2020-09-08_REVISION - M2012032 (2)

Home Browse Search

LhR4Y Sin Ei?A.zvEs 2) Amendment 1 Application—increased total permitted acreage to 88.53, which included the original 33.5 acres for the main portal area, two shafts at 100 x 100 feet each(the Yellow Rose Shaft and the 960 Raise,which are located near the main portal area), and 54.34 acres for Governor Basin, within which the Monogahela shaft was included.Note the Monogahela Shaft that was permitted in the original application was included in the acreage for Governor Basin as part of Amendment 01. As part of the Amendment 01 adequacy review process,Fortune decided to forego the tailings and waste rock removal work in Governor Basin and asked that it be removed from Amendment 01. The intent was always to maintain the Monogahela Shaft in Governor Basin as permitted in the original application. We believe the 0.23 acres for the Monogahela Shaft was inadvertently counted in the Governor Basin acreage when it was removed from the Amendment 01 application, and it should not have been. This brought the total acreage to 50.53. The difference between the 50.3 acres that DRMS mentions in its comments and 50.53 in Ouray Silver's files is the third ventilation shaft (i.e.,the Monogahela Shaft) in Governor Basin. A copy of Drawing C-5 from the original permit application is included in Attachment 5,which shows the 0.23 acres for the Monogahela Shaft. b. Section 3.1 proposes the constructed slopes of the Tailings Storage Facilities (TSF) to be a 2H.• I V and capped with a minimum of 6 inches of topsoil. Please clam what the final slope of the reclaimed TSF's will be. If the proposed final slopes of any reclaimed area are steeper than 3H.• I V,please provide appropriate justification such as a revised Geotechnical Stability Exhibit or any other required information to demonstrate the appropriate Factor of Safety will be achieved in compliance with the enclosed MLRB's Slope Stability/Geotechnical Analysis policy for the generalized, single test strength measurements for non-critical structures. OSMI Response: The final slope of the TSFs will be 3H:1 V where practicable. If needed,the final slope configuration may be a maximum of 2H:1 V. The stability of 2H:1 V slopes was demonstrated in a geotechnical analysis by Lewicki and Associates that was submitted with Amendment 1,Exhibit U. This analysis included characterization of the planned filtered tailings as received from the mill, compaction test results and field compaction requirements,cold weather management plan, and ultimate planned pile configurations. Geotechnical laboratory testing and additional compaction and direct shear tests were conducted on filtered tailings, and estimated material properties were used to compute stability of the tailings stack using the SLIDE program. The results indicate a factor of safety(FOS) of 2.17 under wet conditions. c. The reclamation measures for the shafts detailed in Section 3.2 of the revised Reclamation plan indicate that the area around the shaft will be excavated 4-6 feet down, cut off the casing and removing the associated concrete pad, installing a steel plate and concrete plug, baclflling with overburden and topsoil and revegetated. Please clarify how the removed section of the shaft casing and associated concrete pad will be disposed of. If offsite disposal is proposed,please indicate the facility and distance to the facility that the material will be disposed at. Please also 5 1 P a g e