ARCHIVED REPORTS_XR0012710 - Laserfiche WebLink

Home Browse Search

9 September 6, 1991 -- Quik Stop Markets, Inc. Page 2 Project No. 3-49132-31 470 parts per billion (ppb) TPHG and 21 ppb benzene as well as detectable levels of toluene,ethyl benzene,and total xylenes. MW-I was subsequently destroyed in October 3, 1991 due to concerns that it could connect two water bearing units which appear to represent separate shallow aquifers. On September 11, 12 and 13, 1990,Exceltech drilled five additional exploratory` borings the site and converted three of them to groundwater monitoring wells. They designed to monitoring groundwater located in the lower aquifer. The results e ofdyyses of the soil samples from these borings showed little or no petroleum hydrocarbon Analyses of groundwater samples collected from monitoring wells MW-3 and MW-4 did not reveal any petroleum hydrocarbon detectable levvlls of ethyl benzene and total les from MW-2 ylenes found to contain 1 ppb benzene (Exceltech,September 1990). During the above investigations, a leak was discovered in the subsurface piping for the fueling system at the site. Excavations to remove the contaminated soils revealed that the contamination had affected the tank backfill P nd possibly the soil beneath eho yank backfill. Upon issuance of the proper permits,the overhead canopy,pump and three underground storage tanks (US io were removed lin October continued until 1990. Following tank removal, excavatior. and oil sampling laboratory analyses of soil samples indicated that petroleum hydrocarbon contaminated soil above the water table in the vicinity of the storage tank excavation had been removed. All contaminated soil was removed from the station and properly disposed of (Exceltech November 1990). New double-walled fiberglass USTs were installed at the site and the remaining excavation was backfilled with clean fill. The canopy, pumps, and concrete surface were replaced and the station put back in operation in March 1991. On April 2, 1990, Exceltech, Inc. replaced the destroyed groundwater monitoring well, MW-1,with two monitoring wells, MW-1R.and MW-5. MW-1R was designed to monitor the lower aquifer and MW-5 to monitor the upper or"perched"aquifer. Analyses.of all ta indicated the presence of two aquifers beneath the site. 'It subsurface and analytical da was found that the lower aqui€er had no detectable TPHG or BTEX and the upper aquifer: contained TPHG and some BTEX components(Exceltech,July 1991). Field Operations Prior to sampling,Exceltech personnel measured the depth to groundwater and checked for the presence of floating product at each well using an optical interface probe. A clear acrylic bailer was used to collect a water sample from the wells to check for the presence for floating product, surface sheen, or odor: none was detected. Groundwater samples laboratory analysis were then collected from each well following the procedures outlined in our groundwater sampling protocol (Appendix A). Approximately four well-casing volumes of groundwater were removed from each well before sampling. Groundwater removed from the wells and equipment rinse water were placed in Department of Transportation approved drums and left on-site pending the laboratory analytical results.