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L & M OPERABLE UNIT-THIRD QUARTER 2013 SITE STATUS, REMEDIAL SUMMARY, <br /> AND GROUNDWATER MONITORING REPORT <br /> Introduction <br /> November 1, 2013 <br /> Parcel 2A and from the midline of the former Harrison Street east to Lincoln Street. The MOU <br /> includes monitoring well 2AMW-15 and environmental monitoring of the MOU wells is the <br /> responsibility of the City of Stockton under a separate MRP. Currently, oversight of <br /> environmental management responsibilities of the L&M OU is retained by Stantec on behalf of <br /> CEMC and P66, and oversight of the UOU and MOU is performed by Wallace Kuhl Associates <br /> (Wallace-Kuhl) on behalf of the City of Stockton. <br /> Environmental investigations began at the Site in 1989 and quarterly monitoring and sampling <br /> activities were initiated in 2002. SECOR International Inc.(now Stantec) was retained in late <br /> 2002 for environmental consulting services at the Site. A summary of previous investigations is <br /> included in Appendix B. <br /> 1.2 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 below ground surface (bgs) to 40 ft bgs. Subsurface <br /> material in the shallow zone predominantly consists of silts, silty sands, and silty gravels from <br /> four to 10 ft bgs, and then organic clays, clays, high permeability silts, and lenses of silty sands <br /> and poorly graded sands to depths ranging from 25 to 40 ft bgs. The shallow zone is generally <br /> underlain by low permeability silts and clays (with an occasional, thin, silty sand or poorly <br /> graded sand lens) of highly variable thickness. A deeper groundwater bearing zone (B-Zone) is <br /> encountered at a depth of approximately 42 ft bgs and extends to approximately 50 ft bgs. <br /> Subsurface material in the B-zone consists of poorly graded sands and silty sands. Below 50 ft <br /> bgs, clay and silt with some imbedded sand is encountered and extends to a depth of <br /> approximately 64 ft bgs, underlain by sands and silty sands of varying moisture extending to a <br /> depth of approximately 73 ft bgs. Clay is encountered below the sands to an approximate depth <br /> of 84 ft bgs, underlain by a sand/silty sand layer extending to approximately 92 ft bgs. This <br /> stratum is a water-bearing zone identified as the C-Zone. Below this sand layer, imbedded <br /> clays and silts are encountered to a depth of approximately 115 ft bgs, underlain by a sand/silty <br /> sand layer with some imbedded clay to a depth of approximately 130 ft bgs. This stratum is <br /> designated as the D-Zone. Clay and silt is encountered below this sand layer to a total depth <br /> explored of 140 ft bgs. <br /> Groundwater beneath the Site is influenced by the Stockton Channel to the north and the <br /> Mormon Slough to the south. The groundwater flow direction for the shallow and deeper <br /> groundwater bearing zones is generally to the east-northeast across the Site. <br /> 5tantec 1.2 <br />