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r <br /> SITE HISTORY <br /> 1989 Soil Borings: During February 1989, Delta Environmental Consultants (Delta) <br /> drilled eight soil borings to assess site conditions prior to UST removal and replacement <br /> activities. In,November 1989, four USTs were excavated and removed. Soil samples <br /> were collected from former tanks and product line trench excavations. <br /> 1989 - 1990 Well Installation: Between Dec. ber 1989 and January 1990, Delta <br /> installed groundwater monitoring wells MW-1 through MW-7. Underground piping <br /> was installed to wells MW-2, MW-3, MW-4, MW-5, and MW-7 for future remediation. <br /> Two additional groundwater monitoring wells (MW-8 and MW-9) were installed in <br /> March 1990. <br /> 1990 Groundwater Pumping and Vapor Extraction: During March 1990, groundwater <br /> pumping and vapor, extraction tests were conducted to obtain hydrogeologic data, <br /> hydrocarbon concentration levels,and flow parameters for remedial system design. <br /> . tt <br /> A free-product.skimming system was installed to collect free product from well MW-2 <br /> ` in April 1990.41he skimmer was later moved to well MW-7. Approximately 180 gallons <br /> of free product were skimmed from the wells. <br /> 1991 Well Installation: Off-site groundwater monitoring well MW-10 was installed in <br /> July 1991. <br /> 1992 - 1993 Soil Vapor Extraction: .A soil vapor extraction (SVE) system was installed <br /> and operated full time from September 1992 to September 1993. During the first,year of <br /> operation, the system removed an.estimated,44,980 pounds-of.hydrocarbons from the <br /> subsurface. The system operated intermittently through November 1996. It removed a <br /> total of 17,628,pounds of hydrocarbons,fromhee subsurface. <br /> 2000 CPT Borings: During March 2000,four CPT borings were advanced onsite (CPT-1 <br /> through CPT-4). Cambria collected depth-discrete groundwater samples from each of <br /> these borings.; Total petroleum hydrocarbons as gasoline (TPHg) and benzene were <br /> detected in groundwater from all of the borings at concentrations ranging from 6�to <br /> 439,000 micrograms per liter (µg/L) and from 1.52 to 13,200 µg/L, respectively. The <br /> highest concentrations were from the sample collected at 47 feet below grade (fbg) from <br /> boring CPT-4, located adjacent to the existing: USTs. The complete results of this <br /> investigation may be found in Cambria's July 20,2000 Site Investigation Report. <br /> . t <br />