SITE INFORMATION AND CORRESPONDENCE

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Page 1 of 2 Vicki McCartney [EH] From: Tim Cuellar[tcuellar@advgeoenv.com] Sent: Tuesday, August 28, 2012 11:47 AM To: Vicki McCartney [EH] Cc: Nuel Henderson [EH]; Bill Little Subject: California Stop, 2224 Manthey Road, Stockton CA Attachments: Table 2 GW Results.pdf; 2 - Cal Stop SITE PLAN 03-11.pdf; CA Stop Table 2 Soil and GGWAD.pdf Vicki, We have had a chance to further review the EHD letter (dated 07/16/2012) for the California Stop site. The letter summarizes the conclusions/recommendations reported by AGE in SVE Pilot Test Report - March 2012 (dated 04/19/12). The EHD letter further states that based on historical data collected from borings B1 and B2 at depths between 15' and 25', that one additional SVE well is warranted south (downgradient) of the current UST area without any further assessment (i.e. borings),I would also like to bring to your attention that boring B-3, located immediately west of the UST area, was the most impacted boring of the three borings. However by incorporating well MW-1 (screened 10' to 30') into the SVE well network, the area west of the USTs could be effectively mitigated. Therefore, AGE is in agreement with the EHD that one additional SVE well south of the UST area is warranted and would be sufficient to mitigate SVE impact at the site. However, AGE would like the EHD to reconsider the recommendation to delay the ozone pilot test which was previously approved by the EHD. Ground water has generally fluctuated at depths between 16' and 20'; ground water was last reported at depths of approximately 17' bsg. As the EHD pointed out in the 07/16/2012 letter, significant soil impact has been encountered at the site at depths between 15' and 25', and SVE remediation will not address the hydrocarbon impact at depths generally between 20' and 25'. Additionally, the greatest soil impact was encountered at a depth of 20', which would not be addressed through SVE remediation if in the saturated zone. SVE would not address dissolved impact at the site. Although it would appear MTBE concentrations at some upgradient/cross gradient wells have declined, TBA concentrations at the site generally have sky rocketed in excess of 100,000 ug/l. Additionally, downgradient wells MW-2 and MW-6 continue to have increasing MTBE and TBA concentrations, and continue to be unstable. Based on the above factor's, AGE is of the opinion that proceeding with the ozone pilot test is warranted at this time; it is likely that some sort of ground water/saturated zone remediation will be necessary to close the site. Therefore, we would like the EHD to reconsider the recommendation to delay the ozone pilot 8/28/2012