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The groundwater sample was carefully collected with a clean disposable PVC bailer and poured with minimum cavitation and minimum headspace into the appropriate laboratory prepared container. The water sample was labeled, logged onto a chain-of-custody form, and placed in a chilled ice chest on crushed ice for transport to the laboratory. Upon completion of monitoring water level measurements and/or well sampling, each well was closed and locked. Well purge water was stored onsite in labeled, closed top 55-gallon steel drums. The City will then appropriately dispose the purge water. 5.0 Brief Site Conceptual Model and Subsurface Conditions The project site is located at the Tracy Waste Water Treatment Plant just north side of Tracy, near the northwestern edge of the San Joaquin Valley (see Figure 1). Holocene alluvial fan and fluvial deposits eroded and dissected by streams draining from the nearby Coast Range Hills to the northwest underlie the area. Surficial soils in the region are mapped by the U.S. Department of Agriculture as Capay-Stomar-Zacharias, moderately well drained and moderately fine textured with gravel that form on alluvial fans, interfan basins and stream terraces. These soils are mapped as moderately slow permeability. The underlying alluvium may generally consist of weakly consolidated and irregularly interbedded sand, silt and clay deposits. These subsurface strata may show variable lateral and vertical continuity and extent (Page, 1986; Bertoldi, et al., 1991). Very large groundwater aquifers underlie the Tracy region and produce very large quantities of agricultural and municipal drinking water. Regional groundwater flow is estimated to flow to the north in the waterwater plant region. Paine Slough occurs about one half mile northeast of the site. Large surface water impoundments, a new clarifier as well as large buildings and treatment equipment constructed after 2003,are used by the wastewater plant, and are in close proximity to the new well location to the north, east and south. It is likely that some seepage from these impoundments occurs and may influence the shallow aquifer and groundwater flow direction in the vicinity of the new well. Seepage data from the impoundments was not available. Groundwater data from CH2M 2008 Annual Monitoring Report (Figure 20) for the WWTP showed a north to northwesterly flow direction for the shallow groundwater aquifer at the plant site vicinity. One large impoundment occurs just north of the project site however its influence on the local groundwater flow direction is not known. -One soil sample collected from the upper portion of the shallow aquifer tested for permeability by Wright in 2003 revealed a relatively low hydraulic conductivity (1.56 x 10-5 cm/sec). 5.1 Subsurface Conditions The boring was advanced to a depth of 25 feet into native soil and revealed subsurface conditions similar to those observed in 2008. Sandy clay underlies the surface road gravel and fill soil to depths of about 10 feet. Interbedded sand, clayey sand, and sandy silt occur from depths of about 10 feet to 25 feet and these show vertical and lateral variability under the project site (see Figures 1 and 2, Exploratory Boring Log and Well Detail). The PID meter was not working for field soil vapor when the boring was drilled, however no field evidence of contaminant presence (odor or staining) was noted in any soil sample. Groundwater was encountered in the shallow Page 4 of 9