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r <br /> I" 1620 Executive Court <br /> IIIRICU�= IIRNIR <br /> Sacramento,CA 95864 <br /> ENGINEERING AND ENVIRONMENTAL SERVICES Telephone: (9161485-7222 <br /> FAX: (916)485-8098 <br /> 6 February 1998 <br /> Mr. Charles Leubner <br /> Stockton Unified School District <br /> 1932 N. El Pinal Drive <br /> Stockton, California 95205 <br /> Subject: Work Plan for Installation of Monitoring Well <br /> Stagg High School <br /> Stockton Unified School District <br /> HLI 00817 <br /> Dear Mr. Leubner: <br /> This work plan describes a proposed groundwater investigation at the former site of an <br /> underground storage tank located at Stagg High School. It is submitted in response to the 10 <br /> December 1997 letter from Mr. Steve Sasson of the Public Health Services, San Joaquin County <br /> Environmental Health Division (PHS/EHD) concurring with the Helmick and Lerner Inc. <br /> recommendation for the installation of a monitoring well by the former underground gasoline <br /> tank that was removed in December 1990. The groundwater investigation is intended to evaluate <br /> groundwater for the presence of petroleum hydrocarbons. The monitoring well will be installed <br /> to a depth of approximately 30 to 40 feet below ground surface. A scope of work and schedule <br /> for this investigation is presented below. <br /> BACKGROUND <br /> On 20 December 1990, a 500-gallon underground gasoline tank (Tank#2) was removed from an <br /> excavation located at Stagg High School (refer to Figure 1). Once the underground tank was <br /> removed, one soil sample was collected from the approximate center of the excavation, at a depth <br /> of two feet into native soil beneath the former location of the tank bottom (refer to Figure 2). <br /> Based on laboratory results of the soil sample (refer to Table 1), an additional soil investigation <br /> was requested. <br /> On the 14"' and 15'h August 1997, another soil investigation was conducted during which four <br /> soil borings were drilled using the Geoprobe drilling and sampling method to evaluate the <br /> vertical and lateral extent of petroleum hydrocarbons remaining in soil. All four borings were <br /> drilled to a depth of 25 feet below ground surface, which was 12 feet below the groundwater <br /> surface encountered during the Geoprobe sampling. For each boring, soil samples were collected <br /> at a minimum of five-foot intervals with three samples being submitted for laboratory analysis of <br />