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` ` a • y y <br /> E -EIVEU . <br /> NOV 2 1989 <br /> ENVIRONMENTAL HEALTH <br /> Geological Tcchnics Inc. pfana�R—ICES <br /> 2601SjWSPad T olmnmoadCmiu4bvSpda&u <br /> Moto,CA 95351 <br /> (W9)s38-7805 <br /> October 31,1989 <br /> William Stewart <br /> c/o Ben Curran <br /> Curran Real Estate and Insurance <br /> P.Q. Box 4 �I - <br /> t <br /> 'Ta`cy,CA -0414 <br /> RE: William Stewart's Property, 515 W. 11th Street, Tracy, California; GT-18 <br /> Dear Mr.Curran: <br /> I have received a copy of the comments by the Regional Water Quality Control Board and San <br /> Joaquin County on both the Phase II Ground Water Assessment Work Plan submitted in October <br /> 1988 and on the Soil Remedial Action Plan submitted in June 1989. In the following sections,I <br /> will address their concerns, starting first with the Soil Remedial Action Plan and then the <br /> Ground Water Assessment. <br /> Soil Remedial Plan <br /> 3.1 Detection limits given in the work plan for TPH-gasoline and motor oil are incorrect <br /> according to analytical methods approved by the Department of Health Services. <br /> TPH-gasoline by method 5030/modified 8015(purge and trap)has detection limits of <br /> 2.5 mg/kg in soil and 0.5 mg/l in water. TPH-motor oil by DHS:method GC/FID <br /> (extraction method 3550)has detection limits of 50 mg/kg in soil and 5 mg/l in water. <br /> it+the sW below theWde lion: #,w <br /> tft&Wther, —A.6101.ii <br /> mobile in this it environment. Therefore,the fear that minute amounts may <br /> leach into the water`from higher in the vadose zone soils in unfounded. <br /> 3.2 Composite sampling methods have long been an acceptable method for evaluating soil <br /> that has been excavated and is stockpiled on the surface. True discreet samples can <br /> only be obtained by in situ core sampling via drilling(where an undisturbed sample is <br /> obtained). Once the soil has been disturbed by excavation,a sample can no longer be <br /> called discreet because of the homogenation which takes place during the excavation <br /> process. Therefore,Geological Technics believes that composite sampling methods are <br /> not only the best way to obtain a representative analysis of the stockpiled soil,but that <br /> it is the only way to obtain cost effective, representative analysis. <br />