2012-04-10_REVISION - M1981185 (43)

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The proposed maximum lift thickness and standards for compaction of the lifts are discussed in Section 5.2 — Roadway Grading of the Rule 6.5 Geotechnical Stability Report. • A moisture conditioning range for all types of materials. Moisture conditioning ranges are discussed in Section 5.2 — Roadway Grading of the Rule 6.5 Geotechnical Stability Report. • Information and specifications for the proposed Gabion wall retaining structures, including drawings. The Rule 6.5 Geotechnical Stability Report calls for a single mechanically stabilized earth (MSE) wall in Section 5.3 — Retaining Walls. Sheet C4.91 shows details of this retaining wall as well as a typical section of the retaining wall detailing standard construction of an MSE wall. Exact details for the wall will need to be completed by a structural engineer prior to the start of construction. • Revisions to the proposed Reclamation Plan to address slope stability. The Reclamation Plan can be found in the Construction Drawings (sheet C7.10). All slopes on the Reclamation Plan are 2:1 or greater and follow the existing natural topography. In the "cut- through" section of the road the natural topography was approximately 1.5:1, but the Reclamation Plan shows maximum 2:1 slopes to promote stability. • A revised work plan for the fill removal, placement, compaction and final grading for the road reclamation and closure. As mentioned above, sheet C7.10 shows the final grading and removal of the proposed improvements for the New Access Road. Requirements for the removal of fill, placement and compaction of material to meet the contours shown on the Reclamation Plan will meet the recommendations of the Rule 6.5 Geotechnical Stability Report. • An engineering stability analysis per Rule 6.5 for the access road slopes during operation and final reclamation. The analyses must include models for the fill and cut slopes based on the new geotechnical investigation and the proposed final slopes. Models for the fill and cut slopes can be found in the Appendix of the Rule 6.5 Geotechnical Stability Report. WORK PLAN The following presents a corrective action work plan to repair the New Access Road between County Road 124 and the La Plata River. Prior investigations were initiated to evaluate the condition of the road and determine requirements to repair the road. Based on those recommendations, a design was completed and approved with conditions as part of the 112d permit application. This TR uses more current geotechnical data to further refine the design and prepare the final construction documents for the New Access Road. Prior Investigation In May 2010, a site reconnaissance was conducted by J. Erich Rauber to evaluate the stability of the New Access Road. The investigation focused on an approximately 500 foot long section of the road constructed on a steep hillside adjacent to the La Plata River. This site reconnaissance consisted of reviewing documents, a site walk and digging three test pits in the road. Laboratory tests were performed on the samples taken from the test pits and the results were summarized in the Geotechnical Reconnaissance Idaho Mine Access Road, dated May 29, 2010. Page 3