SITE INFORMATION AND CORRESPONDENCE FILE 1

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San Joaquin County .� Environmental Health Department DIRECTOR Donna Heran, REHS z: 1868 East Hazelton Avenue Q: PROGRAM COORDINATORS (n. { Stockton, California 95205-6232 Robert McClellon,REHS Jeff Carruesco,REHS, RDI Kasey • �'q' / �P Website: www.sjgovLinda .org/ehd Foley,RENS Li F o•R`' Linda Turkatte, RENS Phone: (209) 468-3420 Rodney Estrada, REHS Fax: (209) 464-0138 Adrienne Ellsaesser,REHS February 26, 2014 Messrs. Kirk Larson, PG, and Robert Trommer, CHG State Water Resources Control Board Underground Storage Tank Cleanup Fund PO Box 944212 Sacramento, CA 94344-2120 Subject: 639 Clay Street, W., Stockton, CA Review Summary Report— Closure (Sixth Review) for CUF Claim No. 8542 San Joaquin County Environmental Health Department (EHD) has received and reviewed the Review Summary Report — Closure (Sixth Review) for CUF Claim No. 8542, dated 13 January 2014, from Robert Trommer of the State Water Resources Control Board (SWRCB) Cleanup Fund (CUF) for the above-referenced site. The CUF has determined that the case meets the criteria of the Low-threat Underground Storage Tank Closure Policy (LTCP) and recommended that the case be closed. The CUF addressed the impediments to closure identified by the EHD as follows: Inadequate conceptual site model (CSM) — The CUF states that adequate data are available in GeoTracker to prepare a CSM consistent with the Policy. The EHD concluded that the CSM was not adequate as the most intensely impacted monitoring well on the site is MW-1, located approximately 30 feet downgradient of the easternmost edge of the over-excavation, screened in hydrologic unit 2 (HU2), and there are no additional wells screened in HU2 downgradient of MW-1; therefore the EHD has concluded that the plume of impacted groundwater is not fully delineated in the downgradient direction and that the CSM is inadequate. Secondary source remains — The CUF states that the secondary source as defined by the Policy was removed by excavation in 2003. The area of current concern is the southern former underground storage tank (UST) area, often referred to as the former UST No. 3 area, which was over-excavated in 1994; the 2003 over-excavation was in the so-called UST cluster area approximately 200 feet north of the former UST No. 3 area. Kleinfelder, Inc. reported in 1994 that even with over-excavation, locally as much as 38 feet below surface grade (bsg), "the limit of affected soil (was) not ascertained". A bottom sample from the excavation at 20 feet bsg contained 5,200 milligrams per kilogram (mg/kg) total petroleum hydrocarbons quantified as gasoline (TPHg) and a side wall sample frorn 16 feet bsg contained 2,100 mg/kg TPHg, although benzene and other volatile organic compounds were either not detected or were detected at low concentrations in the five soil samples analyzed. Advanced GeoEnvironmental Inc. 2014 Review Summary Report (Sixth) Response CUF Claim No 8542.doc