Tuesday, October 13, 2009

Double Cut/Double Tripping—how infrastructure can affect economy

Excerpt from U.S. Coast Guard “Proceedings of the Marine Safety & Security Council” magazine.

Many of the locks operated by the U.S. Army Corps of Engineers (USACE) are over 50 years old. Modern tows, however, typically operate with more barges than can pass through a lock at one time, so the tows must be “cut” into sections.

On the Kanawha River near Montgomery, W.Va., for example, only one barge (or the towboat) can fit in the lock chamber at a time. So the towboat pushes the first barge into the chamber, unhooks it, and backs out.

The first barge is then attached to cables and pulled through and out of the chamber (“hauled through,” in river terms) after the chamber water level is raised or lowered to match the river level on the other side of the chamber.

Then the towboat does the same with the next barge, and subsequent barges, and, finally, the towboat enters the chamber. The barges and towboat are then reconnected at the other side of the lock chamber.

Disconnecting, reconnecting, and moving cables during the hauling-through process makes this one of the most dangerous operations on the river for a deckhand. This process also takes a significant amount of time, so USACE is now building larger lock chambers to help alleviate the concerns of inefficiency and safety.

A barge enters the lock chamber on the Kanawha River. USCG photo by CDR Kevin Kiefer.

Two barges and a towboat back out of the lock chamber (after releasing the first barge into the chamber) on the Kanawha River. USCG photo by CDR Kevin Kiefer.

For more information:
Full article and “U.S. Coast Guard Western Rivers Sectors” edition of USCG Proceedings is available at www.uscg.mil/proceedings. Click on “archives” and then “2007-08 Vol. 64, Number 4” (Winter 2007-08).

Subscribe online at http://www.uscg.mil/proceedings/subscribe.asp.

Online survey available at: http://www.uscg.mil/proceedings/survey.asp.

Direct requests for print copies of this edition to: HQS-DG-NMCProceedings@uscg.mil.