The Road to the Garden

When Allegheny County agreed to the lease over 430 acres near Settlers Cabin Park to the Pittsburgh Botanic Garden, the site seemed nearly perfect: great location, wooded slopes, wide plateaus, beautiful vistas, streams for irrigation – quintessential Pittsburgh.

Everyone knew the property sat above abandoned coal mines, like a lot of land in Pittsburgh. What wasn’t obvious was that three of the four streams on the site were seriously polluted with Acid Mine Discharge (pH 2.8) from the mines.  Acid Mine Drainage occurs when iron pyrite in the mines is exposed to oxygen and water, producing salts and heavy metals including iron, manganese, nickel and cobalt.

When Hurricane Ivan dumped 6 inches of rain on Pittsburgh in September 2004, the mines overflowed, and caused flooding and landslides.  It was then determined that the streams could not be used for irrigation.

This was dire news.  Depending on municipal water for the Garden would be grossly expensive in the future, and simply “cleaning” the Acid Mine Discharge on the site was cost prohibitive.

An innovative plan was developed working with Allegheny County, the PA Department of Environmental Protection (DEP), and the U.S. Office of Surface Mining and Reclamation (OSMRE) to remove the mines.  The Garden re-negotiated its lease with Allegheny County to allow a reclamation process known as day-lighting. Removing the mines stabilizes the land, protecting future buildings from mine subsidence.  It cleans the water for irrigation and reduces pollution entering the streams.  The project also included building an intelligent rainwater system that will provide for future irrigation needs.

And so we began extracting the residual coal in the mines before collapsing them in November 2010.  The work continues and will take several more years.