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' Monitoring Well Destruction and <br /> Soil and Groundwater Investigation Report <br /> US Can—Welty Road <br /> September 24,2009 <br /> 2.4 REGIONAL HYDROGEOLOGY <br /> The site is located near the western margin of the Central Valley. Underlying this area are <br /> interbedded clay, silt, sand, and gravel Quaternary alluvial deposits from the Coast Ranges <br /> to west. The soils encountered in this area appear to consist of predominantly fine-grained m terihal <br /> such as silts and clays, with lesser amounts of coarser-grained material such as sands and <br /> gravels. The topography in the area is relatively flat and at approximately 105 feet above mean <br /> sea level. The depth to groundwater generally ranges from approximately 31 feet to 37 feet <br /> below ground surface (bgs). Historical data for the site indicates that the groundwater flow <br /> direction is inferred to be to the east at 0.001 feet per foot. Regional groundwater flow-direction <br /> information and local topography on the relevant United States Geological Survey (USGS) <br /> ' topographic map indicates that groundwater flow in the vicinity of the site is to the east <br /> (California Department of Water Resources [DWR], 2003; USGS, 1980). <br /> 2.5 PREVIOUS ENVIRONMENTAL ACTIVITIES <br /> The site emerged after several non-HPP related environmental investigations were <br /> in <br /> 1995 and 1996 at the Hunter Container property located at 35275 Welty Road. In the pro ess of <br /> 1 investigating a former burn pit and a release from a condensate outlet, petroleum hydrocarbons <br /> were encountered in soil and groundwater on the Hunter Container property in the vicinity of the <br /> former HPP pipelines. As a result, in 1997 Chevron Pipeline Company (CPL) initiated <br /> investigation of the former HPP pipelines in the area near the Hunter Container property. This <br /> HPP investigation area is known as the US Can-Welty Road site, which is the subject of this <br /> report. A summary of site investigation activities and results are included in Appendix B. <br /> Based on the results of previous investigations and the recommendations presented in SAIC's <br /> 2007 work plan and 2008 addendum, the RWQCB concurred that wells MW-3 through MW-5 <br /> could be destroyed if TPH quantified as diesel (TPHd) did not exceed the WQO during the <br />' January 2008 sampling event, and that additional lateral delineation of affected soil and <br /> groundwater was necessary (RWQCB, 2007a and 2008b). Well MW-3 indicated a TPHd <br /> concentration in excess of the WQO during the January 2008 groundwater monitoring event; <br />' therefore, this well was not destroyed. <br /> t 3. SCOPE OF WORK <br /> SAIC implemented the recommendations presented in the work plan and addendum as described <br /> in sections 3.1 through 3.4. <br />' 3.1 PERMITTING, ACCESS,AND SITE SAFETY <br /> To maintain regulatory and legal compliance, protect the health of all involved persons, and <br />' prevent accidents: <br /> • CEMC secured site access agreements with UPRR and private property owners on whose <br /> parcels the scope of work was to be conducted. <br />' • SAIC completed strategic-planning and project-setup activities, including preparing the <br /> site-specific Health and Safety Plan (HASP) and Journey Management Plan (JMP). The <br />' HASP was kept on site, reviewed daily with all on-site personnel, and was available for <br /> review during investigation activities. The JMP was made available to all personnel and <br /> subcontractors prior to mobilization. <br /> 3 P=A -POW <br /> AM/AWR■`® <br /> From science to solutions <br />