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Work is under way to make the Morrison Bridge safer by replacing 50-year-old steel grating with fiber-reinforced polymer panels. The aging grating is slippery, and has contributed to the bridge being the worst in Portland for fatal accidents, according to Multnomah County transportation spokesman Mike Pullen.

He noted that steel grating on the Broadway Bridge was replaced five years ago, and that the annual number of serious accidents on that span has since decreased. The $4.2 million Morrison Bridge project will include replacement of the original steel grating there when the span opened in 1958.

鈥淯ntil recently, there was no material that was lightweight enough that we could cover the bridge and still allow us to open the bridge for a ship,鈥� Pullen said.

The Broadway Bridge was closed completely for 60 days so that crews could work on the entire bridge at once. However, the Morrison Bridge project has required a balancing act, because a determination was made that the bridge should stay open at least partially for the duration of construction work.

鈥淭he Oregon Department of Transportation thought that closing the Morrison Bridge to all traffic would be too disruptive,鈥� said Pullen, because of the bridge’s use as a freeway connection and as the primary route from Portland International Airport to downtown.

General contractor Conway Construction will complete the Morrison Bridge grating replacement in quadrants. Crews have pulled off steel grating on the south side of the bridge’s east leaf, and plan to begin laying down FRP panels for that quadrant next week.

In a way, the bridge is suited for deck replacement to take place in quadrants. The Morrison Bridge is 78 feet wide 鈥� too wide to be covered with one FRP panel, which was possible on the narrower Broadway Bridge. The new Morrison Bridge deck will have a seam where two FRP sheets meet in the middle.

鈥淭he good news is that the joint down the center is where the center of the bridge is, so traffic won’t be crossing it,鈥� Pullen said. If motor vehicles were to frequently cross the joint, concerns may exist about increased wear on the materials.

Timing has been complicated further by a moving bridge: The Morrison Bridge is shorter than the Broadway Bridge, and water levels have been high this year, so one leaf of the bridge is being opened frequently to let boats through. By comparison, Pullen said the Broadway Bridge is opened only for large, oceangoing ships.

The completed Morrison Bridge deck will look similar to the one on the Broadway Bridge, but a different kind of FRP panel is being used. After the deck was installed on the Broadway Bridge, the county found that the holes drilled for installation of the FRP panel collected water, and crews had to drill additional holes to drain the water collected. The new FRP, called ZellComp, is slightly different and will not require crews to drill holes to anchor it.

鈥淭his is the second time we’re installing (FRP),鈥� Pullen said. 鈥淲e have more experience with the materials.鈥�

Pullen said crews expect to finish the project by Thanksgiving. By that time, the county plans to replace all of the steel grating on the six-lane bridge with FRP.

That will include grating underneath the bridge’s south-side sidewalk. Crews will have to temporarily remove some of that sidewalk, which opened in spring 2010, so that FRP can be placed underneath. Pullen said the timing isn’t ideal, but it was out of officials’ hands.

鈥淭hat added to the urgency, so we went ahead and built the sidewalk on the south. Ideally we would have done the grating first,鈥� Pullen said.

The sidewalk replacement project was pushed to the top of the county’s priority list after the narrowness of the former Morrison Bridge sidewalk was identified as a factor in the accidental death of a pedestrian.

鈥淲e can’t always control the order of when we get money and when we get to use it,鈥� he said.