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Memo - Mike Long - _ - April .1, '?9. 2. Monitoring and Leak Detection Currently, BMG is able to collect analyzable data from only 2 ~honitor wells. One of those is near the Rito Seco Creek, and the other is bel~w the tailings and collection ponds. I do not feel this is enough. For leak detection monitoring in general, RCRA policies - for example - call for ~ up-gradient and 3down-gradient wells, at a minimum. With the present configuration, we can only guess that the hydrologic gradient is toward the west so we are uncertain which direction contaminants would flow, should a le k occur. Although it is likely that leakage from the ponds would flow w stward and on trend with the mill area drainage, we cannot dismiss the possi ility that ground water will flow in another direction. A more serious problem may be the leak detection system. Curr ntly, there are three leak detection wells. One is in the Collection Pond, an two others are in the lined ditch that leads upward from the collection pond djacent to the main embankment. All of these leak detection wells tap the ar a between the two layers of 60 ml VLDPE liner. However, except for the moni or wells, there is no way to detect a leak from the tailings ponds that might eave the VLDPE liner and the clay liner beneath. SPECIFIC COMMENTS I will address Mr. Douchane's document and each of the supporting document separately. Matt Lewis Report (April 10, 1992) a. Ground Water Most of the results from ground water wells refer to anal ses taken in the initial phases of the project. Subsequent analyses, xcept from the ponds and from Monitor Well M-9 and a station on Rito Sec Creek, do not exist. The fluids measured in the initial stages in well that are now dry may be inadequate for our purposes. These wells need~to be deepened so that monitor well sampling points can be established b th up-gradient and down-gradient of the tailings facility. b. Air Quality Monitoring No comment. c. Processing Plant Circuit Lewis says that all of the fluids from spills are contain~d in the concrete pad area. However, we saw a small spill from th AVR overflow the concrete pad area. d. Leak Detection System The leak detection system is, in fact, detecting leakage. We have verbal inronnatlon showing that leakage rates are small, but I have not seen 'Hard data. Monitor Well M-9 has been "clean" so far, according to all l~bsl;na:isas, but there need to be mere down-gradient wells. A ;-~.nnaiiz-; r1i,w could by-pass the ,Ingle well. 6i4G needy to be ~.;nr~f,iina fluid volumes from the LD .yells. j