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Phase II Environmental Site Assessment Multi-Modal Station Stockton,San Joaquin County,California Page 4 private properties within the site The GPR study provided information about specific site areas regarding suspected environmental conditions, such as the potential presence of underground storage tanks (USTs) and other buried objects In addition, the GPR investigation was conducted to supplement other safety precautions regarding the location of proposed boreholes ➢ "Perimeter" detection borings were installed along N Stanislaus Street and E Weber Avenue (where underground utilities permitted) in order to evaluate if off site sources had impacted the site ➢ Detection borings were installed along the public right-of-ways of E Miner Avenue, E Channel Street, N Grant Street, and N Aurora Street and on the Union Pacific Railroad right-of-way to evaluate possible site sources that might have moved off site or from one of the six blocks ➢ The final step in the investigation was to evaluate concerns associated with particular properties In general, more attention was paid to the properties identified with RECs and HRECs in the Phase I ESA, and residential properties were not evaluated Additionally, the businesses on parcels without previously identified RECs or HRECs were further reviewed 4.22 Cone Penetration Test Investigations Gregg In Situ, Inc (Gregg) of Martinez, California, advanced five CPT borings (CPT1 through CPT5) at the site The locations of the CPT borings are shown on Figures 5-11, Appendix A The five CPT boring locations were selected to roughly bisect the site on the east-west and north-south axes in order to provide an indication of the hydrogeologic conditions across the site The five CPT logs were evaluated for the presence of potential groundwater-bearing zones and distinct soil changes from the surface to the total depth of each boring i, The CPT logs and pore pressure dissipation tests (PPDTs) are included in the Presentation of Cone Penetration Test Data report prepared by Gregg, located in Appendix B 42.3 Ground Penetrating Radar Investigation A ground penetrating radar (GPR) investigation of selected portions of the site was conducted from May 13 to 29, and August 27 to 30, 2002 The GPR investigation was performed to meet two objectives The primary objective was to garner additional information pertaining to subsurface conditions at the proposed boring locations on selected private properties within the site The secondary objective was to investigate certain properties or portions thereof for evidence of suspect environmental conditions, such as the potential presence of USTs and other buried objects In addition, the GPR investigation was conducted to supplement other safety precautions regarding the location of proposed boreholes The GPR investigation provided additional assurance of the feasibility of drilling at a particular location for two reasons notification of USA does not generally result in identification of utility locations on private properties, and some utilities may be buried at depths greater than five feet bgs as shown in Figure 4, Appendix A A detailed discussion of the GPR investigation, including technology, investigation methodology and instrumentation, is provided in Appendix C The radargrams for the data lines of interest are included in Appendix C The results of the GPR investigation are discussed in Section 6 2 of this report 4.24 Direct Push Boring Investigations Vironex Environmental Field Services (Vironex) of San Leandro, California, advanced the direct push borings at the site (Figures 5-11, Appendix A) The general boring scheme included the advancement of Geoprobe borings to a depth of 15 feet bgs and detection borings to a depth of 45 feet bgs The Geoprobe 1 l �t CONDOR