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U-Haul#709-50 Preliminary Site Conceptual Model Blaes Environmental December 15,2006 4 0 ADDITIONAL GROUNDWATER ASSESSMENT ACTIVITES—MARCH 2006 The following sections present the procedures and results of additional groundwater assessment activities conducted in March 2006 to further define the lateral extent of hydrocarbons in groundwater associated with the U-HauI site The scope of work included the following tasks 1) drill a CPT soil bonng (DP-9) near the southwest corner of the Frontier Motel, 2) install four additional groundwater monitonng wells (MW-13B, MW-13C, MW14-13, and MW14-C), 3) develop the new groundwater monitoring wells, 4) conduct a top-of-casing survey of the new monitor wells, 5) conduct a groundwater sampling event, and 6) report the results of the additional groundwater assessment activities to a Site Conceptual Model for the U-Haul site Note the off-site monitoring wells (MW-I3B and WM13C and CPT sampling location (DP-9) are located on neighboring properties and required access to the Stockton Unified School District property 4 1 GROUNDWATER WELL INSTALLATION—MARCH 2006 Prior to performing well installation activities, Blaes Environmental obtained the appropriate SJC EHD well permits, obtained an off-site access agreement with the SUSD, and generated a site-specific Health and Safety Plan The well permits, SUSD access agreement, and HASP are presented in Appendix E, F, and G, respectively In addition, Underground Service Alert (USA) and a private utility locating service (spectrum Geophysics) marked underground utilities at the drill locations Blaes Environmental contracted a licensed drilling contractor, Gregg Drilling of Martinez California,to install the four groundwater monitor wells The monitor wells installation activities were completed on March 7, 8, and 9h, 2006, and complied with regulatory requirements and the regulatory well permits issued for each well The soil borings for well installation were drilled with a hollow-stem auger drill ng No soil samples were collected from the borings for monitoring wells MW-1313, MW-13C, MW-1413, or MW-14C Monitoring wells MW-I3B and MW-I4B consist of a two-inch diameter PVC well casing with 20 feet of 0 02-mch slotted screen from approximately 40 to 60 feet bgs Monitoring wells MW-13C and MW-14C consist of a two-inch diameter PVC well casing with 20 feet of 0 02-mch slotted screen from approximately 65 to 85 feet bgs The well construction diagrams for the newly installed monitor wells are included as Appendix J The exploratory boring field log of each boring is included in Appendix H The final completion of each well was mounted flush with the ground surface with a traffic-rated well vault Well construction details are summarized in Table 4 Page 11