SITE INFORMATION AND CORRESPONDENCE

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Mr. Carl Navarra .. 1 Page 2 of 3 7500 W. Eleventh Street 29 December 2008 Tracy, CA or the Department of Health Services Maximum Contaminant Levels (MCLs) for public drinking water; The Central Valley Regional Water Quality Control Board (CVRWQCB) requires that these goals be achieved in a reasonable timeframe. The figure provided by TSJCI for the decline of TPHg in MW-3 appears to indicate that many years will be required to achieve background conditions. • In June 2008, the total petroleum hydrocarbons quantified as gasoline (TPH-g} concentration was 21,000 micrograms per liter (pg/L) and the benzene concentration was 690 pg/L; both pollutants exceed concentrations likely to be considered for closure concurrence by the Central Valley Water Quality Control Board (CVRWQCB). • Methyl tert-butyl ether (MTBE) has been detected in the most down-gradient monitoring well during the last two monitoring events; while the detected concentrations have been quite low, the recent presence of MTBE in the well indicates that the plume of impacted groundwater is still migrating, and therefore cannot be considered stable. • TSJCI may characterize the contaminant concentrations in the impacted monitoring wells (except for MW-7) as "very low to trace concentrations", but total petroleum hydrocarbons quantified as diesel (TPH-d), TPH9, benzene, and/or MTBE concentrations exceed primary or secondary MCLs and/or the odorltaste threshold in MW-3, MW-4, MW-7, MW-10 through MW-14, MW-17 and MW-18 during the last reported quarterly monitoring event, and in MW-6, MW-16, MWFP-1 and MWFP-4 when last sampled. MTBE was detected at concentrations as high as 180 micrograms per Liter (pg/L) during the last reported quarterly monitoring event and was detected at concentrations as high as 830 pg/L during the previous event; the EHD does not consider these to be "very low to trace" concentrations. • With the high usage of groundwater in the immediate area for potable water supplies, the EHD does not consider the site, with a large plume of impacted groundwater, a low- risk situation that can be either closed or only marginally monitored. • TSJCI had proposed, and the EHD had approved, a groundwater remediation technology as adequate and necessary for your site based on site conditions and local exposures; a slow-down in Cleanup Fund reimbursements does not alter these factors. For the reasons noted above, the EHD cannot concur with TSJCI's recommendation for site closure or severely reduced monitoring, and directs that you continue to work toward implementation of either the approved remediation plan or propose an alternative remediation plan. The EHD will try to aid you in obtaining the site access agreement for the 7501 W. Eleventh Street site, but has always believed getting access for the approved remediation method (digging a cutoff trench along the site's southern boundary to recover impacted groundwater and free product, if present) would be problematical. Due to an oversight, the EHD must temporarily withdraw approval of the corrective action plan (CAP) to conduct a 30-day public participation period; after which the CAP as proposed, or as modified to address concerns of the public, will be approved. There are other closure criteria that must be met before your site can receive regulatory closure; you must conduct a vapor intrusion evaluation to quantify the risk posed to occupants of structures on your property and the other affected properties. You must also compare contaminant concentrations proposed to be left in place to the San Francisco Bay Regional Water Quality Control Board's (SFBRWQCB) Environmental Screening Levels (ESLs). You must provide an acceptable rational for any contaminant concentrations exceeding the ESLs Closure Request Response Letter 1208