Aberdeen pontoon repair continues
Crews continue making progress on four pontoons built in Aberdeen from Cycle 1. Work on two pontoons was completed in dry docks last summer. The other two pontoons are being repaired on Lake Washington.
The work involves epoxy injections into cracks, waterproofing smaller cracks, post-tensioning, and a carbon-fiber wrap.
Last week crews completed repairs on the first of four ends of the remaining two pontoons that will help support the new SR 520 floating bridge. From inside a nearly 660-ton coffer cell attached to Pontoon V, construction workers completed crack repairs on one end of the 360-foot-long structure.
While crews repair these cracks, they also take the opportunity to repair other anomalies identified during dive inspections. Some of these involve sections where rebar is exposed to water. To conduct the repairs, crews remove the concrete to expose the rebar and clean the steel with brushes and sandblasting. Workers then apply a special bonding agent to the cleaned rebar and surrounding concrete, followed by layers of a high-strength grout, and finally layers of carbon-fiber wrap to help ensure a waterproof repair.
The procedures were developed by an outside expert. Repairs the two remaining pontoons on Lake Washington are scheduled to be completed this spring.