SITE INFORMATION AND CORRESPONDENCE

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Mr. G. Robert Meyer -2- 28 March 1986 ground water around the leak site. This seems to verify that the oil had been trapped in the soil pore spaces, as we had all theorized. The oil is more mobile under these circumstances. Your action of drawing down the water level in 'the pit and in wells #9 and #10 very probably prevents lateral migration of oil from the presently contaminated area. However, I believe that too much drawdown in the pit or wells leaves the oil and emulsion in the soil pores. You should design and implement an oil recovery program as soon as possible to take advantage of the mobility of the oil and emulsion. A first step would be to set the pump intakes at or ,just below the ground water surface in order to pick up primarily oil . From correspondence, discussion with LOF employees, and my inspection of this very flat area, it seems to me that significant lateral migration of the contamination is not likely in the short term. It appears that the westward migration of the plume from the leak towards well #9 was caused by pumping of the well next to monitoring well #1. Since this pump has not operated since the leak was detected and since no other wells nearby are being pumped, little migration should be expected. As such, very little drawdown of the recovery wells is required. Drawdown should be limited to a level that encourages flow of oil and emulsion to the pump pickup but not so low that oil is left in the soil pores. During our meeting of 3 March and in telephone conversations with Mr. Quick, we have discussed the feasibility of artificially raising the ground water table around and in the leak area. This locally high ground water should displace the oil in the soil pores so that it can be removed by pumping out the uppermost ground water layer. If this were done, the recharge areas must be situated so that the contaminated area is surrounded by the ground water ridge thus created. In this way, oil migration would be into the contaminated area where it could be collected and removed. Ilsee two problems with this approach. The plume probably extends under the building and, unless the ground water ridge could be completed under the building, it would probably encourage oil migration to additional areas under the building. The other problem is that, if the ground water ridge got too high, soil that is above the existing level of oil contamination could become contaminated. I 'm not convinced that this would be bad, however. One possible cleanup alternative which should be considered is to totally flood the leak area from the outside in, and therefore from the bottom up. If this would displace the oil in the soil pores, oil , emulsion, and water that rise to the ground surface could be removed. The operation could continue until the water that surfaced was no longer contaminated. It would be reasonable to believe that whatever oil was then left in the soil was not mobile and would no longer pose a threat to water quality. This alternative would of course require that the ground water ridge encompass the entire plume, even that portion under the building. Locally elevating the ground water to facilitate oil removal is only a sugges- tion. You are free to investigate or propose other alternatives for removing the oil from the ground water and the soil . I do not believe that the recent drawing down of the ground water levels in the pit and in wells #9 and #100s accomplishing this.