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operated from approximately 1962 to 1986 and was demolished in late 1988. The site is currently an unpaved vacant lot. 1.2 Site Geology and Hydrogeology Soil beneath the site consists primarily of clay and silt with discontinuous lenses of poorly to well graded sand and gravel. The nearest surface waters are the San Joaquin River, located approximately 1.75 miles west and south of the site, the Calaveras River, located approximately 1 mile north of the site, and the Smith Canal, located approximately 1,320 feet south of the site. The site is currently believed to have four separate water-bearing zones: the A-Zone (screened from approximately 5 to 35 feet below grade [fbg]), the B-Zone (screened from approximately 40 to 51.5 fbg), the C-Zone (screened from approximately 65 to 81.5 fbg) and the D-Zone (screened from approximately 95 to 101 fbg). Depth to water measurements at the site have ranged from approximately 3 to 23 fbg. Groundwater flow direction at the site varies between each water-bearing zone. The A-Zone is variable in groundwater flow direction whereas the B-Zone typically flows to the west, the C-Zone to the east, and the D-Zone to the north-northeast with gradients between approximately 0.0004 and 0.001. 1.3 Previous Environmental Work Environmental investigation of the site has been ongoing since 1986. To date, 28 groundwater monitoring wells, 52 soil borings, 29 soil vapor probes, ten cone penetrometer test (CPT) soil borings, 18 extraction wells, nine sparge wells, five temporary piezometers, and one excavation have been completed. Soil gas sampling was performed at the site in 1989, 2007, and 2008. Groundwater beneath the site was monitored and sampled quarterly from 1994 to 2008, and semi-annually from 2008 to present. A dual vapor extraction system (DVE) operated onsite from 2000 to 2003 removing approximately 2,176 pounds of hydrocarbons before being permanently shut down. 2. Proposed Scope of Work During previous investigation of the former used oil UST, soil samples were only analyzed for total petroleum hydrocarbons as gasoline and diesel, benzene, toluene, ethylbenzene, total xylenes, methyl tertiary butyl ether, lead, cadmium, chromium, and zinc. Therefore, GHD proposes advancing 2 soil borings (B-9 and B-10) to collect soil samples at 4, 8, and 12 fbg in the vicinity of the former used oil UST to investigate current hydrocarbon concentrations in soil, and potential presence of napthlalene, volatile and semi-volatile organic compounds (VOCs and SVOCs), polychlorinated biphenyls (PCBs), Title 22 metals, and polycyclic aromatic hydrocarbons (PAHs) in soil for comparison to the Low-Threat Closure Policy (LTCP) Direct Contact and Outdoor Air Exposure criteria. Historical soil analytical results are included as Attachment B. To complete the proposed scope of work, GHD will perform the tasks below. 11153683-RPT-02-SITE ASSESSMENT WORK PLAN 2