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Stockton Promenade—N Edisol treet USTs& Utility Corridors • Page 3 Underground Storage Tank Removal Report June 8,2009 WKANo.7345.09 Recent excavation activities during construction of the Stockton Promenade identified and ' removed a buried wooden bulk petroleum storage reservoir approximately 50 feet west of the N. Edison Street UST area. Petroleum hydrocarbon impacted soil was encountered and removed to the extent possible without potentially destabilizing the integrity to the Stockton Channel seawall and to the nearby WOTOA employee parking lot, which is located immediately south of the former N. Edison Street UST area. Petroleum impacted soil was also identified during excavation of future underground utility corridors along Tuleberg Levee Road, east of the former Edison Street UST area. WKA is currently completing soil removal and confirmation sampling activities at these areas under RWQCB oversight. ' 1.3 Previous Assessment of WOTOA Property On June 25, 2008, Stantec Consulting Corporation (formerly SECOR International), published a ' report titled, "Pipeline Removal, Abandonment, Soil Excavation, and Parking Lot Reconstruction Report of Findings" for the WOTOA employee parking lot, which is located immediately south ' of the former N. Edison Street UST area. The report was submitted to the RWQCB and summarized the excavation and removal or in place abandonment of numerous underground petroleum pipes crossing the parking lot. Several of these petroleum pipes were abandoned in ' place and were documented as extending beyond the northwestern corner of the parking lot toward the former N. Edison Street UST area. IStantec currently conducts quarterly groundwater monitoring from several wells in the WOTOA employee parking lot. A cluster of four groundwater monitoring wells of varying depths are ' located approximately 150 feet southeast of the former N. Edison Street UST area(MW-20, MW-57, MW-62, and MW-69) in the parking lot. Two additional groundwater monitoring wells are located approximately 220 feet west of the former N. Edison Street UST area(MW-34 and MW-35), on the Southpointe property. Groundwater monitoring conducted during the fourth ' quarter of 2008 indicated that the depth to shallow groundwater was approximately 15.79 feet below ground surface (bgs) in MW-20 and 12.18 feet bgs in MW-34. (Stantec, 2009). The groundwater flow direction during the fourth quarter 2008 monitoring event was generally inferred by Stantec to be towards the southeast in the former N. Edison Street UST area. As 1 reported in the fourth quarter 2008 monitoring data, petroleum hydrocarbon constituents were detected above laboratory reporting limits in MW-20, MW-57, MW-62, and MW-69, but were not detected in MW-34 and MW-35.