Mining Operations as Nonpoint Source Pollution

Mining operations contribute significantly to the acidification problem in the mid-Atlantic region.

Mountaintop Mining

Acidification is caused by:

• abandoned mine drainage - which results from water flowing over or through abandoned mines, and by
• acid air deposition - primarily from the burning of fossil fuel; this produces acid rain

Acidification contaminates the air and water with chemical compounds that either develop acids or deposit metals. The mid-Atlantic area experiences the lowest annual average rainfall pH, is second in the world in acid rain, and has had the heaviest anthracite and bituminous coal mining (highest in sulfur dioxide or SO₂) in the eastern U.S. More than 5,150 stream miles have been contaminated, causing the loss of aquatic life and restricting stream use for recreation, public drinking water and industrial water supplies.

About 4,785 miles of streams with low pH in the mid-Atlantic region have been impacted by extraction of resources, primarily coal. West Virginia and Pennsylvania each have about 2,200 stream miles impacted. Maryland and Virginia have less than 400 impacted miles. And, about 350 stream miles are impacted by air deposition, primarily in West Virginia and Pennsylvania.

The Clean Water Act's Section 303(d) list identifies the stream segments in a watershed which exceed a state water quality limit for one or more constituents. Resources extraction is the leading cause of stream segments being on the the Section 303(d) list in Pennsylvania and West Virginia. The Office of Surface Mining (OSM) has identified more than 500 abandoned mining sites in the region. The majority of the sites are found in western Pennsylvania, north central and southwest West Virginia, and the extreme southwestern Virginia. The OSM estimated that at least $3.8 billion would be needed to remedy all of the known acid mine drainage sites within the region.

EPA is identifying sensitive ecosystems, looking at options to reduce acid emissions, and monitoring environmental indicators which track environmental improvements. Improving a waterbody often takes the efforts of government agencies, watershed groups, businesses, students, and other partners, all working together. The estimated time seems to be from 6 to 11 years to restore a stream from a "dead" stream to a fully functional recreational fishery. Initially, the species least sensitive to the pollution come back. Finally, the most sensitive species.

Acid air deposition results from either:

• dry deposition (gases and dry particles) or
• acid precipitation (acid rain) from sulfur dioxide (SO₂) and nitrogen oxides (NO_x)

Atmospheric SO₂ and NO_x come from burning fossil fuels, mainly coal and petroleum, at both stationary and mobile sources. These pollutants mix with water vapor, forming sulfuric and nitric acids that affect ecosystems, visibility, materials and human health. Excessive amounts of atmospheric nitrogen can adversely affect aquatic biology by producing algal blooms that block the sunlight needed by submerged aquatic vegetation. Decomposing algae deplete oxygen needed by invertebrates, an integral part of the food chain. In the Chesapeake Bay, depleted oxygen has adversely impacted the fish and shellfish industry. The Bay also is the prime breeding area for much of the marine commercial and sport fishing in the mid-Atlantic region. Research indicates that there might be limited recovery in some sensitive systems because NOx reductions under the current acid rain program may not be sufficient in some areas to improve the status of acidified surface waters.

EPA's Clean Air Mapping and Analysis Program (C-MAP) is a geographic information system assessment tool being used to better understand and characterize the benefits of national and regional pollutant emission reduction programs like the acid rain program.

There are three issues with abandoned mines that impact water quality in the mid-Atlantic region:

• acid mine drainage (the most prevalent)
• alkaline mine drainage
• metal mine drainage

The mid-Atlantic Total Maximum Daily Load (TMDL) program, which defines the amount of a pollutant that a waterbody can receive and still meet water quality standards, has completed hundreds of TMDLs for stream segments impacted by mine drainage. The Mid Atlantic Region provides funding through Section 319 grants to assist in cleanup efforts.

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Acid Mine Drainage

Acid mine drainage is water contaminated when pyrite, an iron sulfide, is exposed and reacts with air and water to form sulfuric acid and dissolved iron. Some or all of this iron can precipitate to form the red, orange, or yellow sediments in the bottom of streams containing mine drainage. The acid runoff further dissolves heavy metals such as copper, lead, mercury into ground or surface water. The rate and degree by which acid mine drainage proceeds can be increased by the action of certain bacteria.

There are a number of major environmental problems caused by acid mine drainage. It disrupts growth and reproduction of aquatic plants and animals, diminishes valued recreational fish species, degrades outdoor recreation and tourism, contaminates surface and groundwater drinking supplies, and causes acid corrosion of infrastructure like wastewater pipes.

