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Attachment A <br />L,~#arge North America - Riverbend Mine <br />~oundwater Monitoring and Mitigation Plan <br />~" PURPOSE <br />This Plan is prepared for incorporation into the Colorado Division of Minerals and Geology <br />(DMG) permit. Lafarge North America (Lafarge) has submitted a Temporary Substitute Water <br />Supply Plan to the State Engineer's Office for approval. The temporary substitute supply plan <br />protects senior vested water rights and mitigates depletions of flows in the South Platte River. <br />This Groundwater Monitoring and Mitigation Plan presents the methods for monitoring of <br />groundwater during mining and reclamation, and for mitigating groundwater impacts to wells <br />and trees due to mining at the Riverbend Mine in Weld County, Colorado. <br />BACKGROUND <br />The Riverbend Mine site is in Weld County, Colorado, southwest of the Town of Fort Lupton. <br />The site occupies approximately 1370 acres in portions of Sections 7, 18 and 19 of Township 1 <br />North, Range 66 West and portions of Sections 12, 13 and 24 of Township 1 North, Range 67 <br />West all of the 6th Principal Meridian. The South Platte River flows generally along the east side <br />of the site. The Lupton Bottom Ditch (an imgation ditch) flows through the site. The extraction <br />of sand and gravel will be the "dry" mining method. That is, mine cells will be dewatered to <br />facilitate extraction of the gravel. The reclamation plan of the mine includes unlined cells and <br />lined cells for water storage. <br />Dewatering of the mine cells will lower the groundwater in the surrounding alluvial aquifer. <br />This will be a temporary impact that will cease after the dewatering phase. The lowering of the <br />groundwater levels may impact nearby wells and trees. <br />Historic Use <br />The site has been managed primarily for imgated and non-imgated agriculture using small <br />ditches and laterals. There are existing and proposed gravel mining operations north and south <br />of the site. There are also a few rural residences neaz the site. <br />Monitoring WelllnstaUation <br />Thirty monitoring wells have been installed at the site and a water level monitoring program <br />began in May 2004. The wells were installed outside the limits ofmining so that groundwater <br />can be monitored during and after mining. Locations of the wells aze shown in Figure I . <br />Additional monitoring wells will be installed as requested by the DMG in their Adequacy <br />Review No. 6 dated September 1, 2005. <br />Lafazge West, Inc. Riverbend - 1 - August 2005 <br />Groundwater Monitoring and Mitigation Plan tisWt37_012_021Groundwa~erVtiverbend GW Moa & Mi4gz6on Plan 5-26-OS.doc <br />