CASE STUDY: HIGH RESOLUTION SITE CHARACTERIZATION OF AN LNAPL FUEL OIL CONTAMINATED FORMER RAIL YARD

High resolution site characterization (HRSC) is used to improve conceptual site models and inform remediation. High-density sampling is used to map contaminants down to the centimeter scale. A former rail yard in Meadville, PA has decades of known diesel fuel oil contamination, and a sheen is frequently observed in nearby French Creek. Prior remediation efforts have proved ineffective. Civil and Environmental Consultants Inc. partnered with Columbia Technologies to perform a high resolution site characterization. 26 Optical Image Profiler (OIP) Borings were performed to map the vertical and lateral extent of the hydrocarbon plume. OIP fluorescence is highly correlated with total petroleum hydrocarbon concentrations. A Hydraulic Profiling/Electrical Conductivity Tool was used to collect data on permeability and saturated hydraulic conductivity of the subsurface. Discrete soil sampling was performed at three sites with the highest OIP readings to confirm the fluorescence response. The results show a map of LNAPL thickness ranging from 0.5 to 14 feet thick, decreasing in thickness west of the source zones. The majority of the LNAPL is found between 4 to 19 feet below the ground surface. The LNAPL is interpreted to be bound in fine-grained soils creating a smear zone. The contaminant in these soils is unrecoverable by traditional pumping methods. A discontinuous, but distinct lower permeability stratum requiring higher injection pressures was identified between 18 to 26 feet below the ground surface. This stratum may play an important role in retarding the vertical mobility of LNAPL. This case study shows the utility of high resolution site characterization technologies to improve conceptual site models. This has the potential to lead to time and cost reduction in successful remediation efforts.