Chief Joseph Dam Bridge -- A Slideshow

  • By Jim Kershner
  • Posted 2/06/2015
  • Essay 20322

The Chief Joseph Dam Bridge crosses the Foster Creek ravine at a point just above the creek's confluence with the Columbia River, which is visible in the background. Since 1959, it has carried traffic on Pearl Hill Road from Bridgeport to the Pearl Hill area east of town.

The bridge sits just below the western brow of the Chief Joseph Dam, visible here. The Chief Joseph Dam is a major Columbia River hydroelectric dam built between 1950 and 1956. A previous fill-and-culvert crossing of Foster Creek was built during the dam’s construction.

This map shows Bridgeport to the left, the Chief Joseph Dam to the right. The arrow points to the site of the bridge, over Foster Creek just above where it empties into the Columbia River.

The Foster Creek ravine looks relatively serene in this photo, but in 1957, the highest water in more than 30 years raced down the ravine and washed the fill-and-culvert crossing away. This event prompted the U.S. Army Corps of Engineers to formulate a plan to replace the washed-out crossing. 

In 1958, The Herald-Reporter in Brewster and Pateros ran a front-page headline reading, "Foster Creek Repair Project to be Slated." The story reported that the U.S. Army Corps of Engineers was seeking bids to repair the flood damage. The corps planned to build two new bridges across Foster Creek. One was a concrete bridge to the Chief Joseph Dam powerhouse. The other, which would become known as the Chief Joseph Dam Bridge, was a timber bridge on Pearl Hill Road. 

Construction began in late 1958 and was slowed by another flood in January 1959 that washed out one of the bridge piers under construction. This photo was published in The Herald-Reporter with a caption reading, "No match for Foster Creek is the bridge pier at left of picture. The large runoff of water undermined the pier, the bridge was not complete, and washed out a fill upstream." 

The bridge’s main span was supported by a distinctive Howe truss, with unusual glued and laminated Douglas fir members. This was the only Howe deck truss designed and constructed for highway use in Washington during the 1950s. (A deck truss runs under the roadway and cannot be seen while driving over the bridge.) The Howe truss was invented by William Howe in 1840, and was widely used for railroad bridges in the nineteenth century. This truss, seen in this pre-rehabilitation photo, would become one of the primary reasons the bridge was later determined to be eligible for the National Register of Historic Places. 

The bridge’s historic connection -- and its proximity -- to the massive Chief Joseph Dam was another key reason for the bridge’s eligibility as a historic place. This is the view of the dam from just above the bridge.

By 2003, Douglas County engineers had determined that the bridge no longer met modern load-bearing standards. They adopted an innovative rehabilitation plan designed to reduce the weight of the deck above, while retaining the historic Howe truss. Here you can see the characteristic slant of members of the Howe truss toward the center of the bridge. 

The bridge deck was replaced in 2003 with a fiber-reinforced polymer (FRP) "plastic" deck. This approach earned the project several awards for innovative design. Here, workers are installing the new FRP deck.

By 2010, it became evident that rehabilitating the Chief Joseph Dam Bridge had not been sufficient to bring the bridge’s capacity up to modern standards. Cracks had developed in the bridge deck and other problems had developed in the old timber structure. The old bridge also failed to meet the region's current seismic standards.

In 2010, Douglas County authorities ordered travel to be restricted to one lane down the middle of the bridge to minimize the loading on each truss. They also announced new weight restrictions. 

In 2014, Douglas County finalized plans to remove the old Chief Joseph Dam Bridge. The County scheduled demolition of the old bridge for early 2015.

The bridge will be replaced with a new 240-foot, single-span structure made of post-tensioned, prestrssed concrete girders, with a concrete deck, as pictured here in Douglas County's engineering drawing.

The bridge will be supported with steel H piles (H-shaped piles). The $4.7 million project is funded largely through the Federal Highway Bridge Program.

This slideshow chronicles the history of the Chief Joseph Dam Bridge, a 308-foot-long highway bridge that carries Pearl Hill Road over Foster Creek ravine at Bridgeport in Douglas County. Its name comes from its proximity to the Chief Joseph Dam on the Columbia River. The bridge was built in 1959 and rehabilitated in 2003. It is scheduled for demolition and replacement in 2015.

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