SITE INFORMATION AND CORRESPONDENCE

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page 2, 242 Sutter Street In their letter HGC states that their report presented the extent of onsite vertical and horizontal residual hydrocarbons in the soil and groundwater. However, no cross- sections of the sites subsurface were included. Depiction of the vertical extent of the contamination should be presented in cross-sectional diagrams to place the analytical data in the proper geological/hydrological context. As stated above, no analytical data has been submitted from this site to indicate the vertical definition of the contamination in soil. The analytical results from the grab groundwater sample collected from 86-90 feet bsg in probe 'J' included 24,000 parts per billion (ppb) TPHg and 99 ppb benzene. Vertical definition of the groundwater contamination at this site has therefore not been completed. Hydro-Geo Consultants questions the need for a shallow well located east of MW-1, near probe 'H'. HGC cites the lack of detected contamination in soil and groundwater samples collected from probe 'H', and in wells U-16 and U-17, which belong to another site and are located near probe 'H', as the basis for their determination that a well to monitor the shallow groundwater is not needed in this area. PHS/EHD believes that the well is needed to monitor for potential movement of the shallow plume off site. The wells U-16 and U-17 are screened at depths of 65-75 feet and 110-120 feet respectively. They are not monitoring the shallow plume detected in MW-1 at total depth of 40 feet bsg. Please note that the table of analytical data submitted in their report indicated that the water sample collected from probe 'H' was collected from the 46-50 feet bsg interval, not at 44 feet bsg as indicated on the laboratory data sheet. Please verify which is the correct information and submit it to SJC/EHD. You are again directed to submit a work plan to complete the following tasks: 1. To continue the investigation of the vertical and lateral extent of the documented contamination at this site in both soil and groundwater. 2. To have the site's monitoring wells surveyed to an established benchmark by a licensed surveyor. 3. To initiate and continue quarterly groundwater monitoring and sampling of the monitoring wells. 4. To submit copies of the boring logs for borings H, J, and I. The work plan and boring logs are due October 28, 2002. The surveying of the wells and groundwater monitoring and sampling should be completed immediately. If you have any questions or comments please call Lori Duncan at (209) 468-0337. Donna Heran, REHS, Director Environmental Health Department Lori Duncan, Senior REHS Nuel C. Henderson, Jr., R.G. LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit IV cc: Marty Hartzell, CVRWQCB John T. O'Rourke, HGC