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• GreenlCroissanl Sand and Gravel Mi~esponse to Adequacy Review <br />May 30, 2001 <br />Page 3 <br />in this area and any earthwork contouring is separate from that contemplated <br />for construction materials permitting. <br />6. The 110-foot offset indicated on Exhibit C-3 is intended to keep the mining <br />operation out of the floodway of the Big Thompson River. All mining will take <br />place at least 110-feet from the banks of the river. No in-stream aggregate <br />production will take place and the operation will not use adrag-line or other <br />techniques for which in-stream measures were developed. <br />It is believed that the floodway is contained within the banks of the Big <br />Thompson River in this vicinity. Amore detailed study is potentially a <br />cumbersome task, involving data collection and floodplain modeling if a <br />floodway has not been previously determined. It should be noted that <br />F.E.M.A. maps do not identify floodways (only floodplains) in this area. <br />More elaboration as to the cause for the Division's concern may be helpful. <br />In the past, such floodplain issues have not been areas of concern within the <br />scope of DMG review. Typically these issues are the province of local <br />floodplain ordinances and County engineering review. <br />7. A condition of maximum disturbance will occur some time during Phase 4 of <br />the mining operation, when all mining areas have been exposed and all <br />overburden removed and stockpiled. The following numbers apply to the <br />plans in the proposed 112 permit: <br />Area of Active Extraction, with 0.5:1 slopes: ±19 Acres (1/2 of Cell 4) or <br />2,500 Linear Feet (LF) <br />Volume of 0.5:1 slopes to be backfilled to 3:1: 185,802 CY <br />Volume of overburden in stockpiles, to be backfilled: 57,000 CY (per #8 <br />below) <br />Volume of topsoil in stockpiles, to be respread in Cells 1-4: ± 15,000 CY <br />Linear feet of side slopes with finished contours (Cells 1-4): ±6,300 LF <br />Acreage of finished topsoil spreading: Zero Acres <br />Acreage of area requiring topsoiling: ±30 Acres <br />Acreage of area requiring revegetation, including plant site area: ±30 <br />Acres <br />Plant site area: ±10 Acres <br />