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Memo to Berhan Keffelew CRESSON Leak Collection Audit page 5 consultants in projecting leak detection rates from the Heap Leach Pad. No liner is expected to be leak free. However, leakage rates must fall within acceptable limits. Allen Sorenson has applied this methodology in projecting the acceptable leakage rate from the Cresson Mine Heap Leach Pad - Phase 1 saturated pool area (see attached February 8, 1995 memo to Berhan Keffelew). Assuming one small hole in the liner (0.1 cm) per acre, a 14 acre saturated pool area, and an eventual high-stand average head of 32.25 feet, Al projects the anticipated acceptable maximum leakage as 26,490 galjday. There is no need to wait for the eventual processing saturated pool to reach its projected high stand before we can determine whether the current leakage rate falls below the acceptable projected maximum. If the applicant determines the saturated elevation within the saturated pool area of the heap leach pad the acceptable maximum leakage can be calculated for that head level and saturated pool area. CC&VG should complete this determination in order to compare it with the leak collection production rate determined under (1), above. Furthermore, if CC&VG were to determine and compare the relationship of measured leak collection production with projected acceptable maximum leakage rates as the saturated pool elevation increases, the relationship of head and leakage rate could be defined. This relationship might be indicative of the types and elevation of leaks encountered by the rising saturated pool. (3) Perform chemical mass balance analysis of leakage source The third task is to verify the source of the fluid entering the leak collection layer. Extensive visual observations of the heap leach pad - phase 1 foundation area determined that little ground water exists immediately beneath the composite liner. A dendritic underdrain system was installed to intercept and drain any ground water which did encounter the composite liner from beneath. The Division concurred with the propriety of this standard design approach. However, the assumption by CC&VG that all leak collection system fluids emanate from the processing fluid within the primary liner must be verified. It is impossible to observe the subterranean situation beneath the composite liner. It is also impractical to discretely sample fluids within the leak collection layer, other than at the sump production well. Further, because the complications of quantifying precipitation and evaporation, as well as the volume of fluid within the unsaturated regime of the ore, it is impossible to determine the exact volume of fluid within the saturated pool.