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Chevron Products CompanyPage 2 Chevron Service Station#9-0557,Qouth Center Street,Stockton,California November 28,2001 The ozone reaction is most effective in a gaseous phase, where ozone concentrations are higher at the point of saturation than in liquid. As a result, the method of delivery to the subsurface significantly impacts treatment effectiveness. OS is a process that couples ozone generation with air sparging. Bubbles injected into the subsurface by sparging volatilize dissolved constituents into the gas phase where they react with ozone. The reaction between organic substrates (R) and ozone (03) forms primary ozonides. The ozonide is extremely unstable, and decomposes rapidly, thus mineralizing the substrate. For treating benzene, the reaction is: 03 + C6H6 —), HC-03-05H5 (ozonide of benzene) 403 + HC-03-C5H5 —> 6CO2 + 3H2O A variety of other competing reactions involving naturally occurring organic and inorganic constituents also consume the ozone. Therefore, reagent-dosing requirements are site- specific and should be based on pilot testing. The treatment is commonly performed by injecting target strata at source areas and/or hotspot locations with the carrier gas/ozone mixture. Important factors for successful ozone sparging are the permeability and heterogeneity of the subsurface. These factors, in turn, affect the treatment zone size and the treatment efficiency. Therefore, injection rate and point spacing is site-specific and should be based on pilot testing. Pilot Test Facility Installation The scope of the pilot testing will include the drilling and installation of four(4) dual completion OS sparge points (Figure 2) and the performance of a three-month,minimum, OS pilot test. Details of each activity are summarized in the following bullets. • Pre-mobilization Planning. A site-specific Health and Safety Plan(HASP) will be prepared for all SECOR employees and for reference by SECOR subcontractors. The HASP will be prepared in accordance with procedures outlined in Appendix A. An effort to locate utilities in the proposed work areas will be performed by either Underground Service Alert (USA) or through a private utility locating company. ■ Permitting. The applicable permits for the OS wells will be obtained from SJCEHD prior to drilling. • OS Wells. Four(4) soil borings will be advanced at the locations shown on Figure 2 using 8-inch diameter hollow-stem augers to approximately 45 feet bgs. SECOR will not collect soil or groundwater samples from the boreholes for chemical analysis. Upon completion of drilling, dual completion ozone sparge points will be installed in each of the boreholes (for a total of eight [8] sparge points). The sparge points will be completed to approximate depths of 30 and 45 feet bgs, respectively, in each borehole. Field procedures for the installation of the ozone sparge points are I:\Chevron\90557\REPORTS\Feasibility Study\03—Addendum.doc.