Comparison of Chemical Sediment Analyses and Field Oiling Observations from the Shoreline Cleanup Assessment Technique (SCAT) in Heavily Oiled Areas of Former Mangrove in Bodo, eastern Niger Delta

Trial pitting, borehole drilling, and soil, sediment and groundwater sampling are important components of oil spill response and contaminated land assessment. These investigations provide detailed information of the subsurface geology and contaminant occurrence and transport but have disadvantages including worker safety hazards, cost and time required for completion, and may cause cross-contamination among aquifers. An alternative to such investigations applied in oil spill response is the Shoreline Cleanup Assessment Technique (SCAT) approach, which relies heavily on direct visual observations to assess the severity of oil contamination and guide cleanup efforts. Here, we compare SCAT observations of oil type, surface coverage and pit oiling to collected surface and subsurface sediment samples taken concurrently and analysed for a suite of hydrocarbon constituents. Results indicate that while limited sampling and analysis is required to chemically characterize the contamination, SCAT observations can be calibrated using limited sediment sampling and is sufficient to steer physical cleanup methods. This is particularly evident as even closely spaced chemical samples show high variability. A coarser direct visual observation is fit-for-purpose considering the wide variability in contaminant distribution at even local levels. In this contribution, we discuss the limitations of the different methodologies.