1994-03-23_HYDROLOGY - M1977378 - Laserfiche WebLink

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Sunnyside Gold Corporation March 23, 1994 pegs 3 D) After plugging, sampling locations and frequency will main be dependent upon the overall method of analyses that will be used, and again, monthly analyses will probably be required at a minimum. With respect to the total duration of the post-plugging monitoring, this should be related to the time when the elevation of the mine pool reaches equilibrium. The Corporation has proposed that the monitoring continue for two years after equilibrium has been reached, and for a minimum of at least five years in total. Since these timeframa may have been based more upon tracer detection oonsiderations than upoa the monitoring of pollutant loads, they need to be re-evaluated. E) Along with the specification of what statistical methods will be used to compare pre and post-plugging loadings, it will be necessary to agree upon some decision criteria (e.g., a_ILS change in mean values) that will be used to determine if loadings have changed. F) As we have already discuased with the Corporation,we aced to insure that any material placed inside the mine tunnels for use as a tracer will not itself pose a toxicity problem. The potential for stratification inside the mine pool should be considered. G) 3ome additional detail should be provided wits respect to what actions will be taken if an increase in loading is observed, and what type of bulkhead maintenance will be provided. We recognize that if pre and post-plugging loading comparisons will be made at each individual seep in the basin, the resulting data requirements could be quite extensive, particularly if many new seeps are encountered. It may be possible to reduce the total amount of sampling that will be required by identifying sampling sites that could be used to monitor the cumulative loading from multiple sources - a concept which may have already been suggested to the Corporation. While there may be some complications with relying upon such a method, it may be simpler to adjust the monitoring program to mitigate those complications than to perform an adequate amount of monitoring at individual seeps. Please review the above proposals. If we can agree at least upon some general concepts,we can then get into the details of the program. As we have previously stated, it is our goal to take the agreed upon plan and incorporate it as part of the Corporation's existing CDPS discharge permits. The Division strongly recommends that plugging of the American Tunnel be delayed until this issue is resolved. Sincerely, Patricia A. Nelson, P.E. Industrial Unit Chief Permits and Enforcement Section Water Quality Control Division xc Amelia Whiting, State Attorney Generals Office Jerry Raisch, Vranesch dt Raisch, Attorneys at Law Christpher Hayes, Sunnyside Gold Corporation Greg Parsons, WQCD Tim Horn, WQCD Alien Sorenson, State Division of Minerals and Geology EPA Region VIU Local Health Department MS-3 File