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C A M B R I A <br /> 0 <br /> The soil samples collected at the limits of excavation generally contained no, or low levels of, <br /> gasoline constituents The one exception to this was the 10 fbg sample from ESW-9 which <br /> contained 1,300 parts per million (ppm) of TPHg <br /> The soil samples collected from the bottom of the excavation contained elevated gasoline <br /> constituent concentrations, with the exception of XB-1 These higher levels of gasoline <br /> constituents at the bottom of the excavation agree with the chemical analytical data collected <br /> from the June 2004 soil assessment investigation <br /> SITE CONCEPTUAL MODEL <br /> A site conceptual model (SCM) describes the relationship between the source area, transport <br /> pathways, and potential receptors Cambria developed the SCM for the subject site based on <br /> review of available geological and analytical data Supporting documents for the SCM include <br /> historical soil and groundwater analytical tables, available boring and well logs for the site, two <br /> cross sections, and a list of environmental reports for the subject site These documents along <br /> with the SCM are presented in Appendix F A brief summary of the SCM is presented below <br /> • The fuel release occurred in December 1994 from the former USTs, located in the <br /> southeastern corner of the site <br /> • The highest concentrations of gasoline constituents currently are found in well RW-1A, <br /> located within the former UST complex RW-1A is currently the groundwater extraction <br /> well for the remediation system operating at the site <br /> • The groundwater plume appears to be stable and located primarily onsite <br /> • The plume appears to be limited to the shallow groundwater, as none of the deeper <br /> monitoring wells have been impacted <br /> • Sensitive receptors (domestic wells) are located approximately 825 feet southeast <br /> (crossgradient) of the site These wells do not appear to be threatened by the plume and <br /> are routinely sampled <br /> • Active groundwater extraction and treatment is maintaining a high mass removal rate <br /> • Overexcavation activities (1995 and 2004) removed more than 2,000 cubic yards of <br /> impacted soil from the site <br /> CONCLUSIONS <br /> The overexcavation documented in this report removed impacted soil from the vicinity of the <br /> source area at this site We expect this will have a positive affect on reducing the length of time <br /> 0793 6 <br />