Does a facility need to consider groundwater pathways when determining if a discharge of oil could reasonably be expected to reach navigable waters?

The Spill Prevention, Control, and Countermeasure (SPCC) requirements apply to facilities that could reasonably be expected to discharge into navigable waters (see 40 CFR 112.2). Owners and operators should consider whether onsite conduits such as groundwater pathways could facilitate the transport of discharged oil off-site to navigable waters. Groundwater is often hydrologically connected to navigable waters; therefore, a groundwater oil plume has the potential to migrate and contaminate navigable waters. Oil that repeatedly contaminates soil as a result of frequent spills may form subsurface oil plumes, which have the potential to contaminate navigable waters when precipitation migrates through soil to navigable waters. Therefore, groundwater pathways should be included as a factor in determining a facility’s reasonable expectation to discharge.