ASSESSMENT OF THE LONG-TERM HYDROLOGIC CONDITIONS OF THE NORTH FORK OF THE RIGHT FORK OF MILLER CREEK AND SURROUNDING AREAS, CARBON COUNTY, UTAH FOLLOWING UNDERGROUND COAL MINING

The U.S. Geological Survey in cooperation with the Utah Department of Natural Resources, Division of Oil, Gas, and Mining (UDOGM), studied the effects of underground coal mining and the resulting subsidence on the hydrologic system near the North Fork of the Right Fork (NFRF) of Miller Creek in Carbon County, Utah, from 1988 to 1992. Longwall mining began in August 1988 and continued through November 1991. Soon after mining began, the land surface in the study area started to visibly subside. The subsidence resulted in open fractures at land surface, debris slides, and rockfalls in the canyon above the mined area. Flow in the NFRF of Miller Creek dried up in areas and the water that discharged back downstream increased in dissolved solids from about 300 milligrams per liter (mg/L) to more than 1,500 mg/L during the course of mining. The surface water in this area changed from a primarily magnesium calcium bicarbonate to a magnesium sulfate type. Average sulfate concentration in the NFRF of Miller Creek downstream from the mining affected area increased from 40 mg/L in 1988 to 844 mg/l in 1991 (Slaughter and others, 1995).

During the summers of 2004 and 2005, discharge from springs and streamflow were monitored and water-quality samples were collected to reassess the hydrologic system overlying the mined area. A comparison of data collected during 2004 and 2005 to data collected during and immediately after longwall mining indicate that the changes in streamflow and water quality that occurred to the hydrologic system are still present in the NFRF of Miller Creek. Average sulfate concentration in this area during the summer of 2004 was 1,230 mg/L.

The current study is providing new data on the long-term effects of underground longwall coal mining on overlying hydrologic systems. Results will assist the Bureau of Land Management and UDOGM in managing and mitigating the effects of mining in this and other watersheds.

References Cited Slaughter, C.B., Freethey, G.W., and Spangler, L.E., 1995, Hydrology of the North Fork of the Right Fork of Miller Creek, Carbon County, Utah, before, during, and after underground coal mining, U.S. Geological Survey Water-Resources Investigations Report 95-4025, 56 p.