Historically, jet fuel spills, and leaks in storage tanks and/or underground distribution systems resulted in frequent discharges of petroleum to tidal creeks of the Wood Island Marsh from the North Outfall at Logan Airport. Those discharges resulted in the accumulation of visible oil in surficial sediment over an area of approximately 3.5 acres of the tidal creeks and adjacent mud flats. This condition is considered to be “Readily Apparent Harm” to the environment in accordance with the Massachusetts Contingency Plan (MCP), and in 1998 GZA GeoEnvironmental, Inc. filed a Class C Response Action Outcome (Class C RAO, aka “Temporary Solution”) for the North Outfall on behalf of the Massachusetts Port Authority (MassPort).
Class C RAOs require that Periodic Evaluations (PEs) be performed every five years to evaluate whether site conditions have changed significantly since the filing of the Class C RAO, and whether it has become feasible to achieve a Permanent Solution . GZA prepared the first 5-year PE Report in 2002. In the interim between the filing of the Class C RAO in 1998 and the 2002 5-year PE, MassPort had implemented several remediation projects at the airport, and upgraded and replaced their fuel distribution systems, which greatly reduced or eliminated discharges of petroleum to the North Outfall. As a result, by 2002 visible oil in surficial sediment of the tidal creeks was largely eliminated, therefore there was no longer a condition of Readily Apparent Harm. However, analytical and toxicity tests conducted on sediment samples in 2002 and 2007 (for the second 5-year PE) indicated that contaminant concentrations were still elevated, and that sediments were significantly toxic to benthic invertebrates.
GZA conducted the third 5-year PE in 2012. That evaluation included confirmation that visible oil was not present in surficial sediment, and sediment sampling for analytical and toxicity tests. New England Bioassay performed 10-day and 28-day whole sediment toxicity tests on five sites using the amphipod Leptocheirus plumulosus. Chemical analytical results indicated that contaminant concentrations in sediment had decreased compared to previous sampling rounds, and New England Bioassay’s Leptocheirus survival and growth data indicated that the sediments were no longer toxic to exposed benthic invertebrates. These data allowed GZA to file a Class A RAO (Permanent Solution) on behalf of MassPort in December, 2012.