SITE INFORMATION AND CORRESPONDENCE_1988-1991

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Focused Feasibility Study -2- 13 P arch 1991 Sharpe Site The FS proposes to install the extraction wells, to conduct aquifer tests t evaluate the aquifer characteristics and well yield, to accept or reject extraction wells based on the results of the tests, to abandon the rejected wells and to install replacement extraction wells. Aquifer tests should be performed on monitoring wells (ir the area of the proposed extraction wells) to determine aquifer characteristics prior to the installation of the extraction wells. The abandonment of the extraction wells seems to be unnecessary. Depending on the design of the extraction well , the "rejected" well could be used as a monitor well rather than abandoning the well . The propose approach for the installation of extraction wells appears to be cumbersome and unne essarily costly. The final design of the extraction wells should be based on the cross-sections, the vertical extent of the plume at the proposed well location and on information that could be obtained from a pilot hole. Pilot holes in the area of the proposed extraction well are recommended to confirm the lithology of the target zolle and to collect lithologic samples to design the filter pack and screen so that well 1 sses can be minimized. This approach should prevent the "trial-by-error" approach pr posed in the FS. TREATED GROUND WATER DISPOSAL The FS reviewed only two disposal alternatives for the treated ground wate These disposal alternatives are the discharge to the South San Joaquin Irrigation District Canal (SSJIDC) and injection wells. The FS does not consider the reuse dispos 1 option which is currently used at the Sharpe Site. The treated ground water is tr nsported to San Joaquin CoGen where it is used as make-up water for the steam generation of electric power. In addition, industry in the area of the site may be interested in the effluent because of increasing water restrictions due to the current drought conditions. Sharpe should also consider base reuse of the treated ground Water. It is unclear why the reuse disposal option was not considered in the FS. The FS tends to discourage the injection well disposal option because of the expenses associated with construction, operation and maintenance. The FS fails to con ider the benefits of this disposal option which include the minimization of local dews eying of the aquifer caused by overdraft and to restore the aquifer as a useable drinkwater source through the recharge of the treated ground water. A reuse/recycle optlng n is the preferred disposal option by the Board. Future drafts of the FS must include an analysis of potential reuse and recycle disposal options. EFFLUENT CLEANUP CRITERIA The FS states that the ground water will be treated to reduce the TCE concentrations to levels below 5 micrograms per liter (µg/1) prior to discharge. The concentration of 5 ug/l is the Primary Drinking Water Standard for TCE and will not be accepted as an effluent limit. Best available technologies (BAT) can reduce the concentrtions of TCE to below 0.5 µg/1 (the detection limit) , as has been demonstrated by the North and South Balloon treatment plants. Therefore, non-detect will be considered as the limit Environmental Protection Agency (EPA) Test Methods 601 and 602 and is consistent with the National Pollutant Discharge Elimination System (NPDES) permit (Order No 87-026) for the North and South Balloon Ground Water Treatment Systems. It is unclear why the FS did not consider this effluent limit to be applicable Lo the Central Area Ireatment System.