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Preliminary Subsurface Investigation <br /> City of Stockton, former Western Pacific Railroad Property,Stockton, CA <br /> May 27, 1992 <br /> W0601 AD <br /> ' On March 18, 1992, the wellheads were surveyed vertically and horizontally to a common datum <br /> by a Seigfried and Associates to provide accurate well locations. The well locations are plotted <br /> ' on a map, provided by the City, to show the relationship between the location of the wells and <br /> the possible redevelopment area. The survey data and the City map are provided in Appendix <br /> E. <br /> 4.3 Well Development and Samolinq <br /> On March 18, 1992, the three monitoring wells were developed, monitored, and sampled in <br /> accordance with the site Groundwater Monitoring and Sampling Protocol (Appendix A). Depth <br /> to water readings were taken from each well to determine the groundwater gradient beneath the <br /> ' site. The development and purge water was stored on site in drums approved for hazardous <br /> waste storage pending laboratory analysis. Water samples were collected after purging a <br /> minimum of three well volumes (casing and sandpack). The water samples were submitted to <br /> ' Sequoia Analytical Laboratory (Redwood City, CA) for analysis of California Title 22 Metals, <br /> Volatile Organics (EPA method 8240), and Semi-Volatile Organics (EPA method 8270). <br /> 1 The groundwater gradient was calculated using the wells located on both the former WPRR and <br /> Banner Island properties. On March 18, 1992, the groundwater movement beneath the two sites <br /> was north-westerly with a hydraulic gradient of 0.01 ft/ft or approximately 53 feet per mile. <br /> The groundwater contours are plotted on Figure 2. The groundwater monitoring data is <br /> summarized in Table 2. The field data and well purge logs for the wells located on the WPRR <br /> property are included in Appendix F. <br /> ' 5.0 LABORATORY METHODS <br /> Soil samples collected from the 30 borings were composited by the laboratory according to their <br /> sample grid section (Figure 4). A total of six composite soil samples and the groundwater <br /> R041392.SAY 9 <br />