ARCHIVED REPORTS_XR0003588 - Laserfiche WebLink

Home Browse Search

' 31 May 2005 AGE-NC Project No 04-1239 ' Page 6 of 7 ' borings (40 feet bsg) sand, silty sand, sandy silt, and silt were encountered • A total of fourteen soil samples were analyzed for the constituents listed in Section 2 1 1 TPH-g was detected in soil samples MW9-25, MW9-30, MW9-35, and MW9-40 at ' concentrations ranging from 14 mg/kg to 2,400 mg/kg BTEX compounds were detected in samples MW9-25, MW9-30, MW9-35, and MW9-40 at maximum concentrations in ' MW9-35 of 17 mg/kg toluene, 59 mg/kg ethylbenzene, and 352 mg/kg total xylenes • At the time of the April 2005 ground water monitoring event,depths to ground water ranged from 18 46 feet to 18 71 feet below the tops of the well casings Ground water elevation at ' the site ranged from 7 89 feet to 8 34 feet below MSL,and averaged approximately 8 13 feet below MSL ' • On 11 April 2005, ground water at the site was inferred to be flowing toward the northeast under a hydraulic gradient of approximately 0 01 ft/ft • Petroleum hydrocarbons were detected in well MW-9 during the April 2005 ground water monitoring event TPH-g was detected at a concentration of 62,000 µg/l BTEX compounds were detected at the following concentrations 13 µg/l benzene, 3,100 µg/1 toluene, ' 1,800 µg/1 ethylbenzene, and 7,900 µgd total xylenes c The vertical extent of petroleum hydrocarbon contamination in soil is not yet defined ' c The lateral extent of petroleum hydrocarbon contamination is defined to the south by well MW-11 and to the southwest by well MW-10 5.0. RECOMMENDATIONS Based on the findings of the environmental activities recounted in this report, AGE recommends • Continuation of quarterly monitoring events,the next event should take place in third quarter 2005 • Additional shallow investigation at the former UST area to monitor the core of the dissolved hydrocarbon mass,and additional investigation down-gradient of well MW-9 to monitor the migration of the dissolved hydrocarbon mass The installation of three additional shallow ground water monitoring wells is justified (see Figure 2) ' • Additional investigation of vertical hydrocarbon impact to the site should be completed An installation of vertical ground water monitoring wells within the former UST excavation area and in the down-gradient direction near well MW-9, and cast of the former UST area, is justified (see Figure 2) Advanced CcoEnvironmental,Inc I