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Stantec
<br /> L & M OPERABLE UNIT- FOURTH QUARTER AND ANNUAL 2010 SITE STATUS,
<br /> REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT
<br /> Introduction
<br /> January 31, 2011
<br /> indicated that over the testing period, observed tidal changes (up to 4 ft) had little influence on
<br /> the southerly direction of groundwater flow in the monitoring wells (less than 0.1 ft). Results of
<br /> this multi-phase assessment are provided in ERI's Groundwater Monitoring and Sampling and
<br /> Tidal 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, 313-1, 313-2,
<br /> and 413-1) 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 DP-11)
<br /> were drilled to investigate the following: (1) subsurface lithology; (2) the presence of SPH; (3)
<br /> the lateral extent of petroleum hydrocarbon impacted groundwater east, south, and west of the
<br /> Site; and (4) to investigate potential off-site sources upgradient (north-northwest) of the Site.
<br /> Surficial soil samples were also collected from depths up to 5 ft below ground surface (bgs) to
<br /> evaluate whether the presence of residual concentrations of metals present a threat to
<br /> groundwater quality. Results are presented in the Clayton Group Associates (Clayton) report
<br /> entitled Further Characterization at the West Weber Avenue and North Lincoln Street Site,
<br /> 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 DP-19), and collected grab samples to delineate soil and groundwater
<br /> impacts previously identified in the vicinity of borings DP-1 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 /> In December 2002, a 5-day DPE feasibility test was performed by SECOR International
<br /> Incorporated (SECOR, now Stantec), following the installation of seven DPE wells (DPE-1
<br /> though DPE-7). SPH were reportedly present in wells DPE-1, DPE-3, DPE-4, DPE-6, and
<br /> DPE-7 prior to the initiation of testing. DPE tests were performed utilizing well 2AMW-14 for
<br /> I:\Tidewater\TW Stockton(Parcel 2A-0415)\Reports\QMR\2010\4010-Annual\4Q10 and Annual OSSRQRSRQMR Stockton_FINAL.doc 1.4
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