IDENTIFYING THE PROBLEM:  Chartiers Creek dissects the Pittsburgh Coal seam. Discharges on the east side of the creek are hydrologically separated from ones on the west. The Pittsburgh Coal outcrop crosses Chartiers Creek just south of Bridgeville and Millers Run, southwest of Gladden. 

The primary mining method to extract coal in the watershed was to deep mine. Where the coal outcrops at the surface, a tunnel (drift entry) is started at the outcrop and follows the coal into the ground. Typically these “drift mines” begin at the lowest coal outcrop elevation and the mine is extended up the dip slope. Any ground water will flow down slope on the floor of the mine and out the entry. The mine would then not flood and no pumping would be required.  

Where the coal is below the ground and does not outcrop, a shaft or slope is dug either vertically or on an inclined slope to get to it. Then lateral tunnels are dug to remove, or mine, the coal. These form a network of tunnels, whose ceilings are supported by pillars. This is called “room and pillar mining”. Sometimes the pillars are removed as the mining retracts from a fully developed zone. As these mines are often below the ground water table, seepage must be pumped out to maintain a workable mine. When the mine is abandoned, the pumps are removed and the mine floods, pooling the seepage. The mine slope will direct infiltrating water to a discharge point at the surface outcrop or water will collect in a low point and form a mine pool, which will fill until it reaches the elevation of an outlet, or surface discharge. The outlet could be a shaft to the surface, a drift entry, a man-made cut, such as a strip mine, or a natural fracture in the rock substrata. Nine major discharges from these underground mines have been identified in the Chartiers watershed within Allegheny County.

UNDERSTANDING THE PROBLEM:  The key to cleaning up mine drainage lies in investigating the scope of the problem. An initial two year DEP Growing Greener study of nine major AMD discharges to the main channel of Chartiers Creek between Bridgeville and Carnegie was concluded in July 2003. Aimed at monitoring the flow and chemistry of each surface discharge and gathering and digitizing maps of the deep underlying mines in order to develop a GIS map-based hydrologic model, the study served to update our understanding of this leading threat to water quality in the lower Chartiers watershed, since it was last studied by the 1970 Operation Scarlift survey. 

In that thirty-year span much had changed. New discharges appeared, others disappeared, discharges changed in chemistry and flow, and information about the mines grew. With the completion of the Lower Chartiers Creek Rivers Conservation Plan in March 2001, this study was considered the first implementation of any of its recommendations. It serves as the first step, an understanding of the discharges and their causes, which now advantages us toward remediating AMD impact.  

SOLVING THE PROBLEM:  A two-year DEP Growing Greener restoration project is now taking the next logical step toward remediation by using characterization data to develop and prioritize engineering design options. Objectives include: reviewing hydro-geological setting; reviewing historical mine drainage assessments and studies; summarizing most recent discharge assessments; determining loading calculations for the discharges; assessing how discharges impact water quality on the main channel; identifying key property owners of potential remediation sites; developing a prioritization matrix that facilitates cost-effectiveness evaluation for remediation projects; and developing remediation options for each discharge and a detailed conceptual design for the preferred alternative.

The project is nearing completion, with the final report expected in January 2006. The biological condition of the main channel, public opinion of the project and the potential for industrial and commercial use of treated mine water are also factors to be considered.  Along with other conservation activities in the watershed, this project will draw more attention to building new respect and value for restoring Chartiers Creek.  The creek provides aquatic habitat, recreational opportunities such as canoeing, fishing, and wading, and is the source of water and sink for discharges for industries.  It is the central component of trails and parks in the riparian corridor.