SITE INFORMATION AND CORRESPONDENCE

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Ernesto Renteria, Jr. March 12, 2015 Pimentel Property Page 2 of 4 1650 S. EI Dorado Street Stockton, CA 95219 from the suspected former UST area, and one (B6) from near the east side of the current onsite building. The grab groundwater sample collected from B7, thought to be located upgradient from the suspected former UST location, did not contain detectable concentrations of any COCs; none of the soil samples collected from B7 were submitted for laboratory analysis, but were noted to lack odor and discoloration. Also reported in ASAR, AGE conducted a ground-penetrating radar survey of the site to assess for the presence of a UST still on site; none was found. Two soil gas samples (B5 and B6) were found to contain TPHg and tetrachloroethene (PCE), all three soil gas samples were found to be impacted by BTEX; one of the PCE-impacted soil gas samples (B5) also had an elevated concentration of the leak-detector compound isopropyl alcohol (IPC), indicating that atmospheric air was entering the boring and that the soil gas concentrations detected may not be representative of what was actually in soil gas at that sampling point. AGE concluded that: • Petroleum hydrocarbon-impacted groundwater is limited to the area around boring B2 and is laterally delineated toward the east by grab groundwater data from B1 and B2, and toward the west by B-7; and • There is minimal or de minimis risk to human health from residual petroleum hydrocarbon- impacted soil and groundwater or from soil vapor intrusion. AGE did not recommend further investigation at this time. Following submittal of the various reports to the EHD, the EHD was requested to issue a letter closing the environmental investigations related to the former dry cleaner operation and the petroleum hydrocarbon release from the former UST. As the EHD had not been providing technical oversight of the investigations the EHD could not issue such a letter. Mr. Renteria entered into the Voluntary Cleanup Program with the EHD to review the work completed, provide technical oversight and issue a "No Further Action Required" letter if appropriate. The EHD has reviewed the provided reports and has received comments from the Central Valley Regional Water Quality Control Board (CVRWQCB) regarding the soil gas investigation; those comments were shared with AGE to resolve the issues noted. The CVRWQCB concerns were primarily based on quality assurance and quality control (QA/QC) documentation for all the lab work, sample locations, and quantification of the effects of atmospheric leakage on the results of one of the soil gas samples. The EHD reviewed the QA/QC for the various analytical reports and found the QA/QC for the soil gas analyses to be adequate, but some key information was not part of the reports for the soil and groundwater analyses. The issue was discussed by phone with an AGE representative and revised reports with the QA/QC data were provided, but there are still some information gaps that the EHD will request AGE to complete. Regarding the soil gas results, the CVRWQCB was concerned with the location of the sampling points relative to the former location of the dry cleaning equipment, which would be the more probable location of leaks. As the former location of the equipment was not provided, there is some