U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division
De Sale Restoration Area, Slippery Rock Watershed, PA
PA Voluntary Cleanup

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AMD Damage
Restored Conditions

Cleanup Objectives: Treat acid mine drainage (AMD) from abandoned surface and underground coal mines in western Pennsylvania

Green Remediation Strategy: Employ a sequential series of natural gradient-driven engineering steps involving settling ponds, vertical-flow ponds, and constructed wetlands to passively treat AMD

  • Uses a 16- by 3-foot instream dam to collect contaminated stream water
  • Diverts collected water to an 80,000-square-foot forebay to settle solids and debris
  • Passes the partially settled water into parallel, flushable vertical-flow ponds constructed of limestone and spent mushroom compost to neutralize acidity, raise pH, and remove metals
  • Transfers water next to a horizontal 0.2-acre, 5-foot-deep pond for additional settling
  • Passes settled water to a 1.5-acre free-flowing, aerobic constructed wetland for precipitation of amorphous iron hydroxides
  • Transfers the wetland water to a horizontal-flow limestone bed to remove and recover manganese and provide additional alkalinity
  • Returns treated water to a rock-lined channel emptying into the watercourse approximately 1,000 feet downgradient of the intake point


  • Uses natural intrinsic energy for operation of the multi-step treatment process
  • Avoids air emissions associated with consumption of grid electricity during water treatment
  • Uses passive-energy biological processes for treatment "finishing steps"
  • Returns treated water to its natural hydraulic course
  • Obtained limestone aggregate from a quarry three miles away, at a material and delivery cost of $12 per ton
  • Obtained spent mushroom compost from an agricultural producer 12 miles away, at a material and delivery cost of $10 per cubic yard
  • Completed construction of the treatment system within six weeks, with help from local volunteers, academic students, and mining companies and coordination by the (non-profit) Slippery Rock Watershed Coalition
  • Neutralizes approximately 180 pounds of acid discharge each day
  • Achieves 100% neutralization of the acid discharge and 99%, 99%, and 70% reductions of iron, aluminum, and manganese concentrations, respectively , as compared to intake levels
  • Recovered 30 tons of material (containing approximately 25% manganese oxide) over eight years of operation
  • Derives funds for future AMD treatment systems through sale of recovered manganese and iron oxides to artists or manufacturers specializing in green products

Property End Use: Natural resource conservation area under state programs

Point of Contact: Scott Roberts, PA Department of Environmental Protection

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