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~- -\,,- '\'" Colorado Department of Corrections April 10, 2003 Page 4 Estimated Average Permeability Assuming No Flow throu h the Embankment Dam. 6082 3 0.046 3.7 X 10.6 6085 6 0.056 3.5 x 10-6 6088 9 0.083 1 .7 x 1 0-6 6091 12 0.236 1.9 x 10-6 6094 15 0.328 3 . 5 x 1 0-6 Table 2. Estimated Average Permeability Assuming Flow through the Embankment Dam Equal to Flow throu h the 12-lnch Liner. 6082 3 0.046 3.4 x 1 0-6 6085 6 0.056 3.3 x 1 0-6 6088 9 0.083 1 .7 x 1 0-6 6091 12 0.236 1 . 8x 1 0-6 6094 15 0.328 3.5 x 1 0-6 The analysis results generally indicate little to no difference in the estimated aveTage permeability values under the embankment flow conditions described above, suggesting that the embankment is not contributing significantly to controlling seepage in the reseTvoiT. Although the above results suggest a small amount of vaTiation in the aveTage peTmeability at diffeTent Teservoir levels, in our opinion, the ~ifferences are not large enough to suggest the pTesence of more OT less peTmeable zones at different elevation in the Teservoir side slopes. The results are also in relatively good agreement with the peTmeability of 4 x 10-6 em/see for the oTiginal, natural liner system calculated by GTG in theiT letter date May 29, 1998, and generally suggest that the addition of bentonite did not help to significantly reduce seepage flows thTOUgh the liner. . A final seepage analysis was peTfoTmed to estimate the maximum peTmeability that will allow the DOC to meet augmentation requiTements for the TeseTvoir. Information on maximum allowable, daily seepage rates fOT each month, and correspondin~uired minimum monthly reservoiT volumes provided by Bishop Brogden weTe used. Based on that infoTmation, the highest minimum reservoir volume (21.87 acre-feet) and the lowest maximum allowable seepage rate (1.68 aCTe-feet/month) occur in the month of September. TherefoTe, the reservoir level and maximum allowable seepage rate for that month was used to estimate the maximum allowable permeability value. Based on the analysis results, a maximum allowable peTmeability of 9.0 x 10-7 em/see was calculated. CONCLUSIONS AND RECOMMENDATIONS The analysis results generally indicate calculated average peTmeability values for the bentonite-amended lineT that are significantly greateT than the originally estimated C:\My Documents\MJ\letter5\03-1-21 O.gjm.doc Kumar & Associates, 'nc.