Expediting site closures using a risk-based corrective action approach

A new tool, the Risk Analysis Testing Laboratory (RATL), extends the opportunity for collection of high accuracy data on-site during the risk analysis and remediation feasibility stages of subsurface corrective action. The RATL system is driven by onboard data acquisition and processing hardware and software which provides necessary site parameters to determine potential exposure, prioritize sites, and if necessary, design remediation systems on-site in one mobilization. During the removal of underground storage tanks (USTs) at an abandoned service station facility, elevated concentrations of hydrocarbon compounds in the soils surrounding the USTs, as well as a hydrocarbon sheen were identified on the groundwater at the bottom of the UST excavation area. Although 1,000 tons of hydrocarbon-impacted soils had been removed from the UST area, the vertical and lateral extent of subsurface hydrocarbon impact had not been sufficiently delineated. Groundwater sampling was performed with a modified narrow diameter sampling device at 24 locations in a two day period. A total of 32 soil samples were collected in conjunction with groundwater sampling. The soil samples were field screened on-site using a photoionization detector (PID) for volatile organic compounds (VOC) and were classified by the site hydrogeologists. Based on the field screening, selected soil samples were submitted for GC analysis in the RATL