2012-09-05_PERMIT FILE - C1982057A (2)

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• INTRODUCTION Attachments 20 -D and 20 -E have been consolidated into Attachment 20 -D to address the remediation plan for the entire area associated with the Pond 016/016A slope instability and the "Shrub Plot" slumps. The purpose of this remediation plan is to effectively stabilize the slide areas by containing and conveying the surface water /groundwater away from the saturated areas. A Geotechnical Evaluation and Stabilization/Reconstruction Recommendations Report, prepared by Northwest Colorado Consultants, Inc (NWCC), based on 2008 drilling program, 2009 monitoring and May 2010 observations, is attached. There are a number of factors involved with stabilizing the area: • A portion of permanent Road J/K will be relocated • Pond 016 slide will be stabilized • Shrub Plot slump will be stabilized • Pond 016A will be eliminated by backfilling • Pond 016 capacity verification • Permanent Channel PM -2 will be relocated and extended through the Pond 016A area • Expansion of the disturbance area REIVIEDIATION PLAN • Relocation of Roads J/K A portion of the J and K roads will be relocated through the slide areas once the remediation trench and the permanent channels are constructed. The new road will be approximately 20 feet wide with an overall grade of not more than 10 percent. See Exhibit 20 -13.1, Pond 016 Area Remediation Plan— Existing Conditions, for current road locations and 20 -D.2, Pond 016 Area Remediation Plan and Post Mine Cross - Sections, for the proposed relocation and profile of the landowner access road. The typical construction details for access roads are contained in Tab 13, Transportation Facilities. DRMS is requiring stricter construction criteria than is currently approved in Tab 13. These criteria that SCC must adhere to include: • Materials will be placed in approximate 12 inch lifts • Compaction will achieve a minimum of 95% MDD • Materials placed in the road fill will be in an approximate range of +/- 2% OMC • A sheepsfoot roller will be used, if necessary, to achieved the required level of compaction Pond 016 Slide Remediation Beginning at or above the slide scarp, the slope will be excavated back into competent material and proceed down the face of the slope to the approximate water source located • during the geotechnical drilling program. Additional disturbance is proposed to allow an adequate buffer and equipment access around the area to stabilize the area. TR -73 1 6111