ARCHIVED REPORTS_XR0005666 - Laserfiche WebLink

Home Browse Search

l� 1 Mr Jeff Wong June 26, 2000 Page 2 of 3 Prior to sampling, monitoring wells MW 1 through MW4 were purged of a minimum of three well casing volumes During the purging process the physical parameters of temperature, pH and electrical conductivity were measured Samples were collected after the physical parameters stabilized and water levels recovered to at least 801/o of their pre-purged levels Purged groundwater was contained in appropriately labeled DOT-approved 55-gallon drums, which are currently being stored onsite Purge logs are included in Attachment A Groundwater samples were delivered under chain of custody protocol to Argon Laboratones (ELAP #2359)for analysis of TPHg by EPA method 8015 modified, BTEX by EPA method 8020, 1,2-DCA, EDB, and oxygenated gasoline additives by EPA method 8260B GROUNDWATER ANALYTICAL RESULTS Groundwater samples collected from monitonng well MW 1, located within the former UST excavation, contained elevated levels of gasoline constituents Dissolved TPHg in groundwater collected from MW 1 was detected at 96,000 parts per billion (ppb), benzene was detected at 7,500 ppb, and MTBE was detected at 5,500 ppb Downgradient well MW3 contained TPHg at 1,100 ppb, benzene at 12 ppb, and MTBE at 2,800 ppb Upgradient well MW2 contained TPHg at 1,100 ppb and benzene at 11 ppb Downgradient well MW4 contained TPHg at 150 ppb and MTBE at 300 ppb No BTEX constituents were detected in well MW4, and no MTBE was . detected in well MW2 Groundwater analytical results are summarized in Tables 2 and 3 Laboratory reports and chain-of-custody documentation are included in Attachment B SUMMARY Groundwater levels at the site rose an average of 3 86 feet since last monitored in October 1999 Elevated levels of dissolved gasoline constituents are present in wells MW1, MW2, and MW3 TPHg in groundwater ranged from 150 ppb in well MW4 to 96,000 ppb in well N1W1, benzene ranged from <0 5 ppb in well MW4 to 7,500 ppb in well MW 1, and MTBE ranged from <5 0 ppb in well MW2 to 5,500 ppb in well MW 1 Dissolved gasoline constituents in upgradient well MW2 generally decreased by 35% (TPHg) to 96% (ethylbenzene) since the initial sampling round in October 1999, including MTBE which decreased from 6 2 ppb to non-detect (<5 0 ppb) Dissolved contaminants in MW 1 (drilled through the former UST excavation) decreased by 20% (TPHg) to 87% (MTBE) Dissolved contaminants in downgradient wells MW3 and MW4 generally decreased by 861/6 to 99%, except for MTBE in well MW4 which rose from 52 ppb to 300 ppb MTBE in well MW3 decreased from 39,000 ppb to 2,800 ppb CONCLUSIONS AND RECOMMENDATIONS The lateral extent of dissolved groundwater contamination in the shallow aquifer beneath the site has not been defined, although concentrations in well MW4 suggest that this well is near the plume limits to the east F 1Data1GROUNDZF\TLTLEBLJRG\Reporb\2QM2000 doc