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page 2 , 2085 Fremont 6t , N It is the opinion of SJC/EHD that a comparison of these two sites should have included the entire well network of the Apache Plastics site, especially if ATC thinks the sites plumes are commingled. In addition to previously mentioned Apache well A-MW-6, Apache well A-MW-10 , which is located east of A-MW-2 and is screened from 99- 109 feet bsg, is impacted . The Apache site has two wells (MW-18 and MW-16) that are screened from 85-90 feet bsg, the same as your site's mid-level wells. MW-18 is located next to A-MW-2 and has had reportable concentrations of contaminants, ` including 1 ,2-DCA. MW-16 has been mostly non-detect. These two wells should have been included in the discussion of the intermediate depth of the plume. i The cross-sectional diagrams provided in the Study are confusing. For example, Figure 5, A-A', indicates the lithology from surface to 10-15 feet bsg is silt, but Figure 6 , B-B' indicates the lithology from surface to approximately 20 feet bsg is clay, despite the fact that these two cross-sectional lines intersect each other. Figure 6 also indicates there is continuous sand from approximately 90 feet bsg to 136 feet bsg, but no actual sample data or boring logs have been provided to support this. On Figure 7 it appears that all CPT logs that indicate "stiff fine grained" ATC has interpreted to be sand . While no log exists for Apache well MW- 11 , cross-section Figure 7 makes it appear that there is one, and that it is very different from the log for CPT-11 located just a few feet away. Figure 8, titled 'Geologic Cross-Section B-C Without CPT Lithology', is essentially based on no data at all , as logs do not exist for A-MW-11 , MW- 12 from surface to 70 feet bsg or for A-MW-9 from surface to 60 feet bsg. In addition , the logs of wells MW-1 , MW-5 and MW-8, the wells on your site that exhibit some of the highest concentrations of contaminants in the groundwater, were not included on any cross-section . The water bearing zones crossing these wells are of major importance to understanding this site. The new consultant for the Apache Plastics site, Advanced GeoEnvironmental , Inc. (AGE) has notified SJC/EHD that they have contacted ATC to coordinate quarterly groundwater monitoring and sampling events. In the future all work should be completed on the same day, and results of groundwater monitoring and sample analytical data should be shared . AGE is currently preparing a feasibility study to determine the most effective method for remediation of the groundwater contamination at the Apache Plastics site . Please proceed with preparation of a work plan to continue the investigation offsite of the lateral extent of the contamination in the shallow and intermediate depth intervals . This will require wells east and southeast of Apache wells A-MW-6 and A-MW-10. The work plan is due for submittal no later than September 28, 2007. Please proceed with preparation of a feasibility study for remediation of the groundwater contamination at your site. The feasibility study must compare at least two cleanup alternatives for both their ability to remediate the contamination and cost. The feasibility study is due for submittal no later than September 28, 2007. If you have any questions please call Lori Duncan at (209) 468-0337. Donna Heran , REHS, Director Environmental Health Department I':I�U 4 0/A;V�KZ� «— Lori Duncan , Senior REHS Nuel C . Henderson, Jr. , PG LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit IV cc: James Barton , PG, CVRWQCB Todd Hafner, PG, ATC