Impacts of Steel Mill Slag Leachate on the Water Quality of a Small Pennsylvania Stream

ABSTRACT

Leachate from a 20 million ton steel mill slag dump significantly influenced the chemistry of a small western Pennsylvania stream, Nine Mile Run. Alkalinity, acidity, pH, calcium, and magnesium were significantly altered by the alkaline leachate that seeped from the toe of the 95 hectare slag dump. These leachates increased the mean pH of the receiving stream from 7.7 to 9.3, and the maximum pH measured was 11.1. Alkalinity decreased, and Ca⁺⁺ and Mg⁺⁺ came out of solution forming carbonate flowstone-like layers over the streambed.