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~, BEAR COAL COMPANY INC. 1990 ANNUAL f{YDROLOGY' REPOR'C SUPPLEMENTAL RESPONSE - ALLUVIAL WELLS The Hear No. 3 mine surface facilities, including a coal stockpile, sre constructed on an alluvial deposit located ad.ia- cent to the North Fork of the Gunnison River. During 1981 and 1982, when the mine was being permitted, the Division requested that monitoring wells be installed in the alluvial material. In a February 25, 1982 submittal to the Division, (Permit Exhibit 16, Page X191, the Operator noted that "A comprehensive alluvial (,eroundiaater) monitoring program has been initiated. Three sf~allow groundwater iaells have been established and will be moni- tored on a continuing basis throughout the mining operations to determine any potential impacts on that groundwater". The mining operation was not expected to adversely affect the quality of ground water in the alluvium. The section of the permit which addresses protection of the hydrologic balance is contained on pages 2.05-54 and 2.05-55. No specific determina- tion of the probable hydrologic consequences as required by Rule • 'L .05.6131(b)(iii) is presented in this section probably because no .impact Baas expected. During 1987 the Operator's mining permit was renewed. Page 30 of the Division's June 18, 1987 finding's document for the permit renewal addresses the probable hydrologic consequences of the Bear operation. The second to the last paragraph on page 30 indicates that the Division did not anticipate degradation of the water quality in the alluvial aquifer below the Hear No. 3 facil- ities area. The rationale behind this statement Taas the combina- tion of a loca infiltration rate of pollutants and a large amount of water that flows through the alluvium. Page 17 of the find- ing's document presents the Division's estimate that 5.25 CFS flows through the alluvium. The calculation is derived using a k factor of 0.0328 feet/sec. During 1982, a pump test was per- formed on the alluvial material. The result of this test, cahich is presented in Exhibit 16 of the permit, indicates a k factor of 0.00194 feet/sec. The Division's estimated flo~+ in the alluvial material is therefore believed to be overstated b,y a factor of 16.9, (O.U328/O.OU194). This apparent error in the estimated floc: though the alluvial material probable invalidates the Division's assumption of no degradation of the water quality in the alluvial aquifer below the Bear No. 3 facilities area. Alluvial wells AAI and AA3 are located downstream and up- stream of the facilities area respectively. The results of water • analyses taken from both wells through 1985 did not indicate any degradation of the water in the alluvial material. In 1986, no samples ~+e re sent to the laboratory for analysis but the field 1