SITE INFORMATION AND CORRESPONDENCE_1988-1991

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Focused Feasibility Study -3- 13 March 1991 Sharpe Site MONITORING The FS proposes that weekly analysis of the treatment system for VOCs be performed. This frequency is not sufficient to evaluate treatment efficiencies during start-up and prove-out phases. The monitoring frequencies for the start-up and prove-out phases of the treatment system will be required to be greater than the monitoring frequencies for the full-scale operations. The Central Area Treatment System will be required to perform daily analysis for VOCs for a period of time after the start-up of the treatment plant. In addition, the influent and effluent samples are to be collected at approximately the same time so as to be representative of the discharge during the sampling period. The FS proposes to conduct monthly monitoring of the extraction wells. However, the frequency of monitoring may need to be increased for the start-up and prove-out phases of the treatment system but may ultimately be reduced to monthly or quarterly for the full-scale operations. CONTINGENCY PLAN The FS did not provide any discussion on a contingency plan for the Central Area. Because air stripping is the remedial technology used for ground water treatment in the North and South Balloon Areas, there should be ample information available to generate a contingency plan for the Central Area. The contingency plan should provide those measures that will be taken to prevent downtime of the extraction and treatment facilities. Specifically, this plan should provide the measures that will be taken to install fully functioning extraction wells using the knowledge and experience Sharpe has acquired by operating the other two extraction/treatment and disposal systems. REMEDIAL ALTERNATIVES The FS states that the bulk of the sediments underlying the Sharpe site are not saturated with water. The draft final RI Report stated that only about 25 percent of the subsurface is saturated, which we question. However, assuming that this is correct and that not all of the TCE contamination is in the dissolved phase but is also present in the vapor phase, it follows that the remedial measures taken in the North and South Balloon Areas as well as the Central Area, may account for only a portion of the needed remediation at the site. Sharpe should consider vapor extraction as a remedial alternative for the bulk of the unsaturated sediments at the site. This technology must be considered as a potential remedial response action in the soil FS. CKW:cw