The Pennsylvania State University
University of Maryland
University of Virginia
Virginia Polytechnic Institute and State University
West Virginia University

PTI HOME

Preliminary Assessment of Acid Producing Rock on Future PennDOT Construction (Full Text)

Authors: Barry E. Scheetz and Chad Ellsworth

EXECUTIVE SUMMARY

The objective of this study was to evaluate the geologic formations within the Commonwealth of Pennsylvania as they relate to the potential to form acid rock drainage (ARD). The primary aim of this effort was to assist PennDOT in the avoidance of the potential environmental impacts associated with these pyrite-bearing formations during road construction, as well as to assist in avoiding the negative impacts upon engineered structures that are often associated with ARD. An ancillary objective was to develop predictive models, where feasible, to predict the locations and severity of these environmentally deleterious conditions associated with ARD production. Three broad types of potentially acid-producing forming sulfide-bearing groups were identified. The first group, the black shales predominantly of the Valley and Ridge province, may cause ARD and have been observed to swell, leading to heave of engineered structures in some cases. Based on 94 surface samples of the black shales, a preliminary north/south geographic trend in their net neutralization potential has been identified extending between Centre County and Fulton County. A second group, consisting of the mostly flat lying coal bearing successions of Pennsylvanian age, has long been known to contribute to ARD problems. A general trend in decreasing percent sulfur of the coal measures from the southeast to northwest has been perceived based on large amounts of overburden chemical analyses and been attributed to the initial depositional environment of the coals and overburden formations. The third group, a number of isolated sulfide deposits, particularly those associated with dominantly sandstone lithologies, appear to be in part structurally controlled. A preliminary predictive model has been developed and some important geographic trends have been delineated, however the isolated deposits and some of the black shales deserve more attention in order to identify any spatial and temporal relationships allowing for predictive interpretation. Finally, a flowchart has been developed to assist in delineating the potential for significant environmental and engineering impacts based upon the chemical and mineralogical characteristics of the deposit.