ARCHIVED REPORTS_XR0011159 - Laserfiche WebLink

Home Browse Search

CA � BA Lead analysis- Lead scavengers were a part of a"lead package"that was added to gasoline as an anti-knock package prior to 1991 The "lead package" consisted of EDB, 1,2-DCA, and one or more lead compounds If the 1,2-DCA detected in groundwater beneath the subject site 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 has not been detected in any soil samples collected from this site Soil samples collected during this investigation were analyzed for lead to determine if elevated lead levels are present in the vicinity of the site containing the highest 1,2-DCA levels in groundwater (the well S-1 area) Soil samples were collected in the vicinity of well S-1 (from SB-19) and soil samples were also collected from an offsite boring (SB-20) to provide background lead levels in soil The lead data indicates that there are no elevated lead levels in the vicinity of well S-1 when compared to background lead levels While the lack of detectable levels of 1,2-DCA, EDB, and lead in soil near well S-1 does not exclude the possibility that the 1,2-DCA originates from a release at the Shell site, it is part of a growing body of evidence that suggest the 1,2-DCA may be from another source 1,2-DCA Distribution Figure 2 shows the concentration of 1,2-DCA in groundwater from the most recent grab groundwater samples as well as groundwater samples from the monitoring wells Low levels of 1,2-DCA were detected in groundwater samples east of the site (SB-23, SB-24, and SB-25) and slightly higher levels of 1,2-DCA were detected in groundwater from the bonngs located south of the site (SB-20, SB-21, and SB-22) The highest levels of 1,2-DCA are found in well S-1, near the northern property boundary Overall the data on Figure 2 shows that 1,2-DCA concentrations decline with distance away from the site and also decline with depth Interim Remeduition: Interim groundwater extraction (GWE) was attempted at this site with the understanding that the existing well network was not ideal for pumping groundwater and monitoring aquifer response The primary objective of interim GWE was to remove 1,2-DCA mass from the groundwater Interim GWE removed 0 019 pounds of 1,2-DCA by extracting 6,455 gallons of groundwater over 10 days The 1,2-DCA chemical analytical data collected during the test do not suggest there was a significant decline in concentration in either S-1 or 5-1- 85 The two quarterly monitoring events conducted after the interim remedial activities show a slight decline in 1,2-DCA concentration in well S-1, and no significant change in 5-1-85 At this point, it does not appear that interim GWE was effective However, we will continue to monitor the 1,2-DCA data in well S-1 to determine if this declining trend continues and evaluate if this is a result of interim GWE 0797 11