ARCHIVED REPORTS_XR0005226 - Laserfiche WebLink

Home Browse Search

1 ' ■ The cumulative mass of contaminants removed from the dissolved phase for the site over time as monitored by changes in concentration and/or areal extent in map view. ' ■ The overall effectiveness of the C-SpargeTM remediation system as monitored by one additional indicator to be added during 4th Quarter 2004: 1. Oxidation-reduction potential (ORP) field determinations on groundwater grab ' samples. ORP conditions over 300 my usually indicate the presence of gaseous 03. After significant reduction of MTBE, the quantification of the: - Overall contaminant mass destruction rates (Le., removal efficiency) for the site over time, and to the extent practical; - Contaminant mass destruction rates for the site with distance and direction from ' the injection wells over time. [Note: Reduction of benzene is expected prior to MTBE.] ' 4.4.2 Results of Remediation System Monitoring A summary of depth to water, groundwater elevation and groundwater flow has been described ' previously in this report (Table 1). Groundwater chemistry has been reported in Table 2. The depth to groundwater during the July 16, 2004 groundwater monitoring event for on-site wells (only) ranged from 65.40 to 66.16 feet bgs where measured. The depth to groundwater during the third quarter for the August 13, 2004 groundwater-monitoring event for on-site wells (only) ranged from 66.37 to 66.73 feet bgs where measured. The depth to groundwater during the ' September 13, 2004 groundwater-monitoring event for on-site wells (only) ranged from 66.83 to 67.18 feet bgs. The upper ozone diffusers were a minimum of 5.34, 4.77 and 4.32 feet below the ,. top of water, respectively, during the July, August and September monitoring events. ' 4.5 Analysis of System Effectiveness ' Figures 14 through 20 are cross plots of benzene and MTBE over time. Figures 21, 22 and 23 show the areal distribution of benzene, MTBE and TPHg, respectively, based on isoconcentration maps over time. 4.5.1 Benzene Prior to this monitoring period, and prior to remediation system start-up on June 17, 2004 at the ' Jamar property, benzene concentrations appeared to decline in MW2, MW3, MW4, MWS and MW8. ' Declining trends in benzene concentration were not evident, however, in MW1 and EW1 prior to this monitoring period. During the third quarter monitoring period concentrations of benzene from MW1 and EW1 placed respectively at approximately 7.5 and 9.0 feet from the closest Spargepoint® (IW2 and IW1) declined. The successive decline of benzene in MW1 from the 37,000 ug/L on June 3, 2004 in each of the ' monitoring events following (i.e., July 16, 2004, August 13, 2004 and September 13, 2004) was 5:1268231QM reports12004 3QR.doc 8 ATC Associates Inc.