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In 1986, the U.S. Geological Survey in cooperation with the U.S. Bureau <br />of Land Management and the Colorado Department of Natural Resources, Mined <br />Land Reclamation Division, began a study to determine the processes control- <br />ling the hydrology of reclaimed coal spoils at a surface coal mine in north- <br />western Colorado. However, in order to evaluate this disturbed and changing <br />system, climatologic, soil -water, ground -water, geologic, surface -water, and <br />water -quality data needed to be collected and compiled to aid researchers, <br />regulators, and land managers in conceptualizing the hydrology of potential <br />coal -spoil sites. <br />Purpose and Scope <br />This report lists climatologic, soil -water, ground -water, geologic, <br />surface -water, and water -quality data collected at five sites as part of a <br />study to evaluate the hydrology and geochemistry of a surface coal mine in <br />northwestern Colorado. Monitoring equipment and instrumentation were <br />installed in the summer of 1987. Data were collected during 1988 and 1989. <br />The monitoring equipment and instrumentation were placed on undisturbed areas <br />and reclaimed spoil areas. Reclaimed spoil, as described in this report, is <br />material that has been excavated from a mine pit and then has been replaced, <br />regraded, topsoiled, and revegetated. <br />The study area was at the Seneca II Coal Mine. The mine is divided <br />approximately in half by an anticline. The Lennox coal and the Wadge coal are <br />the major seams being mined. Confined aquifers in bedrock and unconfined <br />aquifers in reclaimed spoil are present in the area. Springs are present at <br />the toe of the reclaimed spoil slope. <br />Air temperature, relative humidity, solar radiation, windspeed, and wind <br />duration were collected at one site. Precipitation was measured at three rain <br />gages. Snow -course data were collected at three sites. <br />Lysimeters were installed at two sites, and water quantity and quality <br />were measured. Soil -water content was measured using soil -water access tubes <br />and a neutron probe. Soil dry density was measured once with a density probe. <br />Eighteen wells in the confined aquifer and seven wells in the unconfined <br />aquifer were installed. Geophysical and geologic logs were recorded for <br />selected cored boreholes. Water levels were measured at the wells. Porosity, <br />grain density, and permeability of selected core were estimated. Mineral <br />composition also was determined. Ground -water samples were collected for <br />water -quality analysis. Two springs that flowed from the reclaimed spoil were <br />monitored, and discharge and water quality were measured. <br />Description of Study Area <br />The study area is located at the Seneca II Coal Mine in northwestern <br />Colorado (fig. 1). The site is about 20 mi west and 5 mi south of Steamboat <br />Springs, Colorado. The area is shown on the U.S. Geological Survey topo- <br />graphic maps of the Milner and Mount Harris quadrangles (fig. 2). The area <br />ranges in altitude from about 6,800 to 8,000 ft. The vegetation primarily is <br />sagebrush and grasses with scattered stands of scrub oak, serviceberry, and <br />01 <br />