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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 LOU. 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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