ARCHIVED REPORTS XR0001519 - Laserfiche WebLink

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On January 5 and 6, 1999, Ramage Environmental conducted a preliminary investigation and evaluation which included the drilling of five on-site sod borings for soil sampling and analysis Three of the soil borings were converted to groundwater monitoring wells The newly installed weils.were developed, surveyed, monitored and sampled on January 11, ' 1999 Sods 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 ' Soil and groundwater beneath the site have been impacted by significant concentrations of gasoline hydrocarbons In soil, the highest concentration of gasoline hydrocarbons was detected in the sample collected at 30 feet below ground surface (bgs) from the soil 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 soil 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 soil ' samples collected for analysis from the previously drilled soil boring B-1 ' Groundwater in the three monitoring wells has been sampled on a quarterly basis The highest concentrations of gasoline hydrocarbons have been detected in MW-2, installed through the former UST excavation To date, the highest concentrations detected in groundwater include 130,000 µg11 of TPH-as-gasoline, 7,800 µg11 of benzene, 64,000 µg11 of toluene, 6,100 µg/l of ethylbenzene, 35,000 µg/l of xylenes, 2 6 µg/l of methyl tertiary Ibutyl ether (MTBE), and 100 µg/I of tertiary butanol (TBA) 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