The U.S. Coast Guard has approved a second extension of the temporary operation status for the Coos Bay Railroad Bridge, extending the closure from Nov. 29 through Dec. 17.

The Oregon International Port of Coos Bay has funded the $6.7 million repair of the rail bridge, which required the temporary closure of the aging span from Monday through Friday.

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.

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.

The Coast Guard's approval is the second extension of the temporary closure, during which time the bridge is closed to marine navigation from 7 a.m. to 5 p.m. each weekday. The bridge will remain in the open position for vessels passing from 5 p.m. to 7 a.m.

The port requested the approval of the special operations from the U.S. Coast Guard 13th District in Seattle. The original request was approved Sept. 17 and an extension was approved in mid October.

Access for vessels is available on 48 hours notice to contractor Osmose Railroad Services project manager Jason Tweet. His 24-hour phone number is (770) 335-3948.

- Staff writer Andrew Sirocchi