Dredging method appears ineffective
By: GEOFFREY STOUTE
MORGAN CITY — Although the results still are very preliminary, it appears the first method of agitation dredging, in which a beam was dragged through fluff in the Atchafalaya River’s Bar Channel, has failed.
U.S. Army Corps of Engineers and Moffatt & Nichol officials delivered the news during the Morgan City Harbor and Terminal District’s monthly meeting on Monday.
The contract for the demonstration project was to determine if dragging a beam across the fluff would keep dredged material in suspension and allow vessels to easily pass through.
The 50-foot long, by 3-foot wide beam, which weighed 35 tons, was dragged across the fluff, beginning Nov. 30 and finished Sunday. The total time spend dragging the beam was 72 hours.
Survey data was collected immediately after the beam was dragged across each area as well as daily for approximately one week. Now, weekly surveys will continue for about the next month.
During the process, the beam — the cheapest, most crude effort used — was dragged in various areas in 50 foot intervals.
Because the first two trials didn’t work, the third was set up closer to the top of the fluff at 50 foot intervals.
The third trial, said Sarah Nash, a project manager at the Corps’ New Orleans District office, “honestly hasn’t shown any promising results at this point, either.”
However, she did stress that the data still is preliminary.
“We’ll go through a full processing and analysis of that data (and) write up a report with the official conclusions, but at this point it doesn’t look like a valuable tool,” Nash said.
That data will be presented to the port upon completion, probably no earlier than the February meeting.
Despite the possible failure, Jonathan Hird of Moffatt & Nichol, a Baton Rouge-based engineering firm the port has retained to help it with its agitation dredging fight, reminded port members that a machine that would shoot out the fluff called a sidecaster as well as injecting water into the sediment both were deemed options for the port to use in its Value Engineering Study to determine possible options to fight the fluff.
“We know the sidecaster’s going to perform well because you’re physically taking material out of the channel and shoving it out of the side,” he said. “The drawback to that is there isn’t a sidecaster fabricator (in the area).”
There is, however, a water injection fabricator.
Hird said those working on the project will meet in January to determine the next step.
Also, Nash reported that a preliminary assessment, which is being used to document the availability of dredged material disposal capacity for the next 20 years, has been drafted and is being reviewed by the Corps’ technical divisions. Once the review is complete, it will be sent to the desk of Col. Edward Fleming, New Orleans District commander, for approval.
Also during Monday’s meeting, commissioners expanded their agenda to grant the Corps right of entry for disposal of dredged spoils.
In other dredging news, the Atchafalaya Bar Channel dredging was completed by Weeks Marine on Nov. 18. While the original contact price was $3.52 million, Corps’ New Orleans District representative Mike Lowe said the Corps was able to use $4 million more of the port’s operations and maintenance funds to do more dredging because they received a favorable bid on the contract.
“We think we have most of the bad areas in the bar channel cleaned out,” Lowe told commissioners. “We do have some issues in the upper bay and also at the end of the bar channel. We think with the money that we had we were able to address quite a good portion of the historically bad areas. ”
Through the month ending Nov. 30, expenditures for the Atchafalaya River and Bayous Chene, Boeuf and Black projects totaled about $3.33 million.