SITE INFORMATION AND CORRESPONDENCE

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Shell Station (former) page 2 1267 Country Club Blvd, Stockton. Response III comment letter CETI did not show that the detected nickel or zinc was at background levels as opposed to being on the margin of a plume of significant dissolved metals contamination; hence EHD's continuing concern on the issue. Regarding the proposed work in Response III, EHD concurs with the location and well design of the proposed S-7. Referring to the well design in Response Letter/Site Investigation Work Plan (Response II), dated 30 April 2004, the proposed well will be 45 feet deep, which should be adequate to monitor the sand interval of interest identified in CPT 2 and CPT4. The screen interval should be limited to the sand interval. If these details are correct, the well is approved. EHD does not concur with the need to evaluate four quarters of monitoring results before deciding whether deeper investigation is warranted. This allows the plume another year to potentially migrate and to impact additional groundwater. The proposed soil boring SB-6 has no specific target depth, other than to state that first water will be sampled. First water has recently been at approximately 16 feet below surface grade (bsg). At this depth, the soil composition has been silt in SB-2 and clay in CPT-6, both Iithologies likely to greatly retard the migration of the contaminants of concern. While the impact on water in the fine- grained interval is of interest, the impact on groundwater in the sand at 41 to 46 feet bsg is of greater concern as this unit is more likely to be a significant contaminant migration pathway. As this portion of the work plan is too vague for EHD to evaluate for technical adequacy, EHD cannot approve this portion at this time. Please submit an addendum describing the target interval(s) for sampling and include the method of sample collection, and the sample containers and preservation methods to be utilized. Please submit a work plan addendum for the borings no later than 30 June 2005. You may contact Michael Infurna at (209) 468-3454 or Nuel Henderson at (209) 468-3436 if you have any questions. Donna Heran, REHS, Director Environmental Healt e rtFEH Michael J. Infurna Jr., 'Senior Nuel C. Henderson Jr., PG LOP / Site Mitigation Unit IV LOP / Site Mitigation Unit IV MI/ C* CVRWQCB — James Barton, Sacramento. c: Cambria — Joe Neely5900 Hollis St. #A, Emeryville, CA. 94608 c: SWRCB-Clean Up Fund — Mark Owens, Sacramento.