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• i CAB R I A We reviewed 1,2-DCA data for other service station sites we work on in California, and we found a few sites with very low 1,2-DCA detections in groundwater, and no sites with 1,2-DCA levels similar to those identified beneath the subject site If the 1,2-DCA found beneath the subject site originates from a fuel release at the site, it is difficult to explain why we do not see more cases with elevated 1,2-DCA levels This analysis suggests that the 1,2-DCA detected beneath the subject site may not originate from a fuel release at the subject site If the 1,2-DCA originates from a fuel release at the subject site then we would expect to find the other associated "lead package"compounds (EDB and lead) in soil and groundwater beneath the site EDB analysis has been conducted at the site and very little has been detected However, EDB is a compound that rapidly biodegrades As such, additional EDB analysis will probably not help deternime if the 1,2-DCA originates from the fuel retailed at this site The lead portion of the"lead package"is less mobile and biodegrades slower than the EDB Therefore, if the 1,2- DCA is associated with the fuel release at the site then we would expect to find elevated total lead levels in the soil near the suspected source area The work plan below proposes additional investigation to evaluate whether or not the source of . 1,2-DCA was a fuel release from the subject site Soil sampling is proposed to determine the background levels of lead at the site and to determine if lead is present in the suspected source area at elevated levels If the results of this investigation indicate the 1,2-DCA originates from a fuel release at the subject site, additional investigation activities will be proposed to assess the extent of 1,2-DCA TECHNICAL RATIONALE FOR PROPOSED SCOPE OF WORK • 1,2-DCA has been detected in groundwater beneath the subject site at concentrations as high as 1,640 ppb I • The source of the 1,2-DCA needs to be verified j • Since 1,2-DCA was introduced into gasoline along with various lead compounds, elevated lead levels should be associated with the near source 1,2-DCA The highest levels of gasoline constituents, and also 1,2-DCA, have been detected in the vicinity of the northern dispenser island Cambria proposes collecting soil samples in the vicinity of boring SB-4 to evaluate the total lead content in the soil Due to the low solubility of lead no groundwater samples will be collected 0797 3