Formatted Title
Application of HRSC Technology to Create an Accurate Three-Dimensional Site Model and Accelerate CSM Understanding and Remedial Alternatives Evaluation
Background/Objectives
Three-dimensional (3-D) modeling combined with high resolution site characterization (HRSC) data enable the visualization of subsurface contaminant distribution. This technology is specifically useful in understanding contaminant distribution with multiple suspected sources since the model interpolates and integrates a large amount of data, including HRSC data, confirmation sampling, and traditional sampling.
A release of hydraulic oil was discovered at a manufacturing facility in western Pennsylvania, including the identification of light non-aqueous phase liquid (LNAPL) across a broad area exterior to the building. The initial discovery indicated that additional assessment was necessary to assess the associated risk and to further advance the conceptual site model (CSM).
Approach/Activities
This investigation included advancing 29 optical imaging profiler (OIP) borings, which included an electrical conductivity dipole (EC) and the hydraulic profiling tool (HPT) both exterior to and inside the manufacturing facility. Inside the building there were access issues due to active plant operations, vertical clearance for the Geoprobe, and open pits under the interior of the building where the presses were located. However, the suspected source was within an active pump room; therefore, it was critical for complete site characterization to investigate inside the building.
Overall, the OIP indicates the degree of LNAPL saturation within the soil matrix whereas the EC and HPT reflect grain size and soil permeability. As the data was collected, a model was developed and updated. Analysis of data by field staff and project management informed decision making and enabled investigators to “chase” the LNAPL distribution to suspected source areas and accurately delineate the contamination in real time.
Results/Lessons Learned
Access issues were able to be resolved by using a small drill rig and a small footprint since space to maneuver was minimal. Thus, the full site was successfully investigated. Data produced by the HRSC indicated multiple sources of LNAPL and LNAPL at different depth intervals that may have been missed by traditional assessment methods. HRSC, however, provides thousands of data points, enabling generation of 3-D models displaying lithology and contaminant distribution. Utilizing the 3-D model, the CSM was more rapidly developed, and the client was able to identify likely active sources. Additionally, the 3-D model helped aid in rapidly screening remedial technologies for LNAPL management.