SITE INFORMATION AND CORRESPONDENCE

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Mr. Robert Garcia • • 29 May 2002 L.eprino Foods,Inc. 2 RW-2 will enhance the capture of the groundwater contaminant plume. We were later notified that RW- 1 and RW-2 were designed as extraction wells, but were never plumbed into the extraction system. The Report shows that TPH-d concentrations in RW-2 increased again over the last two quarters. Therefore, extraction from wells RW-1 and RW-2 is necessary to capture the plume. 2. If natural attenuation is proposed as a remedy for the offsite groundwater plume, then additional sampling for additional parameters is needed to show natural attenuation is occurring. A hydrogeological conceptual model is also required for natural attenuation. Please review EPA Region IX protocols for Monitored Natural Attenuation, and include the necessary analyses in a Work Plan. 3. It appears that RW-4A is capturing the western edge of the plume. However, the northern edge of the plume appears to be migrating offsite at RW-1 and RW-2, between RW-4A and RW-5A. The extent of the offsite plume has not been characterized. Therefore, an offsite groundwater investigation is now necessary to characterize the extent of the plume. 4. Increasing concentrations in MW-6 may be due to expansion of the plume as a result of the shutdown of the extraction system during 2000. However, there are no wells between the source area (RW-5A) and MW-6 to confirm whether the increase is due to a lack of capture at RW-5A. 5. Several perimeter and offsite monitoring wells are sampled quarterly only for water levels and presence of SPP. These wells do not contain SPP. In order to assist in the re-characterization of the extent of the groundwater plume, which may have expanded across the site while the treatment system was inactive in 2000, sampling of all offsite and perimeter wells for TPH-d for two consecutive quarters is required. Please include sampling of wells MW-2, 7, 8, 9, and 10 for TPH-d during the next two quarters. 6. It is premature to begin discussing system shut down when the groundwater plume is not defined, and the extraction system is not capturing the plume. 7. The Regional Board MRP No. 5-00-833 requires that the semi-annual reports include isoconcentration contour maps. Since the annual report includes the semi-annual report for December 2001 and March 2002, quarterly isoconcentration contour maps should be included in the Report. Please include isoconcentration contour maps in future semi-annual and annual reports. Specific Comments: 1.Section 4.1.2 Apparent Hydrocarbon Thickness (paragraph 2, page 9), Section 4.2 Ground Water Analytical Data, March 2002 Analytical Results (paragraph 1, page 11),Figure 4-8, and Table 4-2: • The text in the two sections (4.1.2 and 4.2) give two SPP thickness values and state that SPP is both increasing and decreasing in MW-3 (Section 4.1.2) during the same period of time. • Section 4.2 text, in two back-to-back sentences, gives two separate TPH-d concentrations for the same monitoring well, RW-1. Text on the following page 12 says that one of the concentration values is associated with RW-2. • Figure 4-8 shows that monitoring well MW-17 TPH-d concentration was 120 µg/L during September 2001, while Table 4-2 states that MW-17 was non- detect(<50 µg/L) during the same