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" �- III IIIIIIIIIIIIIIII <br /> 999 <br /> , STATE OF COLORADO <br /> Roy Romer, Govedi <br /> �/H 7r`Y <br /> DEPARTMENT OF NATURAL RESOURCES <br /> MINED LAND RECLAMATION DIVISION <br /> DAVID C. SHELTON, Director <br /> DATE: March 3, 1987 <br /> TO: Tom Schreiner <br /> FROM: Brent C. Anderson <br /> RE: COORS KEENESBURG MINE ANNUAL HYDROLOGIC REPORT REVIEW <br /> Review of the Coors Keenesburg Mine Annual Hydrologic Report has uncovered <br /> several changes in the hydrologic system at the mine. Changes in ground water <br /> quality and quantity are indicated. <br /> Spoils aquifers are developing of the Keenesburg Mine in A pit. Water level <br /> increases occurred in SMW-1 and SMW-2 in 1986. SMW-1 has recovered five feet <br /> (473-4736' ) since January, 1986. SMW-2 recovered approximately ten feet <br /> (4731 -4741 ' ) from January to September, 1986. Opening of B pit near the <br /> western edge of A pit has affected the development of the spoils aquifers in A <br /> pit. Sharp declines in water levels at SMW-2 after the opening of B pit in <br /> October, 1986 indicates that the spoils aquifer is being dewatered by the new <br /> pit. The extent to which dewatering will develop unknown at this time. No <br /> dewatering is currently evident of SMW-1 . <br /> Water quality in Ennis Draw monitoring wells has not changed significantly <br /> during the year. Total dissolved solids for these wells (DH-96, DH-122, FPW) <br /> have remained between 800 and 2200 mirco-mhos/cm during 1986. Water level <br /> data from all three wells indicated a decrease in electro-conductivity in late <br /> summer. <br /> No impacts to the coal -overburden water quality has occurred during the past <br /> year. Wells DH-133, DH-137 and DH-172 all contained water with E.C. 's within <br /> historic ranges. Slight increases in the E.C. of water in DH-137 and DH-172 <br /> were noted from January, 1986 to December, 1986. <br /> Irrigation well LFH-2 located at the Keenesburg Mine was plugged and abandoned <br /> in December, 1986. The well 's utility for irrigation purposes had been <br /> extremely limited due to degradation of water quality of the well . The <br /> decrease in water quality is attributed to low-quality water from an upper <br /> Laramie-Fox Hills aquifer entering the well . The well was designed and <br /> completed in an underlying water-bearing stratum of the Laramie-Fox Hills <br /> aquifer. Leakage of low quality water through a breached or <br /> partially-breached casing or through a cement plug in the open annular space <br /> above the screened interval resulted in contamination of water in the <br /> underlying, better-quality aquifer. <br /> 423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. (303) 866-3567 <br />