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<br />Crown Jewel Project <br />June 25, 1992 <br />Page 8 <br />faith in the ability of a future testing program to adequately idt:ntify <br />representative conditions within [his zone. <br />In such circumstances one normally looks to the performance of other <br />facilities of this type to increase the database. Unfortunately, there is <br />only a limited track record for this modified upstream constructi~~n method. <br />According to Mr. East the first application of this method of modified <br />upstream construction was in 1986. It would take several years from that date <br />before any appreciable height of upstream constructed berms would have been <br />constructed. Thus, we have only recently entered the point that .tny static <br />stability shortfalls in the design would become manifest. Certailtly, no <br />record of response to strong earthquakes as yet is likely. This Lack of data <br />is of particularly concern given some poor experiences with conventional <br />upstream constructed projects impounding slimes in areas of high seismicity. <br />Other state Dam Safety Programs, known to have operating gold minas producing <br />similar slimes, were contacted. They were polled as to their policies <br />regarding upstream construction methods and any experiences with this type of <br />impoundment. No consensus has developed among our peers as Table 1 shows. <br />States straddle the issue with responses ranging from an outright prohibition <br />of such facilities to unconditioned acceptance. The opinions undoubtedly <br />reflected the seismic setting of the particular state. In general, the higher <br />the seismic setting, the less likely the state was to accept such a proposal. <br />TABLE 1 <br />State Dam Safety Approval Policy on Upstream Comments <br />Section Authority Construction <br />Celllomie Yea Not Albwed <br />Cobrado No• Albwed Reportedly has a number of these facilities. <br />Montane No• Albwed Currently one major project is <perating that <br /> impounds slimes that empbys ':he upstream <br /> construction technique for one side of the <br /> facilitY• The operator has been unahb to <br /> document satisfactory stability under static <br /> or seismic loatlings for this eler lent o}the <br /> project. The operator contends that post- <br /> cbsure, this sbrnent will ba kft in a <br /> satisfactory state. In the interi n, the failure <br /> of this component would allow the release <br /> of the slimes into an adjacent ripen pit with <br /> minimal likelihood of any o/faire impacts. <br />Nevada Ye• Albwed Hsvs approved upstream construction <br /> schemes on much coarser, sih~~ sand tails. <br /> Not aware of an upstream con :trusted <br /> project founded on climes. <br />Wechinglon Ves None approved to Echo Bay, Acamera end Hecla Jay mines <br /> date (Aspen Project). All employ conventional <br /> tlams to impound the gold min ng process <br /> slimes. <br />• Exempt by statute, but permhting agencies submit decgna to the Dam Safety offices for review arW comment. <br />