Seattle light rail linked to deaths of 2,000 fish in Lake Washington five months after opening

A light rail line celebrated as a major addition to Seattle’s transit network has been linked to an unexpected fish die-off in Lake Washington. About 2,000 fish have been found dead near electrical cables and equipment hanging beneath the I-90 floating bridge, five months after trains began crossing the lake.

Sound Transit launched service across the bridge in March 2026, connecting downtown Seattle with the Eastside for the first time by rail. The project promised faster commutes and less traffic, but its new electrical systems appear to have created a problem in one of the region’s most important and heavily used bodies of water.

The floating bridge consists of concrete pontoons tethered across Lake Washington. To power the trains, Sound Transit installed electrical equipment that extends below the bridge deck. The lake contains kokanee salmon, cutthroat trout and other native and stocked fish, while boats, swimmers and anglers use its waters throughout the year.

In the weeks after service began, maintenance workers and boaters reported clusters of dead fish near the bridge. Many were floating or had washed ashore close to the electrical cables and other transit equipment. By late summer, Sound Transit and state wildlife officials had recorded about 2,000 deaths.

The location and timing raised concerns that the rail infrastructure was involved. Investigators from Sound Transit, the Washington Department of Fish and Wildlife and other agencies began examining the electrical systems. Early findings suggest that fish may have touched energized components or been affected by electrical fields generated by the equipment. Cables or connectors intended to be insulated or shielded may have exposed fish to damaging currents.

The precise mechanism remains under study. Investigators are considering direct electrocution as well as effects such as disorientation, muscle spasms or physiological stress caused by electromagnetic fields.