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1 <br /> <br /> <br />t <br /> <br />1 <br /> <br /> <br /> <br /> <br /> <br /> <br />INTRODUCTION <br />The purpose of this report is to describe the hydrologic features and <br />characteristics which may be affected by a proposed expansion of the <br />Cooley Gravel Company's Morrison Quarry, the extent to which the expan- <br />sion may have an impact on these features, and measures which may be <br />taken to mitigate any adverse impacts. It is anticipated that this <br />report will be submitted as an exhibit to an Application for Mining and <br />Reclamation Permit for the site of the proposed expansion. Consequent- <br />ly, this report includes information intended to fulfill the permit <br />application requirements of both the State of Colorado Mined Land <br />Reclamation Board and Jefferson County. <br />Our study included an inspection of the site of the proposed expansion, <br />a review of data contained in previous studies, an examination of aerial <br />photographs and detailed topographic mapping of the area, an analysis of <br />the hydrologic characteristics of Strain Gulch and adjacent basins which <br />may be affected by the mining, and an assessment of the potential <br />impacts of the proposed quarry expansion on peak flows during floods, <br />water quality, ground water levels and water rights in the vicinity. We <br />have also included recommendations on measures which may be taken to <br />mitigate the potential adverse impacts identified. <br />This report is supplementary to the following reports which were pre- <br />pared previously in connection with the existing Morrison Quarry: <br />Potential Impacts <br />Thorne Ecological <br />November, 1972 <br />on Environment <br />Institute <br />Hydrologic Analysis of Proposed Land Use Changes in Strain Gulch <br />M.W. Bittinger and Associates, Inc. <br />October, 1972 (contained in Thorne report) <br />Drainage Report for the Strain Gulch Ouatry <br />Leonard Rice Consulting Water Engineers, Inc. <br />April, 1975 <br /> This drainage report is based in part on da[a contained in these pre- <br />' vious studies, and information contained therein will not be repeated <br /> except as necessary for clarity. <br />' During the mining operation there will be some modification to historic <br /> drainage patterns. Following completion of mining and rehabilitation of <br /> the area, drainage will also be modified from the historic condition. <br /> The potential for damaging flash floods from high intensity summer <br /> stotmis exists under the historic condition as well as future conditions. <br /> This report will describe drainage facilities needed during mining so <br /> that the damage potential to downstream areas is not increased sig- <br /> nificantly over the historic condition, and will discuss drainage <br /> considerations after mining has been completed and the area has been <br />t reclaimed. <br /> <br />1 <br />