Twin Cities reminder: Care for what we have

First and foremost, the horrific collapse of an interstate highway bridge over the Mississippi River is a human tragedy. We in the Pacific Northwest share the grief and shock of the stunned residents of Minneapolis and St. Paul.

Sadly, an early and impossibly small death toll will climb as the rubble of a failed 1,900-foot bridge is explored and recovery efforts proceed in the murky waters of the river below. Minnesotans have responded admirably to comfort the injured, console survivors and support and sustain emergency responders. The caring and generosity of spirit are inspiring, but the deeper lesson to take away from this "catastrophe of historic proportions" is to invest time, money and talent in prevention.

The observation is not an indictment of the Minnesota highway system, but a pointed reminder about the need for vigilance in the inspection and maintenance of our own state's 3,000 bridges and another 4,000 watched over by cities and counties.

Engineering experts at Washington State University and the University of Washington have a short list of usual causes of major bridge failures. In the case of the Minnesota collapse, the scouring away of soil around underwater concrete piers might be the first place to look. The erosion of the soil can be hard to spot during inspections because loose soil settles when the river is calm, explains Marc Eberhard, a UW professor of civil and environmental engineering.

The erosion of bridge supports brought down a span 20 years ago on the New York Thruway.

Another suspect is fatigue, from the stresses and strains on steel parts flexing with the loads they carry. Small cracks can be fatal.

Corrosion is another enemy, and the failure of a single pin in 1980 helped bring down an Interstate 95 bridge over the Mianus River in Connecticut. For Minnesota, think weather extremes and de-icing solvents.

The age of the Minneapolis bridge is a factor as well. Since its construction in 1967, bridges simply are not built that way anymore. They now incorporate redundant design features intended to back up and compensate for failures of individual support elements.

Washington has only a handful of steel-truss bridges, but it has plenty of old spans that do not incorporate modern engineering lessons.

This is a time when public officials earn their keep by ensuring that public safety is being watched over and timely work is being done.

No one in the Seattle area who heard of the Minnesota tragedy did not think of the Alaskan Way Viaduct and, secondarily, the warp and woof of a storm-tossed 520 floating bridge. Those replacement plans are where, exactly?

Professor Kenneth L. Carper, of the WSU School of Architecture and Construction Management, quotes an engineer who investigated the Connecticut bridge collapse: "Imagination and fear are among the best tools for preventing tragedy."