Project:
Active Bulk Fuel Storage Terminal
Bottom Line: Using state-of-the-art investigation techniques for plume delineation and developing a risk-based site management strategy.
Summary of Project
The bulk fuel storage terminal site is at a busy commercial port and contains seven aboveground storage tanks that have been used to store diesel fuel and fuel oils custom-blended for various maritime customers. Free-phase diesel fuel was present as LNAPL floating on the shallow groundwater at 5 to 10 feet below grade. Orion conducted investigations to evaluate the distribution, mobility, and recoverability of the LNAPL plume as well as the extent of dissolved-phase hydrocarbon impacts. Orion negotiated with the regulatory agency to establish risk-based cleanup levels.
- Conducted high-resolution site characterization using an ultraviolet optical screening tool (UVOST) to evaluate the lateral and vertical extent of LNAPL. Installed 32 borings downgradient of the bulk storage terminal across a 24,000-square-foot portion of the LNAPL plume. Identified potential areas of concern and installed downgradient and cross-gradient sentinel wells.
- Installed 16 soil borings to measure pore fluid saturations and calibrate UVOST response to LNAPL saturation. Delineated potentially mobile LNAPL by identifying the portion of the plume greater than residual saturation.
- Evaluated transmissivity and recoverability of LNAPL within the potentially mobile plume by performing baildown testing and operating multiple pneumatic pumping skimmers for long-term recovery trends. Identified limitations in reliability of baildown tests caused by tidally induced water table fluctuations. Used long-term recovery data to show that recoverable LNAPL was localized and limited in extent.
- Performed a groundwater investigation to evaluate the lateral and vertical extent of dissolved-phase hydrocarbon impacts. Collected Hydropunch samples from 28 direct-push borings for analysis by an onsite mobile laboratory. Determined that TPHd and naphthalene were the primary chemicals of concern for the site and that regulatory screening levels were not available for these compounds. Conducted a risk assessment to develop site-specific risk-based cleanup levels and confirmed that plume delineation was complete.