2016-08-10_GENERAL DOCUMENTS - M1981185 (2)

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Final -Restoration and Compliance Pian for May Day Idaho Mine Complex Administrative Order for Compliance, Docket No. CWA-08-2012-0011 • Erosion controls were installed (see Figures 9a and 9b), along with any safety features or controls required by DRMS or MSHA. • The road was re-graded to meet the requirements of the geotechnical study. • The new road has a typical section with a 12-foot wide drivable surface with a 1 -foot deep swale for runoff and a 1 -foot bench along the edge of the road opposite the swale. • Six inches of gravel was placed on the drivable portion of the road. • Runoff from the road was detained in a detention pond with athree-stage outlet structure prior to release to wetlands or the La Plata River (see Figure 7), as required by La Plata County. • The existing timber retaining wall was removed and hauled off-site for disposal. • Anew mechanically stabilized earth (MSE) retaining wall was constructed with a maximum height of 10 feet (see Figure 8). • Disturbed areas were graded and seeded with the approved seed mix in Table 2. Any excess soil, subsoil, or rock was removed from the work area and disposed of in upland away from wetlands and any streams. Required stormwater management pond. La Plata County requires that all new development associated vuith the New Access Road capture and detain storrnwater in excess of the existing drainage for the area that is improved. The construction of the new Mine Access Road will increase run-off through the construction of a gravel surface. An engineering evaluation of alternatives to meet this requirement was completed (Appendix G) which determined that the only practicable alternative is the construction of a stormwater detention pond upgradient of the culvert under the road. Construction of the stormwater management pond, while providing water quality treatment which will benefit the adjacent wetlands and aquatic resources of La Plata River, will impact 0.028 acre of wetland. The location of the stormwater management pond is shown on Figures 2 and 3a. Figure 10a is a plan for the pond, and Figure 10b includes details of the pond. The pond was constructed in May-June of 2014 and an as-built of the pond is included in Appendix F June 2016 Bikis Water Consultants, a division of SGM Page 12 Case 1:16-cv-02008-WYD Document 2 Filed 08/08/16 USDC Colorado Page 42 of 82