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• of the undisturbed material to the north of the backfill mater- <br />ial, the saturated zone at the contact of these two -units has <br />built-up from northward groundwater flow in the backfill over the <br />past few years. The result of this situation is that groundwater <br />discharge from the backfill in the downdip area is now occurring <br />at several points. The most obvious discharges are occurring at <br />the Area 2 pit and at the Pond F Spring. Springs and smaller <br />seeps have been observed in the western part of the mining area. <br />These will be located and quantified during the upcoming spoil <br />spring survey. <br />QUANTIFICATION OF BACRFZLL GROUNDWATER FLOW SYSTEM <br />in order to project probable hydrologic consequences for the <br />entire Eckman Park operation it is necessary to quantify the <br />backfill flow system in a area which has reasonable data control <br />and is likely to have reached a "steady state" condition. The <br />eastern backfill area was chosen for this analysis as the flow <br />system is not effected by existing open pits, and the area has <br />been reclaimed for a long enough period that "steady state" <br />conditions are more likely to prevail. More importantly, almost <br />all the groundwater flow from this area discharges either at the <br />Pond F Spring or the Area 2 Pit, both of which have some dis- <br />• charge rate data. Water balance and flow net analyses were <br />performed on the eastern backfill area to quantify the ground- <br />water flow system. <br />WATER BALANCE <br />Recharge <br />The figure of 3 inches of recharge per year for the backfilled <br />areas at the CYCC operation is considered reasonable for the <br />analysis as this is probahly representative of backfill areas <br />which are fully consolidated and have established vegetation. <br />The lysimeter study at the Seneca mine showed a considerable <br />decrease in recharge rate over the three year study period. <br />Discussion with Bob Williams, the principal investigator on the <br />study, indicated that the reduction in measured recharge was most <br />likely due to establishment of vegetation and compaction of <br />spoils materials. The trend of decreasing recharge rate did not <br />indicate that conditions had stabilized so that lower recharge <br />rate values would be expected in future years. Consequently, the <br />recharge rates of less than 3 inches per year would appear to be <br />reasonable for a fully stabilized reclaimed areas at the Seneca <br />Mine. If the Seneca study is re-activated, as is currently being <br />considered, than this assumption may be confirmed. <br />• <br />6 <br />