile runoff and 

leachate and compares concentrations of constituents in coal pile runoff found in the studies with 

EPA’s National Recommended Water Quality Criteria (NRWQC) values1

. This memo also 

 

1

 NRWQC values are set by EPA under Section 304(a) of the Clean Water Act (CWA). EPA developed these criteria to protect 

aquatic life and human health. Organism populations or humans exposed to a pollutant concentration exceeding its criteria are at 

an increased risk for health effects (U.S. EPA, 2009). 
Memorandum 

April 19, 2013 

Page 2 

discusses environmental impacts on groundwater from coal pile runoff and leachate. 

Documented environmental effects include reductions in macroinvertebrate and bacterial density, 

vegetation kills, and toxicity to fish (Brofft et al., 2002; Carlson and Carlson, 1994; Swift, 1985; 

Tan and Coler, 1986). 

 

2.0 POLLUTANTS IN COAL PILE RUNOFF AND LEACHATE

An important component in assessing coal pile runoff and leachate impacts on surface 

water and groundwater is identifying the associated pollutants and their concentrations. Table 

2-1 lists typical pollutants and their concentration ranges in coal pile runoff based on a field 

study at 11 plants (U.S. EPA, 1974). Table 2-1 also includes EPA’s NRWQC for each available 

species to provide context for the concentrations observed in coal pile runoff. 

As a general note regarding the pollutant concentrations observed in EPA’s 1974 study, 

and as other investigators have pointed out (Davis and Boegly, 1981), the results have limitations 

but are still useful for comparative purposes. The magnitude of the concentration ranges reported 

demonstrate that coal pile runoff has the potential to exceed NRWQC and pose a threat to 

aquatic environments. 
Memorandum 

April 19, 2013 

Page 3 

Table 2-1. Common Pollutants and Concentrations in Coal Pile Runoff 

Pollutant 

Range of 

Concentrations 

Measured in 

Coal Pile 

Runoff (mg/L) 

National Recommended 

Water Quality Criteria Values (mg/L) 

Freshwater Saltwater 

Human Health for the 

Consumption of: 

Acute Chronic Acute Chronic 

Water + 

Organism 

Organism 

Only 

Aluminum 825–1,200 0.75 a 0.087 a — — — — 

Ammonia 0.35–1.77 b b c c — —

Chloride 3.6–481 860 230 — — — —

Copper 1.6–3.4 d d 0.0048 e 0.0031 e 1.3 —

Iron 0.06–93,000 — 1 — — 0.3 —

Magnesium 89–174 — — — — — —

Nitrate 0.3–2.25 — — — — 10 —

Phosphorus 0.23–1.2 — — — 0.0001 — —

Sodium 160–1,260 — — — — — —

Sulfate 133–21,920 — — — — — —

Zinc 0.006–23 0.12 e 0.12 e 0.09 e 0.081 e 7.4 26 

pH (standard 

units) 

2.1–7.8 — 6.5–9 — 6.5–8.5 5–9 —

Source: U.S. EPA, 1974. 

Note: EPA’s 1974 study did not test for metals of most interest to the current rulemaking (e.g., arsenic, mercury, 

selenium). Two non-detect values were reported for ammonia. All other pollutants were detected in all samples. 

Blanks indicate that NRWQC values are not available, or require known water pH and temperature to be calculated. 

mg/L – Milligrams per liter. The study did not specify the form of each metal (total or dissolved). 

a – Total recoverable (pH 6.5 – 9.0). 

b – Freshwater criteria are pH, temperature, and lifestage dependent. 

c – Saltwater criteria are pH and temperature dependent. 

d – Freshwater criteria calculated using the Biotic Ligand Model (BLM). 

e – Dissolved. 

3.0 IMPACTS OF COAL PILE RUNOFF ON FLORA AND FAUNA

Two studies at the Savannah River Site, a Department of Energy (DOE) site, in South 

Carolina, which received discharges from the D-Area power plant, described the observed 

impacts of coal pile runoff on flora. A 1994 study described a coal reject pile (i.e., coal that 

cannot be crushed by the mill and therefore cannot be burned in the boiler) that was covered by a 

layer of soil and repeatedly became exposed during heavy rainfall events, causing coal pile 

runoff. In a wide band surrounding the direction of the coal pile runoff flow, trees and understory 

vegetation either died or exhibited severe sublethal stress. A separate band of vegetative stress 

observed at the site did not align with the flow of coal pile runoff, but instead followed the flow 

of groundwater. In a study conducted at the site, analysis of the water available to root systems 

determined that the water was highly acidic and saline, and contained elevated concentrations of 

aluminum and manganese, both found in coal (Carlson and Carlson, 1994). In a similar study 

conducted at the Savannah River Site in 2002, bacteria samples taken from sediments at varying 
Memorandum 

April 19, 2013 

Page 4 

depths and in different proximities to coal pile runoff flows indicated that exposure to coal pile 

runoff greatly reduced the diversity of bacteria species (Brofft et al., 2002). 

