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May 24,1995 • -2- • 943-2847 The response levels or ALR's for the Cresson Project have been previously identified az follows: Low Volume Solution Collection Fill Flow Rate less than 50 percent exceedance 50 percent to 10 percent exceedance 10 percent to 2 percent exceedance above 2 percent exceedance Action Pump collected leachate Increase LVSCS measurement from weekly to daily intervals and repair any observed liner damage Advise DMG of the LVSCS pump rate and improve water management to reduce flowrate Advise the DMG and reduce the LVSCS flowrate through the following measures: • reduce head on liner; • plot rate of LVSCS flowrate versus solution elevation; • note when LVSCS flowrate falls within acceptable envelope; and • maintain solution levels within acceptable limits during all periods of operation. LINER LEAKAGE EVALUATION A probabilistic analysis was next performed using the Excel add-on program Crystal Ball. The Crystal Ball program uses simulation to model the full range of possible values and measures the likelihood of occurrence for each possible value. Repetitive Monte Carlo sampling of the distributions for the head and defect area was performed. tt was assumed that the defect diameter would follow a normal distribution. The head waz modeled as a triangular distribution for various depths. Thereby, the distribution for the defect area and head was incorporated into Equation [I] to determine the probability distribution for liner leakage. Van Zyl (1990) estimated that defect sizes may have a coefficient of variation of 50 percent. Defects were modeled with a normal distribution for an average diameter of 2 mm and a standard deviation of I mm. One defect was assigned per acre of geomembrane. In the event of that a fraction of a defect was calculated, the number of defects was rounded up to the next integer value. The elevation versus gecembrane surface area was provided by the Cripple Creek & Victor Gold Mining Company (CC&V). This information is presented in Table 1. CONCLUSION The results of this investigation vary from the original analysis performed by Golder (1994) for the following reasons: The geomembrane surface area used in the calculations reflects the actual surface area versus elevation for the Phase I Pregnant Pond geomembrane after construction; Flow was calculated based on calculating the head on a defect Cor discreet sections. The Pregnant Pond was divided into 14 intervals, each corresponding roughly equal to I acre of geomembrane area. The previous analysis used an average head over the entire Pregnant Pond;and Flow waz calculated based on an integer value of defects. Colder Associates loc.