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Stantec
<br />L & M OPERABLE UNIT- THIRD QUARTER 2010 SITE STATUS, REMEDIAL SUMMARY,
<br />AND GROUNDWATER MONITORING REPORT
<br />Introduction
<br />October 27, 2010
<br />In September 2006, SECOR, along with Entact Environmental Services, commenced pipeline
<br />abandonment and removal activities at 525 West Weber Avenue in the Waterfront Towers
<br />Parking facility in accordance with Stantec's Pipeline Removal, Abandonment, Soil Excavation,
<br />On -Site Horizontal SVE Well Installation, and Horizontal SVE Well Installation Beneath Delta
<br />View Apartments Report and Work Plan for Pipeline Removal, Abandonment, and Soil
<br />Excavation in Waterfront Towers Parking Lot dated February 10, 2005. A report entitled
<br />Pipeline Removal, Abandonment, Soil Excavation, and Parking Lot Reconstruction summarizing
<br />remedial activities and parking lot restoration at the Waterfront Towers Parking facility was
<br />submitted on June 25, 2008.
<br />On May 31, 2007, optimization of the DPE/SVE system, in accordance with SECOR's Work
<br />Plan for Additional DPE Feasibility Testing and Expanded Remedial System Installation, Dated
<br />January 4, 2006, was completed and permitted to operate by the City of Stockton. A soil vapor
<br />extraction system start-up and dual phase augmentation report was submitted on June 25,
<br />2008.
<br />On June 21, 2007, well MW -6 on the MOU was destroyed and abandoned on behalf of the RDA
<br />and under the supervision of Golden State Environmental due to planned excavation and
<br />construction activities.
<br />From July 28 through September 26, 2008, additional assessment activities were conducted at
<br />the Site. Five B -zone groundwater monitoring wells (MW -56 through MW -60), seven C -zone
<br />groundwater monitoring wells (MW -61 through MW -67), and seven D—zone groundwater
<br />monitoring wells (MW -68 through MW -74) were installed. Results were summarized in Stantec's
<br />Additional Deep Groundwater Zone Assessment Report dated January 26, 2009.
<br />In November 2008, Treadwell and Rollo (T&R) on behalf of the RDA abandoned monitoring
<br />wells MW -8, MW -10, MW -11, MW -39, MW -40, MW -41, and MW -53 due to excavation activities
<br />on the UOU. These wells have yet to be reinstalled at the site.
<br />1.3 REGIONAL GEOLOGY/HYDROGEOLOGY
<br />The shallow groundwater bearing zone (A -Zone) primarily extends from the ground surface to
<br />depths ranging from approximately 25 ft bgs to 40 ft bgs. Subsurface material in the shallow
<br />zone predominantly consists of silts, silty sands, and silty gravels from four to 10 ft bgs, and
<br />then organic clays, clays, high permeability silts, and lenses of silty sands and poorly graded
<br />sands to depths ranging from 25 to 40 ft bgs. The shallow zone is generally underlain by low
<br />permeability silts and clays (with an occasional, thin, silty sand or poorly graded sand lens) of
<br />highly variable thickness. A deeper groundwater bearing zone (B -Zone) is encountered at a
<br />depth of approximately 42 ft bgs and extends to approximately 50 ft bgs. Subsurface material in
<br />the B -zone consists of poorly graded sands and silty sands. Below 50 ft bgs, clay and silt with
<br />some imbedded sand is encountered and extends to a depth of approximately 64 ft bgs,
<br />underlain by sands and silty sands of varying moisture extending to a depth of approximately
<br />73 ft bgs. Clay is encountered below the sands to an approximate depth of 84 ft bgs, underlain
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