A Look at Acid Mine Drainage in Pittsburgh
What we're doing about this top pollutant


Pittsburgh’s Coal Mining History
Pennsylvania has a rich history rooted in the coal mining industry. Used to fuel the steel and iron industries, Pennsylvania had been one of the leading producers of coal in the country (Pennsylvania Historical and Museum Commission 2003). Coal mining began in Pennsylvania in the mid-1700's, fueled by the Colonial iron industry. Bituminous (soft) coal was first mined in Pittsburgh about 1760 at "Coal Hill" (present day Mount Washington). The coal was extracted from outcrops along the hillside and transported by canoe to the nearby military garrison at Fort Pitt. By 1830, the city of Pittsburgh (dubbed the "Smoky City" for its heavy coal use), consumed more than 400 tons of bituminous coal per day. Coal remained significant well into the 20th century due to the energy needs of both World Wars.
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Map from DCNR showing the bituminous coal fields across western Pennsylvania.
The Problem with Abandoned Mines
Pennsylvania’s coal mining heritage has not come without cost, though. For the first 200 years, it was mined without formal regulation and little thought of environmental consequences. Following the extraction of all the available coal from one site, operators would move to another mine site and leave the original mine abandoned, failing to remediate the environmental impacts caused by mining. Over 15 billion tons of coal was removed from Pennsylvania’s ground, and 250,000 acres of mine land were left abandoned.

These abandoned mines exist within many Allegheny County watersheds, leaking acid, heavy metals and other pollution into nearby creeks. The problem is so big that more than 4,000 miles of Pennsylvania streams are effectively dead — uninhabited by fish or insects — because of this pollution.


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Abandoned mine discharge in the Montour Run Watershed showing iron in the water and coating the stream bottom. From here, this discharge enters a treatment system installed by the Montour Run Watershed Association.
Milk Run AMD Treatment System
In Pennsylvania, conservation districts, watershed groups, and others have taken a lead role in cleaning up these abandoned mine sites with assistance from federal and state agencies. Recently, ACCD was able to treat the Milk Run abandoned mine drainage (AMD) discharge, the largest AMD discharge in the Montour Run Watershed.

Milk Run was so named for the milky color that appears when aluminum solidifies and enters the water. Aluminum is particularly harmful to fish and other animals that live in streams. Construction of the Milk Run AMD treatment system was completed in July of 2019. The system treats water that discharges from a drainpipe in an abandoned underground mine in the Pittsburgh coalbed and removes the aluminum and acidity.

Metals are retained in settling ponds while clean water is discharged back into the stream. The Milk Run system removes 72,000 lb/year of acid and 7,000 lb/year of aluminum pollution that previously flowed into Montour Run. Since the project was completed, water quality has improved in both Milk Run and Montour Run. Visual confirmation of improvement includes fish moving farther up Milk Run to just below the system discharge location. The project was a huge win for the watershed and those that live in and around it.


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The aluminum from the Milk Run AMD discharge is removed from the water before flowing back into the creek.
The project would not have been possible without these great partners:
  • Montour Run Watershed Association
  • Range Resources
  • BioMost, Inc.
  • Continental Communities II LLC (landowner)
  • Redwoods Estates, LLC (landowner)
  • PA DEP
  • Washington County Conservation District
  • Independence Conservancy
  • Stream Restoration Incorporated
  • US Office of Surface Mining’s Watershed Cooperative Agreement Program
  • S. Kent Rockwell Foundation
  • Foundation for PA Watersheds