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Geological Audit Services, Inc. <br /> Environmental Professionals <br /> V ® 1803 March Lane, Suite A•Stockton, CA 95207-6414•(209)956-0264•Fax(209)956-0700 <br /> March 30, 1995 <br /> SC-93-03-673-02 <br /> Mr. Michael Infurna <br /> San Joaquin County PHS/EHD <br /> P. O. Box 388 APR <br /> Stockton, CA 95201041995 <br /> L'NV/O Al <br /> Subject: SESOIL Modeling Program RM1 S R�jCS 1rH <br /> Yellow Submarine <br /> 140 West Harding Way, Stockton, California <br /> i <br /> Dear Mr. Infurna: <br /> i-jeological Audit Services, Inc. (GeoAudit) has prepared this letter in response to questions <br /> from the PHS/EHD regarding the SESOIL risk assessment model generated for the site <br /> located at 140 West Harding Way in Stockton, California. The SESOIL model was <br /> submitted to the PHS/EI-ID in a report dated Junuary 20, 1995, as an addendum to the <br /> Closure Summary Report (CSR) submitted in August 1993. This letter is intended to <br /> provide additional information for review of the CSR and addendum to obtain site closure. <br /> The PHS/EHD requested additional information concerning sources of variables used to <br /> generate the risk assessment model and requested modifications to the model using;different <br /> variables. <br /> SOURCES OF VARIABLES <br /> Intrinsic Permeability: Two independent referenced were used to obtain intrinsic <br /> permeability (1P) values for the site. Tables 1 and w list various IP values and the sources <br /> of each Table. Each refe:reitce provided similar ranges for 1P. The IP used to generate the <br /> model are within the silty-sated range. <br /> Porosity: Average porosity of the original model (35%) was obtained from llydrvloff For <br /> Engineers (1982), also summarized in Table 1. However, the: PHS/EHD has requested a risk <br /> assessment model with a 55% porosity. <br /> Transmissivity (hydraulic conducfi%-JUh A trans missivity of 3,000 m/yr was used in the <br /> original model. This value was obtained from an example problem in the SESOIL program <br /> {0� 1 <br /> Full Spectrum Environmental Services o Hydrogeology <br />