ARCHIVED REPORTS_PHASE II ENVIRONMENTAL SITE ASSESSMENT

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WGIR Southwest, Inc. 6.0 GEOLOGY AND HYDROGEOLOGY 6.1 Physical Setting The Port is located on the delta of the San Joaquin River near the center of the Great Valley Geomorphic Province of California. The Great Valley Province lies between the Sierra Nevada Province on the east and the Coast Ranges Province on the west. Approximately 30 miles west of the site, the San Joaquin River joins the Sacramento River and empties into the Suisun Bay. Continuing westward, waters of the Suisun Bay pass through the Carquinez Straight and into San Pablo Bay north of San Francisco Bay. The San Joaquin River passes within about 1,200 feet west of site. Municipal waste water treatment ponds are located southwest of this portion of the river. The Stockton deep water channel lies about 4,000 feet north of the Leamer site. The site is located within a 500-year FEMA flood zone area. Land classified as national wetland inventory is present within 0.2 mile to the west and a smaller wetlands area is located about 0.3 mile southwest of the site. The Learner site is a relatively level property with a graded perimeter soil berm that has been • coated with an asphalt emulsion. The average surface elevation of the property is about six feet above mean sea level (amsl). A topographic survey conducted in 1998 by Siegfried Engineering, Inc. shows there are numerous localized lower areas across the parcel with higher areas recorded near the site boundaries, coinciding with the perimeter berm. Outside the southern property line, the topography slopes downward into the South Ditch storm water drainage channel which is approximately eight feet deep. The majority of the site ground surface is bare soil, with areas of sparse weedy native vegetation. 6.2 Geologic Conditions Geologically, the property is underlain by alluvial deposits of Quaternary Age, consisting specifically of clay, silt, sand and gravel of the Modesto formation. These deposits in turn overlie sedimentary rocks of Cretaceous to Tertiary age deposited upon crystalline basement rocks. The USDA Soil Conservation Service (SCS) has identified the soil underlying the site as the "Yellowlark" component which has a surface texture of gravelly loam. Yellowlark soils consist of interbedded sands, silts, clays and gravels in varying combinations; fine- grained soils, predominantly clays, generally increase in abundance to a depth of at least five feet below grade. • 704. PRI.05 14 July 21, 2008