SITE INFORMATION AND CORRESPONDENCE

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ExxonMobil Oil Corporation • - 2 - • 3 May 2007 75 Alpine Ave., Stockton On 27 April 2007 (prior to receiving the Report), I received a phone call from ETIC and yourself, to request for modifications to the schedule. In a letter dated 2 January 2007, 1 approved a schedule proposed by ExxonMobil Oil Corporation: • All groundwater and vapor wells shall be installed by 28 February 2007. • A report of investigation and risk assessment shall be submitted by 27 April 2007, and this report will include proposed locations for deeper wells. • The deeper wells shall be installed by 27 June 2007, with a report due by 29 August 2007. During our phone conversation, ETIC requested that the installation of deeper wells be postponed until additional offsite shallow wells could be installed, in order to complete the lateral definition of the groundwater plume and to establish groundwater flow direction more accurately. A time schedule for the additional work was not proposed at that time. The Report's Figure 9 (enclosed) provides locations for three additional off-site shallow monitoring wells to the east, southeast, and north of the site. ETIC also stated that, during a separate phone conversation with the Baptist Church located to the north of the Site, it was discovered that the Church has an operating domestic well that supplements City of Stockton water. ETIC did not provide the distance from the Site to this domestic well. As a result of this discovery, ETIC requested the change in the schedule to conduct a sensitive receptor survey, to identify additional domestic or municipal wells. Again, a time frame for the work was not proposed. During the conversation, I agreed to change the schedule for the vertical definition, and approve an additional investigation for the lateral definition of the groundwater plume and a sensitive receptor survey. I asked that the Baptist Church domestic well, and any other domestic wells identified in the sensitive receptor survey, be evaluated for threats from the groundwater plume and sampled for petroleum hydrocarbon constituents by ExxonMobil, if deemed necessary by Regional Board staff. I suggested that ETIC check additional nearby USTs sites for direction of groundwater, which may be viewed and downloaded from reports on Geotracker. Your request for a revised schedule is appropriate and necessary, to allow ExxonMobil Oil Corporation and ETIC additional time to continue the lateral definition of the groundwater plume prior to completion of the vertical definition, and to conduct a sensitive receptor survey. The new schedule is as follows: • An additional investigation report of lateral extent of the groundwater plume, and a sensitive receptor survey with a domestic well evaluation shall be submitted by 31 July 2007. This report will include a workplan with proposed locations for the deeper wells. The deeper wells should take into account the geology of the site as reported in the boring logs and as revealed during fieldwork, be constructed to intercept any preferential pathways for contaminants and provide vertical definition of the groundwater plume. Dependent upon plume configuration and presence of preferential pathways at each location, Regional Board staff may require additional monitoring wells in more than the two targeted aquifer zones, to complete vertical definition of the contaminant plume.