OPERATION AND MAINTENANCE CONSIDERATIONS FOR A PASSIVE TREATMENT COMPLE

Passive systems require no electricity and use environmentally-friendly materials such as limestone aggregate and spent mushroom compost to provide a costeffective alternative to conventional chemical treatment of mine drainage. Although requiring significantly lower maintenance compared to conventional systems, passive treatment is not a no-maintenance solution. Between 1999 and 2001, a 6-component (Phase I) and a 22-component (Phase II) passive complex were installed at the Harbison Walker Restoration Area (Ohiopyle State Park, Fayette County, PA) to treat numerous mine discharges associated with an old surface clay and coal mine. In combination, the two facilities are treating over 227 million liters (60 million gallons) of severely degraded mine drainage per year, neutralizing ~227 kg/day (~500 lbs/day) of acidity and preventing over 45 kg/day (100 lbs/day) of metals from entering a High Quality Cold Water Fishery. Because of the significant benefit to the stream, development and implementation of an Operation and Maintenance Plan was imperative to insure long-term, consistent, functioning of this facility. To date, periodic site inspections and monitoring have identified the need for flushing of solids from the treatment media, for revegetation of selected areas, for replacement of damaged pipes, and for removal of debris from spillways and ditches. Water monitoring, an integral part of the O & M Plan, has enabled documentation of the individual and combined effectiveness of each component and advancement of passive treatment technology.