ARCHIVED REPORTS_XR0003254 - Laserfiche WebLink

Home Browse Search

14.September 199$ AGE-NC Project No. 98-046$ Page 3 of 10 round water'sam le w water as collected from the excavation. Laboratory anal sis•of the round g P rY Y g sample, detected elevated levels of benzene (1,000 ppb), toluene (2,000 ppb), ethylbenzene (800 ppb), total xylenes (6,400 ppb); and TPH-g (17,000 ppb). In.August 1995,additional petroleum hydrocarbon impacted soil'was .xcavatc 'and removed from _the'former diesel UST location and soil samples collected for analysis. aboratory analysis of the soil samples collected from the four'sidewalls of the excavation detected benzene (5.9 ppm),toluene (46 ppm),ethylbenzene(23 ppm),total xylene(150 ppm),TPH-g(3,800 ppm),and TPH-d(45 ppm). The majority of the reported;detections of petroleum hydrocarbon compounds were from the east and west sidewalls of the excavation. Subsequently, the City of Stockton backfilled and compacted the excavation. Site Characterization ' in,1996,The Twining Laboratories, Inc. conducted a site investigation to assess the lateral extent of petroleum hydrocarbon impacts,to soil and ground water at the site. The site characterization • activities consisted of the advancement of seven soil probes (SB-1 through SB-7) and the collection of soil and in-situ ground water samples for laboratory-analysis (Figure 2). Laboratory analysis of soil samples detected BTEX, TPH-d, TPH-g and methyl_tertiary-butyl ether -(MTBE) for samples -collected from soil probe baring/'SB-5�-.,)If addition, relatively"16w' concentrations of petro hydrocarbon P s ban compounds were detected for soil samples collected from P P SB-4 and SB-7., The analytical results of ground water samples collected from the soil probe borings suggested that ground water has been extensively impacted by BTEX, TPH-d, TPH-g and MTBE. The greatest petroleum hydrocarbon impacts to ground water were reported for soil probe-boring locations SB-5 and SB-7 located north of the former diesel UST location.'Laboratory analysis of ground,water samples collected from soil probe SB=5 detected benzene (6,500 ppb),,toluene :(35,000 ppb), ethylbenzene (4,500 ppb), total xylenes (25,000.ppb), TPH-d (320,000 ppb), TPH-g (93,000 ppb), and MTBE (560 ppb). 2:3. SITE HYDROGEOLOGIC CONDITIONS According,to information presented in The Twining Laboratory's Site Characterization report (Twining,.1997),the depth.to groundwater has been observed to.fluctuate from approximately 7 to 14 feet bsg at the site. Ground water flow direction was reported to be toward the north. Advanced GeoEnviron mental,Inc.