SITE INFORMATION AND CORRESPONDENCE_FILE 1

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Shell Branded Service Station page 2 2494 E. Fremont St, Stockton Based on this data, the lateral and vertical extents of methanol and 1,2-DCA are not defined. Further investigation is required. A site conceptual model (SCM) should be prepared for this site using existing data that shows the relationship between contaminants, retention/transport media, and receptors. The SCM is a written description supported by maps, geological cross-sections, tables, and diagrams that provide information about the site. The SCM should include the following: 1. Local and regional plan view maps showing location of sources, extent of contamination (i.e., an interpretive drawing - not merely a plot of laboratory results), direction and rate of groundwater flow, and locations of receptors. "Receptors" include, but are not limited to, all supply wells within 2000 feet of the source area; 2. Cross-sections showing subsurface geologic features, depth of groundwater, man-made conduits, monitoring well construction, and an interpretive drawing of the vertical extent of soil contamination; 3. Plots of key chemical concentrations vs. time (e.g., plots should be shown for monitoring wells that demonstrate significant trends in contaminant concentrations); 4. Summary tables of chemical concentrations in different media; 5. Dissolved and adsorbed contamination mass estimates supported by calculations; 6. Boring and well logs (including construction/screening). As new data is collected, the SCM should be updated and the update should be submitted to EHD in quarterly monitoring reports. Work plans should be submitted in a timely manner to collect data in areas where the soil and groundwater plume is undefined. SHELL is hereby directed to submit a site conceptual model to EHD by July 15, 2003. A work plan for the methanol and 1,2-DCA lateral and vertical delineation investigation is due by June 30, 2003. SHELL is to take immediate steps to gain access to offsite parcels for the required subsurface investigation. The work plan due June 30, 2003 is to include ALL and any municipal encroachment permits, private parcel access agreements, and EHD well permit applications and fees needed to conduct the drilling required to collect the soil and groundwater data.