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-5- <br />Finally, the overburden dumps could then be finally graded, slightly higher <br />than originally proposed, thus eliminating the need for the superelevated <br />lowgrade ore disposal structures. <br />Drainage and Erosion Control Amendments <br />Bob Liddle has prepared a detailed review of the proposed amendments to the <br />approved drainage erosion control plan. Geotechnically, my mayor concern <br />relates to the topic of consolidation settlement, discussed in several <br />instances above. All the drainage and erosion control facilities located upon <br />waste dumps or the North Pit landslide are subject to possible consolidation <br />settlement, which could compromise their structural and hydrological design <br />integrity. The four proposed "flow attenuation areas" might be particularly <br />susceptible to settlement dfsorientation, which could result in increased <br />erosion and discharge from the affected areas. <br />I believe that Homestake Mining Company should project the consequences of <br />consolidation settlement for their proposed drainage and erosion control ~ ~ <br />facilities. Particular attention should be focused upon the "flow attenuation <br />areas" susceptibility to settlement disorientation. I believe it will be <br />necessary to implement an appropriate topographic monitoring program, in order <br />to determine the character of consolidation settlement occurring at the Pitch <br />Project site. It may be possible to design those facilities in anticipation r <br />of consolidation settlement, if its character can be demonstrated to be <br />predictable at the Pitch Project. <br />I must also observe that the vast majority of the proposed drainage network <br />requires the existence of the South Pit lake, which does not now exist. ~ .~~ <br />Without the excavation of the South Pit, a significant redesign and amendment (~~` <br />of the amended plan would be necessary. At the moment, this presents a (~J' <br />significant quandary. Lacking a drainage plan to implement, should the <br />operator default prior to excavation of the South Pit, it is extremely <br />difficult to calculate appropriate surety for the existing situation at the <br />Pitch Project. At this point in time, surety should include funds with which <br />to complete the appropriate redesign, as well as necessary unknown earthwork. <br />This problem could be resolved upon the submittal of a request for approval of <br />temporary cessation, should same be forthcoming from the operator. <br />Reclamation Costs <br />Homestake Mining Company has also submitted a proposed amended Exhibit L, <br />presenting the company's projection of reclamation costs for their amended <br />post-mining reclamation plan. I have not completed an item-by-item review of <br />the operator's costing, which I gladly defer to you. However, I have <br />conceptually reviewed the proposal for gross items. <br />In keeping with my discussion above, I believe the operator's first item <br />within their reclamation cost rendition grossly understates the regrading <br />effort which would be necessary to complete stabilization regrading of the <br />North Pit landslide mass, if the operator were to default. At this point in <br />time, I estimate that approximately 5,000,000 cubic yards of material would <br />