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~. <br />• As the snowmelt recharge period ends, the groundwater discharge <br />will continue from the storage in the backfill. As the water level in the <br />backfill declines, the hydraulic gradient decreases with a resulting <br />decrease in the discharge rate. <br />Since there is little or no groundwater inflow from surrounding <br />areas, we assume the backfill area will be a closed system. Recharge to <br />the system will account for almost all of the discharge from the system <br />during a year's time. <br />Estimated of Base and Peak Flows <br />Based on actual flow data at the CYCC Mine, they estimate that <br />approximately 83% of the backfill recharge was discharged during the two <br />month period corresponding to the snowmelt period. The remaining 17% of <br />the recharge was discharged during the remaining 10 months. Therefore, <br />based on these assumptions, the base and peak flows are estimated as <br />follows: <br />u <br />PEAK FLOW <br />2L~1 ~"-` <br />Total Recharge X 83% = 82.5 Acre feet X .83 = 68.47 Acre Feet <br />Cc.JR~ 1~z°~Jiu <br />68.47 Acre Feet discharged over 2 months = 255 gpm average discharge d.91 i~~as <br />0,5~ r~ ~ zb haw <br />BASE FLOW e.59 ^~~ <br />Total Recharge X 17% = 82.5 Acre Feet X .17 = 14. Acre Feet <br />o.oS <br />14.03 Acre Feet discharged over lOmonths = 10.5 gpm average discharge a.~3 <br />,Ojr z3 c~ ~~ <br />Based on the above assumptions, peak flow would average approximately <br />255 gpm and base flow would average 10.5 gpm. <br />33oac- <br />These projected flows are based on assumptions made by CYCC and ~'~~~7?c <br />USGS for the Peabody Seneca II Mine for typical dragline spoil backfill <br />conditions. <br />We believe that these assumptions may not be entirely valid for <br />the HG Mine. Where the dragline spoil at Seneca and CYCC may be of rather <br />uniform compaction and density from the reclaimed surface to the aquatard <br />below, the HG backfill will have very different characteristics. The HG <br />Mine was mined first using scrappers, then later using 85 ton haulage <br />trucks to haul spoil material to the backfill areas. As a result of the <br />roads and ramps, there are numerous compacted zones throughout the backfill <br />~4pn l Qw <br />~12,.\ l,~~lc~ C'1 ~'C ~~ic'k fi 1~ LlY~I ~-`~O , i~ y C'cr~ Pc ~c~W ~ ^'~ <br />Revised 'November, 1986 <br />• <br />