ARCHIVED REPORTS_DRYWELL CLOSURE AND INVESTIGATION

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NOA Drywell Closure and Investigation Page 3 of 26 May 30, 2014 2.4 Physical Setting Based on a review of the United States Geological Survey (USGS) 7.5-Minute Topographic Series, Lodi North, California Quadrangle Map (2012), the Site lies at an approximate elevation of 50 feet above mean sea level (MSL) in a relatively flat region, see Plate 3, Appendix A. 2.5 Geologic Conditions ' The Site geologic conditions were obtained from the Department of Conservation, the United States Geological Survey (USGS), the California Geological Survey (CGS), the UC Davis Online Soil Survey, and on-site drilling activities. 2.5.1 Regional Geology The subject property is located in the Great Valley Geomorphic Province. The Great Valley is an alluvial plain in the central region of California, approximately 50 miles wide and 400 miles long. Sediments have been deposited almost continuously into the Great Valley trough since the Jurassic. To the west the Great Valley sedimentary rocks overlie the Franciscan Assemblage of the Coast Range Geomorphic Province and to the east onlap onto the granitic rocks of the Sierra Nevada Geomorphic Province.' The surficial geology of the Site is composed of Pleistocene age arkosic alluvium forming the Mokelumne River alluvial fang. The sediments are chiefly sand. ' Atwater (1982)' describes the surficial geology of the subject property as consisting of Pleistocene age loose sand eolian deposits, loose sand and silt fluvial deposits, and compact silt and very fine sand (Qm) of the Modesto Formation. ' The ground surface elevation of the Site is approximately 50 feet above MSL. According to the California Soil Resource Lab online soil survey', the subject property is located within a zone classified as Tokay-Urban land complex. Fifty percent is Tokay, 35 percent is Urban, and 15 percent are inclusions. The Tokay series includes coarse loam, with 0 to 2 percent slopes, is well drained, and consists of alluvium derived from granitic rock sources. The landform classification includes fan skirts and landscape consists of valleys. 2.5.2 Site-Soecific Geoloav 1 According to borehole logs completed during soil sampling activities, included as Plate 4 and Plate 5, Appendix A, subsurface conditions at the subject property down to 76.5 feet bgs mostly consist of fine to coarse-grained clean sand and silty sand. A summary of the subsurface conditions obtained from the borehole logs are included below in Table 1. California Geologic Survey, 2002,California Geomorphic Provinces, Note 36 s Marchand, D.E.and Atwater, B.F., 1979, Preliminary Geologic Map Showing Quaternary Deposits of the Lodi Quadrangle,California; USGS Open-File Report 79-933, scale 1:62,500 3 Atwater, B.F., 1982,Geologic Maps of the Sacrament-San Joaquin Delta, California, Lodi South. USGS Miscellaneous Field Studies Map MF-1401, Scale 1:24,000 °LIC Davis California Soil Resources Lab, Online Soil Survey, http://casollresource.lawr.ucdavis.edu/sollweb/ ' 902 Industrial Way•Lodi, CA 95240•209.367.3701 • Fax 209.333.8303 ®2014 Neil O.Anderson&Associates,Inc.