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"AMRLY GIMUMWATM Mf]WTt7q p*RS+�FiT <br /> 6131 Ne fit Avenue Stockton Cal fomla <br /> 1.0INTRODUCTION <br /> This report documents the results ofroundwater monitoring onrtonng conducted by Aegis <br /> Environmental, Inc (Aegis), for the period of February through July 1991, at the Shell Oil <br />' Company (Shell) service station located at 6131 Pacific Avenue in Stockton, California <br /> (Figure 1) The monitoring included quarterly collection of water samples and monthly <br /> depth-to-water measurements from the three groundwater monitoring wells on site, MW-1, <br />' MW-2, and MW-3 This report is based, in part, on information obtained by Aegis from <br /> Shell and is subject to modification as newly acquired information may warrant <br /> 2.0 SITE DESCRIPTION <br />' The Pacific Avenue Shell site is an active service station that retails regular-leaded, <br /> regular-unleaded, and super-unleaded gasolines Details of the site's facilities were <br />' reported to Shell by Aegis in a "Site Assessment Report," dated January 4, 1991 The site <br /> is located in a commercial/residential area of Stockton <br />' 3.0 BACKGROUND <br /> During March 1990, Aegis drilled and sampled fourteen soil borings on site (report to <br /> Shell dated June 18, 1990) Analysis of the samples indicated concentrations of total <br /> petroleum hydrocarbons (TPH), as gasoline, up to 17,000 parts-per-million (ppm) In <br /> June 1990, three underground fuel storage tanks (UST), of single-wall steel construction, <br /> and associated piping were excavated and removed from the site Analysis of sal <br /> samples collected from beneath the former tank locations indicated concentrations of TPH <br /> up to 19,000 ppm Three new UST, of double-wail fiberglass construction, were installed <br /> in a new tank basin (Figure 2) In July 1990, Aegis conducted drilling and sampling of five <br /> additional soil borings on site Groundwater monitoring wells MW-1, MW-2, and MW-3 <br /> (Figure 2) were installed in three of the borings (report to Shell dated January 4, 1991) <br /> Depth-to-liquid measurements have been collected on a monthly basis, except for August <br /> 1990, and sampling of groundwater has been performed on a quarterly basis since the <br /> installation of the three wells <br /> r4 n rRni IR1nwA rco iRAr%m1Tv^ni e G <br /> 4.1 Groundwater <br /> The depth-to-liquid measurements I <br /> q , collected since the three wells were installed, are <br /> summarized in Table 1 The measurements were collected according to the Aegis <br /> standard operating procedures (SOP) included in Appendix A <br /> 90-020B RPr <br />