Wednesday marked the halfway point in the nine-day Interstate 5 Bridge trunnion replacement project, and Oregon Department of Transportation officials say the work is on track to wrap up on Sunday as scheduled.
The primary goal of the project is to replace a cracked trunnion at the top of the northbound bridge’s south tower. The trunnions are the axles for the sheaves — a pair of 20-foot-diameter pulley wheels at the top of each tower that move the cables that connect the lift span to the counterweights.
Only one of the trunnions was cracked, but all of the pieces were more than a century old, so ODOT opted to replace both trunnions and their sheaves, as well as the south tower’s cables. The north tower’s components were replaced in a similar operation in 1997.
Most of the swap-out work is finished; crews began removing the old trunnions and sheaves on Monday using a barge-mounted crane, and both sets of parts were gone by Tuesday afternoon. As of Wednesday afternoon, the new trunnions and sheaves were all in place and crews were in the process of installing the new cables, ODOT spokesman Don Hamilton said. Test lifts of the bridge will likely begin Thursday.
Crews have also been taking advantage of the bridge closure to perform smaller routine tasks such as patching potholes, striping asphalt and upgrading the bridge lighting, according to a Wednesday press release from ODOT.