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Attachment TP4UGD <br /> Page No.TP4UGD-3 <br /> Permit No. CO-0044768 <br /> Remedial Goals and Objectives <br /> The Tailings Pond No 4 Upland Groundwater Diversion Project's goal would be to minimize the <br /> potential for groundwater to contact mill tailings through the use of hydrological control installations <br /> in order to reduce am,potential for impact on the Animas River from dissolved metals. <br /> Site Loading Estimate <br /> The site loading estimate for this project was based on visual observations and weighing potential <br /> impact based on assumptions and observations using data extrapolations from tests on similar <br /> material <br /> —Observations and Assumptions <br /> • The drainage area behind Tailing's Pond No. 4 is approximately 150 acres. Surface streams <br /> do not exist in this area. <br /> • It is assumed that 15 percent of the precipitation is lost through evaporation and <br /> transpiration and that SGC's existing diversion structures capture 60 percent of the near <br /> surface groundwater flow and any surface runoff from the drainage area. <br /> • It is assumed that if oxygenated water percolates and contacts tailings material dissolved <br /> metals will be picked up by the migrating water. <br /> —Methodologn for Estimation of Potential Loading <br /> • It x\as assumed that the annual precipitation on the drainage area would be the average of <br /> Red Mountain and Silverton weather stations due to topography. <br /> • The assumption N\as made that not all of the water could contact tailings and 15 percent was <br /> the estimated quantlt', of migrating groundwater that potentially could contact tailings. <br /> • Loading\\as calculated based on 1:1 leach test results from similar material (le. tailings <br /> from the same source) These results were divided by 20 to account for groundwater type <br /> exposure This dilution (20:1) is consistent with dilutions used for TCLP testing <br /> —Estimation of DissoIN ed Zinc Loading Potential <br /> • Based on the abo\e methodology for estimation, it is estimated that the potential exists for <br /> an annualised dail\ loading of 9 pounds of dissolved zinc. <br />