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N Site Background Information - Fernando 's Place AGE-NC Project No. 00-0769 Page 5 of 5 • A release of petroleum hydrocarbons (TPH-g) and benzene, toluene, ethylbenzene and xylene (BTEX) compounds occurred from UST number #3 (boring MWl ) and likely from the common UST area of UST# 1 and UST #2 (boring PB 1), shallow soil impact near ten feet bsg supports this concept. The dispenser at the northeastern boundary of the site may have also been a release point. The UST fuel release mostly likely contained fuels with 1 ,2-DCA and did not contain MTBE. • Once released to the subsurface, the contaminants migrated to a vertical depth of approximately 30 or 35 feet bsg, at whichpoint the contaminants migrated laterally towards the southeast at well MW-2. The plume was also release during a lowered water table cycle, demostrated by absorbed contamination at depth near 50 or 55 feet bsg with significant concentrations.. The most significant mass of hydrocarbons are found below the UST area proper at borings PB 1 and a boring from well MW- 1 . Vadose-zone contamination at the site is present in the immediate vicinity of the former UST excavation from depths of approximately 10 to 50 feet bsg. A "smear zone" hydrocarbon impact at the site is laterally more extensive (30 to 40 feet) . • Once released to the subsurface, the dissolved hydrocarbons and 1 ,2-DCA contaminant migrated to a vertical depth of approximately 50 feet bsg at the former UST#1 area (MW- 1 ). The hydrocarbons migrated in a dominate southeast direction from the former UST# 1 area to the area of wells MW-2. A separate release of petroleum with 1 ,2-DCA occurred at UST #2 and UST #3 , which migrated vertically to 55 feet bsg. • The migration of dissolved hydrocarbons appears to have maximized at a vertical depth of approximately 50 feet bsg suggest ahigh concentration zone between 50 feet and 60 feet bsg. • There are relatively reduced detections of dissolved hydrocarbons from depths between 100 feet bsg and total depth of the monitoring well network at 200 feet bsg. The vertical extent of dissolved hydrocarbons has not been defined in the release area near well MW- 1 , or east (down-gradient) at well MW4. • The majority of the deep, grab ground water and deeper monitoring well samples have demonstrated residual hydrocarbon impact after multiple years of ground water monitoring, demonstrating a possible deep and submerged non-aqueous phase petroleum (NAPL) source at the former UST area. • The vertical and the lateral extent of TPHBTEX11 ,2-DCA has been defined by samples collected south of the site at well MW-9 . • Data gaps for dissolved hydrocarbons remain, vertically and laterally somewhat west of the site; northeast of wells and east of the well network. Advanced GeoEnvironmentaf, Inc.