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Memorandum to Greg Roush• • <br />March 23, 2001 <br />Page 3 <br />10, <br />.-. 20 <br />L <br />11 <br />N <br />0 30 . <br />40 . <br />10 <br />.0 <br />-10 ~ <br />c <br />3 <br />O <br />•-20 ~ <br />0 <br />-30 <br />Distance from Pit Center (ft) <br />RESULTS <br />MAX. THEOR. WATER LEVEL DECLINES <br />from Starter Pit Dewatering <br />0 Top of <br />-_____=====P;epose~~it= _______________________ <br />------------------ - _ ----------------------- <br /> <br />-- -- <br />Pie~eve - t~tert~ W~eF ~' _ _ - _ _ =~Iy=gattt~etieai ~~it <br /> <br />_______________________ _______________ _______ <br />----------------------- ------------fiBfi -aflE~-- <br />------------------------ ----------------------- <br />________________________ ____________ Q~ui~`e~===- <br />------------------------ ---------------- ------- <br />------------------------ ---------------- ------- <br />------------------------ ---------------- ------- <br />------------------------ ---------------- ------- <br />_Purrl~ingTime=363_days _______________ _____ <br />Trartsmissivity (gpd/ft) <br />t 50,000 ~ 100,000 t 200,000 Figure 1 <br />Figure 1 shows three theoretical drawdown curves for the range of aquifer transmissivities across <br />the site. The shape of the water table is pazabolic with greater drawdown away from the pit for <br />higher aquifer transmissivities. Tables 1 - 3 shows the theoretical drawdowns for an aquifer <br />transmissivity of 50,000 gpd/ft, 100,000 gpd/ft, and 200,000 gpd/ft respectively. The greatest <br />potential impact shown in Table 3 is 5 feet of drawdown approximately 2000 feet away. <br />We propose that the operator use the appropriate table for the aquifer transmissivity (using <br />Hurr's Transmissivity Map) beneath the proposed pit location to estimate the theoretical impacts <br />of starter pits. Each table shows the maximum theoretical drawdown and the expected <br />drawdown. The expected drawdown is 50% less than the theoretical and is based on our <br />estimate of the effects of mitigating factors discussed below. Starter pits are best located at least <br />2000 feet away from existing wells in areas of lower aquifer transmissivity. <br />LEONARD RICE CONSULTING V1/ATER ENGINEERS, INC. <br />ZOOO CLAY STREET. SUITE 900. DENVER. COLORADO 802 1 1-5 1 1 9 • PHONE (309) 45$-9589 • FA% (309) 455-01 15 <br />