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1 INTRODUCTION ' Kaiser Steel Corporation implemented a surface and ground water monitoring program at the Colorado Coal Mine # 1, located one mile north o[ Walsenburg, Colorado, in April 1984. The original program consisted of five surface water stations and 46 ground water wells. The purpose of gathering this ' information was to satisfy the requirements of stipulations 1 and 4 of the permit and also to provide adequate hydrologic data for input into future mine expansion, water rights mitigation and potential impact analysis of mining on the hydrologic balance. On February 6, 1987, the CMLRD approved a technical revision which reduced the monitoring requirements of the site to one surface station and 24 ground water wells. In June, 1988, the CMLRD also approved a technical revision which reduced the monitoring to those wells surrounding the disturbed area of the site. ' Currently, no mining operations exist on the property. The most recent activities consisted of a test pit opened in the northern portion of the permit boundary in 1981. The purpose was to examine coal quality and mining conditions. Historic underground mining operations on and adjacent to the property also ' occurred in the early 1900's. Much of the monitoring program was aimed at defining hydrologic conditions of these historic workings. ENVIRONMENTAL SETTING in the study area, topography consists of gently rolling grasslands to moderately rugged, partially ' timbered slopes. The grasslands are underlain by the easily eroded lower coal, shale and sandstone sequence of the Vermejo Formation. The timbered slopes are underlain by sandstone belonging to the Raton and Upper Vermejo Formations. These slopes are marked by relatively steep eastward-facing escarpments. ' Elevations in the study area vary from 6250 feet along the eastern margin to 6475 feet in the west-central area. The normal undulating topography is interrupted by linear features Cormed by regional faulting and the ' intrusion of igneous dikes. Several east-west trending dikes form linear topographic ridges cutting across the general topography. The most prominent dike in the study area is the Maitland Dike. Normal faults cross the area, trending in anortheast-southwest direction. ' Surface water drainage across the permit arcs is to the east-northeast via the Gordon and Maitland Arroyos. These waters Oow to the Cucharas River which feeds the Huerfano River. The entire study area is within the Arkansas drainage system. Surface runoff is derived largely from intense thunderstorms in the ' summer and fall. The streams in the study area are ephemeral. From conversation with people living in the area, Oow in the Maitland and Gordon Arroyos occurs infrequently, generally once or twice a year. Average annual runoff from Huerfano County is 0.3 inches, or about 3% of the average annual precipitation. ' The climate in the permit area is semi-arid. Average monthly temperature for the years 1961 to 1981 range [rom 34°F in January to 71.9°F in July and the mean annual temperature is 51.5°F. Winds of 10 to 30 miles per hour are common. ' Precipitation is mainly from intense, short-duration thunderstorms during the month o(July and August. A review of precipitation data for the years 1961 through 1981 shows the mean annual precipitation is 15.4 ' inches. TWo dry periods exist in the records, 1962 and 1981. Evapotranspiration and infiltration account for approximately 97% of precipitation.