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C A M B R 1 A Ms.Victoria McCartney August.31,2005 '�✓ Between December 1989 and January 1990, Delta-installed groundwater monitoring wells MW-1 through MW-7. Underground piping was installed to wells MW-2 through MW-5 and MW-7 for future remediation. Two additional groundwater monitoring wells (MW-8 and MW-9) were installed'in March 1990. During March 1990, groundwater pumping and vapor extraction tests were conducted to obtain hydrogeologic data, hydrocarbon concentration levels, and flow parameters for remedial system design. In April 1990, a free-product skimming system was installed to collect free product from well MW-2. The skimmer was later moved to well MW-7. Approximately 180 gallons of free product were skimmed from the wells. Off-site groundwater monitoring well MW-10 was installed in July 1991. A soil vapor extraction (SVE) system was installed and operated full time from September 1992 to September 1993. During the first year of operation, the system removed an estimated 14,980 pounds of hydrocarbons from the subsurface. The system operated intermittently through November 1996,removing a"total of.17,628 pounds of hydrocarbons from the subsurface. During March 2000, four CAT borings (CPT-1 through CPT 4) were advanced on site. Cambria �> collected depth-discrete groundwater:,samples from each of these borings. Total petroleum hydrocarbons as gasoline (TPHg) and benzene were detected in groundwater from all the borings at concentrations ranging from 688, to 439,000 parts per billion (ppb) and from 1.52 to 13,200 ppb, respectively. The highest concentrations were from the sample collected at 47 feet below grade (fbg) from boring CPT-4, located adjacent to the existing USTs. Complete investigation results may be found in Cambria's July 20,2000 Site Investigation Report. During June 2002,Cambria advanced seven CPT borings(CPT-5 through CPT-11). Soil samples were collected from CPT-5 only, and they provide vertical definition of TPHg, benzene, .and methyl tertiary butyl ether(MTBE) near the existing USTs. Depth-discrete groundwater samples were collected from all the borings. Groundwater analytical data collected from borings CPT-6 through CPT-8 define the lateral extent of petroleum hydrocarbons to the welt, southwest, and south of the source area. Groundwater samples from the CPT-9 through CPT-11 contained primarily TPHg and benzene and, to a lesser extent, MTBE. The highest concentrations of gasoline,constituents were detected at depths ranging from 65 to 73 fbg.'The highest TPHg and benzene-'concentrations were detected east of the former USTs in boring CPT-11 at 65 fbg.� Cambria's January 21, 2003 Site Investigation Report describes this investigation. On October 7, 2004, Cambria submitted a Site Conceptual Model which summarized previous activities and recommended additional CPT borings. 2 .N