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Geological recknus Inc Page 2 Additional Site Characterization Work Plan Project No 724 2 June 27,2002 presence of significant levels of BTEX, MTBE and TPH-G The results also indicated that the pump-island was a major source of contamination ' • In September and October 1997 five Strataprobe soil borings (SP-1, SP-4 SP-5, SP- 5A & SP-6) were installed at the site Groundwater samples collected from these borings indicated the presence of low to moderate levels of TPH-G to a depth of 60 ' feet bgs • In August 1999, one deep screened monitoring well (MW-101) and one soil boring SB-201 were installed at the site The purpose of these borings was to define the vertical extent of the groundwater plume Soil samples collected by use of the SimulProbe Maxitool from the soil borings tested positive for BTEX and TPH-G compounds to a depth of 111 feet Porewater samples, also collected with the SimulProbe, revealed the presence of BTEX and TPH-G to a depth of 111 feet bgs • An abandoned domestic well located at an adjacent residence was destroyed in accordance with SJC/EHD directives on April 20, 2001 • A discretely screened deep well (MW-201) was installed in October 2001 The results of this endeavor suggested that the contamination extended to a depth of 128 ' feet below grade surface (bgs) This depth was the target of a SimulProbe'sampling effort and the soil sample from this elevation contained detectable TPH-G • Thiee quarterly monitoring events have been completed since the installation of deep well MW-201 This well was completed with a screened interval of 148 150 5 feet bgs i2.0 PROPOSED INVES'T'IGATION In their letter correspondence dated April 29, 2002, the SJC/EHD instructed Mr Valentine to submit a work plan for additional site characterization The directive contained the following specific elements I The work plan must address the definition of the vertical and lateral extent of the ' contamination under the same scope of work, 2 The vertical extent of the contamination must be defined first, with lateral definition to follow, 3 A site conceptual model with geologic cross sections must be included 2.1 Site Conceptual Model ' Geological Technics Inc (GTI) has developed a site conceptual model in accordance with the SJC/EHD directive and has completed cross section diagrams (see Figures 5 - 6) To ' k date, a total of 19 borings have been completed at the site, which measures approximately 3b+, 80 x 65 ft With the exception of the five Stratprobe borings in 1997, no off site characterization has occurred since the USTs were removed in 1987 When the Strataprobe 1