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S ECOR In February 2002, GRI supervised the drilling of five off-site geoprobe soil borings (B-1 through B-5) downgradient of the subject site. Soil and groundwater samples were collected at each of the geoprobe locations. Petroleum hydrocarbon and fuel oxygenate constituents were not detected in soil. Four groundwater samples (B-1, B-2, B-4, and B- 5) contained MtBE at concentrations ranging from 3.0 to 10,000 ppb. On May 28 and 29, 2002, GRI oversaw the installation of five off-site groundwater monitoring wells (MW-13 through MW-17) to depths ranging from approximately 20 to 21 feet bgs. Petroleum hydrocarbon constituents were not detected in soil, with the exception of one soil sample (MW-16-S9.5) that contained MtBE at a concentration of 0.040 ppm. MtBE was the only constituent detected in groundwater samples from the newly installed monitoring wells; concentrations ranged from 28 to 3,900 ppb. In December 2002, GRI supervised the installation of four off-site groundwater monitoring wells (MW-18 through MW-21) completed at a depth of 20 feet bgs, and 15 ozone sparge (OS) points (SP-1 through SP-15) completed at depths between 30 feet and 37 feet bgs. With the exception of MtBE (0.0067 ppm) in a 10-foot soil sample from boring MW-19, petroleum hydrocarbons and fuel oxygenates were not detected in soil samples. Groundwater samples from well MW-19 contained TPHg and MtBE at 60 ppb and 200 ppb, respectively. An OS system was also brought on-line on December 20, 2002 and was initially configured to cycle through each OS point 16 times a day for 5 to 15 minute periods. SENSITIVE RECEPTORS f la >ff_3 A sensitive receptor survey and a half-mile radius water well survey were performed by Alisto in 1999. No basements or subways were found within a 300-foot radius of the site. An off-site subsurface utility survey indicated the presence of a sanitary sewer trench adjacent to the subject site. A search of California Department of Water Resources (DWR) and Banks Information Solutions files indicated that seven water wells had been installed within a half-mile radius of the subject site; however, the wells could not be located based upon the information provided by DWR. Additional water supply wells were not identified during field reconnaissance of the area (Alisto, 1999). MONITORING AND SAMPLING The current monitoring well network consists of 24 wells (MW-1 through MW-6, MW-8 through MW-24, and CC-WS) that are monitored and sampled quarterly. During the fourth quarter 2005, the site wells were monitored and sampled on October 25, 2005, with the exception of wells MW-14 and MW-21. Well MW-14, which was sampled during the second quarter 2005 after two previous quarters of being inaccessible due to a damaged stovepipe well box, was not accessible as it was again found damaged beyond repair. SECOR suspects that the past and recent damages associated with the well box and well casing are the result of the operators of large 18-wheeler trucks who use the vacant lot area to turn their trucks around. SECOR submitted the December 22, 2005 Work Plan for the Reinstallation of Off-Site Well MW-94 to replace the damaged well and well box. The work plan was approved by the SJCEHD in correspondence dated January 10, 2006. Well MW-21, which is located in the city right-of-way, was inaccessible, as it was found paved over. The well box is scheduled to be uncovered, raised to grade, and resurveyed by TRC during the first quarter 2006. IMP ARM111951Reports%QSR&QRPS 2005/11195 QSR& QRPS 4Q05.doc