Crews started retrofitting 13 of the 136 dangling anode cables last week, CEO Dow Constantine told a committee meeting Thursday. The agency plans underwater cameras and dive inspections to gauge whether the cages work. If the pilot succeeds, all 136 cables will get the same treatment.

"It is a cage or sleeve design," Constantine said, describing it as off-the-shelf equipment borrowed from aquaculture companies. The barriers are tubes or capsules of synthetic mesh, about a foot in diameter, fastened around the cable strings before they are lowered back into the water.

The problem surfaced through an unusual channel: amateur divers exploring the sunken ruins of concrete pontoons that went down in 1990 spotted fish carcasses on the silty lake floor in 2025 and again this summer. Some cables had been allowed to reach the lake bottom, creating a path for stronger current. The divers reported their findings in late July to conservation groups, who alerted the Washington State Department of Transportation, which notified Sound Transit on Aug. 3.

A month later, Constantine went public after a dive contractor hired by the agency surveyed the whole corridor and counted dead fish at many cables. Sound Transit quickly lifted 32 cables off the lake bed, where mortality appeared worst.

The cables are part of the electrically powered 2 Line segment that opened on the floating bridge March 28 and has added roughly 30,000 daily riders to the regional transit system. The system generates "stray current" that, if unchecked, can seep into rebar and structural steel, rusting the concrete bridge and track ties from within. The 136 anode cables carry a low-level current designed to divert that harmful current away from pontoons and anchor cables.

Sound Transit initially estimated 2,000 fish died, though decomposition made an exact count impossible. A senior scientist with the Muckleshoot Tribe said the die-off appears to include endangered Chinook and sockeye salmon. A state Fish and Wildlife expert also reported evidence of yellow perch, sculpin, smallmouth bass and possibly cutthroat trout. The discovery dismayed Native and sport-fishing advocates who have fought for years to preserve Northwest salmon runs.

Lake Washington, carved by retreating glaciers, reaches depths of about 200 feet in places, but the fish kills were clustered in shallower near-shore areas where cables tended to touch bottom. Constantine said the electric field was "higher than expected or anticipated."

Recent reconnaissance dives this fall found very few dead fish, a sign that lifting the shallow cables in August was effective, said spokesperson Rachelle Cunningham. The agency has not yet calculated costs for the August dive investigations or the November pilot project.

The stakes extend beyond one lake. The I-90 corridor is a critical link in the region's growing light rail network, and the fish kill has raised questions about how the agency monitors environmental impacts of electrified infrastructure in sensitive waters. For now, the mesh cages represent a small-scale test of whether a simple fix can protect a resource that tribes and fishing communities have long depended on.