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3.0 <br /> SITE AND SUBSURFACE CONDITIONS <br /> 3.1 SITE CONDITIONS <br /> The general topography of the site is characterized as being level, with berms, drainage channels and <br /> lagoons associated with the WPCF bordering the site on the north and east and a vector control facility <br /> on the south. The level site occupied by the NCPA Combustion Turbine Project#2 borders the site on <br /> the west. The site and area landforms are a product of grading and alterations to the landscape resulting <br /> from site development associated with the adjacent WPCF and the NCPA Turbine. The elevation of the <br /> site is approximately 5 feet above mean sea level. <br /> 3.2 SUBSURFACE CONDITIONS <br /> 3.2.1 Subsurface Materials <br /> The results of our field exploration indicate that the subsurface materials generally consist of relatively <br /> flat layers of sedimentary deposits. Silty sands/sandy silts were encountered to depths of approximately <br /> 10 feet. A half foot thick layer of very dense material was encountered in CPT 3 and 4 between depths of <br /> 2 and 4 feet. A similar cemented silty sand layer was encountered by Kleinfelder during subsurface <br /> exploration adjacent to the site. The silty sands/sandy silts were underlain by a zone of clayey sand to a <br /> depth of approximately 13 feet below ground surface. A sand layer approximately 2 to 4 feet thick <br /> underlies the clayey sands to a depth of approximately 20 feet in all borings. <br /> For CPT borings 1 and 2, the sand layer was underlain by silty clays/clayey silts to the maximum depth <br /> investigated. In borings 3 and 4, the sand layer continued to depths of 40 feet and 30 feet respectively. <br /> This sand layer was then underlain by silty clays/clayey silts to the maximum depth explored,50 feet. <br /> Shear wave velocities were collected at intervals within the CPT soundings. Based on these results, the <br /> subsurface materials onsite generally have shear wave velocities of approximately 700 to 800 feet per <br /> second at a depth of approximately 10 feet below ground surface, and increasing to approximately 1500 <br /> feet per second at 50 feet below ground surface, the maximum depth explored. Waveforms for the <br /> soundings and the associated shear wave velocity calculations can be found in Appendix A of this report. <br /> 3.2.2 Groundwater <br /> Groundwater flow is considered to be governed by topography, subsurface geologic conditions (rock <br /> units/aquifers), and geologic contacts. Aquifers below the site are characterized as a sedimentary basin <br /> system with aquifer zones controlled by sediment grain size and porosity. Depth to groundwater is <br /> anticipated to have seasonal variation. <br /> Historical groundwater levels in the area, based on data available from DWR, generally vary from <br /> approximately 3 to 20 feet below ground surface in a two mile radius of the site over the past 30 years. <br /> Groundwater monitoring information at this site indicates the gradient direction is toward the east- <br /> southeast and static groundwater level in February 2008 was reported at about 9 feet below the ground <br /> surface in monitoring well WSM-2 located near the southeast corner of the Site. <br /> A study conducted by Kleinfelder Engineering dated February 23, 1993 for the adjacent site reported <br /> encountering groundwater in all borings at depths of approximately 7 feet. <br /> Based on the results of pore pressure readings (Appendix A), groundwater was encountered in all CPT <br /> soundings at a depth of approximately 10 feet below ground surface. <br /> IMProject No.5593-01-05 C A R LT O I,i <br /> 7/29/2008 5 Engineering Inc . <br /> NCPA GFS.doc <br />