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L & M OPERABLE UNIT - FIRST QUARTER 2012 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT Appendix B Page 2 3TP-1 through 3TP-4, 4TP-1 through 4TP-3) to determine the location of suspected underground structures including underground storage tanks (USTs), sumps, and pipelines. Additional soil borings were drilled (2AB-1 through 2AB-4, 2BB-1 through 2BB-3, 3B-1, 3B-2, and 4B-1) and groundwater monitoring wells were installed (2BMW-1, 3MW-1, and 2AMW-12 through 2AMW-15) in suspected areas of contamination. A preliminary endangerment assessment was performed on the parcels to evaluate the environmental health risk associated with residual petroleum hydrocarbon concentrations in soil and groundwater. Details are presented in T&R’s Site Characterization Report, South Shore Parcels, Stockton, California, dated December 13, 1999. In 2001, additional assessment activities were conducted by T&R in the vicinity of the Site within Parcel 3. Results are included in T&R’s report entitled Subsurface Investigation for Area 3, dated August 17, 2001. In September 2001, a total of 11 Cone Penetrometer Test (CPT) borings (DP-1 through DP-11) were drilled to investigate the following: (1) subsurface lithology; (2) the presence of SPH; (3) the lateral extent of petroleum hydrocarbon impacted groundwater east, south, and west of the Site; and (4) to investigate potential off-site sources upgradient (north-northwest) of the Site. Surficial soil samples were also collected from depths up to 5 ft below ground surface (bgs) to evaluate whether the presence of residual concentrations of metals present a threat to groundwater quality. Results are presented in the Clayton Group Associates (Clayton) report entitled Further Characterization at the West Weber Avenue and North Lincoln Street Site, Parcel 2A, dated December 18, 2001. In May 2002, Clayton initiated quarterly monitoring activities, installed eight additional CPT soil borings (DP-12 through DP-19), and collected grab samples to delineate soil and groundwater impacts previously identified in the vicinity of borings DP-1 through DP-6. In addition, Clayton performed a soil gas survey in July 2002 involving the installation of 111 Gore-Sorber® modules to investigate the areas of greater petroleum hydrocarbon impact. Results are summarized in Clayton’s Site Delineation Report, dated August 6, 2002. In December 2002, a 5-day DPE feasibility test was performed by SECOR, following the installation of seven DPE wells (DPE-1 though DPE-7). SPH were reportedly present in wells DPE-1, DPE-3, DPE-4, DPE-6, and DPE-7 prior to the initiation of testing. DPE tests were performed utilizing well 2AMW-14 for approximately 45 hours; simultaneously on wells DPE-4 and DPE-6 for approximately 28 hours; and simultaneously on wells DPE-1, DPE-3, and DPE-7 for approximately 26 hours. Results of DPE feasibility testing indicated the following: (1) a calculated radius of influence of 31 ft west of well 2AMW-14, and lower estimated radii of influence to the south and east due to the presence of low permeability clays and lower induced vacuum readings in wells DPE-3, DPE-4, and DPE-7; and (2) the removal of an estimated 196.38 pounds (lbs..) of total petroleum hydrocarbons in gasoline range organics (TPHg) from soil and groundwater, 97.02 lbs.. of total petroleum hydrocarbons in diesel range organics