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Influence Study Report, The Stockton Group Site, West Weber Avenue and North Lincoln
<br /> Street, Stockton, California, dated June 11, 1999.
<br /> Between August and October 1999, T&R oversaw a geophysical survey on Parcels 2A, 3, and
<br /> 4, which involved the excavation of exploratory test pits (2ATP-1 through 2ATP-5, 2BTP-1,
<br /> 3TP-1 through 3TP-4, 4TP-1 through 4TP-3) to determine the location of suspected
<br /> underground structures including underground storage tanks (USTs), sumps, and pipelines.
<br /> Additional soil borings were drilled (2AB-1 through 2AB-4, 2BB-1 through 2BB-3, 36-1, 313-2,
<br /> and 4B-1) and groundwater monitoring wells were installed (2BMW-1, 3MW-1, and 2AMW-12
<br /> through 2AMW-15) in suspected areas of contamination. A preliminary endangerment
<br /> assessment was performed on the parcels to evaluate the environmental health risk associated
<br /> with residual petroleum hydrocarbon concentrations in soil and groundwater. Details are
<br /> presented in T&R's Site Characterization Report, South Shore Parcels, Stockton, California,
<br /> dated December 13, 1999.
<br /> In 2001, additional assessment activities were conducted by T&R in the vicinity of the Site within
<br /> Parcel 3. Results are included in T&R's report entitled Subsurface Investigation for Area 3,
<br /> dated August 17, 2001.
<br /> In September 2001, a total of 11 Cone Penetrometer Test (CPT) borings (DP-1 through DPA 1)
<br /> were drilled to investigate the following: (1) subsurface lithology; (2) the presence of separate
<br /> phase hydrocarbons (SPH); (3) the lateral extent of petroleum hydrocarbon impacted
<br /> groundwater east, south, and west of the Site; and (4) to investigate potential off-site sources
<br /> upgradient (north-northwest) of the Site. Surficial soil samples were also collected from depths
<br /> up to 5 feet below ground surface (bgs) to evaluate whether the presence of residual
<br /> concentrations of metals present a threat to groundwater quality. Results are presented in the
<br /> Clayton Group Associates (Clayton) report entitled Further Characterization at the West Weber
<br /> Avenue and North Lincoln Street Site, Parcel 2A, dated December 18, 2001.
<br /> In May 2002, Clayton initiated quarterly monitoring activities, installed eight additional CPT soil
<br /> borings (DP-12 through DPA 9), and collected grab samples to delineate soil and groundwater
<br /> impacts previously identified in the vicinity of borings DPA through DP-6. In addition, Clayton
<br /> performed a soil gas survey in July 2002 involving the installation of 111 Gore-Sorber® modules
<br /> to investigate the areas of greater petroleum hydrocarbon impact. Results are summarized in
<br /> Clayton's Site Delineation Report, dated August 6, 2002.
<br /> SECOR/Stantec Investigations:
<br /> In December 2002, a 5-day DPE feasibility test was performed by SECOR, following the
<br /> installation of seven DPE wells (DPE-1 though DPE-7). SPH were reportedly present in wells
<br /> DPE-1, DPE-3, DPE-4, DPE-6, and DPE-7 prior to the initiation of testing. DPE tests were
<br /> performed utilizing well 2AMW-14 for approximately 45 hours; simultaneously on wells DPE-4
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