State transportation officials say the floating bridge in Brookfield is closed indefinitely to vehicles.
Transportation Agency Secretary Neale Lunderville says some of the old wood and floatation devices have become waterlogged and the bridge has started to sink.
The 330-foot bridge on Route 65 over Sunset Lake is made of 380 floatation devices that keep it on top of the water. It was originally built in 1936 but was rebuilt in 1978.
The bridge is closed to vehicles each winter. But when the Vermont Transportation Agency went to reopen the wooden bridge this spring, it was no longer as buoyant.
Transportation officials believe it needs to be replaced.
The bridge will remain open to pedestrian traffic.
Drivers using Route 65 will be detoured along local streets.