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Stantec <br /> April 30, 2010 <br /> Page 4 of 14 <br /> Reference: First Quarter 2010 Site Status, Groundwater Monitoring and Remedial Summary Report-Stockton <br /> Terminals Technical Committee Facilities <br /> Zone Depth to Groundwater General Approximate <br /> Water Elevation Flow Direction Hydraulic <br /> (feet btoc) (feet msl) Gradient <br /> (ft/ft) <br /> First Quarter 2010 A 0.00 to 11.16 -2.46 to 2.02 Variable 0.001 to 0.007 <br /> Southeast <br /> B 0.74 to 8.36 -1.89 to 1.64 Southeast 0.003 to 0.005 <br /> C 1.42 to 8.41 -1.37 to 0.91 Southeast 0.001 to 0.002 <br /> D 2.98 to 8.55 -2.72 to-0.51 Southeast 0.001 to 0.003 <br /> San Joaquin River elevations at the Rough and Ready Island gauging station in Stockton <br /> (Station ID: RRI) ranged from 2.98 to 6.51 feet above msl (http://cdec.water.ca.gov/) on <br /> February 1, 2010 according to the California Department of Water Resources. The Rough and <br /> Ready Island gauging station is located approximately two miles northwest of the Site. <br /> Groundwater elevation data from ST Services monitoring wells (Appendix E) were used along with <br /> the STTC data in the groundwater elevation contour maps. ST Services well OW-6D was not <br /> resurveyed during the site-wide resurvey that took place during October 2008 and therefore data <br /> collected from this well was not used for contouring. <br /> 3.2 VERTICAL GRADIENTS <br /> Vertical hydraulic gradients between each of the hydrostratigraphic zones were calculated for <br /> selected well pairs by the method shown in Table 5. During first quarter 2010, all well pairs had <br /> downward flow. Vertical gradients, which ranged from 0.008 to 0.105 feet per foot, were within <br /> historical ranges (Table 5). <br /> 3.3 SPH MONITORING RESULTS <br /> The presence of measurable SPH or SPH sheen in each of the groundwater zones was monitored <br /> during first quarter 2010. The table below lists wells in which visible SPH sheen or measurable <br /> SPH were reported. <br /> Wells with Visible Wells with <br /> SPH Sheen Measurable SPH <br /> First Quarter 2010 TS/RW-1 None <br /> Measurable SPH or a visible sheen has historically been reported in 20 of the "A" zone wells <br /> currently part of the monitoring network during at least one monitoring event. Long-term trends <br /> indicate an overall decrease in the amount of SPH beneath the site (Appendix G). <br /> 3.4 ANALYTICAL PROGRAM <br /> Groundwater samples were collected and analyzed in accordance with the MRP and Stantec's <br /> standard procedures (Appendices A and C, respectively). Details regarding the analytical program, <br />