ARCHIVED REPORTS XR0001521 - Laserfiche WebLink

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gasoline, 38 µg11 of benzene, 310 µg11 of toluene, 4 8 ofµg11 ethylbenzene and 6,800 µg11 of xylenes On January 5 and 6, 1999, Ramage Environmental conducted a preliminary investigation and evaluation which included the drilling of five on-site soil borings for soil sampling and analysis Three of the sod borings were converted to groundwater monitoring wells The ' newly installed wells were developed, surveyed, monitored and sampled on January 11, 1999 Soils encountered beneath the site consist of a fining-upward sequence of fine- grained siliciclastic sediments The depth to static groundwater beneath the site ranged from 39 31 to 40 34 feet bgs Groundwater flow was to the south-southeast at a gradient of 0 05 foot/foot A metal detection survey conducted at the site, on January 13, 1999, discovered strong metallic signals in the vicinity of the former UST excavation The metal may be drums of waste not accounted for from earlier site investigation activities and other material used to backfill the former UST excavation ' Sal and groundwater beneath the site have been impacted by significant concentrations of gasoline hydrocarbons The five oxygenate compounds were not detected in any of the sod or groundwater samples analyzed during the investigation In soil, the highest concentration of gasoline hydrocarbons was detected in the sample collected at 30 feet below ground surface (bgs) from the sod boring for MW-2 This sample, collected directly beneath the former UST excavation, contained 2,400 mg/kg of ' TPH-as-gasoline and detectable concentrations of toluene, ethylbenzene and xylenes Laterally, the extent of impacted sal appears to be limited to the footprint of the former UST excavation Vertically, the extent of impacted soil beneath the former UST excavation is defined at a depth of approximately 55 feet bgs, on the basis of sod samples collected for analysis from the previously drilled soil boring B-1 In groundwater, the highest concentration of gasoline hydrocarbons detected was from the sample collected from MW-3, adjacent to the northwest corner of the former UST ' excavation This sample contained 120,000 µg/I of TPH-as-gasoline, 7,800 µg/l of benzene, 64,000 µg/l of toluene, 4,300 µg11 of ethylbenzene and 28,000 µg11 of xylenes ' These concentrations are above Title 22 Maximum Contaminant Levels for these compounds The lateral extent of impacted groundwater is undefined to the north (upgradient), west and south (downgradient) of the former UST excavation However, the lateral extent is defined to the northeast of the former USTs by MW-1 Vertically, the Possible impact to deeper groundwater-bearing zones has not been investigated 4