The City proposes to construct a new four-lane roadway with turn pockets, bike lane(s), and sidewalk(s) between SR 240 and Queensgate Drive. The approximately 700-foot-long bridge will likely require six or seven spans with piers located in the river, be constructed in a radial curve, span an irrigation canal, and be sloped at approximately seven percent in profile.

Phase 1 included a bridge type, size, and location study (TS&L) to determine the type of bridge structure, the potential construction methods, and the anticipated construction cost.  This included review of published geotechnical reports and selected “as-built” information of local structures, review of geologic and seismic maps, a geologic reconnaissance, test pit explorations and infiltration testing, two exploratory borings, and laboratory testing of selected soil and rock samples.  We also performed preliminary engineering analyses to evaluate foundation alternatives and estimate foundation support depths, assess slope stability between the canal and river, and obtain preliminary seismic design criteria.  Phase 2 included exploratory borings at two potential interior pier locations and discussion pertaining to the feasibility of over-water foundation alternatives and construction.  To assist with the project permitting, Shannon & Wilson completed the Geology and Soils Technical Report for the Environmental Assessment.

In late 2014 and early 2015, the design team presented the project to a Washington State Department of Transportation (WSDOT)/ International Association of Foundation Drilling (ADSC) joint committee, and a WSDOT/Associated General Contractors (AGC) joint committee to evaluate constructibility concerns related to the proposed drilled shafts, temporary work bridge, and hillside construction.