Dredging method fails; water injection next
By: JEAN L. KAESS
MORGAN CITY — The first agitation dredging efforts produced “no significant impacts” on the fluff in the Atchafalaya River Channel.
Jonathan Hird of Moffatt & Nichol, a Baton Rouge-based engineering firm retained by the Morgan City Port to aid its agitation dredging fight, said the crude method known as bottom profiling was not as successful as had been hoped.
The demonstration project was to determine if dragging a large beam across the fluff — a pudding-like substance suspended in the channel that fouls vessel engines — would keep the material in suspension and allow vessels to easily pass through.
There still are two other methods for agitation dredging left to be tested.
The next, in terms of cost, is water injection dredging. For explanation purposes, it essentially works like a pressure washer shot under water to agitate and suspend material.
The fabrication necessary to produce the equipment for testing WID can be produced locally.
A third option, which Hird said definitely would work, is extraordinarily expensive — in the range of $1 million.
Sidecasting physically removes fluff from the channel. However, there isn’t a sidecaster fabricator in the area. That option is not currently being pursued.
Any of the options that prove viable would be used to maintain the channel between dredgings by the U.S. Army Corps of Engineers.
Another issue with the fluff problem is finding hard data to indicate whether the channel and its associated issues are tidal or wind driven, Hird said.
Collecting data from the channel is an issue because placing instrumentation in the channel would be a hazard to navigation and finding instruments that look far enough into the channel from the bank has proven difficult, Hird explained.
In other action during Monday’s meeting, the port board learned Director Jerry Hoffpauir and several consultants, as well as Terrebonne Parish officials, are monitoring the state’s master plan with regard to its diversion projects. Those plans call for moving sediment from this area that has too much to others that are starving for it could cause silting concerns.