East 11th Street over Hylebos Waterway

East 11th Street over Hylebos Waterway (Tacoma, WA)

Type: Double Leaf Trunnion Bascule
Location: Tacoma, WA
Owner: City of Tacoma

Stafford Bandlow Engineering personnel is providing mechanical engineering services for the rehabilitation of this double leaf trunnion bascule bridge from inception through completion.  Services included development of a Bridge Design Report and preparation of plans, specifications and cost estimates for the design of all machinery and currently include construction services.

The project was initiated following failure of a drive shaft.  SBE performed a scoping field inspection and a subsequent load rating of the machinery in accordance with the governing standard and determined that the existing machinery was undersized and inadequately supported.  A new design was provided to address the deficiencies identified through the field work and load rating and resulted in outright replacement of the span drive machinery.  The support machinery also required repairs due to fire damage that occurred while the bridge was nonfunctional.  As part of the scoping field visit, SBE identified that the fire damage had caused deformation of the primary support girder for one leaf which resulted in misalignment of the main trunnions.  SBE subsequently performed field alignment of the trunnions to assess the extent of the damage and ultimately incorporated a plan to realign the components into the contract plans.