When the subject of transportation comes up, much of the state's political focus is on replacing the viaduct along Seattle's waterfront and building a new 520 floating bridge across Lake Washington. But there are other transportation "mega-projects" that need our attention as well.

For example, in Vancouver, the I-5 and I-205 bridges are critical to our economic vitality. These two bridges are the only connection between Vancouver and Portland where Interstate 84, the main east-west highway, and I-5, the main north-south roadway, meet.

On Dec. 3, we got a glimpse of what would happen if that connection were severed when flooding forced the closure of I-5 near Chehalis. The only option for truckers headed from Seattle to Portland was a 440 mile detour through Yakima.

The I-205 bridge just east of the Portland International Airport is relatively new. Completed in 1983, this wide sweeping span carries motorists unobstructed. However, the I-5 bridges just down river are another matter. While the I-5 roadway through Vancouver was widened recently in preparation for a new span, the current structures are two side-by-side drawbridges; one built in 1917 and the other in 1958.

The bridge carrying northbound traffic was built while America was fighting World War I. It was so heavily used, initially by Model T Fords, that the five-cent-a-car toll was removed by 1929 when the construction bonds were paid off. Traffic remained heavy, and the southbound structure opened about the same time the Soviets launched Sputnik. Both are drawbridges, frequently closed when barges and sailboats move east and west along the Columbia.

Recently, the Washington and Oregon transportation departments announced that the preferred replacement option for the I-5 bridges is to build a new wide high-rise span that would allow tugs and barges to easily sail under it without stopping traffic. The proposed replacement would be accompanied by a side-by-side light rail structure that would connect downtown Vancouver and Portland.

The earliest that construction could begin is 2010 at an estimated cost of $4.2 billion, a price that's likely to increase as we get closer to the starting date.

The Vancouver-Portland metropolitan area already experiences traffic congestion. In some instances, heavy traffic stopped growth in east Vancouver until additional interchanges could be added to State Route 14, which traverses the north side of the Columbia between Vancouver and Pasco.

That congestion will get much worse if some activists get their way. They want the four lower Snake River dams removed, which would severely restrict barge traffic on the Snake and Columbia rivers.

Port of Clarkston officials estimate that, if the dams located between Pasco and Clarkston were torn down and barge navigation halted, it would take an additional 120,000 rail cars, or more than 700,000 semi-trucks annually to carry the cargo now being moved by barge on the Columbia-Snake river system.

Breaching also adds to our problem with "greenhouse gases." For example, port analysts say that barges can move one ton of cargo 514 miles on a gallon of fuel, compared with 202 miles by rail and 79 miles on trucks.

Furthermore, the highway and rail network along those rivers can't take that increase in traffic as configured today. But the biggest bottleneck will be our bridges. Consider between Longview and Stevenson, a 100-mile stretch running through the heart of Portland-Vancouver, there are only four bridge crossings on the Columbia, and two of them have only two lanes.

There is no doubt that the I-5 bridges must be a top priority for both Washington and Oregon.

Our state's transportation infrastructure is getting old and replacing it will be expensive. But we should not make our traffic problems even worse by removing the dams that connect our vital water transportation corridor along the Columbia and Snake rivers.

Don C. Brunell is president of the Association of Washington Business and may be reached at 360.943.1600 or donb@awb.org