Employing Passive Treatment for Abandoned Mine Drainage

“Pennsylvania has documented in the current 303(d) list of impaired waters that there are 4,036 miles of surface waters impaired from abandoned mine drainage sources, 3,876 miles from agriculture, and 1,753 miles from urban runoff/storm sewers.” — PA Department of Environmental Protection, Bureau of Watershed Management, Division of Watershed Protection

Pennsylvania has a 200-year history of coal mining, producing more than 25 percent of the nation’s total coal output and presently ranking fourth in the nation in annual coal production by state. The state’s relationship with this fossil energy source began in support of the iron industry, and then shifted to sustain expanding steel mills in the late 1800’s, and saw bolstered production through two World Wars. Today, more than half of the Commonwealth’s electricity is provided by coal. As the industry expanded, the local mine often assumed the name of the owner or a nearby train stop associated with the mine. Names such as Edna No.2, Standard Shaft and Jane Mine Station still dot the region and refer to the names of coal mines around which the communities grew.
Today, many of those communities are known as the source of large flows of polluted water from the abandoned underground mines. Abandoned mine drainage or ”AMD,” degrades both habitat and water quality, often producing an environment devoid of most aquatic life and unfit for desired uses.

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According to the Pennsylvania Department of Environmental Protection (DEP), drainage from thousands of abandoned coal mines has contaminated more than 4,000 miles of streams and associated ground waters in Pennsylvania and is the most extensive water-pollution problem affecting Pennsylvania’s major river basins. Because coal-mine drainage can contain toxic concentrations of acidity, metals, and sediment, many of the distinctively orange-colored rivers are nearly “dead” or severely impaired compared to a stream’s natural state. Degradation can leave streams with little or no plant or animal life, undrinkable, and a threat to the health, safety and general welfare of neighboring communities. Presently, the estimated cost for restoring Pennsylvania’s damaged watersheds ranges from $5 billion to $15 billion.

Historically, mine drainage would have been treated using chemicals, or by building and maintaining a treatment plant to neutralize acid and remove high levels of metals present in the water. In the past 15 years, a more natural “passive” treatment has been developed which has served many grassroots watershed groups well and at significantly less overall cost.

The concept behind passive treatment is to allow the naturally occurring chemical and biological reactions that aid in AMD treatment to occur in the controlled environment of the treatment system, and not in the receiving water body.

Limestone has proven to be the material of choice in neutralizing acid. Metals are removed by aerating the water after which the metals are allowed to settle out in ponds. Finally, the water is passed through wetlands, where the roots of plants act as a filtering media as the water flows past them.

Passive treatment conceptually offers many advantages over conventional active treatment systems. The use of chemical additives and energy consuming treatment processes are virtually eliminated with passive treatment systems. Also, the operation and maintenance requirements of passive systems are considerably less than active treatment systems. However, it should be noted that not all AMD problems are economically treatable using passive means and chemical treatment systems are often employed in certain situations.
WPC’s Freshwater Conservation Program works directly with grassroots watershed organizations to clean-up AMD impacted streams left behind by abandoned mining operations. The Program has helped groups install several AMD treatment systems and has assisted with the assessment of several hundred miles of impacted waterways. For more information, please contact Mark Killar, watershed manager, Freshwater Conservation, at 724-459-0953 (ext. 101) or e-mail Mark at mkillar@paconserve.org.