ARCHIVED REPORTS XR0001095 - Laserfiche WebLink

Home Browse Search

ws F, 7 4 , 3 L� • t 'l 2 January 2004 IF F AGE-NC Project No 95-0121 ' Page Sof 6 L � 1 3 t lo,IF r, • Ground water data collected from VW-I through VW-7 are representative of shallow ground }` h ' water conditions, however, ground water data collected from wells MW-1 through MW-9 were generally between 6 and 16 feet below the ground water table, and probably yields t l = `samples more representative of deeper ground water conditions (Table 2) 3 • Between July and September 2003,approximately 0 43 feet to 0 65 feet of floating petroleum ' product was encountered at soil vapor extraction well VW-1 on four separate occasions, between 3 and 6 gallons of ground water was hand-bailed from the well during each incident until the petroleum product was no longer observed and no longer detected utilizing a Sollnst ' Interface Probe Well VW-1 has a screen interval between 15 and 30 feet bsg, which is screened across the lower sand of the site aquifer,thus demonstrating the release of adsorbed hydrocarbons from the fine grained soils at approximately twenty to twenty-five feet,into the lower sand x • Free product was not detected in any other vapor wells(screened 5 to 20 feet bsg),which are exclusively screened across the upper sand unit at the site, most likely demonstrating the tsuccess of the operation of the soil vapor extraction system < 4 • The core of the dissolved petroleum hydrocarbon plume appears to be located at depths ' between 25 feet and 53 feet bsg in the area of'deeper screened wells MW-I through MW-4, ` MW-7 (Figure 5) and more apparent at the top of the water table at depths between 17 feet and 20 feet bsg in vapor wells VW-1 and to a lesser in vapor well VW-4(Figure 4) A review ' of current and previous ground water samples suggest the core of the plume 1s impacted by TPH-g, TPH-d, BTEX, MTBE (Table 3) • The lateral and vertical extent of dissolved petroleum hydrocarbons is not fully defined at the ' ' site, further assessment is warranted west-northwest of well MW-7, north of MW-2 and' R ` north-east of well MW-4 (Figure 4) Since the approval of the CAP in December 1995, the local and regional ground water elevation has ni increased significantly(approximately 10 feet) and has maintained a depth to water of near 18 feet bsg The CAP was properly designed to mitigate dissolved.and adsorbed shallow contamination, with a water table level at approximately 25 to 30 feet bsg AGE believes that the sustained increase I of ground water elevation has significantly decreased the potential effectiveness of SVE/IAS as a stand alone treatment for impacted soil and ground water due to a reduction of the thickness of the impacted vadose zone and an inereased,thickness, and volume, of impacted soil (and ground water) in the saturated zone The impacted soil is primarily fine'grained within sand units,which may make l the upward and lateral path of sparged air through the'saturated zone unpredictable and stripped hydrocarbons unrecoverable The limited overall effectiveness and reliability of IAS technology to , _ remediate deeper and saturated impacted sand unit and ground water likely will require a re- evaluation of the method to remediate ground water and reduce the hydrocarbon mass ! Advanced GeoEnviranmental,Inc 4 l , 3