Laserfiche WebLink
contaminants present in the Site groundwater Most of the LUST sites have or are currently <br /> ' undergoing remediation and monitoring These sites are discussed in detail an the Site <br /> Assessment Report (Treadwell & Rollo, 2003) The most likely offsite source areas that have or <br /> ' potentially have contaminated the Site groundwater include <br /> • Commingled groundwater plumes from the Chevron, Mobil, and Scotties Service Stations, <br /> • Aged Chevron fuel pipeline along West Grant Line Road that has carried various refined fuel <br /> ' products including gasoline, diesel, andjet fuel since it was installed in 1965, <br /> • Former Wheel Country/Service Station, <br /> ' * Former Shell Station (7-11 Store), and <br /> In 1996, groundwater contamination was found to extend from the former Chevron Station to the <br /> Tracy Wash & Lube facility and east onto the Site property(Figure 2) (Treadwell&Rollo, <br /> ' 2003) The former Chevron site was determined to be the source of the contamination and <br /> Chevron paid for the cost of remediation at the Tracy Express Wash& Lube (SJC, 1999) <br /> 3.4 Local Groundwater Flow Direction <br /> ' The historic and currentoundwater flow direction was evaluated in order to identify dentify the proper <br /> ' placement of offsite bonngs The regional groundwater flow direction is generally to the north <br /> toward the Old River branch of the San Joaquin River(SJC, 1996) Currently, the local flow <br /> ' direction is to the north-northwest with the former Shell and Wheel Country Stations located <br /> upgradient of the Site <br /> ' However, historically groundwater flowed to the northeast from at least 1986 (first monitoring <br /> wells installed) to 1991 This is based on monitoring reports from the Mobil and Shell Station 4 <br /> ' faciIities (KE, 1986, 1987 & 1988 and HLA, 1986 & 1991) Therefore, the commingled plumes <br /> from the Chevron, Mobil, and Scotties Stations would have been located upgradzent of the Site <br /> ' prior to 1991 Chevron installed their first monitoring wells in 1995 and Scotties initially <br /> . installed wells in 2000, after the flow direction had changed to the north-northwest The reason <br /> Field Investigation Work Plan 5 2 September 2003 <br /> TREADWELL &ROLLO,INC <br />