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The new Sellwood Bridge will start to look more like a bridge by the end of the week.

Starting tonight, 27 precast concrete girders as long as 109 feet and weighing as much as 75,000 pounds will be delivered by truck to the span’s eastern end. The bridge will be closed starting today at 7 p.m. through as late as Friday at 4 p.m., according to Multnomah County.

Knife River Construction prefabricated the girders with prestressed steel cables at a site in Harrisburg. After delivery, the project’s construction manager – Slayden Construction Group Inc. and Sundt Construction Co. – will install the girders by crane, said Mike Pullen, communications officer for the county.

“All you can see now is individual columns,” he said. “By Friday, they’ll be connected. A man could walk from the river’s edge to where the bridge starts on Sixth Avenue.”

The girders – horizontal beams that carry the weight of the bridge deck and pavement built on top – will form the southern half of the bridge’s east approach. The northern half of the east approach will be built later.

Prefabrication will allow installation of the girders in a tight space near residential neighborhoods, Pullen said. The girders are prestressed with steel cables providing tension.

“One thing (is) it’s like a factory,” he said. “It helps quality control. It also means that you don’t need as much space in restricted neighborhoods. We’d need to rent more land (otherwise).”

The $307.5 million project is on schedule, and the new bridge is expected to open in September 2015, Pullen said.

By the end of the year, retaining walls will be built along Oregon Route 43 so that traffic can be shifted and more room can be created for work on a two-level interchange under the bridge’s western span. Three steel arch spans will be installed in November, Pullen said.