SITE INFORMATION AND CORRESPONDENCE

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Flag City Chevron • - 5 - • 20 March 2012 6421 Capitol Ave., Lodi, San Joaquin County groundwater since the Site pump and treat system was shut down in August 2004 was the east-southeast at approximately 0.001 feet per foot, until New West Petroleum offsite extractions wells became active in 2009 and flow direction changed to radially inward towards their extraction wells until completion of operations in May 2011. New West Petroleum has completed remediation rebound testing and is in the closure process, and groundwater flow direction was east-southeast in June 2011. Residual Mass Estimate: The consultant calculated that approximately 1.54 pounds (0.25 gallons) of MTBE remains in approximately 4,433 cubic yards of subsurface soil at the Site. The highest MtBE concentrations in soil were near the southwest dispenser. Approximately 1.75 pounds (0.28 gallons) of MtBE remains in groundwater. The residual mass of MTBE remaining in groundwater at the Site has only been estimated to the south, southwest, and west due to the New West Petroleum groundwater plume that was drawn onto the northern and eastern portion of the Site. Risk Assessment Analysis: A fate and transport modeling was performed for dissolved MtBE from the subject site to CSA 31-2 using conservative assumptions consisting of MtBE groundwater concentrations over three times the highest on-site sample result. The results of analysis showed that CSA 31-2 was unlikely to be impacted by MtBE from a soil or groundwater source at the Site; however, downgradient monitoring well MW-10, located 240 feet southeast of the site, may be minimally impacted by MTBE (<3.0 ug/1). Monitoring through 2011 at New West with new monitoring wells showed that the core of the New West plume is-currently principally located to the northeast of the Site. New West installed their own monitoring wells next to MW-10, and they have not seen impacts at that location. MtBE has not impacted groundwater sampled from the Site's MW-10, since'installation in May 2000. Based on conservative fate and transport modeling which does not include MtBE biodegradation, residual MTBE in soil is estimated to reach a target concentration of non-detect, <5.0 ug/kg in approximately 8 years. Additionally, the potential for vertical migration of MtBE as soil gas into the Site commercial building (station and mini mart) was assessed. The risk to residential adult and child receptors and to occupants of the onsite building is minimal, as the annual average concentration inside the building would not exceed the Indoor Air ESLs (9.4 micrograms per cubic meter (ug/m)), or Soil Gas ESLs (9.4 ug/m3)at a rate of 0.024 ug/m2/day. None of the CDCs exceeded the ESLs for soil, and only MtBE (15 to 21 ug/L) in groundwater, at the three wells not impacted by New West's MtBE plume (MW-11A, MW-14, MW-17), exceeded the Water Quality Objective (WQO) of 5 ug/L in December 2006.