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BEAR COAL COMFANI' INC. <br />1990 ANNUAL [IYDROLOGY' REFOR'f <br />SUPPLEMENTAL RESPONSE - ALLUVIAL WELLS <br />The Bear No. 3 mine surface facilities, .including a coal <br />st.oclcpile, are constructed on an alluvial deposit located ad.ia- <br />cent to the North Fork of the Gunnison River. During 1981. and <br />1982, when the mine was being permitted, the Division requested <br />that monitoring [Jells be installed in the alluvial material. In <br />a I~ebruary 'L5, 1982 submittal to the Division, (Permit Exhibit <br />16, Paee 491, the Operator noted that "t1 comprehensive alluvia.L <br />(groundwater( monitoring program has been initiated. Three <br />shallow groundwater wells have been established and will be moni- <br />tored on a continuing basis throughout the mining operations to <br />del:ermine any potential impacts on that groundwater". <br />1'he mining operation was not expected to adversely affect <br />the qua.Lity of ground water in the alluvium. The section of the <br />permit. cahich addresses protection of the hydrologic balance is <br />contained on pages 2.05-54 and 2.05-55. No specific determina- <br />tion of the probable hydrologic consequences as required by Rule <br />'L.05.6(311blliii) is presented in this section probably because <br />no impact. caas expected. <br />lluring 1987 the Operator's mining permit sass renewed. Page <br />30 of the Division's June 18, 1987 finding's document for the <br />permit renecaal addresses the probable hydrologic consequences of <br />t.hP Bear opet•ation. The second to the last paragraph on page 30 <br />inrti.r_ates that the Division did not anticipate degradation of the <br />water qua.l.it}- in the alluvial aquifer below the Bear No. 3 facil- <br />ities area. The rationale behind this statement was the combina- <br />tion of a .locJ infiltration rate of pollutants and a large amount <br />of" water that. f'iocas through the alluvium. Page 17 of the find- <br />ing's document presents the Division's estimate that. 5.'L5 CFS <br />flows through the alluvium. The calculation is derived using a Ic <br />f'act.or of 0.0328 feet/sec. During 1982, a pump test was per- <br />formed on ttre alluvial material. The result of this test, which <br />is presented in Exhibit 18 of the permit, indicates a k factor of <br />O.OOl9~# feet/sec. The Division's estimated floc) in the alluvial <br />mat.eria.l is therefore believed to be overstated by a factor of <br />16.9. 10.0328/0.00194). This apparent error in the estimated <br />flow though the alluvial material probably invalidates the <br />Di.vision's assumption of no degradation of the water quality in <br />the alluvia]. aquifer below the Bear No. 3 facilities area. <br />Alluvial wells AA1 and AA3 are located docanstream and up- <br />stream of the facilities area respectively. The results of water <br />analyses taken from both wells through 1985 did not indicate any <br />degradation of the caster in the alluvial material. In 1986, no <br />samples ,were sent to the laboratory for analysis but the field <br />1 <br />