Over 95% of the acid problem is located in western Pennsylvania, almost all of West Virginia, southwestern Virginia, and far western Maryland. The northern Appalachian coal fields (bituminous or soft coal) extend from northwestern Pennsylvania, south of the New York state line and west of the Susquehanna River, through western Pennsylvania and southeastern Ohio, and through most of West Virginia and into western Maryland and southwestern Virginia, eastern Kentucky, and northeastern Tennessee. Runoff water, polluted by acid, iron, sulfur and aluminum, has often drained away from the mines and into streams. Mine drainage is particularly heavy in the western and, to a lesser extent northeastern, Pennsylvania, and northern and south central West Virginia. Northeastern Pennsylvania is largely anthracite coal.

Alkaline Mine Drainage

The drainage from some mines is alkaline with high levels of metals. Generally, the rock that produces alkaline drainage has calcite and/or dolomite present.

Metal Mine Drainage

The mid-Atlantic region has a number of abandoned metal mines, some from the era of the Civil War. These mines produced lead, gold, and other metals. Drainage from these mines can contain high levels of these metals.

Two methods can treat water to eliminate or reduce contamination by acidity and heavy metals.  The active treatment method uses alkaline chemicals to neutralize acid-polluted waters . However, the chemicals are expensive and the treatment facility is expensive to construct and operate. The passive treatment method uses a treatment system that employs naturally occurring chemical and biological reactions to minimize acid mine drainage with little maintenance.

Active Treatment

Limestone (calcium carbonate)

Limestone with the highest calcium content is preferred. The advantages of using limestone include low cost, ease of use, and formation of a dense, easily handled sludge. The disadvantages include slow reaction time, loss in efficiency of the system because of coating of the limestone particles with iron precipitates, difficulty in treating acid mine drainage with a high ferrous-ferric ratio, and ineffectiveness in removing manganese.

Hydrated Lime (calcium hydroxide)

The coal mining industry uses hydrated lime as the preferred neutralizing agent because it is easy and safe to use, effective, and relatively inexpensive. The major disadvantages are the voluminous sludge that is produced (when compared to limestone) and high initial costs incurred because of the size of the treatment plant.

Soda Ash (sodium carbonate)

Soda ash briquettes are effective for treating small acid mine drainage flows in remote areas. Major disadvantages are higher reagent cost (relative to limestone) and poor settling properties of the sludge.

Caustic Soda (sodium hydroxide)

Caustic soda is especially effective for treating low flows in remote locations and for treating acid mine drainage having a high manganese content. Major disadvantages are its high cost, dangers involved with handling the chemical, poor sludge properties, and freezing problems in cold weather.

Ammonia

Anhydrous ammonia effectively treats acid mine drainage having a high ferrous iron and/or manganese content. Ammonia costs less than caustic soda and has many of the same advantages. However, ammonia is difficult and dangerous to use, and can affect biological conditions downstream from the mining operation. The possible off-site impacts are toxicity to fish and other aquatic life forms, eutrophication and nitrification. Fish species generally have low tolerance to un-ionized ammonia and toxicity levels can be affected by pH, temperature, dissolved oxygen and other factors. Ammonia use is not allowed in all states and, where permitted, additional monitoring is required.

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Passive treatment method uses a treatment system that employs naturally occurring chemical and biological reactions to minimize acid mine drainage with little maintenance.

Passive Treatment

Constructed Wetlands

Wetlands are passive systems, a relatively new treatment technology. Constructed wetlands use soil-borne and water-borne microbes associated with wetland plants to remove dissolved metals from mine drainage. Wetlands are generally more effective in removing iron than manganese. Wetlands are most useful in the treatment of small flows of a few gallons per minute. Initial design and construction costs may exceed tens of thousands of dollars. Optimum sizing and configuration criteria are still under study. Seasonal variations in metal removal efficiency have been noted, with lesser amounts removed in cold weather.

Open Limestone Channels/Anoxic Limestone Drains

This simply constructed passive treatment method uses open ditches filled with limestone (anoxic drains are covered). The dissolution of limestone adds alkalinity and raises pH, but a coating of limestone by iron and aluminum precipitates affects the performance of this treatment method.

Diversion Wells

Acidic water is diverted to a well containing crushed limestone. Iron precipitate coating is prevented by the turbulence of the flow through the well. The system works well, but needs periodic replenishment of limestone.