OR 241: Isthmus Slough, East Approach
Hamilton’s work on this accelerated bridge construction (ABC) project involved the replacement of a failing wood superstructure on the east approach to this bascule bridge — a key connector for commuters and commercial traffic in the Oregon Coastal town of Coos Bay. Other project elements included workbridge construction, precast slab erection, precast barriers, drainage system, and the protection of utilities.
Using ABC techniques, the entire east approach was replaced with one 13-day closure, thereby minimizing impacts to the public and avoiding the cost of a detour bridge or the disruption of a six-month closure. Hamilton was able to accomplish this by building the entire substructure underneath the existing bridge, including driving more than 20 pilings to depths ranging from 90 to 120-feet in water with a six foot tidal variation. The accelerated bridge construction required certain materials to be fabricated off-site and assembled on-site, without disruption to traffic.
The success of this project and accomplishing the aggressive work schedule depended upon meticulous attention to detail and a close, collaborative relationship between the owner/designer, Hamilton, and suppliers. The project team engaged the local community, local emergency response agencies, public officials, school districts, businesses, and the media to manage public expectations and provide advance notice of closures to avoid inconveniences and safety issues.
In a relatively small community (30,000 population) with few alternative route options and strong dependence on vehicle mobility, the greatest contribution to the community on this project was the minimal disruption, which not only made life more convenient for residents but allowed emergency response teams’ quick and safe response times.
Major Project Elements