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Ms. Christine E. Johnston <br />1992 AHR Response <br />August 25, 1994 <br />Page 4 <br />12. The construction and reclamation of the waste pile utilizes the Best Construction Techniques Available <br />(BCTA) for minimizing [he hydrologic impacts associated with the mine's waste. These techniques include <br />the routing of water around the refuse disposal area, quickly diverting water off the pile, and compacting <br />the waste to 90% compaction with two-Foot lifts or less to minimize the permeability of the structure. The <br />reclamation of the pile should improve the surface water quality around the pile by limiting the exposure <br />of the waste [o surface runoff. <br />Historic baseline data for GP-1 was re-evaluated in conjunction with the 1993 AHR. This data shows the <br />TDS and total manganese levels being within the range of the baseline data. Specific conductance appears <br />to approximately twenty percent higher than the maximum ruorded baseline value. MCC can not account <br />for the discrepancy between the TDS and the specific conductance. Total iron concentrations in two cases <br />in 1992 exceeded the baseline range. The 1991 and 1992 iron concentrations in GP-1 are measured as total <br />iron, and concentrations appear to be directly correlated with [he amount of total suspended solids in the <br />sample. TR-71 proposes to discontinue [he monitoring of total metals in groundwater walls in favor of <br />monitoring the dissolved form. <br />Furthermore, MCC is monitoring three other wells on the refuse pile, which have never had adequate water <br />for sampling. There is very little groundwater within the Lower Refuse Pile. <br />Surface water from the refuse pile is diverted west to MB-2R, formally MB~i. The Sylvester Gulch flume <br />is located upstream from most of [he refuse pile and east of the pile. The appropriate surface water station <br />to examine would be the Lower Station on the North Fork of the Gunnison River. The 1992 data does not <br />show a consistent, significant difference in chemical parameters between the two sites. <br />13. A lithologic log of well SOM 128H is provided for incorporation into Exhibit 12. <br />14. MCC has been performing the leachate monitoring program described in Exhibit 51, but it has been <br />inadveRenlly omitted and MCC has not been providing it within the AHR. MCC is providing the data <br />from [he discharge of MB[i for the last four years as Appendix K, of the 1993 AHR. <br />I5. There does not appear to be a question 15. <br />16. The SB series of holes were developed to acquire soils information. Their role as monitoring wells <br />apparently ended with the drilling of the MW series of holes. Page 33 of Exhibit 51 has bun modified <br />to avoid further confusion in the future. <br />17. The tables reporting ground water data in the 1993 AHR hes the total depth of the wells included in the <br />table above [he static water levels. In addition, attached is a table for incorporation into the 1992 and 1993 <br />AHRs, as well as Exhibit 12 of the permit which summarizes well completion information. <br />18. MCC concurs with the Division's recommendation. The attached Technical Revision provides MCC's <br />proposed change in the monitoring plan to drop the requirement to re-sample stations where indicator <br />species ere outside of [he established range and add an annual full suite analysis for all stations. The <br />annual sample would be collected during the September sampling. The full suite will include major cations <br />and anions which can be used to compare with the TDS. <br />