Sound Transit said Thursday it is installing mesh tube cages around a device believed to be killing fish on the I-90 floating bridge.
Thirteen cages, made of off-the-shelf supplies commonly used in aquaculture, were added to over a dozen pontoons. The anode strings are wires connected to floating pontoons that emit electrical currents to prevent corrosion. Sound Transit believes fish, including salmon, are being electrocuted when they swim near the wires.
In August, CEO Dow Constantine announced that an unusual number of fish, including salmon, had been discovered on the bottom of Lake Washington near the 2 Line’s Crosslake Connection. The cages were designed with fisheries staff from the Muckleshoot Indian Tribe and the Washington State Department of Fish and Wildlife. Cameras were also installed inside the mesh tubes to monitor fish activity.
If the first 13 cages work as planned, Sound Transit said it will add them to all 136 pontoon anode strings on the bridge.
Analysis
Why This Matters
- Salmon are a culturally and ecologically important species in the Pacific Northwest; preventing further deaths supports regional conservation efforts.
- The mesh cage design offers a low-tech, low-cost solution that could be replicated on other bridges with similar corrosion-protection systems.
- The collaboration with the Muckleshoot Indian Tribe and state wildlife officials sets a precedent for co-management of infrastructure impacts on fisheries.
Background
Sound Transit operates the light rail 2 Line across Lake Washington via the I-90 floating bridge. The bridge's concrete pontoons are protected from corrosion by electrical currents delivered through anode strings. In August 2025, agency CEO Dow Constantine reported an unusual number of dead fish, including salmon, near the crossing, leading to the suspicion that the current was electrocuting them. The mesh cages are designed to physically block fish from contacting the wires.
What to Watch
- Whether the first 13 cages show a measurable reduction in fish deaths, monitored by the installed cameras.
- The timeline for Sound Transit's decision to expand to all 136 anode strings if the pilot succeeds.
- Any further environmental monitoring or regulatory review of the anode system's impact on aquatic life.
Checked
10 claims in this story checked against 1 source: 9 supported.
Show each claim
- SupportedSound Transit is installing mesh cages around a device believed to be killing fish beneath the I-90 light rail.KUOW: “Sound Transit said Thursday it’s installing 13 mesh tube cages to wrap around a device believed to be killing fish.”
- SupportedThe cages use off-the-shelf aquaculture supplies and are intended to prevent further fish deaths.KUOW: “The cages are made of off-the-shelf supplies commonly used in aquaculture, the agency said”
- SupportedSound Transit said Thursday it was installing the cages.KUOW: “Sound Transit said Thursday it’s installing 13 mesh tube cages”
- SupportedThirteen cages were added to over a dozen pontoons.KUOW: “Last week, divers added the new cages to over a dozen of the pontoons”
- SupportedThe anode strings are wires connected to floating pontoons that emit electrical currents to prevent corrosion.KUOW: “The wires are connected to floating pontoons that emit electrical currents that prevent the steel and concrete from corroding.”
- Partly supportedSound Transit believes salmon, as well as other fish, are being electrocuted when they swim near the wires.KUOW: “In August, Sound Transit CEO Dow Constantine announced that an unusual number of fish, including salmon, had been discovered on the bottom of Lake Washington near the 2 Line’s Crosslake Connection on the I-90 floating bridge. The suspected culprit: underwater wires, called anode strings. The agency believes that fish are being electrocuted when they swim by the wires.”
- SupportedIn August, CEO Dow Constantine announced that an unusual number of fish, including salmon, had been found on the bottom of Lake Washington near the 2 Line’s Crosslake Connection.KUOW: “In August, Sound Transit CEO Dow Constantine announced that an unusual number of fish, including salmon, had been discovered on the bottom of Lake Washington near the 2 Line’s Crosslake Connection on the I-90 floating bridge.”
- SupportedThe cages were designed with fisheries staff from the Muckleshoot Indian Tribe and the Washington State Department of Fish and Wildlife.KUOW: “were designed with fisheries staff from the Muckleshoot Indian Tribe and the Washington State Department of Fish and Wildlife.”
- SupportedCameras were installed inside the mesh tubes to monitor fish activity.KUOW: “Cameras were also installed inside the mesh tubes to monitor any fish activity.”
- SupportedIf the first 13 cages work as planned, Sound Transit will add them to all 136 pontoon anode strings on the bridge.KUOW: “If these first 13 cages work as planned, Sound Transit said it will add them to all 136 pontoon anode strings on the bridge.”
