From the ITD Vault 25 Years Ago (Feb. 1987)
Bennett Bay Bridge offers best of form and function

When construction on the Bennett Bay Centennial Bridge, designed to carry four lanes of Interstate 90 traffic to and from Coeur d'Alene, was completed in the fall of 1990, the perfect marriage, in a bridge designer's eyes, was made – the union of aesthetic beauty and structural integrity. Almost immediately, praise began pouring in from inside the bridge construction community. Even now, more than a year later, the fruits of that union are being realized.

The physical dimensions of the project bring to mind an image of gray overkill - 44,000 tons of concrete and reinforcing steel; 1,730 feet long and 240 feet high - yet a photograph of the bridge shows nothing of the sort. Indeed, the Bennett Bay Centennial Bridge, with its $16.2 million price tag, is slim, sleek, and unobtrusive.

The Coeur d'Alene area, in which the bridge is located, is not only one of the most scenic regions in Idaho, it's one of the most beautiful areas in the country. Bennett Bay is enclosed on three sides by steep, forested slopes, then opens onto Lake Coeur d'Alene in the southwest. The slopes give the bay a vivid sense of enclosure, and an area full of diverse landforms serves to enhance the project's visual impact.

But aesthetics are only a part of the total product. The other, more important part is function. The initial work on the project started as early as 1983, with environmental assessments, preliminary designs and cost analyses. Later, following expert evaluations and subsequent recommendations, the original 14 design alternatives were narrowed to one, a prestressed concrete segmental structure.

Construction started in 1988. Once under construction, durability was of chief concern. The bridge is designed to carry the weight of three lanes of modern truck traffic in each direction, with additional safeguards to protect against both wind and earthquake damage. Included among the safety features, the bridge deck is reinforced with steel, which in turn is supplemented with epoxy coating. A modified latex concrete wearing surface has also been placed on the deck to prevent erosion caused by de-icing agents and other chemicals.

This dual protective system will ensure that the bridge will last well into the next century, and beyond. To date, the bridge has received three awards: The 1990 Portland Cement Association Concrete Bridge Award; the 1991 Outstanding Civil Engineering Achievement Award by the American Society of Civil Engineers, Inland Empire Section; and the 1992 Concrete Reinforcing Steel Institute Design Award. It is presently being considered for a fourth.

"It is rewarding to be recognized for outstanding achievement by your peers," Dick Jobes, the Department's Bridge Engineer, said. "We are quite proud of the Bennett Bay Centennial Bridge and the engineering work that went into it."

The bridge has won awards and supporters from throughout the bridge designing community. And when it opens to traffic in the late summer or early fall of 1992, motorists will be singing its praises, dazzled by the surrounding beauty, and comforted by the underlying strength.

Editor’s 2017 Note: The Bennett Bay Bridge remains one of the department’s most-awarded bridge structures. Compared to the $16.2 million cost of the bridge and road back then, construction of the bridge alone alone would cost approximately $51 million today. Right-of-way acquisition, engineering cost and roadway approach work would bring that number even higher.


Published 02-10-17