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at 3725 Tracy Boulevard, approximately 1400 feet north of the Quality Cleaners: The predominant soil type beneath the site is fine grained soils(silt and clay). There is a coarse-grained layer(sand) at approximately 15 fbg beneath the site that appears to be laterally continuous across most of the site. An additional coarse-grained layer was encountered at approximately 75 fbg in boring CPT- L There is a lack of soil logging below depths of 25 feet bgs. Based on review of GeoTracker, the following language was excerpted from a March 15, 2010 report prepared by Ami Adini&Associates,Inc.,regarding the Frontier Transportation site located at 425 Larch Road, approximately 2300 feet north of the Quality Cleaners: Previous assessments indicated alternating 5-foot layers of silty clay and sand down to 25 feet bgs near the UST area. Cross sections in this report depict laterally discontinuous layers of sands, clayey sand/silty sand at depths of five to 25 feet bgs. A sand layers is depicted as occurring at 35 feet bgs however, the basis of this stratum is soil samples from one 40-foot deep boring. Based on limited stratigraphic data locally there does not appear to be any confining units in the upper 40 feet bgs. 4.0 CONCEPTUAL SITE MODEL Based on the foregoing Sections 1.0 through 3.0, the following is a Conceptual Site Model (CSM) prepared in general accordance with Section 2.3.2 of the July 2015 DTSC Advisory. Information presented below will be considered with regard to identifying contaminant sources, potential release mechanism(s), and pathway(s) for vapor migration. The CSM may be subject to revision based on the work proposed herein. Soil Types and Subsurface Geology According to the United States Department of Agriculture Web Soil Survey, the Site is underlain primarily by Capay Clay. This unit is described as alluvium derived from mixed rock sources, having 0 to 2 percent slopes, and deposited on basin floors. The upper 60 inches consists of moderately well drained clay with moderately low to moderately high ability to transmit water. The soil underlying the area proximate to the dry cleaners suite consisted predominantly of brown, dense, damp clay with some medium sand(CL) from the ground surface to approximately 10 feet bgs. At 10 feet bgs, the subsurface consists predominantly of brown and red, well-graded wet gravels (GW) or fine to medium grained silty sand (SM). Soil borings advanced approximately 100 to 200 feet north-northeast of the dry cleaner suite consisted of brown, dense silty sand(SM) to approximately 10 feet bgs; medium grained silty sand(SM)was encountered below 10 feet bgs. Sampling and Analysis Workplan Tracy Corners Shopping Center 3225 North Tracy Boulevard Tracy,California 95376 Partner Project Number SM14-129814 Docket Number HAS-VCA 14/15-108 August 15,2016 Page 14