SITE INFORMATION AND CORRESPONDENCE

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Flag City Chevron • - 9 - • 20 March 2012 6421 Capitol Ave., Lodi, San Joaquin County The groundwater plume to the north and east of the Site was primarily the New West Petroleum MtBE plume. In 2007, Site MtBE concentrations had declined to 21 ug/L (MW-17). The Site consultant stated in the 24 January 2007 meeting that, based on current declining concentration trends, the western Site MtBE plume should reach WQOs within a couple of years. With the data and the interpretation that the "eastern" plume is the New West Petroleum plume and the "western" plume is the residual Site's plume, AGE estimated the volume of the Site MTBE plume as 0.28 gallons of MTBE remaining in groundwater. Additionally the Site MTBE plume as defined by monitoring wells MW-1, MW-5, and MW-9 and extraction wells EX-1, EX-2, EX-3, EX-4, EX5, EX-6 and EX-8 has been adequately characterized laterally and vertically and shown through analytical data to be stable and declining. Recommendation: Based upon the available information, Regional Board Staff concur that Flag City Chevron has adequately assessed and remediated MTBE-impacted soil and groundwater associated with the Site release, and that based on declining concentrations in groundwater and minimal soil impacts, the residual contamination beneath the subject site from the Site release will continue to attenuate in place, does not represent a substantial contribution to commingling with the New West Petroleum MtBE plume, and will not pose a threat to human health and/or the environment. Threats from soil, soil vapor intrusion, and groundwater have been addressed. Public participation was conducted from 17 April 2006 to 16 May 2006, with all comments adequately addressed. Regional Board staff recommends issuance of a letter of "No Further Action Required" for the Site and rescission of CAO 5-00-700. The Responsible Parties and the SJCEHD concur with the closure. Attachment 1: Figure 1 Location Map Attachment 2: Figure 2 Site Plan Attachment 3: Figure 4 UST Removal Soil Sample Locations Attachment 4: Figure 9 Geologic Cross Section E — E' Attachment 5: Figure 17 Sensitive Receptor Survey (2005)