WORK PLANS - Laserfiche WebLink

Home Browse Search

McCormick and Baxter 3 12 July 1990 9) An annual evaluation of the collected data and a modification of the extraction system if it is determined that (1) the target areas are not being captured, or (2) remedial action goals outside the target areas are being exceeded. This annual evaluation also provides for the shutting down of extraction wells when remedial action goals are met, and the reevaluation of an extraction well if concentrations have not decreased within five years. 10) Treatment at the SRWCF. An application has been sent to Stockton (23 March 1990) regarding these additional flows. Approval has not yet been given. Our comments on the draft RAP, dated 8 December 1990, appear to be adequately addressed in this final RAP. The phased approach to the extraction of contaminated ground water is consistent with the approach we've taken on other RI/FS projects. The proposed six month evaluation of the initial extraction system and the various steps in the performance monitoring program provide ample opportunity to evaluate the effectiveness of the ground water extraction system and to modify it as needed. The number of additional monitoring wells and piezometers for the initial system appear adequate to (1) verify the areal and vertical extent of contamination, and (2) to determine the effectiveness of the initial extraction system and to make necessary adjustments. The proposed pilot testing of a biological soil treatment process should generate the data needed to evaluate the technical and economic feasibility of soil treatment at this site. Finally, McCormick and Baxter has applied for a permit to discharge the extracted groundwater from the initial system into the SRWCF sewerage system. Hence, this final Phase I RAP is adequate. However, I do have some minor concerns that should be addressed during the design of the extraction system and/or during the implementation of the Phase I program. 1) Based upon the consultant's capture zone analysis the three downgradient wells south of the freeway will be required to capture the target areas within zones B through D, and to meet remedial action goals. The initial extraction system does not include these wells. As part of the six month evaluation of the initial extraction well system, the consultant should re- evaluate the design of the extraction wells within the area south of the freeway. 2) Figure 7-7 indicates that 26 piezometers will be installed with the initial extractions system, however, Figure 7-12 states that 18 will be installed. This needs clarification. 3) Extraction wells and monitoring wells (including the Gold Bond wells) should be sampled on a quarterly basis. Water elevations should be taken monthly in all wells and piezometers. Reduced frequency of sampling and water level measurement should not be proposed until at least one full year of data has been collected, and a rationale for the reduced frequency is presented.