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ameO <br /> Mr. C. Dean Hubbard <br /> California Regional Water Quality Control Board <br /> February 1, 2012 <br /> Page 4 <br /> better characterize potential future exposure to shallow soil. Soil samples will be collected from <br /> the borings surrounding and at the former GMX-13 location at 1.5, 4, 6.5, and 9 feet bgs to <br /> provide data on current TPHc and benzene, toluene, ethylbenzene, and xylenes (BTEX) <br /> concentrations in shallow soil, and to better characterize potential future exposure to shallow <br /> soil and volatile soil impacts. In addition, a soil sample will be collected from the boring at the <br /> former GMX-13 location at 12 feet bgs to determine current concentrations of volatile <br /> constituents at this location and depth, to determine if concentrations have decreased over the <br /> past 10 years due to natural attenuation of BTEX constituents. <br /> Soil samples for TPHc analysis will be collected in stainless steel or butyrate sleeves sealed <br /> with Teflon sheets, plastic end caps, and silicon tape. Soil samples for BTEX analysis will be <br /> collected using U.S. EPA Method 5035. Soil samples surrounding GMX-02 and GMX-13 will be <br /> analyzed for TPHc using U.S. EPA Method 8015M. Soil samples surrounding GMX-13 will also <br /> be analyzed for BTEX using U.S. EPA Method 8260. <br /> Soil samples will be labeled and stored in an ice-cooled chest until transfer to a California- <br /> certified laboratory under AMEC chain-of-custody procedures. All borings will be grouted to <br /> ground surface using a tremie pipe upon completion. <br /> SCHEDULE <br /> It is anticipated that field activities can commence approximately four weeks after receipt of <br /> work plan approval, depending on subcontractor availability. Analytical results will be received <br /> approximately two weeks after samples are submitted to the laboratory. After analytical results <br /> have been received, AMEC will review the data and will share preliminary findings with the <br /> Water Board. Based on the findings, AMEC will either propose additional sampling (if needed), <br /> or will prepare an investigation report and update the SLRA. The investigation report will <br /> document field activities and analytical results once all data are collected. The report will include <br /> a description of field and analytical methods, tables, and figures presenting analytical results, <br /> and a discussion of the results of the investigation. <br /> Please contact either of the undersigned if you have any questions or require additional <br /> information. <br /> Sincerely, <br /> AMEC Environme t & Infrastructure, Inc. <br /> PGM <br /> ardM. Gilmore, PG #8492 Gary R"Foote, P 45044 <br /> Senior Geologist Principal Geologist <br /> MMG/GRF/bfw <br /> X:\6000s\6628.001\4000\WorkPlan 020112\Text.doc <br />