Increases in the demand for coal in the late 1800's led to the development of large mine complexes covering many square miles. When the mines where abandoned and the pumps shut down, the mines filled with water. The water eventually found ways out to local rivers and streams. In larger mines covering many square miles, pumps could not keep up with the amount of water infiltrating and boreholes were drilled at the low point of the mine to relieve built up water pressure to keep higher areas of the mine dry for work. One of these boreholes located outside the Borough of Portage fountains over 10 feet in the air from a 12 inch pipe at some times of the year.
Surface mining is the extraction of coal by removing the surface of the ground.
Draglines are machines which can now remove up to a depth of 200 feet in a single pass. Prior to enactment of Federal legislation, miners were not required to restore the site of a surface mine. They left the overburden rock behind where it could leach acid and metals into streams to add to the discharges from the abandoned deep mines. Acid mine drainage from surface mines does not usually produce the thousand gallon per minute flows that come from abandoned underground mines. Even with reclamation of the surface, where the strip mine intercepts underground flows of water, the broken up rock returned to the pit can leach metals and acids and appear on the surface as polluted seeps or springs.