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<br />l~ <br />Ms. Richael Michels <br />Larimer County Planning Division <br />June 20, 1995 <br />Page 8 <br />10. Drainage report. The site is located within the Cache La Poudre River 100-year <br />floodplain. The floodplain definition is located in Exhibit C of the DMG permit <br />application. This information was taken from November 17, 1993 FEMA Panel <br />#080101 208. A portion of the Cache La Poudre floodway also passes through the <br />site. This is due to the under sizing of the I-25 bridge passing over the river north of <br />1 Harmony Road. The topography on the site dips to the southeast, therefore, surface <br />water coming onto the property is generally from the northwest and water drains at <br />the southeast corner. <br />The Wellington Downs operation will have no significant impacts on the floodplain, <br />therefore, no new hydraulic calculations were performed. We do not feel that a <br />HEC-2 computer model is wan•anted in this particulaz case. The creation of a <br />temporary lake during the mining phase could decrease the flood levels during the <br />occupance of an intermediate regional flood by creating extra storage azea for the <br />flood waters and other surface water drainage. <br />Listed aze the measures Connell will take to limit the negative impacts of mining in <br />the floodplain. <br />a) All processing equipment will be aligned to minimize impact of flood <br />waters. Processing equipment will not be water tight. Any processing <br />equipment with materials which could degrade water quality during flood <br />stages shall be raised above flood levels. <br />Processing equipment will be properly anchored to prevent floatation, <br />collapse, or lateral movement of the structures due to flooding events. The <br />conveyors will move within the designated process area during the life of <br />' the operation. The floor of the scale house will be elevated a minimum of <br />one foot above the 100-year floodplain elevation and will be anchored. <br />b) The size of topsoil and overburden stockpiles will be limited. The topsoil <br />and overburden stockpiles will be placed outside the floodway and aligned <br />in the direction of the flows (see Exhibit C). Stockpiles remaining in one <br />' location for longer then one growing season shall be seeded to reduce <br />erosional effects. <br /> <br /> <br />