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CaliforniWegional Water Quality Corol Bo, rd <br /> Central Valley Region <br /> N" <br /> Robert Schneider,Chair <br /> Linda S. Adams ,Arnold <br /> .Secrewn�lor Sacramento Main Office Schwarzenegger <br /> 1-nwrmuuemnl 11020 Sun Center Drive#200.Rancho Cordova.California 9567(}6114 1, <br /> Pmlec non Phone(916)464-3291 -FAX(9 16)4 64-464 5 <br /> http�//www.waterboards ca.govicentralvalley <br /> 25 October 2006 nECETWED <br /> Ms. Jennifer Sedlachek OCT 2 7 2006 <br /> ExxonMobil Oil Corporation <br /> 4096 Piedmont Ave, #194 ENVIRONMENT HEALTH <br /> Oakland, CA 94520 PERMIT/SERVICES <br /> WORKPLAN REVIEW, MARLER PROPERTY(AKA JH GRIFFIN MOBIL SERVICE), <br /> 75 E. ALPINE AVENUE, STOCKTON, SAN JOAQUIN COUNTY <br /> I reviewed the Risk Assessment and Well Installation Work Plan (Workplan), received <br /> 2 October 2006 and submitted by your consultant ETIC Engineering Inc (ETIC). The <br /> Workplan was written in response to my 20 July 2006 letter that requested a workplan to <br /> characterize the vertical and lateral extent of petroleum hydrocarbons and evaluate threats <br /> from soil vapor migration at 75 Alpine Avenue in Stockton (Site). The maximum soil analytical <br /> results from an investigation conducted in 1999 were: Total Petroleum Hydrocarbons as <br /> gasoline (TPHg, 15,000 mg/kg), Benzene (B, 54 mg/kg), Toluene (T, 1,300 mg/kg), <br /> Ethylbenzene (E, 370 mg/kg), Xylenes (X, 2,500 mg/kg), Methyl tert-Butyl Ether (MtBE, <br /> 0.91 mg/kg), and Tertiary Butyl Alcohol (TBA, 40 mg/kg). Maximum grab groundwater <br /> analytical results in 1999 were: TPHg (280,000 Ng/L), B (32,000 Ng/L), T (71,000 pg/L). <br /> E (51400 pg/L), X (29,000 Ng/L), MtBE (440 pg/L), and TBA (130 pg/L). <br /> The Workplan includes diagrams of previous soil and groundwater investigations (enclosed <br /> Figures 1 and 2). The Workplan proposes the installation of five shallow groundwater <br /> monitoring wells (MW-1 through MW-5) and eight soil vapor wells (V1 through V8) to <br /> characterize the lateral extent of soil, groundwater and soil vapor for petroleum hydrocarbons <br /> (enclosed Figure 3). Soil and groundwater analyses include: USEPA Method 8015 Modified <br /> for total petroleum hydrocarbons as gasoline; benzene-toluene-ethylbenzene-xylenes (BTEX) <br /> by USEPA Method 8021 B; five fuel oxygenates and two lead scavengers by USEPA Method <br /> 8260B. <br /> In a 3 October 2006 phone conversation with Mr. Ted Moise of ETIC, a phased approach for <br /> the investigation was discussed to install the shallow monitoring wells first and, after first <br /> reviewing the soil and groundwater data, install the vapor wells in a second phase of the <br /> investigation. I stated that: <br /> 1. The vapor wells are necessary to determine if there are threats from soil vapor <br /> intrusion into the adjacent and nearby residences, and into a nearby church/child <br /> daycare center, and should not be delayed until a later phase. <br /> 2. The soil vapor intrusion study should focus primarily on the Site property boundaries, to <br /> determine if there are any threats to adjoining properties, especially the residence <br /> California Environmental Protection Agency <br /> fir)Recycled Paper <br />