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500 kV Tower Replacement

Location:
Charles City, VA
Completed:
2017

Scope of Work

The scope of work included demolishing and replacing two existing 425 feet tall, 500 kV transmission river towers in Virginia’s James River. Cianbro’s primary tool was a new state-of-the-art Manitowoc MLC650 crane with 459 feet of boom and a 32 feet jib, which is the tallest crane boom ever placed on a barge. Cianbro also furnished and installed h-pile supported cast-in-place concrete foundations for two anchor towers, removed the existing concrete foundations and installed the new anchor towers. 

Project Details

  • The mobilization phase included utilization of 60 feet by 120 feet steel deck barges, a 120 feet by 120 feet segmental material barge, 132 feet by 132 feet segmental crane barge, 100 feet by 100 feet segmental crane barge, Manitowoc 4000 crane, Manitowoc 300T Ringer, Manitowoc MLC 650 and two Manitowoc 4100 cranes
  • Land tower foundation work included excavation, pile driving (96 total, 55 feet h-pile), formwork/rebar installation and concrete placement for eight 14 feet by 13 feet by 4.5 feet foundations (270 cubic yards of concrete)
  • River tower demolition included the use of an MLC 650 to transfer existing tower sections to the material barge and from the barge to land for shearing and disposal
  • River tower installation included coordination of tower segment assembly and transport from the lay down yard, which was located 10 miles upstream, to the installation site - tower segments measured 100 feet by 90 feet and weighed approximately 68 tons
  • Managed Environmental Concerns including the Stormwater Pollution Plan and In-Water Work Windows

Lean, Innovative, and Unique Project Solutions

In order to transport the MLC650 crane from the laydown yard to the work site, which was on a river obstructed by a bridge with a limiting low-chord clearance of 120 feet above, Cianbro had to partially assemble the crane at the laydown area and complete assembly (including approximately 500 feet of boom) on the river near the work area. Further, the crane configuration was critical due the tower height, weights and lift radius.  These challenges were coupled with the fact that a crane with this boom length has never been utilized on a barge.  Over the course of six months, Cianbro engineers and lift directors worked directly with the engineers at Manitowoc during the development of the crane lift chart that was customized for this project.

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