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• lr•rxuuuc: rlun The Eagle #5 and #6 Mines are underground coal mines, located approximately seven miles south of Craig, Colorado (Figure 1). The aerial extent of the underground workings in the #5 Mine was approximately 2,040 acres at the end of 1990 and since active mining in the #5 Mine ceased in 1990 this acreage has not changed. Approximately 348 acres had been mined in the #6 Mine at the end of 1992. The mains connecting the 5 and 5A portals in the #5 Mine are still used for access to the #6 Mine. The coal extraction is from the Cretaceous Age Williams Fork Formation, in the "E" Seam in the #6 Mine. Hydrologic monitoring has been conducted at the mine site since 1980. This report presents the results of year 1992 monitoring. The complete 1983 through 1991 monitoring is presented in the respective Annual Reports for each calendar year. The hydrologic monitoring is divided into two parts: 1) groundwater, and 2) surface water. The monitoring locations are shown in Figure 2 and summarized in Table i. The water quality monitoring includes field parameters (Table 2), water quality parameters (Table 3), and NPDES parameters (Table 4). The water quality samples are analyzed by ACZ Laboratories, Inc., Steamboat Springs, Colorado, a USEPA certified laboratory. This report includes data collected specifically to meet requirements of the Colorado Division of Minerals & Geology (DMG), as well as data collected to meet the requirements of the Colorado Wastewater Discharge Permit System (NPDES permits). A complete listing of all the water quality data is submitted separately. GROUNDWATER MONITORING Bedrock Three sandstone aquifers are monitored at the site. They are, in ascending order: Trout Creek Sandstone (2 wells), Middle Sandstone (6 wells), and Twentymile Sandstone (3 wells). The #5 and #6 Mines are between the Trout Creek Sandstone and the Middle Sandstone. WATER LEVELS The potentiometric levels, represented by water levels in the two Trout Creek Sandstone wells, recovered to the levels measured in 1986 through 1988. The recovery of the two wells is apparently from reduction in pumping for use since both wells are used for water supply as well as monitoring. The 1992 levels in both the No. 5 Mine Well and the Okie Plaza Well appear to be 45 to 70 feet lower than the levels measured when monitoring was initiated in 1985 and 1987, respectively. Water level fluctuations of 20 to 200 feet are also observed but no seasonal pattern is evident or • expected. It is likely that the fluctuations are related to pumping for use. 1