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<: <br />-2- <br />Summary of Mine Site Observations <br />Data received to date from the North Thompson Creek Mine (pg. 4-119 of <br />volume I) and coal mines within the adjacent North Fork of the Gunnison <br />Basin show that streams develop along fracture and fault lines, that the <br />highest occurrence of mine inflows is from faults and fractures associated <br />with the perennial and ephemeral stream channels, that mine inflow rates <br />fluctuate in response to snowmelt and precipitation events, and that mine <br />inflows from faults and fractures are not significantly reduced by sealing <br />in shaley overburden. Even with limited extraction techniques used by the <br />North Fork mines to prevent subsidence under perennial and ephemeral stream, <br />underground coal mines beneath streams do induce stream depletions. <br />Snowmass will mine under an ephemeral stream and adjacent to and under two <br />perennial streams, North and Middle Thompson Creeks. Fractures associated <br />with these stream valleys are contributing inflows to the mines and depleting <br />water in these streams and their alluviums. Mine water is discharged into <br />the North Thompson Creek drainage. Therefore, any water depleted through <br />mine inflows from Middle Thompson Creek will be removed from that drainage <br />system. <br />Concerns <br />During mining, the inflow water can be pumped back to the surface and <br />eventually be returned to the surface stream (North Thompson Creek). <br />[9hen the mining operations stop and the pumps are turned off, the depletion <br />of the stream will continue until the mine cavity, fractures, faults, and <br />overlying depleted aquifers have compZ etely filled (recharged). During <br />this period, water depleted from North and 14i ddle Thompson Creeks wi 11 <br />reduce the surface water available to downstream water right holders. <br />Another concern is that Snowmass Coal Company ma~_y not have sufficient <br />water rights for the consumptive use of water at the mine site. Numbers <br />related to the mine discharge rates and water consumption conflict <br />(see pages 3-50, 3-58, 4-I09, 9-118, and 4-129 to 4-126). The permit <br />application does not contain an augmentation plan or copies of the absolute <br />water rights held on mine inflow waters. There is no information on the <br />priority of water rights held by Sno~,miass Coal Company. Pages 4-115 <br />discusses the effects of mining on surface water flows. Page 4-1I6 and <br />4-1I7 give the flow records for North Thompson Creek (U.S.G.S. station <br />N9-0828). Mine inflows equal or exceed stream flows in the dry year <br />1977, and are about IOe of the average stream flows during the dry months <br />for the period of record. <br />