Hydrology of a surface coal mined area in Randolph County, Illinois

Ground water was monitored from October 1980 to April 1983 and surface water was monitored from October 1980 to September 1982 in the 0.6-square-mile basin of Plum Creek Tributary in Randolph County, Illinois, to determine effects of surface mining for coal. During the study period, the basin was being surfaced mined. The mine pit advanced about 100 feet into the basin every month, reducing the basin 's drainage area from an initial area of 0.6 square mile in October 1980 to 0.2 square mile in May 1982. The average daily flow of Plum Creek Tributary was 0.49 cubic foot per second. Periods of no flow occurred 18 percent of the time. Total recoverable iron at Plum Creek Tributary exceeded the Illinois Environmental Protection Agency 's (IEPA) effluent standards. Mining activity may have been the cause. Ground-water levels of nine wells declined during the monitored period. The largest was a 35-foot decline in 16 months. Ground-water samples had dissolved-solids concentration that exceeded the IEPA 's limit for potable supply for all geohydrologic units except the unconsolidated sand. Chloride concentrations exceeded IEPA 's limits in all bedrock units except for a limestone unit. (USGS)