Watershed Restoration & Abandoned Mine Drainage
Abandoned/Acid Mine Drainage
Abandoned or acid mine drainage (AMD) is a significant consequence of pre-regulatory mining. If you see a stream with orange waters or banks lined with orange scum, the likely culprit is AMD. Typically, AMD appears at or around areas where there have been mining operations. When the mines were active, water that seeped underground was either pumped to the surface, or allowed to exit via a gravity-based system. When the mines closed, however, water filled the voids, creating vast underground pools of contaminated water. Continuously replenished by rain, snowmelt, and runoff, these pools produce immense water pressure. Drainage outlets and seeps provide some outlet, although occasionally flooding and blowouts result. One solution is the construction of a borehole: a vertical shaft is drilled into a mine to allow water to drain. Unfortunately, while this does relieve pressure, exiting water is often diverted into nearby streams. Consequently, boreholes are a chief contributor to the AMD problem.
Indirectly, culm banks and mine-scarred sites also emit AMD. When rain or snowmelt seeps through the piles, the runoff – laden with metals and other contaminants – makes its way into the ground and nearby waterways. Banks also block creeks and streams, diverting their waters underground into the mine pools, and thus leaving sections of the stream channel dry and the water recharged with the AMD chemicals.
AMD and Its Effects
In Pennsylvania, nearly 5,000 miles of waterways are impacted by AMD, many of which are in northeastern Pennsylvania. AMD forms through the interaction of certain minerals found in mine waste – specifically, pyrite – with oxygen and water. When the three combine, sulfuric acid and dissolved iron result. Whether through direct release from seeps or boreholes, or through runoff through the culm banks, the acid produced far exceeds what can be processed naturally by local waterways. As a result, the metals in the discharge drop out suspension, coating streambeds, banks, and detritus with an orange or yellow-orange coating. Sulfur compounds add the smell of rotten eggs to the sludge.
The presence of AMD makes affected waters more than impotable; in truth, it impacts the entire ecology of an area’s ecosystem. Metals concentrations are elevated, and pH levels are lowered. Both can seriously impair water quality. First, the chemical levels of AMD-impacted streams are simply inhospitable to many plants and animals. Secondly, the slime creates an unsuitable habitat for many invertebrates, which rely on the streambed for food, shelter, and reproduction. AMD can also hinder the photosynthesis process in plants, as well as clog the gill structures of a variety of organisms, impeding respiration. Finally, as smaller organisms decline, so too will higher-level species, which depend on them for food. In this way, AMD can have dramatic effects on stream ecology, in sections rendering waterways biologically dead.
Pollution to Solution
Addressing areas affected by AMD is a priority for Earth Conservancy. As with reclamation, improvement to local waterways cannot occur without intervention. Education is a crucial step. Often, residents have grown accustomed to orange waterways, either ignoring them or believing little can be done. Part of EC’s mission is to increase awareness about the damage abandoned mine lands do to the region, as well as the solutions that do exist.
The second step is action. AMD can be mitigated. Currently, many agencies, organizations, and private individuals are working to reduce the effects of AMD. Visit our Links page to discover others working towards this goal. Information about EC’s water and watershed restoration projects is available through the Abandoned Mine Drainage sub-menu.