Mammoet installs safety lanes

2 June 2020

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Mammoet has installed the remaining 72 shoulder spans on the northbound lanes of the New Orleans Causeway in Louisiana by means of SPMTs atop a barge.

The shoulders are located between the crossovers, giving motorists and first responders a safe place to pull over when there are breakdowns or accidents.

All 180 spans of both the north- and southbound lanes were set without a single incident. This endeavour is considered the most significant improvement to the almost 39km (24 mile) long bridge since the second span was completed in 1969.

To reduce the duration and quantity of traffic disruptions on this key bridge, each of the 26m (84ft) long northbound spans were initially rough set approximately three feet from the final set location as a preparatory step to the lane closures. During these overnight lane closures, other contractors on the Boh Bros. Construction team would sawcut and remove the precast concrete guardrails from the existing bridge spans and coat the cut area with epoxy.

While this was happening on the bridge above, Mammoet’s team would reconfigure the trailers to ensure accuracy of the final set. Once both tasks were complete, the spans were lifted and set into final location against the newly coated epoxy of the existing bridge spans. Once the guardrail removal process began, the team could not stop until the new spans were set into final location to ensure traffic could still safely pass.

Mammoet said setting spans using SPMTs rather than utilising two crane-barges increased overall safety of the span erection operation, decreased the risk of damaging the existing bridge and increased production. Despite the challenge of forecasting the rough seas in the shallow coastal Lake Pontchartrain, this method allowed for the installation of an average of four spans weighing approximately 147t (325,000lbs) each per day, instead of the planned three spans per day.

Late last year, the Mammoet team assisted in the successful placement of an additional 108 spans on the southbound lanes, using the SPMTs as a cantilever. The trailers were balanced with counterweight and driven roughly 5m off the end of the barge to reach the location where they could be properly secured.