SITE INFORMATION AND CORRESPONDENCE_FILE 2

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llft� N-00 Response to SJCEHD`s 8.19-08 Letter---Page 6 Joe's Travel Plaza,15600 S.Harlan Roast 9115103 <0.50 9/10108 7.3 MW-7 3/9/05 42 9/28/05 110 12/09/05 14 9/10/08 35 MW-8 9/18/07 35 12117/07 120 3113108 <0.50 6/02/08 29 9/10/08 74 Upon review of Table 1 (as illustrated in the excerpts provided above) it is clear that MTBE concentrations routinely fluctuate at this site, sometimes for as long as 12 to 18 months, before they ultimately trend.downward. Based on this analysis, it could be premature to assume that the statistically insignificant increase in MTBE concentrations observed in well MW-13A/B is indicative of an overall upward trend in concentrations such that further site investigation and/or active remediation will be necessary. At the August 2007 meeting it was agreed that Stratus would prepare and submit a Site Conceptual Model for the site as well as a Final Remediation Ilan and to date neither of these documents have been submitted to the EHD. If continuous remedial action is not effective then evaluation of shorter-term remedial actions should be considered.,3 13 Based on the historical contaminant concentration trends shown in the attached Exhibits, it appears that over time, natural attenuation will adequately remediate this site. As active remediation no longer appears to be necessary, preparation of a Site Conceptual Site Model and Final Remedial Action Plan no longer appear to be warranted. Mr. Dhoot requests instead, that his consultants, Stratus, work with EHD to set risk-specific closure goals and then conduct a vapor monitoring survey and risk assessment to determine whether such goals have already been met, and if not, how to achieve them in the most time and cost-effective manner. The EHD was informed on August 14, 2008, that MW13AB and MW13C have been found and restored and would be sampled on September 10, 2008. Data from these wells is necessary to determine if the contaminant plume is defined to the northwest and if contaminant concentrations are declining in the direction.14 14 Stratus did recover lost wells MW-13A/B and MW-13C and the wells were sampled on September 9 and 10, 2008. Analytical results indicate MTBE concentrations are relatively stable in MW-13A/B(110 [tg/L when last sampled in September 2007 and 1301,g/L when sampled in September 2008). Analytical results of the September 2008 samples from well MW-13C confirm the MTBE plume has been vertically defined. In the Stratus Environmental, Inc. letter dated July 3, 2008, it states Stratus would like to submit a work plan to evaluate soil vapor migration. The EHD approved of this proposal. The vapor 6