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Historic UST Investigation Report 630 N.California Street June 1,2011 Page 2 On March 30, 2011, Condor conducted a Site reconnaissance. The vent pipe was observed to be located immediately south of the west doorway to the warehouse along the exterior building wall. Plastic tubing was inserted into the top of the vent pipe and threaded down to ground level until resistance was encountered. A photoionization detector (PID) was attached to the free end of the tubing and allowed to purge ambient air from the tubing. After approximately 10 minutes of continuous operation, the PID did not detect volatile organic compounds (VOC). Based on the former use of the warehouse for storing vans and automobiles, Condor concluded that there is a high probability for a fuel UST having been in operation from the 1940s until the 1970s. PREPARATION ACTIVITIES Condor obtained a boring permit from the San Joaquin County Environmental Health Department (SJCEHD) after submittal of the Historic Underground Storage Tank Investigation Work Plan, 630 N. California Street, Stockton, California, dated April 13,2011 (Work Plan). The Work Plan included a Site Specific Health and Safety Plan (HASP). Underground services alert(USA)was notified at least 48 hours in advance to identify utilities in and near the work area. Prior to performing work, all site personnel reviewed the Work Plan and signed the HASP. Cruz Brothers Locators was subcontracted to locate Site utilities, and located a metal object approximately four feet in diameter near the vent pipe. Condor subcontracted concrete coring at the proposed boring locations as well as above the metal object near the vent pipe. A hand-auger was advanced to approximately 3.4 feet bgs and the metal object was confirmed with a magnet. SAMPLING PROCEDURES The direct push borings were hydraulically advanced using a 2-inch-diameter conical bit. The bit and associated push rods were thoroughly cleaned before each boring was advanced using a laboratory-grade, non-phosphate detergent and deionized water and double-rinsing with deionized water. Upon completion of the borings and sampling, the borings were grouted to surface with neat cement. Continuous core soil samples were collected from the borings with a 1.75-inch outside diameter(O.D.), 5-foot-long core barrel fitted with a clean, single use, polyethylene liner. The soil sampling equipment was cleaned prior to collecting the samples as described above. During the sampling, the core barrel was driven in 5-foot intervals. The sample liner was extracted from the core barrel and used for geologic logging and field observations. The soil samples were logged according to the Unified Soil Classification System (USCS). Portions of the soil samples were placed in polyethylene bags and checked with a PID for the presence of VOCs. Geologic logs (Attachment B) inlcude field observations of USCS soil type, PID measurements, and the presence of staining or odor. Soil samples were collected from the borings for laboratory analyses based on field observations and PID measurements. The soil cuttings were placed in a 55-gallon drum, sealed,labeled,and left on-Site to await disposal pending results of the laboratory analyses. Each soil sample collected for laboratory analyses was cut from the liners. The liners were sealed at the ends with Teflon® sheeting, capped, and labeled. Soil samples were placed in chilled coolers and transported under chain-of-custody procedures to Argon Laboratories (DHS# 2359) in Ceres, California for analysis. LABORATORY ANALYSES All 15 collected soil samples were analyzed for the following constituents by the method indicated: BTEX by EPA Method 8260B; oxygenates [t-butanol (TBA), methyl tert-butyl ether (MTBE), di- isopropyl ether (DIPE), ethyl tert-butyl ether (ETBE), TAME, 1,2 DCE, and 1,2-dibromoethane (EDB)] by EPA Method 8260B; TPH-G by EPA Method 8015M; and total extractable petroleum hydrocarbons %44 ' CONDOR