Montour Run Watershed Association

North Fork Project

Under MRWA sponsorship, a new facility was installed to treat acidic, metal-bearing drainage from an abandoned underground coal mine on property at the Pittsburgh International Airport, adjacent to the Findlay Connector in Findlay Township, Allegheny County. The system is preventing about 16 tons (32,300 lbs) of acid and more than 16 tons (32,000 lbs) of iron compounds annually from entering the North Fork of Montour Run. Prime subcontractor was BioMost, Inc. The $674,281 total project cost was funded with $337,367 from the DEP’s Growing Greener program and $100,000 from OSM's Watershed Cooperative Agreement Program. In addition, in-kind services valued at $189,120 were provided by the PA Turnpike Commission in conjunction with the building of the Southern Beltway's Findlay Connector. Also, matching cash, goods, and services valued at $47,794 have been provided by BioMost and its partners.

Tasks that were entailed included design, permitting, erosion and sedimentation controls, clearing, access road construction, dewatering, grading, and revegetation of the restoration site, which is situated at the Pittsburgh International Airport. The system consists of:

· A mine drainage conveyance pipe running beneath the Findlay Connector, including alkaline bedding stone, installed by the Turnpike Commission for purposes of de-watering the Clinton Block mine complex.

· Three settling ponds installed by the Turnpike Commission for mine de-watering and modified for long-term use during the course of this project. A significant portion of the dissolved iron precipitates and settles in these ponds.

· A pair of vertical flow ponds that can operate either in parallel or in series. These are basically limestone- and mulch-filled basins that neutralize acidity and generate alkalinity.

· A 1/3-acre treatment wetland that completes the precipitation of the iron.

Based on the results of initial after-construction sampling, this passive treatment system has reduced the acidity from an influent level of about 110 mg/l CaCO₃to an effluent level of -166 (net alkaline). The iron has been reduced from an influent level of 95 mg/l to an effluent level of less than 1 mg/l.

The acid and iron loadings to the receiving stream from the North Fork site have also been reduced, and the health of an estimated 2 miles’ length of this stream has been substantially improved. Water quality in the main trunk of Montour Run has also been positively impacted by the cleanup of the North Fork, improving the survivability of fish and other aquatic life.


PO Box 15509 Pittsburgh PA 15224-0509	© 2008 Montour Run Watershed Association