Vaughn Bay bridge closes for nine months

Gateway news services

A nine-month road closure began Monday on South Vaughn Road on the Key Peninsula to allow Pierce County to demolish the Vaughn Bay bridge and build a new one in its place.

The road will be closed between 92nd Street KPN and the Key Peninsula Civic Center through April. A 2.2-mile detour will divert traffic around the construction zone via Olsen Road KPN and 92nd Street.

The new bridge will be a 219-foot, single-span, concrete-girder structure with two 12-foot lanes and 6-foot shoulders. Stormwater treatment embankments also will be installed at several locations to treat road runoff.

The existing five-span concrete bridge was built in 1966. In 2002, Pierce County Public Works and Utilities engineers determined that the bridge was vulnerable to earthquakes due to its simple spans-and-supports construction.

The bridge beams were not restrained against movement, and the beam supports were not big enough to accommodate such movement.

In the event of a major earthquake, or even a minor quake in the wrong direction, it was determined that the bridge beams could slip off their supports and cause the bridge to collapse.

The bridge appeared to be in good condition otherwise, and the engineers initially thought they could seismically retrofit the structure.

But upon closer inspection, they discovered fairly extensive cracks that penetrated the thickness of the concrete bridge deck, as well as reinforcing steel that was showing signs of degradation.

The county began to secure funds for bridge replacement in 2003. The single-span design will meet current seismic standards.

“As we all know, this is a time when budgets are strained and money is tight,” Field Engineering Manager Jerry Bryant said. “We need to ensure that the projects we pursue and the money we spend provides the greatest possible value to Pierce County taxpayers.”

Replacing the bridge will cost more than a retrofit, but it avoids having to spend money for retrofitting that will be removed later when the bridge is replaced.

“We have to make the bridge safer,” Bryant said. “But we don’t have to spend twice as much money to do it.”

Nearly all of the $2.86 million project cost will be covered by a Federal Bridge Replacement Fund grant administered by the Federal Highway Administration. The remaining $137,000 will come from the county road fund.

The old bridge will be removed and the new one constructed in accordance with all applicable environmental regulations and requirements, which include specific limitations as to when and how the work may proceed.

The project will offer environmental benefits by removing 36 concrete pilings that affect hydrology, debris and sediment flow at the mouth of Vaughn Creek.

In addition, embankments constructed with the new bridge will treat the majority of stormwater runoff.

Scarsella Brothers, Inc., of Seattle is the construction contractor.