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National Water-Quality Assessment Program

Ground-Water Quality in Unmined Areas and Near Reclaimed Surface Coal Mines in the Northern and Central Appalachian Coal Regions, Pennsylvania and West Virginia

U.S. Geological Survey Scientific Investigations Report 2006-5059

By Steven D. McAuley and Mark D. Kozar

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ABSTRACT

Findings are presented from investigations during 1996-1998 by the U.S. Geological Survey National Water-Quality Assessment Program. Ground-water quality in 58 wells downgradient of reclaimed surface coal mines is compared to ground-water quality from 25 wells in unmined areas (background concentrations) in the bituminous coal fields of the northern Appalachian coal region (high-sulfur coal region) in Pennsylvania, Maryland, and West Virginia and the central Appalachian coal region (low-sulfur coal region) in West Virginia. Ground water in the mined high-sulfur coal region has significantly greater median concentrations of sulfate, hardness, calcium, and specific conductance compared to the unmined high-sulfur coal region and to both mined and unmined areas in the low-sulfur coal region. Ground water in mined areas had median values of mine-drainage constituents (sulfate, iron, manganese, aluminum, hardness, calcium, magnesium, turbidity, and specific conductance) that were significantly greater than medians for wells in unmined areas. Mine-drainage constituents include cations such as calcium and magnesium that become elevated compared to levels in unmined areas because of exposure of acidic mine drainage to calcareous materials. The transport of pyrite-oxidation products from the mined site and subsequent neutralization reactions by calcareous materials at the mine site or along the flow path are likely processes that result in greater concentrations of mine-drainage constituents in mined areas compared to unmined areas. Mine-drainage constituents generally exceeded unmined-area background concentrations within about 500 feet of mined sites but were at or below background levels in wells more than 1,000 feet downgradient of mined sites. Concentrations of sulfate, hardness, and total dissolved solids were greatest at well depths of 50 to 150 feet but generally were less than background concentrations in wells deeper than 150 feet. Concentrations of iron, manganese, and aluminum exceeded background concentrations in many wells less than 150 feet deep.

In mined areas, median ground-water ages are nearly as old in hill locations as in valley locations. Older ground-water age correlates with increased distance from mined areas. The lack of significant correlation among mine-drainage-constituent concentrations, ground-water age, distance from mined areas, and topographic locations may be the result of factors such as (1) mixing of ground-water ages in wells open to fractures with variable depths, lengths, and interconnections; (2) disturbance of rock from blasting; and (3) variations in slope and terrain relief in the study area.

Table of Contents

Abstract
Introduction
     Purpose and Scope
     Description of the Study Area
     Geohydrologic Framework and Ground-Water Flow
     Methods
Ground-Water Quality in Unmined Areas and Near Reclaimed Surface Coal Mines
     Comparison of Water Quality Between Mined Areas and Unmined Areas
          Variations of Water Quality Related to Regional Differences in Coal Sulfur Content
          Background Water Quality in Unmined Areas
          Major Water Characteristics and Mine-Drainage Constituents
          Trace Elements
          Volatile Organic Compounds
          Relation to Drinking Water Standards
     Spatial and Temporal Relations and Local Extent of Mine-Drainage Constituents in Mined Areas
          Lateral Distance From Mined Area
          Vertical Extent and Relation to Depth of Wells
          Relation to Topographic Location
          Relation to Ground-Water Age
Summary and Conclusions
Acknowledgments
References Cited
Glossary of Selected Terms
Appendix 1--Dissolved gas and recharge temperature data
Appendix 2--Chlorofluorocarbon data and apparent ground-water-recharge dates
Appendix 3--Site identification numbers

This report is available online in Portable Document Format (PDF). If you do not have the Adobe Acrobat PDF Reader, it is available for free download from Adobe Systems Incorporated.

View the full report in PDF 10.9 MB

A full listing of NAWQA activities is available at http://water.usgs.gov/nawqa/