The bridge foundations were built of cased drilled shafts extending 35 ft to 50 ft below grade, close to energized overhead power lines and light rail electrification wires. The site’s artesian groundwater also caused wet drilling conditions. Despite the limited access and small footprint, the team installed 17 drilled shaft bridge foundations and 20 jack shafts for the hydraulic elevator system. Crews installed piles for the tower foundation, lifted the bridge span across the tracks and operated heavy equipment, all while the trains kept running. 

The $9.4-million project included unique design elements such as the requirement that the elevator towers be independent of the main span for maintenance reasons. The bike wheel gutters on the stairways are also unique and a first for Portland. 

Photo courtesy Stacy and Witbeck Inc.

For the main bridge span across the tracks, the team decided to “fly” the bridge in as a single span during a two-hour nighttime shutdown of rail traffic. The team also developed detailed sequence plans that described crane capacity, pick loads and outrigger pad placement as well as load requirements for the 50-ton load. The plan minimized impacts to rail operations and reduced the amount of time working within the railroad right-of-way. 

The team scheduled major construction activities around community needs whenever possible. Utility, road and driveway construction were phased to allow access, and crews supported business deliveries by physically moving their materials through the construction zone. The project included 53 subcontractors and suppliers, with the project goal for disadvantaged business participation set at 8%. The team achieved 18% participation for disadvantaged businesses, with contracts valued at more than $1.6 million.