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QUARTERLY GRCIUNPWATER MONITORING RIFORT <br /> 420 West Kettteman Lane Lodi California <br />' 1.0 INTRODUCTION <br /> This report documents the results of quarterly groundwater monitoring conducted by <br /> Aegis Environmental, Inc (Aegis), on January 21, and March 12, 1992, at the Shell Oil <br /> Company (Shell) service station located at 420 West Kettleman Lane in Lodi, California <br /> (Figure 1) The monitoring included collection of depth-to-groundwater measurements <br /> from the three wells, MW-1, MW-2, and MW-3, and water samples from two of the wells, <br /> r MW-1 and MW-3, on site (Figure 2) This report is based, in part, on information obtained <br /> by Aegis from Shell and Emcon Associates (Emcon) of Sacramento, California, and is <br /> subject to modification as newly acquired information may warrant <br /> 2.0 SITE DESCRIPTION <br /> The West Kettlemen Lane Shell service station retails regular and premium-unleaded <br /> gasolines The site is located in a commercial area of Lodi Details of the site's current <br /> facilities were reported to Shell by Aegis in a "Site Assessment Monitoring Well Installation <br /> Results Report," dated March 26, 1991, and a "Pre-Tank Replacement Site Assessment <br /> Results Report," dated October 16, 1989 <br /> 3.0 BACKGROUND <br /> In September 1989, fifteen soil borings were drilled and sampled at the site The results <br /> of the investigation were reported to Shell in the October 16, 1989, report The borings <br /> ranged in depth from 11-1/2 to 21-1/2 feet below surface Analysis of soil samples collected <br /> from one boring along the south edge of the existing underground storage tanks, at <br /> 15 feet below surface, indicated concentrations of toluene and total xylenes ranging from <br /> 0 003 to 0 012 parts-per-million (ppm) Analysis of the sod samples from the remaining <br /> borings adjacent to the existing dispenser islands and underground storage tanks <br /> indicated total petroleum hydrocarbons (TPH) and benzene, toluene, ethylbenzene, and <br /> 1 total xylenes (BTEX) were below detection limits (BDL) Concentrations of toluene at <br /> 0 004 ppm were detected at approximately 5 feet below surface to the northwest quadrant <br /> of the site, in the location of the formerly proposed tank basin However, analysis of a <br /> soil sample collected at 10 feet below surface from one boring in the northwest quadrant <br /> indicated TPH, as gasoline, at 1,060 ppm <br /> In September 1990, Aegis installed and sampled the three groundwater monitoring wells <br /> at the site <br /> Aegis performed monthly measurements of depths to groundwater and quarterly sampling <br /> subsequent to the initial well installations The first, second, and third quarterly <br /> groundwater sampling was conducted in January, April, and July 1991, respectively <br /> Measurements of the depths to groundwater were changed from monthly to quarterly in <br /> June 1991 <br /> w � <br /> 89-01 3A OMR 1 <br /> r� <br />