WyDOT scopes the bridge for structural damage.

Travelers were delayed through Snake River Canyon earlier this week as WyDOT engineers took a look at the Snake River Bridge. The inspection took place on Tuesday and Wednesday, closing down all but one lane of traffic through the Hoback Junction area.

“We have a snooper truck that we [used] to look at the structure underneath the bridge,” said Ted Wells, a WyDOT engineer. “The bridge is a wood and concrete structure and we [looked] for deterioration in the wood and concrete.”

According to information provided by WyDOT, the bridge has some structural damage. In August of 2006, WyDOT lowered the speed limit across the bridge to prevent further damage to the bridge ends.

“We keep an eye on the bridge and inspect it every year,” said Wells. “All of the bridges in the state are inspected every two years. But we inspect the Snake River Bridge every single year.”

As part of bridge inspections in this state, WyDOT engineers measure and record bridge dimensions, clearances and alignments. They record waterway data as well as the condition of the overall structure, including such elements as bridge girders, decks, railings, columns and pilings.

“Our inspections are based on a variety of factors which may result in a bridge being rated as structurally deficient or functionally obsolete, but that does not mean that the bridge is unsafe,” said Keith Fulton. “It just means it may need repair or possibly replacement.”

According to information provided by WyDOT, 95 percent (1,838) of the bridges the department maintains in this state are classified as being in “acceptable” condition. The remaining 91 bridges are listed as being structurally deficient or functionally obsolete.

WyDOT also has information about city and county owned bridges across the state, 71 percent of that number (597) are listed as being in “acceptable” condition. The remaining 29 percent (248) are listed as being structurally deficient or functionally obsolete.

When WyDOT owned and locally owned bridges in the state are combined, 88 percent of the 2,774 total bridges are classified as being in “acceptable” condition. The remaining 339, or 12 percent, are listed as being structurally deficient or functionally obsolete.

WyDOT defines structurally deficient to mean there are “elements of the bridge that need to be monitored and/or repaired.” The organization is quick to point out that a bridge that is listed as “deficient” does not mean the bridge is unsafe to traverse. Functional obsolescence is defined as being “how well the bridge meets current and anticipated traffic volumes and types.”

The terms are intended to be used as a classification system to determine eligibility for federal funds to repair or replace bridges. They are not intended to be a safety classification.

Bridges are evaluated not only on their physical condition but load ratings.

Physical inspections are conducted by inspectors who look for “deterioration of bridge elements.” Deterioration includes finding rusted steel components, cracked concrete or even peeling paint.

Bridge load ratings identify the maximum weight a bridge can carry on a repeated basis, without causing damage to the bridge.

In the event that bridge inspectors determine a bridge is unsafe, WyDOT will restrict bridge use or close the bridge to traffic altogether.

In light of the recent Minneapolis bridge collapse, U.S. Secretary of Transportation Mary Peters has called for all states to immediately inspect any bridges of a similar design. Wyoming has two such bridges, the I-25 service road over the South Fork of the Powder River near Kaycee, and Fremont County Road 298 over the Wyoming Canal 40 miles northwest of Riverton.

The Snake River Bridge is similar in design, one of the reasons it was inspected this week. It is also listed as being structurally deficient. The Snake River Bridge is scheduled to be replaced in 2010.