SITE INFORMATION AND CORRESPONDENCE

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Flag City Chevron • - 4 - • 20 March 2012 6421 Capitol Ave., Lodi, San Joaquin County increasing concentrations of MtBE from an initial 700 ug/L up to 900 ug/L in May 2003. Groundwater at MW-8A remained impacted until groundwater monitoring ceased, however concentrations had declined to 74 ug/L in December 2006. Four additional off- site wells MW-19A/B and MW-20A/B were installed upgradient of this site in May and December of 2004, and in April 2005, the SJCEHD issued the URF for a release from New West Petroleum on Banner Avenue, located to the north of the Site. Between 2002 and 2004, MtBE concentrations within the MtBE plume declined significantly between the Site and Rocky's Restaurant as treatment continued. On 17 August 2004, the pump and treat system was shut down when concentrations of MTBE declined to less than 20 ug/L in influent samples. The vertical and lateral extent of the Chevron groundwater plume continued to shrink after completion of remedial action to a maximum concentration of 15 ug/L at MW-11A (December 2006). The Site pump and treatment system appears to have drawn an off-site plume from New West Petroleum. Since pump and treatment shutdown in August 2004, the groundwater flow direction at the Site has changed from south towards the extraction wells to the southeast. Sensitive Receptor Survey: Prior to 1997, a single SJC water supply well, located approximately 10 feet north of the Site, supplied water to the Site and the SJC fire station located directly to the east of the Site. The original SJC well was decommissioned in 1996 and replaced by CSA 31 Wells 1 (CSA 31-1) and 2 (CSA 31-2). A sensitive receptor survey conducted in 1997 identified five public supply wells within 2,500 feet of the site. The nearest well (RDW-1) was located 150 feet southwest of the site, and was properly abandoned in March 2002. The 3 B's well, located 450 feet west of the Site, became impacted with MTBE from the 3 B's.release in June 2005 and was destroyed in June 2009. CSA 31-2, 700 feet southeast of the Site, is the nearest downgradient supply well and is non-detect for CDCs (sampled quarterly by New West Petroleum through June 2011). CSA 31-1 is 1,600 feet to the east-southeast of the site. CSA 31-3 public supply well (Former Flying J Well) is upgradient of the Site and approximately 1,100 feet to north of the Site at the Flying J Truck Stop, which is north of Highway 12 and the New West Petroleum site. A truck wash process supply well drilled in 2009 is located approximately 1,500 feet north of the Site. Site Geology and Hydrogeology: Soil beneath the Site consists of laterally discontinuous beds of sands, silts, and clays from surface grade to 30' bgs. Less permeable sandy silts and sandy clays are present from 30' to 40' bgs, 50' to 70' bgs, and 80' to 90' bgs. Poorly graded (highly permeable) sands and silts are present between 40' and 50' bgs, 70' and 80' bgs, 90' and 110' bgs and at depths greater than 120' bgs. Groundwater levels beneath the Site between 1991 and 2005 have ranged from 5' to 15' bgs. Since 1991 the flow direction of groundwater has varied in all directions with a relatively flat gradient of 0.001 to 0.003 feet per foot. During the operation of the pump and treat system, ground water flow was redirected radially toward the Site P&T extraction well system. The flow direction of