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7 1 <br /> r Emcon Associates <br /> 1433 North Market Boulevard • Sacramento CaliYd4'�c�'y�,5diU44 1 (916)928-3300• Fax(916)928-3341 <br />. <br /> ,' SERVICE February 13, 1995 <br /> P-A I.. Project 0805-118 03 <br /> Ms Diane Hinson <br /> Public Health Services �� <br /> Environmental Health Department <br /> County of San Joaquin <br /> Stockton, Cahfonua <br /> Re ARCO Service Station No 760, Located at 225 South Cherokee Lane, Lodi, <br /> California, and ARCO Service Station 548, Located at 1612 Hammer Lane, <br /> Stockton, California <br /> Dear Ms Hinson <br /> On behalf of ARCO, EMCON has prepared this letter in response to a letter dated <br /> November 18, 1994, from the San Joaquin County Public Health Service/Environmental <br /> Health Department (PHS/EHD) to ARCO Products Company (ARCO) The PHS/EHD's <br /> letter reviewed ARCO's September 14, 1995, site comparison report for ARCO Station <br /> No 548, located at 1612 Hammer Lane, Stockton, California and Station No 760 <br /> located at 225 South Cherokee Lane, Lodi, California <br />. The purpose of calculating the mass of total petroleum hydrocarbons as gasoline (TPHG) <br /> in soil was to develop a datum to compare the two sites The procedures used in the <br /> comparison report was consistent for both the sites to make them comparable Any <br /> attempt to estimate the mass of petroleum hydrocarbons based on soil analytical data in <br /> soil borings is at best a professional estimate, and is based on sample location, soil type, <br /> and distribution of petroleum hydrocarbons Tables 1 and 2 summarize the mass of TPHG <br /> in soil for ARCO station Nos 760 and 548 respectively <br /> The PHS/EHD, in its letter requested that ARCO address the following concerns <br /> regarding the comparison report, and the calculation of mass of petroleum hydrocarbons <br /> in soil and groundwater <br /> 1 The concentration used in the area between the isoconcentration lines should be <br /> representative of the most conservative value Specifically, for the area between <br /> the outer isoconcentration line and the inner line, please use the outer line value <br /> instead of the inner line value <br /> 2 Groundwater data must be included in the mass volume determination <br /> 3 The distances used in the volume calculations should be measured in a <br /> conservative and consistent manner <br /> 4 A determination of the total volume of each constituent would be helpful, or, <br /> possibly, a total volume of TPH as gasoline and a total volume of all BTEX <br /> constituents combined <br />