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C A M B R I A <br /> fuel oxygenates (TAME, DIPE, TBA, ETBE, and MTBE) once a year by EPA Method <br /> 8260. We will also perform an EPA Method 8260 confirmation analysis for MTBE on the <br /> groundwater sample found to contain the highest concentration of MTBE (by EPA Method <br /> 8020) each quarter. <br /> Complete Definition of Hydrocarbon Plume: SJCPHS/EHD requested a work plan that, when <br /> implemented, will completely define the hydrocarbon plume. Cambria believes complete <br /> definition of the hydrocarbon plume for this site cannot be proposed in one work plan, as <br /> there are many unknown variables that cannot be accounted for. We believe a phased <br /> © approach is a better method for defining the hydrocarbon plume. Collecting data from one <br /> phase of investigation will aid in determining the best approach for subsequent phases of <br /> investigations. <br /> Cambria proposes the first investigation phase involve assessing the vertical extent of <br /> hydrocarbons in soil beneath the site and installing additional groundwater monitoring wells <br /> to assess the lateral extent of hydrocarbons in groundwater. <br /> • Based on data collected from the on site borings we will be able to determine if hydrocarbons <br /> are present in soil at depth. If hydrocarbons are found at depth, soil boring or well can then <br /> be proposed in a second phase to delineate the lateral extent of hydrocarbons at depth. <br /> The wells proposed for this first phase of work will likely define the lateral extent of <br /> hydrocarbons in the shallow groundwater at this site. If the lateral extent of hydrocarbons in <br /> groundwater is not define by this phase of work, we will then know in what area definition is <br /> not complete, and additional wells in this area can be proposed in a second phase of work. <br /> Cambria's detailed scope of work for the first phase of work to delineate the hydrocarbon <br /> plume at this site is discussed below. <br /> Feasibility Testing: SJCPHS/EHD requested a work plan that proposes enough vapor <br /> extraction and air sparge wells to perform feasibility testing. We believe installation of these <br /> wells is premature until further delineation of the extent of the hydrocarbon plume has been <br /> completed. Currently, the vertical extent of hydrocarbons in soil is not known at this site. <br /> Because of this, the depth of sparge wells cannot yet be determined. We will propose <br /> additional vapor extraction wells and/or sparge wells, if appropriate, for feasibility testing <br /> once we have further characterized the hydrocarbon plume beneath the site. <br /> • <br /> 0854 2 <br />