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) vrdnrgeological and Environmentol Consultants <br />Prior to construction of the Golden cell, the land was below the 100 year flood plain <br />elevation of 4874 and thus could mitigate a flood swell or higher stage in the river that was <br />above this value. Based on a pre- mining topographic map developed by Deere and Ault <br />(11/25/2008) and a survey of the Golden Cell by King Surveyors (5/19/2009), <br />approximately 60 percent of this area that was once part of the flood fringe that could <br />mitigate flood stage levels has been removed. The Golden Cell with L.G. Everist's pits to <br />the west has removed approximately 90 percent of the area that was historically at or below <br />the 100 year level. Removal of this area has significantly impacted the ability of the river to <br />dissipate stage levels and prevent flooding on the east side of the river. <br />Colorado Division of Reclamation, Mining and Safety (DRMS), L.G. Everist Fort <br />Lupton Sand and Gravel, Permit No. M- 1999 -120, Bachofer Property Flooding as <br />Result of Reclamation Slurry Walls, October 22, 2010 <br />Conclusions <br />DRMS acknowledges several possible causes of flooding on the Bachofer property that <br />includes greater aquifer discharge due to higher groundwater levels as a consequence of <br />mounding from the slurry walls. Other reasons include mounding on the east bank, which <br />have caused active seeps and /or artesian groundwater conditions. However, DRMS <br />discounts these explanations as possible causes of flooding because they are not supported <br />by the results of the USGS Report (Arnold et al., 2010). The USGS report explicitly <br />concludes that mounding would occur on the upstream side of lined pits such as the L.G. <br />Everist pits located directly west of the Bachofer property. Furthermore, the report does <br />state on page 68 "Groundwater -level changes near the South Platte River generally are less <br />than 2 feet because the river lessens the hydrologic effects of the pits by contributing or <br />receiving water as water levels change ". Although USGS does not explicitly state that a <br />higher river stage and possible flooding could result, the fact that the river is attenuating the <br />mounding effect close to the river substantiates the hydraulic connection and relationship <br />between river and aquifer. Higher groundwater levels on the west side coupled with the <br />hydraulic barrier created by the mounding suggests that most of the alluvial groundwater <br />flow will be redirected into the river. <br />The possibility that ground water is mounded on the east side of the river and manifested by <br />active seeps is highly unlikely. There are no active seeps on the Bachofer property or on <br />nearby properties. The presence of mounding on this area would also not create artesian <br />conditions. For artesian conditions to occur a much higher recharge source outside the area <br />would need to be available and the alluvial aquifer would have to be overlain by <br />impermeable clay to create a pressure head. The hydraulic head in the alluvial aquifer <br />system is solely due to elevation head. <br />There is some evidence to suggest that higher groundwater levels exist on the east of the <br />river at or about the time that the pits were lined. Data obtained from the Colorado Division <br />of Water Resources well listing report shows two wells in the vicinity of the Bachofer <br />property with a continuous monitoring record that dates back to 1989 and 1994, <br />respectively. Well SB02N6631ACD, is located approximately 1 mile south of the study <br />10 <br />