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SUNNYSIDE BASIN <br /> FILE NO. M-77-378 <br /> DISCUSSION: <br /> The reclamation plans previously incorporated into Permit No. <br /> M-77-378 for Sunnyside Basin will remain unchanged with the <br /> exception that a groundwater interceptor ditch (es) and/or drainage <br /> pipes will be added. The ditch (es) or drainage pipes will <br /> intercept and divert near surface groundwater around the backfilled <br /> Lake Emma hole. This will reduce near surface groundwater flow <br /> into the Sunnyside Mine and more nearly approximate pre-Lake Emma <br /> collapse hydrologic conditions (minimal groundwater entered the <br /> Sunnyside Mine workings under Lake Emma prior to collapse) . The <br /> intercepted water will be diverted to the rock trench on the South- <br /> end of the backfilled Lake Emma hole to either flow as surface flow <br /> to Eureka Creek or reenter the near surface groundwater flow <br /> system, either of which was the probable path prior to the Lake <br /> Emma collapse. The maximum anticipated total groundwater flow to <br /> be intercepted will be 2500 GPM (based on previous Terry Tunnel <br /> flows) . <br /> Previous reclamation plans focused on the immediate collapse area <br /> as the point of interception and diversion. Because of the depth <br /> and near vertical dip (into the hole) of the bedrock contact in <br /> this area, interception and diversion was deemed impractical <br /> (economically and environmentally) . A test drilling program to <br /> define the bedrock contact above the immediate collapse area was <br /> carried out during the fall of 1992 (concurrent with backfilling <br /> the Lake Emma hole) . Bedrock contact was defined along a 460 foot <br /> segment where interception and diversion would be feasible. This <br /> segment is on the NE side of the backfilled lake Emma hole (plate <br /> 1) . <br /> It appears that groundwater can be intercepted and diverted (from <br /> entering the Sunnyside Mine) along the entire east side of the <br /> backfilled Lake Emma hole. This might entail continuing the 460 <br /> foot segment to the south by following the rock contact and if the <br /> contact becomes too deep, offsetting segments, always providing a <br /> drainage path to the rock trench. By offsetting segments it might <br /> also be feasible to intercept and divert groundwater along the <br /> north side of the backfilled hole. It will not be possible to <br /> reach bedrock on the west side, however , a ditch or drain pipe <br /> might intercept some of the shallower groundwater moving in the <br /> upper fraction of the glacial till . <br />