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40, -we San Joaquin County .C, Environmental Health Department DIRECTOR Donna Heran,REHS 1868 East Hazelton Avenue Stockton, California 95205-6232 PROGRAM COORDINATORS ` Robert McClellon,REHS Jeff Carruesco, REHS,RDI cq' •.....•ci�P Website: www.sjgov.org/ehd Kasey Foley,REHS F o R Linda Turkatte,REHS Phone: (209) 468-3420 Rodney Estrada, REHS Fax: (209)464-0138 Adrienne Ellsaesser,REHS January 22, 2014 Messrs. Kirk Larson, PG, and Robert Trommer, CHG State Water Resources Control Board Underground Storage Tank Cleanup Fund PO Box 944212 Sacramento CA 94244-2120 Subject: 701 Charter Way E., Stockton, CA 2014 Review Summary Report Response CUF Claim No 12741 San Joaquin County Environmental Health Department (EHD) has received and reviewed the Review Summary Report- Closure dated 02 January 2014 for the fifth annual review of the site from Robert Trommer of the State Water Resources Control Board (SWRCB) Cleanup Fund (Fund) for above-referenced site. The Fund has recommended case closure. The Fund evaluation indicated the impediments to closure identified by the EHD (incomplete conceptual site model, remaining secondary source, and not meeting Policy direct contact criteria) had already been adequately addressed. The Fund determined that the case meets all eight general criteria, groundwater specific criteria by Class 2, has the active service station exemption for vapor intrusion to indoor air, and the case meets the direct contact/exposure to outdoor air through a professional site-specific risk assessment performed by the Fund. Impacted soil and groundwater have been undergoing remediation through dual phase extraction (DPE). Since the vapor extraction portion of the system was initiated in January 2011, approximately 5,225 pounds of hydrocarbons have been recovered from subsurface soil, and the mass recover rate has declined to low levels. Groundwater extraction was initiated in February 2011 and approximately 320 pounds of petroleum hydrocarbons have been removed, but groundwater samples have been slow to exhibit the effects of DPE, perhaps due to residual contaminant mass in saturated zone soil not being fully addressed by the DPE. Depth to water has been approximately 28 feet below surface grade during remediation, while impacted soil extends to 45 feet bsg. The Fund gives the plume length as less than 250 feet and benzene concentrations less than 3,000 micrograms per liter (pg/1) to fit groundwater specific criteria Class 2. The EHD notes that the benzene concentrations have been less than 3000 pg/I in the most intensely impacted monitoring wells only during the last two or three monitoring events. The EHD also notes that contaminant concentrations have been increasing sharply in monitoring well MW-6 over the last two monitoring events. MW-6 is located toward the south of the former UST system. As the benzene concentrations less than 3000 pg/I have been only achieved recently during active 2014 Review Summary Report Recommendations Response CUF Claim No 12741.doc