EFFECTS OF SURFACE MINING ON STREAM WATER QUALITY IN THE WILLS CREEK WATERSHED, SOUTHEASTERN OHIO: PH, SPECIFIC CONDUCTANCE AND SULFATE TRENDS

High specific conductance and sulfate values in stream water are associated with surface mining and acid mine drainage in a watershed. Water quality data collected from 1969 through 1991 from five USGS sites located along Wills Creek indicate a decrease in water quality through time that can be correlated with surface mining in the watershed. The sites are distributed through the watershed with two sites each in the northern and southern regions of the watershed. The other site is located in the middle of the watershed at Cambridge, Ohio. The water quality records spawn the time period 1964 through 1991, although the distribution is not equal across the watershed. The two northern sites records water quality data from 1965 through 1982. The site at Cambridge records water quality data only from 1964 through 1977. The two southern sites record water quality data only from 1980 through 1991 and are located nearest to one of the heaviest mined areas of the watershed. Surface mining in the watershed occurred from the 1950s through the 1980s. The majority of the surface mining occurred in the northern and southern portions of the watershed during the 1970s through the mid-1980s.

Specific conductance values as high as 2216 microsiemens per centimeter and sulfate values as high as 1100 milligrams per liter have been recently recorded from streams draining an area that was heavily mined in the southwestern portion of the watershed. This area forms part of the headwaters for Wills Creek. The earliest data from 1964 through 1977 from the middle and northern sites does not show much evidence of mining with specific conductance values varying between 456 and 1300 microsiemens per centimeter and sulfate values between 66 and 580 milligrams per liter. The data from the southern sites collected from 1980 through 1991 shows distinct evidence of the impact of mining. Specific conductance values range from 502 to 3350 microsiemens per centimeter and sulfate values range from 130 to 1800 milligrams per liter. These dates correspond to the heaviest mining in the southern area of the watershed. The pH values in the watershed vary between 6.6 and 8.6 for all five USGS sites and mainly lie between 7.7 and 8.6. Limestone is interbedded in the strata that contains the coal and would be present in mine spoil and reclamation material buffering the pH of the water.