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QUARTERLY MONITORING REPORT THIRD QUARTER 1992 ' MAJOR MART PROJECT ' 1.0 INTRODUCTION AND BACKGROUND This document has been developed to report on investigative and remedial activities completed ' at the Major Mart site located at 1235 East Alpine Avenue in Stockton, California (Figure 1 and Figure 2) during the third calendar quarter of 1992. The report is organized to address the reporting requirements discussed in the San Joaquin County Public Health Services' (the ' County's) letter dated November 12, 1991 to American Real Estate Group (AREG) To respond to the County's requirements, this report is presented in two sections The first section reports ' on the results of the third quarter groundwater monitoring program, while the second section discusses the status of the overall remedial program with an emphasis on work completed during the quarter The second section also presents a revised remedial plan which has been developed ' from data generated by recent investigation activities In the interest of continuity, this report actually covers the time period of July 1992 through October 1992, an extension of one month beyond the calendar quarter This extension of the time period covered is required to logically ' report on a series of related activities which were completed during September and October Future quarterly reports will revert to coverage of regular calendar quarters Work completed at the site prior to this quarter consisted of removal of three gasoline and one waste oil tank in June 1990 Soil from the tank removals was stockpiled onsite The results of soil sampling conducted at the time of the tank removal indicated that elevated levels of total petroleum hydrocarbons (TPH-G) and benzene, toluene, ethylbenzene and xylene (BTEX) were found beneath the gasoline tanks No elevated hydrocarbon compound concentrations were found in the waste oil tank area In August 1991, an initial soil and groundwater field investigation was conducted to evaluate the extent of hydrocarbon presence at the site. The soil program consisted of sampling of three soil borings to 90 feet below grade in the area of the former gasoline tank area The analytical results of the samples indicated only benzene and xylene were found in elevated concentrations in a limited number of samples with the maximum concentrations found being 0 076 mg/Kg of benzene and 0 270 mg/Kg of xylene. The highest concentrations were found in the boring identified as MW-3 at depths of approximately 41 to 55 feet below the surface The groundwater investigation program consisted of converting the three soil borings to monitor wells and sampling of the groundwater No free product was observed nor was Total Fuel Hydrocarbons detected in any of the wells Only benzene and xylene were found in the groundwater at maximum concentrations of 130 µg/L and 21 µg/L respectively Fecal coliform was also found in elevated concentrations of 2 to 6 MPN/100ml in two of the wells (MW-2 and MW-3) Further details of this initial investigation effort are available in a report titled "Remedial Investigation" by Woodward-Clyde Consultants dated September 1991 �r ISTKCIRPTSVAREG3QTR WP 1 11/13192