Documented sources have also shown that coal pile runoff can create surface water 

conditions that are toxic to fish and macroinvertebrates. Taylor Brook in western Massachusetts 

receives coal pile runoff directly from a 50,000-ton coal pile. Minnows in the brook exhibited 

disrupted metabolisms and juvenile mortality. Based on a profile of the coal pile runoff water 

chemistry, the authors determined that aluminum, iron, and manganese were the pollutants most 

likely contributing to the adverse effects to fish. The authors conducted laboratory tests that 

replicated stream conditions, from which they concluded that the poor health of fish was 

primarily a function of the elevated aluminum concentrations (Tan and Coler, 1986). The effect 

of coal pile runoff on macroinvertebrates was studied at Georges Creek in Maryland. At 

sampling sites immediately downstream of the coal pile runoff discharge, macroinvertebrate 

densities were very low relative to sample sites upstream of the discharge. Adversely affected 

areas of Georges Creek were found to be acidic and had elevated concentrations of manganese, 

aluminum, zinc, iron, and sulfate (Swift, 1985). 

4.0 IMPACTS OF COAL PILE RUNOFF AND LEACHATE ON GROUNDWATER

Groundwater is stored in aquifers, which are underground rock formations composed of 

materials such as sand, soil, or gravel that supply groundwater to wells and springs which, in 

turn, are often used as a direct source of drinking water. Groundwater and drinking water 

supplies can be degraded by the pollutants present in coal pile runoff and leachate (Cross, 1981). 

The extent to which pollutants from coal piles reach underground aquifers depends on the 

location of the aquifer relative to the coal pile, the nature of intervening geologic formations, and 

the porosity of the soil (Cross, 1981). Coal pile leachate can create groundwater conditions that 

make the water unsafe for humans to drink (Cook and Fritz, 2002). Studies of groundwater 

contaminated by coal pile runoff or coal pile leachate have found lead in concentrations that 

exceed state maximum contaminant levels (MCLs), as well as elevated sulfate, iron, aluminum, 

chromium, and nickel concentrations (Anderson, 1990; Cook and Fritz, 2002; Washburn, 1998). 

Cook and Fritz (2002) measured the lead concentration of a contaminated groundwater site to be 

62 μg/L, which exceeded the state of Indiana MCL of 15 μg/L. Washburn (1998) reported the 

following trace metal concentrations in the groundwater at a contaminated site: 

 Aluminum: 301 mg/L; 

 Chromium: 0.182 mg/L; 

 Iron: 216 mg/L; 

 Nickel: 1.66 mg/L; and 

 Sulfate: 8,430 mg/L. 
Memorandum 

April 19, 2013 

Page 5 

5.0 REFERENCES

Anderson, M.A., 1990. A Hydrogeochemical Investigation of Metalliferous Coal Pile Runoff and 

its Interaction with Soil and Groundwater. Dissertation. 

Brofft, J.E., J.V. McArthur, and L.J. Shimkets, 2002. Recovery of Novel Bacterial Diversity 

from a Forested Wetland Impacted by Reject Coal. Environmental Microbiology, 4 (11): 764-

769. 

Carlson, C.L. and C.A. Carlson, 1994. Impacts of Coal Pile Leachate on a Forested Wetland in 

South Carolina. Water, Air, and Soil Pollution. 72: 89-109. 

Cook, A.M., and S.J. Fritz, 2002. Environmental Impacts of Acid Leachate Derived from CoalStorage Piles upon Groundwater. Water, Air, & Soil Pollution, 135 (1-4): 371-388. 

Cross, F.L., 1981.Coal Pile Environmental Impact Problems. Pollution Engineering. 13(7): 35-

37. DCN SE01881. 

Davis, E.C. and W.J. Boegly, Jr., 1981. A Review of Water Quality Issues Associated with Coal 

Storage. Journal of Environmental Quality, 10:127-133. 

Swift, M.C., 1985. Effects of Coal Pile Runoff on Stream Quality and Macroinvertebrate 

Communities. Journal of the American Water Resources Association, 21 (3): 449-457. 

Tan, B. and R.A. Coler, 1986. Effects of Coal Pile Leachate on Taylor Brook in Western 

Massachusetts. Environmental Toxicology and Chemistry. 5: 897-903. 

U.S. EPA, 1974. Development Document for Effluent Limitations Guidelines and New Source 

Performance Standards for the Steam Electric Power Generating Point Source Category. 

Washington, D.C. (October). 

U.S. EPA. 2009. National Recommended Water Quality Criteria. Washington, DC. DCN 

SE01908. 

Washburn, F.A., 1998. D-Area Coal Pile Runoff Basin Groundwater Treatability Study 

Preliminary Report. September.