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File No. M- 77-378 <br /> Page 4 <br /> Tailings Pond No. 4 Upland Groundwater Diversion <br /> Since the decision to implement final closure of the Sunnyside Mine and Mayflower Mill, activity <br /> at the Tailings Pond No. 4 facility has been geared towards complementing the area final <br /> reclamation plan. <br /> This has included; <br /> 1) placing project reclamation material (ie. tailings and mine waste)to create a sloping <br /> top-surface with drainage to the back of the pond and off the ends. <br /> 2) capping and planting of any areas brought to final grade. <br /> 3) lowering the upland diversion ditch to the final reclaimed location where it can also <br /> carry surface runoff from the reclaimed pond top-surface. <br /> 4) lining the relocated upland diversion ditch with 40 mil PVC to minimize infiltration. <br /> 5) systematically using borrow areas above the pond to completion so the final slopes <br /> can be vegetated. <br /> While implementing this last item, Sunnyside found near surface rock contact and subsurface <br /> water. In order to keep this water from saturating and destabilizing the reclaimed slopes, <br /> Sunnyside installed toe and chimney drains which drain into the lowered - lined upland diversion <br /> ditch. In addition, through a zone where the subsurface water was found, Sunnyside installed a <br /> drainage cutoff wall to intercept and divert this subsurface water into the lined upland diversion <br /> ditch in order to prevent this water from passing under the tailings and potentially contacting <br /> tailings material. The cutoff wall was constructed of roller compacted (and some poured) <br /> concrete keyed into the rock contact. This wall was raised to above the diversion ditch level with <br /> drain pipes to allow the intercepted water to drain into the lined diversion ditch and around the <br /> tailings pond. <br /> Sunnyside proposes to extend this concept where practical (technically and economically) along <br /> the remaining hillside contact with Tailings Pond No. 4. The proposed work would entail: <br /> 1) identifying the strike length where extension of the groundwater cutoff wall is <br /> technically and economically feasible by trenching above the lined diversion ditch to <br /> define bedrock contact and location of groundwater flows. <br /> 2) installation of impermeable barriers to impede groundwater flow on the bedrock <br /> contact in areas identified where groundwater flow is occurring and installation of an <br /> interception structure is feasible. <br /> 3) installation of piping and drains where needed to capture and/or provide a drainage path <br /> to the lined up-land diversion ditch. <br /> 4) covering of all barriers, trenching, and piping and planting according to the reclamation <br /> plan for the area. <br /> This diversion of groundwater to a surface diversion is covered under Sunnyside's existing <br /> Well Permit No. 043089-F, T.P.4 Diversion issued by the Office of the State Engineer. <br />