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California Regional Water Quality Control Board <br /> • Central Valley Region 0 <br /> . � <br /> Karl E.Longley,ScD,P.E.,Chair <br /> Arnold <br /> ,Linda S.Adams Sacramento Main Office Schwarzenegger <br /> Secreiaryfor 11020 Sun Center Drive#200,Rancho Cordova,California 95670-6114 Governor <br /> Environmental Phone(916)464-3291 •FAX(916)464-4645 RECEIVED�a g- <br /> Protection http://www.waterbouds.m.gov/antralvalley RE EIVED <br /> 10 July 2008 JUL 14 20H <br /> Ms. Jennifer Sedlachek <br /> ExxonMobil Oil Corporation ETEC ENGINEERING <br /> 4096 Piedmont Ave, #194 <br /> Oakland, CA 94520 <br /> DOCUMENT REVIEWS, FORMER MOBIL STATION 99CAS (AKA MARL ER PROPERTY, <br /> AKA JH GRIFFIN MOBIL SERVICE), 75 EAST ALPINE AVENUE, STOCKTON, <br /> SAN JOAQUIN COUNTY(LUSTIS #390857) <br /> 1 reviewed the Well Installation and Risk Assessment Report (Report) and the Subsurface Investigation <br /> Work Plan (Workplan), received 19 June 2008 from your consultant ETIC Engineering, Inc. (ETIC). <br /> Both documents were submitted in response to my 3 May 2007 letter (Letter). The Report documents <br /> the installation of groundwater monitoring wells MW6 and MW7; presents a screening risk assessment <br /> using soil, groundwater and soil vapor data collected in 2007 at the site; and includes a sensitive <br /> receptor survey. The Workplan proposes the installation of six Cone Penetrometer Testing (CPT) <br /> geotechnical borings with Membrane Interface Probe (MIP) logging, in lieu of the deep monitoring wells <br /> directed in the Letter. <br /> The Report states that two of three offsite shallow groundwater monitoring wells approved by Regional <br /> Board staff letter on 3 May 2007 were installed in September 2007 to the north (MW6) and <br /> in October 2007 to the southeast (MW7) of the site. The third offsite well was not installed, due to a <br /> property owner to the east of the site, when contacted by ETIC and Regional Board staff, verbally <br /> refusing access. On 25 July 2007, Regional Board staff sent a certified letter requesting access to the <br /> property owner with a return receipt postcard that was subsequently received in this office, though no <br /> response to the access request has been received from that property owner to date. In order to <br /> address Regional Board staffs concerns with delineation of your groundwater plume to the east of the <br /> site, the Workplan proposes three CPT/MIP borings in the City of Stockton right of-way across Ei <br /> Dorado Street. Additionally, San Joaquin County Environmental Health Department records show that <br /> in November 1987, two 8,000-gallon gasoline and one 500-gallon waste oil underground storage tanks <br /> (LISTS) were removed from 3300 N. EI Dorado (east of your site), at which time soil confirmation <br /> analyses did not detect petroleum hydrocarbons. <br /> The Report compares the results of groundwater, soil and soil vapor investigations conducted in 2007 <br /> with the San Francisco Bay Regional Water Quality Control Board Environmental Screening Levels <br /> (2007 ESLs) in a TIER 1 screening human health risk assessment. The Report states future worker <br /> exposure onsite to soil and groundwater at depths greater than 10 feet would require a site specific <br /> worker health and safety plan, to include the use of personal protective equipment. Soil vapor data <br /> detected petroleum hydrocarbons which did not exceed the 2007 ESLs for commercial property. <br /> California Environmental Protection Agency <br /> Q* Recycled Paper <br />