Issaquah-Fall City Road Bridge Piers

Michels Construction, Inc. installed 12 drilled shafts to serve as piers for a new bridge over North Fork Issaquah Creek, a fish passageway. Six shafts were 2.5 meters in diameter and about 50 feet deep, and six were 3 meters in diameter and approximately 70 feet deep.

Due to original rebar cage design, the permanent slip casing would not fit around the outer extent of the cage. Rather than add time and cost to bring new cages in, crews refabricated cages in the field by narrowing their upper 11 feet. Once cages were modified, additional crosshole sonic logging (CSL) testing was performed to confirm competent concrete meeting specifications.

The bridge doubles traffic capacity on a vital connection route between Sammamish and surrounding communities. As a result of the project, North Fork Issaquah Creek was moved from a culvert under the roadway into a stream channel spanned by the bridge.