Crane work is usually measured in height. On Myrtle Beach, it is being measured in distance below the surface and out to sea.
To help prevent erosion along the 60 mi. of South Carolina coastline known as the Grand Strand, tourist towns along the path have invested in a series of stormwater infrastructure improvements. These deepwater ocean outfall projects involve running large pipelines under the seabed, at strategic intervals, that extend 1,500 ft. offshore.
The jobs need cranes to lower sections of pipeline below the surface.
ALL Carolina Crane Rental of Wilmington, a member of the ALL Family of Cos., has provided cranes for several of these projects. The most recent is taking place in Myrtle Beach, where two crawlers, a 220-ton Manitowoc 14000 and 220-ton Link-Belt 248HSL, are setting 84-in. concrete pipe at 24th Avenue North.
Billy Madden, sales representative with ALL Carolina Crane Rental of Wilmington, highlighted the benefits of the new project; "This part of the beach has historically experienced heavy flooding, with some hotel parking lots seeing two to three feet of water after a rain. The new outfall will alleviate these issues by tying into the storm sewer and directing excess water deeper into the ocean."
The challenges of beach construction are many, chief among them getting cranes far enough over the water to extend pipe to 1,500 ft. That's why virtually all these projects begin with the cranes having to first build a trestle that follows the planned path of the pipeline.
Madden said the Link-Belt arrived at the job site first to help build the trestle. First, it drove sheet pile and round pilings, then set custom steel girders and placed crawler mats on top. The completed structure enables the 14000 and the 248HSL to walk out over the Atlantic Ocean.
For the actual pipe setting, the Manitowoc 14000 is single-picking and setting the pipe sections.
"We specified the 14000 for our customer, Manson Construction, because its higher capacity is better suited to the heavier concrete pipe sections," Madden said. "The heaviest section weighed 55,000 pounds."
Previous outfall projects used smaller-diameter 54-in. pipe made of a lighter-weight material, chlorinated polyvinyl chloride (CPVC).
The Link-Belt 248HSL has remained on the job to run pipe sections from flatbeds out to where the 14000 is positioned. The Manitowoc 14000 is configured with 164 ft. of main boom and 221,000 lbs. of counterweight while the Link-Belt 248HSL is working with 155 ft. of main boom and 168,000 lbs. of counterweight.
Once lowered below the surface, the concrete pipe sections are positioned inside a specially constructed steel setting box that prevents ocean currents from shifting the pipe during installation.
Manson Construction crews working in scuba gear then guide the sections together underwater. The pipe joints use a wedge-style connection system designed to permanently lock the sections together once installed.
Space constraints added another layer of complexity to the project. Assembly of the crawlers took place directly at a public beach access point measuring only about 50 ft. wide. A 110-ton all terrain crane assisted with assembly because the tight quarters left little room to maneuver.
"The beach access was extremely narrow, so every step had to be carefully coordinated," Madden said.
Complicating matters further, the project's laydown yard was located five to eight mi. away from the beachfront job site. Crane components, crawler mats, pipe sections and support materials all had to be trucked in piece by piece to avoid overwhelming the limited staging area.
Despite the logistical challenges, the project represents another successful collaboration between ALL Carolina Crane Rental and Manson Construction on a unique type of coastal infrastructure work rarely seen outside of major shoreline restoration efforts.
For more information, visit allcrane.com.
