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APR 20 '94 03=50PM OGDEN PROJECTS ENVIRONMENTAL DPT P.3i10 <br /> Letter to: Mr. Jon Marshack <br /> April 20, 1994 <br /> Page 2 <br /> Prior to sampling, wells will be purged until PH, electrical conductivity and <br /> temperature are reasonably stabilized. <br /> For all lead, TR.PH, and TPH-diesel samples, in-line field filtration will be <br /> used to prevent the entrainment of air into the sample. Any samples to be <br /> analyzed for volatile constituents such as BTEX and TPH-gasuline, however, <br /> will not be in-line filtered. <br /> - Each groundwater sample will be analyzed for the following analytes at the <br /> following quantitation and detection limits as noted: <br /> Purgeable TPH - Gasoline Range Hydrocarbons (EPA 8015m): <br /> 50 ppb (0.05 ppm) <br /> Extractable TPH - Diesel Range Hydrocarbons (EPA 8015m): <br /> 50 ppb (0.05 ppm) <br /> TRPH - USEPA Method 418.1: <br /> 1000 ppb (1.0 ppm) <br /> BTEX - Semi-Volatile 14ydrocarbons (EPA 8020): <br /> 0.5 ppb (0.0005 ppm) for benzene, toluene and etbylbenzene and total <br /> xylenes <br /> Total Lead - TIC (EPA 239.2): <br /> 1 ppb (0.001 ppm) detection limit, <br /> 5 ppb (0,005 ppm) quantitation limit. <br /> Detection and quantitation limits will be similar provided there are no analytical <br /> interferences due to the sample matrix. <br /> At the request of the San Joaquin County Public Health Services, the Work Plan, in its <br /> entirety, is enclosed for your review and approval. <br /> We have employed 10einfelder, Inc.,with offices in Stockton,to carry out sampling and their <br /> sub-contractor,Sequoia Analytical,of Sacramento,to perform laboratory analyses. Sampling <br /> from all four wells will be performed monthly and associated groundwater monitoring <br /> reports will be submitted to the Regional Water Quality Control Board' The groundwater <br /> reports will include as a minimum a summary of all collected sample analyses in tabular <br /> form and a brief summary of any unusual conditions encountered during sampling and/or <br /> analysis. Each analysis .will report both detection and quantitation levels- <br /> 0:WAMCKAGMkWP\ST0CKTON V WSHACX <br />