On an accelerated schedule, the crane and support tub for a 1,000 ton barge derrick were moved from an aging and deteriorated 55-year-old barge to a much newer 400 x 100 x 25 ft barge in excellent condition. The derrick had been recently updated and certified, and with its relocation onto the new barge, is now set for many more decades of use.

Because the estimated weight of the derrick and tub prior to the move was about 1,600 tons, lifting with other derricks was impactable, so alternative means to relocate them was the most logical way to proceed. Accordingly, the barge and derrick owners, Boyer Logistics and Pacific Pile, canvassed likely moving contractors and agreed that Nordholm Companies, the local company with the most experience with skidding large items, and the naval architecture and structural engineering to back up the move as their best choice to do the transfer.

The tub was supported on two box beams running through built up windows in the tub. 8 each 300 ton capacity skid beams, 2 each corner, with headers and tilt caps to allow articulation along the load path running on Teflon pads in track supported by steel crane mat and pushed by 2 each 70 ton push-pull jacks moved the assembly about 400 feet from the stern of the old barge to the bow of the new barge. Ballasting was also provided by Nordholm.

As the job developed, a weak barge structure to cross became the major concern for the engineering team. The old barge had decades of cut up and rusted structure under the likely load path. The new barge had nice longitudinal bulkheads to skid along, but the plate thickness was very thin, 5/16 thick plate. The bulkheads met ABS ratings, which did not anticipate that a 2000 ton load would be moving over them. Dealing with this weak structure meant very careful structural analysis was required to safely move the tub and derrick. Ultimately, with reasonable load spread on the decks of both barges, under-deck reinforcement proved not necessary, and the move happened safely and on schedule.