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Potentially affected portions of Fish Creek and the lower reaches of <br />Trout Creek below Fish Creek have previously been evaluated with respect to <br />AVF criteria in the review of two coal permits - the Foidel Creek Mine <br />(C-82-056) and Fish Creek Tipple (C-81-036). Selected alluvial deposits along <br />Fish Creek and lower Trout Creek were determined to be AVFs by the Division as <br />referenced in the respective permit findings documents. <br />The previous AVF finding made by the Division at the time of initial permit <br />approval for Seneca II Mine included an exemption for operations conducted <br />prior to August 3, 1977 within or adjacent to an AVF. The lands to which this <br />grandfather clause apply are located within the Grassy Creek drainage. A <br />45 acre area near the confluence of Little Grassy Creek and Grassy Creek and a <br />40 acre area along Little Grassy Creek which have been identified as AVFs <br />remain exempt and, as such, were not reevaluated. <br />Non-exempted areas in the Fish Creek drainage basin were reexamined in 1986, <br />in conjunction with a regional AVF study conducted by the Division, to <br />identify if any significant impacts would occur from the proposed operations <br />at Seneca II Mine. <br />The areas which were reexamined as potential AVFs within the Fish Creek basin <br />include alluvial bodies alon two tributaries of Fish Creek, referred to as <br />Cow Camp Creek and Bond Creek, and the reach of Fish Creek between Cow Camp <br />Creek and the confluence with Trout Creek. Based on the Division's review of <br />materials submitted by the applicant on May 27, 1981 and infrared aerial <br />photography reviewed more recently, the alluvial bodies adjacent to Cow Camp <br />and Bond Creeks did not meet the requirements for AVFs. This negative <br />determination was made in both instances due to the fact that the meandering <br />nature of the channels severely limits the farmable acreage within each <br />drainage. <br />During the Division's review of the adjacent Foidel Creek life-of-mine permit <br />revision (C-82-056), the Division reevaluated potential AVFs in Twentymile <br />Park. <br />Infrared photography and field investigations indicated that the Fish Creek <br />alluvial body was, in places, flood irrigated, and was generally <br />sub-irrigated, potentially farmable land. Based on these investigations, the <br />Division has determined that the Fish Creek alluvial body met the criteria of <br />an AVF. This AVF extends the length of Fish Creek to its confluence with <br />Trout Creek and along the length of Trout Creek to its confluence with the <br />Yampa River. <br />Effect of Mining on Identified Alluvial Valley Floors <br />Water quality data were supplied in the renewal application from monitoring of <br />surface water stations on Cow Camp and Bond Creeks, tributaries to <br />Fish Creek. Mining in the Fish Creek drainage basin began in 1982. Since <br />that time increases in both flow and total dissolved solids (TDS) <br />concentrations have been observed. Whereas flow in the channel immediately <br />below the mine, Cow Camp Creek, was ephemeral prior to mining, perennial flow <br />is now observed at the permit boundary. This effect is attributable to spoils <br />aquifer discharge, as well as an increase in runoff from mined lands, and a <br />decrease in evapotranspiration due to removal of vegetation from mining <br />areas. Recent observations have indicated, however, that stream flow is not <br />-34- <br />