ARCHIVED REPORTS_XR0002074 - Laserfiche WebLink

Home Browse Search

"` rr Mr Harlin Knoll Page 2 of 3 A Ground Zero technician purged a minimum of three well casing volumes of groundwater from monitoring wells MW 1, MW4 and MW5 on May 21, 2002 The wells were purged using an electric, submersible pump During the purging process temperature, specific conductance, and pH were measured and recorded All downhole equipment was decontaminated prior to and between each use by washing with a solution of laboratory-grade detergent and then double-rinsing with water Groundwater samples were collected using dedicated, disposal bailers after physical parameters stabilized and water levels recovered to at least 80% of static levels The samples were decanted into 40-m1 glass vials preserved with dilute hydrochloric acid and placed in an ice chest refrigerated to a temperature of approximately 4°C The samples were transported to Argon Laboratories (ELAP #2359) under chain of custody protocol and analyzed for TPHg and BTEX utilizing EPA methods 8015M and 8020, respectively Purged groundwater and decontamination rinsate were contained in labeled Department of Transportation (DOT) approved drums pending disposal Copies of field purge logs and water level measurements are included in Attachment A Groundwater Analytical Results Elevated levels of dissolved gasoline constituents were detected in the groundwater sample collected from well MW5, and relatively low levels were detected in samples collected from well MW1 No gasoline constituents were detected in the sample collected from well MW4 Well MW5 contained TPHg at a concentration of 72,000 parts per billion (ppb), benzene at 4,600 ppb, toluene at 2,800 ppb, ethylbenzene at 1,900 ppb, and xylenes at 10,000 ppb Well MW1 contained TPHg at a concentration of 230 ppb, benzene at 3 5 ppb, ethylbenzene at 6 4 ppb and xylenes at 3 5 ppb No toluene was detected in well MW1 No gasoline constituents were detected in the sample collected from well MW4 Analytical results are summarized in Table 3 Laboratory data sheets and chain of custody documentation are included in Attachment B Figure 3 presents a benzene isoconcentration map from the most recent analytical results Attachment C contains graphical representations of TPHg and benzene concentrations over time in site wells SUMMARY AND CONCLUSIONS Groundwater flowed in an easterly direction The potentiometric surface at the site fell approximately 0 11 feet between February 2002 and May 2002 The water level lies above the screened interval in all site wells except for well MW3 TPHg and BTEX were not detected in well MW4, while concentrations of dissolved TPHg and BTEX increased in wells MW1 and MW5 since last sampled in February 2002 Despite the recent spike of contaminant concentrations in wells MW1 and MW5, the overall trend at the site appears to be a decreasing . one (Attachment Q G 1DaWGROUNDMKNOWLES HAMIREP0RTSIQMR12QM2002 doc