SITE INFORMATION AND CORRESPONDENCE

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Mr. Roy Thim • -3- • 18 November 1993 3. The work plan states that due to the large area of ground water contamination in Zone A, the interim remedial methods should be tested and evaluated before full-scale remediation is undertaken. As we have stated previously, remediation should be conducted in phases since adjustments are necessary until the site is completely cleaned up. We concur that pilot testing of remedial measures such as soil vapor extraction or pump-and-treat is necessary. However, pilot testing a trench which is essentially used for free phase petroleum product (FPPP) appears superfluous, particularly when this FPPP recovery method has been in place at Time Oil since 1988 as stated in EMCON's April 1992 Feasibility Study for Floating Product Removal Interim Measures. As also stated in Boards staff's 13 July 1992 letter to you, the FPPP removal interim measures should be implemented right away if monitoring indicates the presence of measurable FPPP. 4. The work plan states that EMCON is currently conducting a Phase II assessment to determine the lateral and vertical extent of petroleum hydrocarbon contamination. The status of the investigation was not described in the work plan. 5. The work plan lists tasks which will provide additional data required to evaluate potential remedial alternatives and states that these tasks will be placed on an accelerated schedule. We believe that adequate data already exist to proceed with the evaluation of remedial alternatives, at least in Zone A. The additional data which will be obtained during the Phase R investigation can be used to refine the evaluation. A schedule for implementaion of the tasks to be placed on a fast track was not provided in the work plan. 6. The work plan proposes to continue using the passive devices due to difficulties in handling or treating water and also to minimize the potential to adversely affect uncontaminated areas by causing artificial fluctuations in ground water. As previously stated, the potential for spreading contamination can be eliminated by placing the interim remediation measures away from non-STTC members whose site contamination has not been fully defined or may be spread by the interim measures. Also, an extraction system can be designed so that the ground water consistently flows into the system regardless of ground water elevations, and to ensure it captures the entire plume so that degradation of unaffected areas does not occur. Summary 1. We have previously approved the proposed free product recovery measures without the enhanced biodegradation. These measures and the proposed enhanced biodegradation must be implemented as soon as possible.