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_ A <br /> ENVIRONMENTAL HEALTH <br /> DEPARTMENT <br /> pPpHIN C SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> Donna K.Heran,R.E.H.S. <br /> 304 East Weber Avenue, Third Floor Carl Huggins, <br /> R. .H.S., S. <br /> Director Mike Huggins,R.E.H.S.,R.D.I. <br /> At Olsen,R.E.H.S. . Stockton, California 95202-2708 Douglas W.Wilson,R.E.H.S. <br /> �. : <br /> Program Manager 8 g Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.s. <br /> /FOR Laurie A.Cotulla,R.E.H.S. Robert McClellon,R.E.H.S. <br /> Program Manager Fax: (209) 464-0138 Mark Barcellos,R.E.H.S. <br /> PAUL ZUMBERGE ;SPR 13 2005 <br /> FRONTIER TRANSPORTATION INC <br /> 3577 W PHILADELPHIA STREET <br /> CHINO CA 91710 <br /> RE: Frontier Transport,Inc. SITE CODE 2251 <br /> 425 Larch Road RO: 252 <br /> Tracy,CA 95376 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed Addendum to <br /> Interim Remedial Action Plan dated March 21, 2005, prepared and submitted by Biophysics <br /> Environmental Assessments, Inc. (BEA) on your behalf for the above-referenced site. In this <br /> addendum, BEA proposes to install three monitoring wells to further delineate contaminant <br /> migration in the shallow zone; and upon completion of delineation,BEA proposes that excavation <br /> be performed in the former underground storage tank (UST) source area intersected by <br /> monitoring well MW-3R to remove free-phase source contamination. <br /> EHD approves the installation of three monitoring wells to total depth of approximately twenty <br /> feet below surface grade(bsg). One well will be located approximately 40 feet northeast of MW- <br /> 9; one well will be located approximately 8 feet west of the shop building and 40-feet southeast of <br /> MW-14; and one well will be located approximately 10 feet north of the shop building and <br /> approximately 10 feet northwest of MW-13 EHD assumes that the screen interval for each well <br /> will be between 5 and 20 feet bsg; however, specific information for the wells' construction has <br /> not been presented. Monitoring wells can not be installed using direct push technique as <br /> proposed in this addendum as wells installed utilizing this method do not have an adequate <br /> annular space to meet the State of California grouting requirements. Please submit a work plan <br /> with revised details for installation and construction of the monitoring wells to EHD for approval; <br /> include information concerning the groundwater analyses and soil collection and analyses. <br /> Data do not show that the plume, consisting mainly of methyl tertiary butyl ether (MTBE), has <br /> expanded 260 feet westward down-gradient of the former UST source area, but instead has <br /> expanded approximately 160 feet down-gradient from the UST source area. Dissolved MTBE at <br /> concentrations exceeding 1,000 micrograms per liter (µg/L) extends approximately 100 feet west <br /> of the former UST source area; however, EHD cannot find documentation that dissolved MTBE <br /> at concentrations greater than 1,000 parts per million (ppm) extends approximately 260 feet <br /> westward from the source in the first water, as stated in the addendum. <br />