SITE INFORMATION AND CORRESPONDENCE

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Mr. Robert Garcia - 2 - . 25 May 2000 3. The report states, "Operation of recovery wells RW-1, RW-2, and RW-3 has not been required for capture of groundwater impacts at the site." These recovery wells are downgradient of the two plumes, and monitoring data from RW-1 and RW-2 wells may supplement the current program. MW-11 is currently monitored on a quarterly basis and is directly adjacent to RW-3, so monitoring of RW-3 is not needed. Therefore, Leprino needs to evaluate the feasibility of converting RW-1 and RW-2 to monitoring wells. 4. The data results from recovery well RW-4a are unclear. The report states that data are unavailable to evaluate the flow rate at RW-4a. Also, the report does not clearly present the amount of product removed from RW-4a. Leprino needs to clarify the total volume of product removed and the average flow rate at RW-4a. 5. Figures 4-7 and 4-8 illustrate the northwestern free-phase product plume in two different locations. Due to the position of the replacement well further north of the approximate plume location(as illustrated in Figure 4-7), it is likely that the free-phase product plume spread north by the initiation of pumping in the new recovery well location. This is contrary to the plume location illustrated in Figure 4-8. Therefore, Leprino needs to evaluate the effect on the northwestern free-phase plume of the relocation of recovery well RW-4. 6. Appendix C contains a Diesel Oil Extraction Log for wells MW-1, MW-4, MW-12, MW-14, RW- 4, and RW-5. Leprino needs to clarify the purpose of this log and the data presented in this log. 7. Leprino needs to evaluate the effectiveness of MW-14a as a replacement well for MW-14. Currently, MW-14a appears to be placed crossgradient of the northwest free-phase product plume. Staff is concerned that monitoring data from MW-14a provide little value for the evaluation of the northwest plume. 8. The Monitoring Well Fluid Level Measurement Data table should show the total depths and screened interval for the shallow and deep wells. This information is essential for thorough review of the data presented in the report and evaluation of recommendations. 9. Future report site maps should show the location of the former Mobil facility (Mobil), paved areas on Mobil, monitoring well locations in relation to the Leprino and Mobil, and new structures added or changed as a result of the plant expansion. Also;figures need to note abandoned monitoring wells and/or extraction wells as such. 10. In Figures 4-4 and 4-5 legends,the total extractable hydrocarbon (TEH) concentrations are in µg/l. Leprino should determine if the unit value is correct. 11. The report states that the data show, "dissolved and free-phase impacts are limited to within the Leprino property boundary." According to the data, the free-phase product appears to be contained within the facility boundary. However,MW-11, along the northern property boundary, contained TEH during the first and second quarter 1999 (data are not available for third and fourth quarter as the well was obstructed during construction-related activities). The detection of TEH in MW-11 is consistent with historic data presented in the Table 4-2. Therefore, the data do not show that the dissolved phase plume is confined within the property boundary.