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MMAM a <br /> 1.0 INTRODUCTION <br /> This workplan report is being submitted at the request of San Joaquin County Public Health <br /> Services, Environmental Health Division (PHS/EHD) for the additional investigation of soil and <br /> !:>I groundwater contamination at the City of Stockton (City) Smith's Canal Pumping Station located <br /> on Fontana Avenue in Stockton, California (Figure 1). The site was formerly occupied by the <br /> = 3 Waste Water Treatment Plant which utilized a 5,000-gallon underground (u/g) diesel storage <br /> tank for use by auxiliary power generators (Figure 2). <br /> 2.0 BACKGROUND <br /> An estimated 1,100-gallons of diesel fuel was reportedly leaked from the above referenced <br /> 5,000-gallon fiberglass tank as a result of an inadvertent puncture. The tank was repaired and <br /> "a returned to active service. <br /> In May 1988, Ensco Environmental performed a limited investigation, advancing a single soil <br /> -= boring (B-1) beneath the northern (fill) side of the tank to a maximum depth of approximately <br /> =� 17 feet below grade. A soil sample collected from this boring at 17-17.5 feet below ground <br /> surface recorded 130 parts per million (ppm) total petroleum hydrocarbons as diesel (TPHD). <br /> As a result of this initial investigation, the PHS/EHD required an investigation to assess the <br /> extent of contamination at the subject site. <br /> Phase I of a subsurface investigation was conducted, on October 17 and 18, 1989, by <br /> WaterWork Corp./RESNA Industries, Inc. (RESNA). Six soil borings were drilled at the <br /> subject site to depths ranging from 16 to 36 feet below grade. Four of these borings were <br /> l <br /> completed as two-inch diameter groundwater monitoring wells (MW1 to MW4). Soil boring <br /> locations are shown on Figure 2. Soil samples collected during drilling activities were analyzed <br /> for the presence of benzene, toluene, ethylbenzene, and xylenes (BTEX) and TPHD. Field <br /> observations and laboratory analyses of soils collected from the soil borings (Table 1) indicated <br /> soil at the site has been impacted. TPHD was detected in all borings with the exception of <br /> MW1, at depths varying from 10 to 15 feet below grade. Groundwater was initially encountered <br /> RM'0RTSM?-I292.FNL 1 <br />