Evaluation of Natural Amelioration of Acidic Deep Mine Discharges for Watershed RestorationEPA Grant Number: R825794
Title: Evaluation of Natural Amelioration of Acidic Deep Mine Discharges for Watershed Restoration
Investigators: Dzombak, David A. , Aljoe, William W.
Current Investigators: Dzombak, David A.
Institution: Carnegie Mellon University
EPA Project Officer: Hahn, Intaek
Project Period: June 1, 1998 through May 31, 2001 (Extended to September 30, 2001)
Project Amount: $610,484
RFA: Ecosystem Restoration (1997) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Hazardous Waste/Remediation , Land and Waste Management , Ecosystems
Acid mine drainage (AMD) from abandoned underground coal mines has caused substantial, cumulative damage to aquatic ecosystems throughout Appalachia and in some other areas of the U.S. for the duration of this century. For example, mine drainage long has been the most significant source of water quality degradation in Pennsylvania, resulting in pollution of at least 2,417 miles of streams. The chemistry of contaminated mine discharges varies from highly acidic, low pH waters which are contaminated with Fe, Al, Mn, and SO4, to alkaline, circumneutral waters which have Fe and Mn as the primary contaminants. This variation affects the method and cost of water treatment. Highly acidic waters require controlled physical-chemical treatment techniques that are expensive. Marginally acidic waters can often be treated with passive techniques such as anoxic limestone drains and compost wetlands at a lower cost. Alkaline mine waters can be treated with passive techniques such as settling ponds and aerobic wetlands at a cost that is usually attractive to reclamation organizations.
In some areas where deep mines were abandoned many years ago and AMD impacts on water quality have existed for a long time, significant changes in the chemistry of some mine pools and discharges have been observed over time. For example, in several areas of western Pennsylvania, deep mine discharges that were reliably described as highly acidic in the 1960s and 1970s are now alkaline. Because of the natural amelioration of water quality at these sites, low-cost passive treatment techniques are now feasible where, 20 years ago, the only water treatment option was expensive physical-chemical treatment. However, not all abandoned mine pools undergo, in a 20 year period, a natural amelioration of water quality
This project will investigate the hydrologic and geochemical factors responsible for temporal improvements in mine water quality through study of approximately 30 mine discharges associated with a particular mine pool in Western Pennsylvania: that associated with the Uniontown-Connellsville syncline. Almost all the deep-minable coal was removed from this basin prior to 1970, and an extensive study of mine pool discharges in this basin was conducted in 1974-75 in conjunction with Pennsylvania's Operation Scarlift.
The degree of mine water quality improvement over the 23-25 years since the 1974-75 study will be assessed, and hydrogeologic and geochemical factors responsible for water quality changes will be investigated. This will represent the first systematic attempt to document natural amelioration of coal mine drainage water quality across an entire mine pool and a period of 20+ years.
Improved understanding of mechanisms responsible for natural amelioration of AMD will improve our ability to predict long-term changes in mine water chemistry, and will thus enable development of innovative restoration strategies that focus on accelerating the natural, in-mine processes that improve water quality over time. The study will also provide an opportunity to explore through long-term field data the effects of mine flooding, hydrogeology, overburden geochemistry, and mining methods on mine water quality. The project will be conducted in collaboration with the Pennsylvania Department of Environmental Protection, and with the assistance of Mr. William Aljoe, an AMD expert formerly with the U.S. Bureau of Mines.