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PUBL?C HEALTH S&VICES G/�a' coL <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue,Third Floor• Stockton, CA 95202 <br /> 209/468-3420 <br /> Ll <br /> JAN 2 0 196 <br /> KYLE CHRISTIE DON RODGERS <br /> ARCO PRODUCTS COMPANY ROSE V RODGERS CO TR ET AL <br /> PO BOX 5077 1321 S LINCOLN ST <br /> BUENA PARK CA 90662-5077 STOCKTON CA 95206 <br /> RE: ARCO STATION 92168 SITE CODE: 1056 <br /> 441 W CHARTER WAY <br /> STOCKTON CA <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) has reviewed the <br /> 3rd Quarter 1997 Status Report prepared by Emcon and provides the following comments and directives. <br /> It is important to note that his site is one of seven sites in the immediate vicinity which are considered <br /> to be significant contributors to a large undefined commingled soil and groundwater plume. Data <br /> from adjacent sites confirms the presence of fuel hydrocarbon contaminants at depths in excess of <br /> 100 feet below grade surface. <br /> The soil vapor extraction system currently operating at this site continues to effectively remove volatile <br /> fuel components from the subsurface as designed. PHS/EHD will periodically evaluate the effectiveness of <br /> the system as required per corrective action regulations. <br /> The vertical and lateral extent(three-dimensional)of contaminant distribution in both soil and groundwater <br /> is currently undefined and must be addressed in the next scope of work adhering to the directives provided <br /> below. Reviews of data from early to recent investigations indicate the lack of vertical definition below 40 <br /> feet below surface grade and borehole/monitor well soil and groundwater data support the absence of <br /> lateral definition. This letter presents a directive for an immediate full three dimensional definition and <br /> investigation of soil and groundwater contamination by fuel hydrocarbon constituents resulting from an <br /> unauthorized release documented at your site. <br /> The results of recent groundwater sampling indicate the presence of significant concentrations of dissolved <br /> hydrocarbons (MW-1, 2, 3, 4 and 5 - Benzene; 8200, 3000, 9500, 7200 and 5200 ug/I respectively on <br /> 8/21/97). This observation is made recognizing all monitoring wells screen intervals are now drown by <br /> rising ground water. Groundwater elevations have risen from approximately 44' to 25' below grade <br /> surface (bgs)since 1992. All monitor wells are screened from approximately 55' to 30' bgs. Given these <br /> conditions the installation of additional boreholes and monitor wells on-site and off-site is necessary. <br /> MTBE has been analyzed by EPA Method 5030/8020 modified to date. Raised method reporting limits <br /> due to high analyte concentration have resulted in sample dilutions for all analyses performed. The most <br /> recent data set indicates that all groundwater samples analyzed resulted in raised method reporting limits <br /> due to matrix interference.Fuel additives are likely to be present in the subsurface environment at this site. <br /> You are required to analyze all water and selected soil samples for Tertiary Butanol, MTBE, DIPE, ETBE, <br /> 1 <br /> A Division of San Joaquin County Health Care Services <br />