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10 <br /> Executive Summary _ <br /> The Lipton (formerly Van den Bergh Foods Company) facility, located at 1400 Waterloo <br /> Road, Stockton, California was identified as having a leaking underground storage tank (UST) <br /> site by the San Joaquin County Public Health Services, Environmental Health Division <br /> (County), and was assigned a site code 22073 Three USTs, containing gasoline, Stoddard <br />' (petroleum) solvent and diesel, were excavated from a common excavation on May 26, 1986 <br /> Evidence of significant impact from petroleum and associated chemicals were confirmed in <br /> the native soil of the excavation The tank excavation was subsequently backfilled <br /> Between 1987 and 1996 several corrective actions were implemented to mitigate the impact <br />' from the source to the soil and groundwater These included source removal actions and <br /> subsurface investigations to characterize the nature and extent of soil and groundwater impact <br />' The field actions included the drilling and sampling of eleven (11) soil borings, installation of <br /> sax (6) groundwater monitoring wells, installation of one vapor observation well, excavation <br /> of approximately 330 cubic yards of soil from the source area, backfilling and paving of the <br /> area, and completion of fourteen rounds of groundwater monitoring <br />'• The source removal actions included removal of the leaking USTs in May 1986, and <br /> excavation of approximately 330 cubic yards of heavily impacted soil in the source area in <br /> May 1995 In addition, since the facility is paved, the potential for infiltration of rainwater to <br /> the subsurface, the primary pathway for migration of contamination has been mitigated <br /> During the corrective actions, it was determined that total petroleum hydrocarbons (TPH <br /> ) as <br /> diesel was the only contaminant of concern at the site in soil, with the potential to exceed a <br /> secondary taste and odor action level of 100 pg/L in the groundwater This was indicated to <br /> be the groundwater cleanup goal by the County However no maximum contaminant level <br /> (MCL) has been established for TPH as diesel The average TPH as diesel concentration <br /> measured in the groundwater never exceeded the 100 pg/L action level, while the TPH as <br />' diesel concentrations in the vadose zone were found to steadily decrease over time <br /> The results from soil borings samples tested indicated that the vertical TPH as diesel impact <br /> in the vadose zone was 13 1 mg/Kg at a depth of 70 feet below ground surface, immediately <br /> below the source, and the lateral TPH as diesel impact in the vadose zone was estimated to be <br /> approximately 80 feet from the source area in 1993, and approximately 40 feet from the <br /> MZ/0&13-97/VDBF/9740009 BK IV <br />