Geohydrology, water availability, and water quality of Jefferson County, West Virginia, with emphasis on the carbonate area

Content Provider	Semantic Scholar
Author	Kozar, Mark D. Hobba, W. A. Macy, Jo Ann
Copyright Year	1991
Abstract	Jefferson County, an area of approximately 212 square miles, is a rapidly growing area in the eastern panhandle of West Virginia. Approximately 86 percent of the county is underlain by folded and faulted carbonate rocks. The remaining 14 percent of the county is underlrin by folded shale and metamorphic rocks. Spring discharge data indicate that the Chambersburg Limestone of the Trenton Group, the Beekmantown Group, and the Conococheague Formation have yields of more than 1,300,000, 290,000, and 175,000 gallons per day per square mile, respectively. These carbonate units also have the greatest densities of mapped sinkholes per square mile of outcrop. Results from three dye-tracer tests indicate that flow rates in the carbonate aquifer range from 70 to 840 feet per day parallel to strike, and 30 to 235 feet per day perpendicular to strike. Areal aquifer analyses indicate that the horizontal hydraulic conductivity parallel to strike is four to nine times greater than it is perpendicular to strike. Based on streamflows and water-table gradients, estimates of transmissivity parallel to strike were 3,900 and 4,100 feet squared per day, and 800 and 1,100 feet squared per day perpendicular to strike. Water samples from 62 wells and 8 springs were analyzed for most common dissolved constituents and bacteria in July 1988. Nitrate concentrations ranged from less than 0.1 to 63 mg/L (milligrams per liter); the median was 5.8 mg/L. Chloride concentrations ranged from 1.3 to 270 mg/L; the median was 12 mg/L. There was no significant difference in the concentrations of nitrate or chloride when comparing 1974 to 1988 data. Manganese concentrations ranged from less than 1.0 to 680 jug/L (micrograms per liter); the median was 1.0 Mg/L. About 53 percent of the samples contained fecal coliform bacteria, and the median count was 1 colony per 100 milliliters. About 70 percent of the samples contained fecal streptococcal bacteria; the median count was 6 colonies per 100 milliliters. The ratios of fecal coliform to fecal streptococci indicate that most of the contamination is derived from animal wastes. Of the 30 wells and springs sampled and analyzed for 22 pesticides in the organochlorine and organophosphate classes, only 9 samples contained detectable concentrations of pesticides (DDE, endrin, dieldrin, and heptachlor). Eight of the nine samples were from wells or springs in or near orchards. Three wells, two springs, and two streams were sampled quarterly. There were no significant increases or decreases in common dissolved constituents, but alkalinity was generally highest during the spring of 1989. Quarterly samples at twc sites on the same small stream show that average annual concentrations of 18 of 25 common constituents increased in the downstream direction. INTRODUCTION Jefferson County is primarily an agricultural area in eastern West Virginia (fig. 1), approximately 50 mi (miles) northwest of Washington, D.C. Many people who work in the Washington, D.C. area are relocating to this predominantly rural county. From 1970 through 1980, the population in the county increased 42 percent (Jefferson County Planning Commission, 1986, p. n-2). As the population increases, the demand for potable and dependable water supplies increases. Most of the county is underlain by carbonate rocks, most of which have undergone some degree of karstification. Ground-water recharge in the karst areas occurs directly through sinkholes, caves, streams, and by direct infiltration of precipitation. Ground-water velocities can be rapid, and contaminants entering the ground-water-flow system can affect a large prt of the aquifer in a short period of time. Because of the increasing need for potable water supplies and concern fc~ the vulnerability of the existing water supply to contaminants, the U.S. Geological Survey, in cooperation with the Jefferson County Commission and the West Virginia Department of Natural Resources, conducted a countywide investigation of the ground-water resources. Purpose and Scope This report presents the results of a study to (1) delineate the ground-water-flow system in the carbonate aquifer in Jefferson County, (2) describe the geohydrologic framework Tvithin the county, (3) assess the overall ground-water quality, and (4) identify areas where changes in water quality have occurred. Most of the populated areas, farms, orchards, industrial areas, and many of the new developments are underlain by carbonate rocks. Therefore, most of the data-collection activities were concentrated in the carbonate areas. Description of the Study Area Jefferson County, an area of approximately 212 mi2 (square miles), is in the eastern panhandle of West Virginia. It is the easternmost county in the State. The county is bounded on the northwest by Opequon Creek, on the northeast by the Potomac River, on the southeast by the Blue Ridge Mountains, and on the southwest by Virginia (fig. 1). Most of the county is in the Shenandoah Valley of the Valley and Ridge physiographic province (fig. 1). The Shenandoah Valley has a subdued and gently rolling topography. In the valley part of the county, elevations range from about 400 to 600 ft (feet) above sea level (Beiber, 1961). The southeastern edge of the county is in the Blue Ridge physiographic province. In this part of the county, elevations range from about 1,100 to 1,700 ft abor'e sea level (Beiber, 1961).
File Format	PDF HTM / HTML
DOI	10.3133/wri904118
Alternate Webpage(s)	https://pubs.usgs.gov/wri/1990/4118/report.pdf
Alternate Webpage(s)	https://doi.org/10.3133/wri904118
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article