In 2003, the British Columbia Ministry of Transportation initiated a design competition for the detailed design of the Needles Bridge crossing over Arrow Lake. When constructed, this bridge will be the longest fixed link lake crossing in the province at a length of 1087 m. Arrow Lake was created in 1969 by the construction of the Hugh Kennleyside Dam; and in 1967 a previous crossing design project was initiated but ultimately was never advanced. This paper describes the unique design methodology and risk management approach employed during the recent design competition project, and presents some of the significant challenges and constraints faced during alignment optimization. Geometric design played a key role in the overall design economy of this large structure. A bathymetric survey was combined with conventional survey data and used to optimize the subsurface and shoreline horizontal geometry. The survey amalgamation improved the overall economy through minimized pier heights and optimal positioning of the navigation span. Geotechnical and structural requirements were integrated early into the design process in a true multi-disciplinary approach to design. Moreover, because the lake level is a function of the downstream dam, the reality of significant water level fluctuations introduced additional constructability constraints that required careful consideration by the design team. The resulting final design of the structure contains one horizontal curve and three vertical curves and is a successful blend of geometric, geotechnical and structural expertise. The risk management strategies used throughout the course of the project significantly contributed to keeping the design project on schedule and on budget. As a result, an economical combination of superstructure, substructure, foundations and approaches was integrated together to provide a low life cycle cost alternative to the existing inland ferry service on Highway 6 at Arrow Lake.
