Laserfiche WebLink
S E C O R <br /> IConceptual Site Model <br /> Chevron Service Station #9-6171 <br /> March 25, 2005 <br /> Page 11 <br /> 4.2 Chemical Concentrations versus Distance <br /> Concentrations of TPHg, benzene, and MtBE vs distance from the former UST pit are <br /> presented in Figures 18 and 19 Based on these figures it is apparent that concentrations <br /> of TPHg vary across the site and that there are no observable trends as the distance from <br /> the former UST pit Increases Groundwater monitoring well MW-3 has the highest <br /> concentrations of TPHg (6, 400 ppb) and benzene (1 ppb) It Is Important to note that the <br /> data for groundwater monitoring wells MW-4, MW-8, MW-9, MW-10, MW-12, MW-13, and <br /> MW-14 are reported as zero for the sampling event conducted on October 11, 2004 This <br /> is due to either Insufficient water or Inaccessibility to the well box on that sampling date <br />' The inability to collect groundwater samples from those locations effects how the trend is <br /> displayed on the graphs, showing drastic increases from zero in wells along the same <br /> gradient It is likely that the concentrations beneath the Chevron service station are similar, <br /> with the marked increase in concentration occurring in the offsite groundwater monitoring <br /> wells <br /> To identify any petroleum hydrocarbon migration from the Chevron service station, <br /> groundwater monitoring data from several other area service stations are plotted with <br /> respect to their distance from the former UST pit on the existing Chevron site There are <br /> elevated concentrations of benzene, TPHg and MtBE at the Shell service station and <br /> Canepa's Carwash (Figures 18 and 19) These sites are southeast and cross-gradient from <br /> the Chevron service station <br /> I <br /> I <br /> I <br /> I <br /> I <br /> �i <br /> N1FileslProiects\Chevron\RetaiA#9-6171\Site Conceptual Model\FINAL_CSM doc <br />