Since construction was completed in 1915, the Coos Bay railroad bridge has provided a vital link for local businesses shipping goods outside the area.

Built by Willamette Pacific Railroad, which became part of the Southern Pacific Railroad shortly after construction, the bridge was first used in December 1915. The first passenger train crossed the bridge shortly thereafter, in August 1916.

Decades later, the bridge has the distinction of being the largest operating swing span in the United States. At 458 feet in length, the swing span allows a 200-foot-wide shipping channel from each side of the center support pier, enough for a Panamax-sized vessel (the largest ship that can make it through the Panama Canal) to pass.

Since 1915, the bridge has undergone some repairs and modifications, but corrosion has been eating into the span's life expectancy. As early as the late 1920s and during the '30s, rectangular piers were enclosed above the mudline in steel and concrete to give the support members more protection. Similarly, a steel and concrete jacket was secured to the swing span central pier in 1936. In 1989, the footing at pier 10 also was retrofitted.

In recent years, deferred maintenance and age have taken a heavy toll on the bridge. Inspections in 1995, 1999 and 2002 uncovered harsh continued deterioration of the structure.

According to a bridge rehabilitation study prepared by Jacobs Civil, Inc., for the Oregon International Port of Coos Bay, the original paint coating system on the bridge trusses has gradually disintegrated. The report indicates significant corrosion of steel is occurring in some members on all the spans and particularly the main swing span.

That could affect the bridge's ability to hold the capacity weight of loads that cross the bay and the report indicates the deterioration will require extensive repairs or replacements of certain portions.

An underwater condition inspection of the bridge conducted by the Oregon Department of Transportation in 1999 also found several pile in the approach trestles in need of replacement. Piers 8 and 9, which support the main swing span, were found to be only a few feet above the bottom of the original footings and the report indicates the foundation pile were exposed to marine borers.

Despite the obvious damage, operationally, the bridge seems to work well, even after being struck by a barge late in 2003 - a blow that angled one of the dolphins and required temporary repairs to allow the tracks to realign correctly.

Within a 10-minute time span, Mark White, Central Oregon & Pacific Railroad bridge tender, can contact Coos Bay pilots and watch as the span silently whirrs into its closed position, allowing trains to pass.

White said he turns the bridge by remote these days but that's not how the swing span originally operated. An approximately 20,000-pound engine, initially powered by kerosene, was first responsible for opening and closing the span. The engine was later converted to run off electricity and now is no longer operating.