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1 <br /> ' CPT investigations performed at the Site have found layers of soil described as silty sand at <br /> depths between 105 and 120 feet bgs. Sand and/or sandy gravel layers have also been <br /> encountered at depths ranging from 105 to 120 feet bgs in borings located at the former Arco <br /> 1 and former Texaco sites (Delta, 2000). This layer is typically only 2 to 3 feet thick. One <br /> objective of this investigation was to assess this silty sand or sand layer beneath the Site by <br /> drilling, soil sampling and monitoring well installation. The sand layer was not encountered <br /> in the boring CT-8-130, which is located near the southwest corner of the site. An <br /> approximately two foot thick sand seam was encountered in the boring for well <br /> CT-MW-9-120 located on the eastern side of the site. An estimate of intrinsicpermeability of <br /> this layer is 10-11 to 10"9 cm2. Hydraulic conductivity is estimated at 10" to 10-3cm/sec <br /> ' (Fetter, 1994). Based on petroleum hydrocarbon impact in this deeper permeable zone <br /> observed at various locations on this Site and the surrounding sites, a hydraulic connection <br /> with shallower impacted groundwater is apparent. Observations and results from drilling and <br /> ' monitoring well installation will be discussed in more detail in Section 2. <br /> The shallow aquifer beneath the site can best be described as stratified. As discussed above, <br /> PSC has identified four permeable zones beneath the site to a depth of 130 feet bgs. In <br /> summary, these zones are somewhat consistent and include: <br /> • "Shallow" Zone—saturated silt and silty sand, 2 to 5 feet thick, less than 37 feet bgs; <br /> • "A" Zone — saturated silty sand soil, 2 to 15 feet thick, approximately 40 to 60 feet <br /> 1bgs; <br /> • `B" Zone— saturated silty sand, 10 feet to over 20 feet thick, approximately 70 to 90 <br /> feet bgs; and <br /> • "C"Zone—saturated silty sand, approximately 102 to 122 feet bgs. <br /> Groundwater flow direction in the shallow zone is variable from southwest to southeast. <br /> Groundwater flow in the A and B Zones appears to be variable, also in a south to <br /> southeasterly flow direction. Flow direction and gradient for the lower permeable zones is <br /> difficult to measure because of the difference in vertical datum used in the surveys for the <br /> different sites. Better groundwater elevation data will be obtained after all the wells are <br /> resurveyed for the conceptual model prepared for the commingled plume. <br /> 1.4 Topography and Surface Water <br /> ' The elevation of the Site is approximately 10 feet above mean sea level (MSL) (USGS, 1987). <br /> The Site is generally flat and storm water drains to storm sewers located along Lincoln Street. <br /> Mormon Slough flows generally toward the west and passes within approximately 3,000 feet <br /> north of the Site before draining into the Stockton Deep Water Channel and San Joaquin <br /> River. Walker Slough flows generally toward the west and passes within approximately <br /> 7,000 feet south of the Site before draining into the San Joaquin River. <br /> The San Joaquin River and several of its major tributaries namely, the Stanislaus, Calaveras, <br /> and Mokelumne rivers drain the Eastern San Joaquin Subbasin. The San Joaquin River flows <br /> Monitoring Well Installation <br /> and <br /> BioSparge Evaluation Report <br /> Prepared For:Sam Lee Bakery Group,Inc. 6 Prepated By:PSC Industrial Outsourcing,LP <br /> Sane Lee—Lincoln Street 20091203-MW Installation&BioSparge Evaluation Report(Finap.doc Report Daze:December 3,2009 <br />