New signs of foundation failure prompt closure of SE 408th Street Bridge between Auburn and Enumclaw

King County has informed Muckleshoot tribal leaders of safety concerns that will compel the closure of the Southeast 408th Street Bridge near State Route 164 between Enumclaw and Auburn in Southeast King County on Oct. 15.

The nearly 100 year-old bridge, located on a local residential county-maintained road on the Muckleshoot Indian Reservation, shows new signs of foundation failure and cracking, prompting the need to close the bridge before the storm season begins.

The SE 408th Street Bridge spanning a tributary of the White River has been slowly deteriorating over the years. However, during a recent inspection, engineers discovered new signs of foundation failure and fatigue. The stream channel is changing, which is causing water to undermine the foundation. The bridge deck and supports are also beginning to crack. Given the heightened degree of deterioration, the bridge must be permanently closed before winter storms and flooding place even greater stress on the bridge.

The rural stretch of SE 408th Street that will be closed carries only about 250 vehicles a day and is mostly used by local residents. Alternate routes are generally easily accessible and detours of less than a mile can be expected depending on the destination.

Meanwhile, the County is talking with Muckleshoot tribal leaders about various future options, given the poor condition of the bridge. Options include potential repair, replacement or permanent closure of the structure. Given rapidly declining revenues for County roads, there is currently no revenue available for repair or reconstruction. The Road Services Division's extreme revenue shortfall has led to numerous service and personnel reductions. Capital improvement projects all across the county have also been canceled.

As plans are being finalized to close the bridge, engineers will continue to monitor the aging structure. If new signs of distress are discovered, the bridge may need to be closed before Oct. 15.

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