SEATTLE— The U.S. Army Corps of Engineers failed to consider how ship traffic harms critically endangered orcas when it approved plans to expand Seattle Harbor, the Center for Biological Diversity said today in a notice of its intent to sue the agency. This declining population of orcas is down to just 72 individuals.

The port expansion aims to accommodate massive container ships, but those ships will harass and disturb Southern Resident killer whales while they search for salmon, their favored food. Noise disrupts foraging and the starving orcas’ ability to find food. The project would also dredge up toxic contaminants as it deepens and enlarges the channel.

“This project will dredge up pollutants to bring in more and bigger ships, worsening two major threats to these endangered orcas,” said Catherine Kilduff, a Center attorney. “The Trump administration OK’d the Seattle Harbor expansion without analyzing that harm. Killer whales are starving to death, and increasing boat noise and traffic would accelerate their decline. We need to take better care of our last Southern Resident orcas.”

Scientists have estimated that the doubling of ship traffic between 1950 and 2000 has doubled noise intensity every 10 years. Larger ships and tending vessels will create more noise around Seattle Harbor, the heart of these orcas’ habitat. Studies have found Southern Resident killer whales spend up to 25% less time feeding when disturbed by boat noise.

The project would dredge about 925,000 cubic yards of materials from the bottom of waterways around Seattle Harbor, the heart of Southern Residents’ critical habitat in the Salish Sea. The Army Corps considers more than 20% of that material so toxic it requires a special hazardous material process. Yet much of the pollution will be suspended in the water and ingested by salmon, then orcas.

Persistent organic pollutants such as DDT and PCBs have been found at high levels in Southern Residents, often stored in their fat cells. Those pollutants get released into the orcas’ blood stream when they’re malnourished and can harm reproduction, development and their ability to forage for food.

Urgent action is needed to prevent Southern Residents from spiraling toward extinction. Over the past year, the Center has filed lawsuits demanding the Trump administration expand critical habitat protections for these orcas, look at how salmon fishing harms prey availability, and establish a whale-protection zone to minimize vessel noise and disturbance.