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GEOMATRIX <br /> Ms. Kristen Rocha <br /> Regional Water Quality Control Board <br /> Central Valley Region <br /> August 13, 1999 <br /> Page 2 <br /> chest. Following collection of soil and groundwater samples, the borehole will be backfilled <br /> with cement grout. <br /> Geomatrix will submit the soil and groundwater samples to a State of California certified <br /> analytical laboratory under Geomatrix chain-of-custody control. The soil sample will be <br /> analyzed for total petroleum hydrocarbons (TPH) as crude oil (C$-C36 carbon range)by EPA <br /> Method 8015 Modified; for polynuclear aromatic hydrocarbons (PAHs)by EPA Method 8270 <br /> SIM, and for benzene, toluene, ethylbenzene, and xylenes (BTEX)by EPA Method 8020. The <br /> groundwater sample will be analyzed for TPH quantified as gasoline (C6 to C12 carbon range) <br /> using EPA Method 8015 Modified; TPH quantified as diesel (C10 to C24 carbon range) using <br /> EPA Method 8015 Modified; BTEX using EPA Method 8021B; and PAHs using EPA Method <br /> 8270 SIM. The TPHd analyses will be performed both with and without silica gel clean-up <br /> procedures on the sample extract prior to analysis. <br /> Geomatrix will prepare an amendment to the existing Site Status Report that reports the results <br /> of the investigation and finalization of site assessment for submittal to the RWQCB. This <br /> report will include our recommendations for further work or site closure. Geomatrix plans <br /> perform this work on August 17, 1999 and submit the amendment to the RWQCB no later <br /> than September 24, 1999. <br /> Please call Elizabeth Lu at (925) 842-1343 or either of the undersigned if you have questions <br /> regarding this letter. <br /> Sincerely yours, <br /> GEOMATRIX CONSULTANTS, INC. <br /> Michael R. Keim Dawn A,Zemo, C.E. <br /> Project Scientist PrincilA Hydrogeologist <br /> and Vice-President <br /> -�� <br /> LBJ/MRK/DAZ/pp <br /> [:\Doc Safe\5000s\5223\Mansfield adds .doc <br /> Enclosures: Figures 1 and 2 <br /> cc: Ms. Katie Hower, Chevron Environmental Management Company <br /> Mr. Michael Infurna, Public Health Services San Joaquin County <br />