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- 4 - <br /> 2. The existing permit documents do not contain any information <br /> regarding the geotechnical design criteria or geotechnical monitoring <br /> schemes for the various tailing dam structures at the Climax Mine. <br /> Failure of a tailings dam (or a part thereof) could cause serious <br /> water quality degradation and could jeopardize off-site areas. A <br /> minor failure has apparently occurred at a location on the Dam No. 1 , <br /> so it seems that there is a potential for other such occurrences. <br /> The amendment should include geotechnical information of sufficient <br /> detail to allow an evaluation of the short and long term stability of <br /> the five tailings dams at the Climax Mine. Discuss construction <br /> design, safety factor analysis, underdrain criteria, etc. Also, <br /> include the monitoring scheme used to verify stability, including any <br /> monitoring for mass movement and water table development. Such plans <br /> should be developed if they are not already being implemented. For <br /> example, establishment of piezometers (or monitoring of existing <br /> piezometers) will provide information regarding tailing water content <br /> or water table development which may have short or long term <br /> implications for seepage control , revegetation, etc. Organized <br /> visual monitoring of dams can provide valuable information. <br /> 3. Application of rock to the dam faces will probably serve to stabilize <br /> the dam structures; however, improper loading could actually <br /> contribute to mass instability. This problem may be exaggerated if <br /> the tailings become saturated. The amendment should discuss the <br /> engineering design details necessary to ensure long term mass <br /> stability of the tailing dams. <br /> Also, have you given any consideration to rock placement and sizing <br /> techniques? This issue is important as it relates to surface erosion <br /> stabilization. Improperly placed riprap can actually lead to surface <br /> runoff channelization and subsequent surface incision. <br /> Finally, it is our understanding that the waste rock is an acid <br /> producing material . How will the use of acid producing riprap affect <br /> acid drainage from the tailings and how will it affect future <br /> revegetation efforts? <br /> 4. We recommend the use of some type of organic amendment procedure to <br /> attempt revegetation of the rock-faced dams. Discuss your plan for <br /> attempting to vegetate the dam faces. <br /> 5. The amended plan should give consideration to the manner in which <br /> limited topsoil resources will be utilized. Have you attempted to <br /> prioritize topsoil placement activities? If so, what are the <br /> conclusions? <br /> Also, further operating plans should be designed to allow topsoil <br /> salvage prior to expanding waste rock dumps, tailing ponds, roads, <br /> etc. Please consider adding this component to your amended plan. <br /> This suggestion specifically applies to the McNulty Dump and <br /> Mayflower Tailings Pond areas. <br />