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ATTACHMENT 1• <br /> ASSESSMENT ACTIVITIES <br /> WESTERN GEOLOGIC RESOURCES, 1989 <br /> ' WGR performed a soil-vapor survey in 1989 Twelve temporary soil-vapor sampling points <br /> were installed at the locations shown in Figure 2 Vapor samples were collected from each location at <br />' 5 feet below ground surface (bgs) and at 15 feet bgs The highest concentration of total volatile <br /> hydrocarbons (TVH) found at 5 feet bgs was 2,500 ppm, at VP-11 Vapor Points VP-1 and VP-12 <br /> also contained elevated concentrations of TVH at 5 feet bgs (680 ppm and 390 ppm, respectively) <br />' Soil-vapor samples collected from 15 feet bgs contained concentrations as high as 91,000 ppm TVH <br /> (VP-11) Concentrations of TVH in excess of 50,000 pprn were found in Vapor Points VP-1 and <br />' VP-12 at 15 feet bgs Volatile hydrocarbons were also found in Vapor Points VP-2, VP-3, VP-4, <br /> VP-9, and VP-10, but at lower concentrations (3,100 ppm, 410 ppm, 15 ppm, 220 ppm, and 1,800 <br />' ppm,respectively) The highest concentrations were in the vicinity of the former tank pit <br /> Following the soil-vapor survey, WGR installed five monitoring wells Five borings were <br />' drilled on the site and were completed as Monitoring Wells MW-1 through MW-5 in February and <br /> March 1989 Groundwater sampling confirmed that the highest concentrations were in the vicinity of <br /> the former tank pit <br /> EARTH TECHNOLOGY CORPORATION, 299n <br />' In 1991,Earth conducted cone penetrometer tests(CPT)and groundwater sampling at the site <br /> The CPT data provide general lithologic descriptions as well as the ability to collect discrete ground- <br /> water samples (Earth, November 1991) This work further confirmed that the highest concentrations <br /> were in the vicinity of the former tank pit. <br /> GROUNDWATER TECHNOLOGY, INC., 1992 <br /> In March 1992, GTI installed Monitoring Wells MW-6 and MW-7 as well as Vapor Well <br /> VW-1 at the locations shown in Figure 2 Well MW-6 was installed across Plymouth Road, down- <br /> gradient from the site, to determine the extent of the plume Well MW-7 was installed upgradient of <br /> the known extent of contamination to further delineate the plume Well VW-1 was completed in the <br /> vadose zone,to be used as a vapor-extraction well in the future <br />' MonitoringWell MW-8 was installed in December 1993 to further define the downgradient <br /> g <br /> limits of the plume extending from the property <br /> In June 1994, GTI installed Monitoring Well MW-9 and Soil Borings SB-1 through SB-4 <br />' The locations of Well MW-9 and Soil Borings SB-1 through SB-4 are shown in Figure 2 <br /> GM_4UCHMONnDATACHEVRON CHEV N Z ABEIWAM COM-ACT Audd da <br />' GERAGHTY&MILLER,INC ��� <br />