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y sl 1 e' _ .. 1 . - � __ !�r�._ 1 - — . -... t ' « __` 1_7� ' x ,._-•` r• '" — r^',r _""' r-i-- 1^�-'-�.�=k Asa 1 1 12 February 2002 AGE-NC Project No 97-0312 ' Page 2 of 18 r ' Laboratory analysis of the initial ground water sample collected from UST-1 also Indicated the presence of hydrocarbons TPH-g, TPH-d and benzene were detected at concentrations of 330 micrograms per liter(µg/1), 880 µg/1 and 4 5,µg/1, respectively Analytical results of ' soil and ground water samples are summarized in Tables 3, 4, 5 and 6 • September/December 1992 - Ground water monitoring was performed during the third and fourth quarter of 1992 at the site High concentrations of petroleum hydrocarbons were reported in the ground water samples during both monitoring events According to ESE documents, free product was pumped from UST-1 prior to sampling during both quarters • 1993 - The well box for UST-1 was found to be in poor condition, and evidence of Infiltration of water and fuel from the surface was noted, floating +free product was encountered in UST-1 Groundwater monitoring and sampling were performed dunng the ' second,third and fourth quarters of 1993 Additionally,weekly ground water extraction was performed as interim remediation It was reported by ESE that water quality improved due ' to pumping activities Interim pumping was reduced to biweekly beginning in 1994 • March 1995 - Three additional ground water monitoring wells(UST-2,UST-3 and UST-4) were installed on-site to delineate the petroleum hydrocarbon-Impact to ground water Pilot lie borings for the three wells were advanced to 85 feet bsg,well screens were recorded between 65 and 85 feet bsg Laboratory analysis of soil samples collected from the pilot bonngs detected petroleum hydrocarbons in samples from boring UST-4, located southeast of the area of concern, at depths of 25 feet, 30 feet, 35 feet, 40 feet and 45 feet bsg Hydrocarbon compounds were not detected in any of the soil samples analyzed from borings UST-2 and UST-3, defining the maximum horizontal extent of impacted soil in the northwest and northeast directions Initial ground water sampling during the second quarter of 1995 contained low concentrations of TPH-g and TPH-d in samples collected from UST-4 • June 1997 - One ground water monitoring well (UST-5) and soil vapor well (VP-1) were Installed on-site to address shallow ground water near the former UST area, rising ground water had drowned the screen Interval of UST-1 The pilot boring for UST-5 was advanced ' to a depth of approximately 74 5 feet bsg, the well screen of UST-5 was recorded as placed between 54 5 feet and 74 5 feet bsg Laboratory analysis of soil samples collected at depths_ between 5 feet and 55 feet bsg from boring UST-5 detected petroleum hydrocarbons • ' September 1997- Six product USTs were removed from the site A total of nine UST soil samples (TI-E through T6-17) and thirteen piping/dispenser soil samples (P1 through P13) were collected and analyzed TPH-g`and TPH-d were detected in the samples collected beneath the USTs at concentrations as high as 2,500 mg/kg and 32,000 mg/kg,respectively TPH-g and TPH-d were detected in piping/dispenser samples at concentrations as high as 1,200 mg/kg and 16,000 mg/kg, respectively (Table 1) Excavation of approximately 400 • cubic yards of hydrocarbon-Impacted soil was performed after removal of the USTs Excavated soil was stockpiled on site Procedures and findings were summarized in the UST I Advanced GeoEnvironmental,Inc I 4