King County Road Services has scheduled an emergency closure of Tolt Hill Bridge 1834A where Northeast Tolt Hill Road crosses the Snoqualmie River, west of the City of Carnation. Tolt Hill Bridge 1834A will fully close to traffic starting at 8 p.m. on Friday, June 16. Detours will be in place for travelers.
Following the 2007 collapse of the eight-lane bridge on Interstate 35W in Minnesota, and the federal decision to allow heavier trucks on roadways, the Federal Highway Administration (FHWA) developed new requirements for rating the load that a bridge can carry.
The new requirements for load ratings require all bridges to be evaluated by 2022 using the new criteria. For the first time, agencies are required to review gusset plate connections, which are thick sheets of steel bolting together structural elements of truss bridges. There are about 36,000 bolts fastening the plates on the two 300-foot long steel trusses of the Tolt Hill Bridge.
King County’s structural engineer reviewed the work of the private firm that designed the Tolt Hill Bridge. The County discovered discrepancies between the design calculations for the bridge and the plans provided by the private firm to the builder for construction. While an investigation continues, the bridge will be closed beginning at 8:00PM on Friday, June 16 for an indefinite time to design and implement repairs.
The bridge currently shows no visible issues, and has been inspected on a biweekly basis since March 8, 2017. The last bridge inspection took place on June 13, 2017.
No dates have been set yet for repair work or reopening the bridge.