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1117 Lone PalmAvL <br /> Modesto, Calk � <br /> '1 <br /> www.atc-ei 111 <br /> 209.5. <br /> Fax 209.579.. <br /> ASS O C I ATE S I N C . <br /> April 13, 2001 <br /> 54.62574.0002 <br /> Mr. Jeff Wong <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> 304 E. Weber Avenue, 3rd Floor <br /> Stockton, CA 95202 <br /> Subject: Workplan for Subsurface Investigation at Smiths Canal Pump Plant, Fontana <br /> Street and Smiths Canal, Stockton, California; Site Code 1102 <br /> Dear Mr. Wong: <br /> ATC Associates Inc., on behalf of the City of Stockton, has prepared this workplan for <br /> performing a subsurface investigation :at thesubject site (Figure 1). This additional work was <br /> discussed in a meeting between San Joaquin County Public Health Services Environmental Health <br /> Department (PHS/EHD) and City of Stockton County on April 4, 2001. This work is being <br /> ( performed at the direction of PHS/EHD to evaluate the lateral extent of the groundwater plume <br /> to the north of the site. <br /> The scope of work includes obtaining permits, advancing five soil borings and collecting soil and <br /> groundwater samples, laboratory analysis of selected soil and groundwater samples, and preparing <br /> a summary report. The scope of work is described in detail in the following paragraphs. <br /> BACKGROUND <br /> An estimated 1,100 gallons of diesel fuel was reportedly leaked from a 5,000-gallon fiberglass tank as a <br /> result of an inadvertent puncture. The tank was repaired and returned to active service. <br /> In May 1988, Ensco Environmental performed a limited investigation, advancing a single soil boring <br /> (13-1) beneath the northern (fill) side of the tank to a maximum depth of approximately 17 feet below <br /> grade. A soil sample collected from this boring at 17-17.5 feet bgs recorded 130 parts per million <br /> (ppm) total petroleum hydrocarbons as diesel (TPHd). As a result of this investigation, PHS/EHD <br /> required further assessment of the extent of contamination at the subject site. <br /> A subsurface investigation was conducted on October 17 and 18, 1989 by WaterWork Corp. Six soil <br /> borings (SB-1, SB-2, MW-1, MW-2; MW-3;:and MW4) were drilled at the subject site to depths <br /> ranging from 16 to 36 feet bgs. Four of these borings were completed as two-inch diameter <br /> groundwater monitoring wells (MW-1 through MW-4). Soil boring locations are shown on Figure 2. <br /> Soil samples collected during drilling activities were analyzed for the presence of benzene, toluene, <br /> w:\62574\62574.02\reports\pumpwkp.doc 1 <br /> l <br />