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Additional Assessment Workplan White Arrow 2402 South California Street Stockton,California 95206 Partner Project Number 14-117725.2 October 8,2014 Page 12 manufacturing facilities: Stockton Fire & Enamel Brick Company (1917) and Pacific Clay Products (1950- 1972). An oil house and a 600-gallon oil aboveground storage tank (AST) were located at the former southern boundary of the subject property in the 1917 Sanborn map and were no longer visible in the 1950 Sanborn map. Additionally in the 1950 Sanborn map, a fuel underground storage tank (UST) was depicted at the former southern boundary of the subject property, west of the former AST. The UST was no longer depicted in the 1972 Sanborn map. The Phase I presumed that the 1950 UST replaced the 1917 oil house and AST, however, no additional information regarding installation and removal dates, sampling activities, or length of use of these tanks or oil house was provided by any historical sources or regulatory agencies. The boundary of the subject property is currently immediately adjacent to the north of the former features. Based on the potential for a release and the lack of additional information pertaining to closure activities, the Phase I concluded that the former AST, UST, and oil house represent a recognized environmental condition (REQ. Partner conducted a Phase II Subsurface Investigation (Phase II), report dated May 9, 2014 at the subject property to identify the location of on-site USTs, former tankholds, and/or other associated features and to investigate the potential impact of petroleum hydrocarbons, volatile organic compounds (VOCs), and/or metals to soil as a consequence of a release or releases from the current and former on-site industrial activities. The scope of the investigation included 12 soil borings. Evidence of a release was detected during the Phase II, primarily in the vicinity of the former fuel oil tank and oil house, located at the central-southern portion of the subject property (see Figure 2 for a map indicating the May 2014 boring locations). Based on the concentrations of diesel fuel detected, the high potential for natural attenuation, the depth to groundwater, the limited lateral and vertical extent of impacts (evidenced by the lack of diesel detections in borings B3 and B6 and lack of diesel detection at B4-15), and the lack of VOC detections in soil, the Phase II concluded that the impacts do not appear to represent a significant concern to the subject property or human health. The EHD directive indicated that, although the concentrations were relatively low, a reduction in environmental uncertainties in the form of additional sampling to define the extent and mass of contaminants in the area of concern is warranted. Geology and Hydrogeology Based on borings advanced during this investigation,the underlying subsurface consists predominantly of brown, soft to very stiff, damp to moist silt (ML) from the ground surface to approximately 15 feet below ground surface(bgs)with varying traces of fine-grained sand. According to the State Water Resources Control Board (SWRCB) GeoTracker Website, a nearby Leaking Underground Storage Tank (LUST) site is McBillin Real Estate Investment at 2154 South EI Dorado Street in the City of Stockton, which is approximately 0.32 miles northwest of the subject property and is overseen by the San Joaquin County Lead Oversight Program as Case Number 1910. The information available on the GeoTracker Website indicates depth to groundwater ranges from 30 to 40 feet bgs with a varying direction of flow. PARTNER