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All About Dredging

Yearly dredging of the federal entrance channel has been a necessity since the harbor's dedication in 1964. In the early years, dredging was accomplished by the U.S. Army Corps of Engineers through contracts with private dredging operators. Since October 1986, the job has been accomplished by the dredge "Seabright" which was acquired through a joint venture by the Corps of Engineers and the Port District at a cost of $3.2 million dollars. The Port District now operates the dredging program.

Dredging activity usually begins in early November and continues through the storm months and into April. The program is designed to maintain a design depth of 20 feet in the harbor entrance at low tide. It is important to stay ahead of the weather. Two days of violent storms with accompanying movement of sand, can close the entrance and preclude the passage of all vessels.

About the Dredge Seabright

The dredge "Seabright" operates in much the same manner as a common vacuum cleaner. An eighteen-inch diameter nozzle bearing a rotating cutter or series of water jets is lowered to the bottom where the sand is agitated into a slurry. The mixture is then sucked up by means of a 1200 horsepower diesel pump and discharged to a desired location through a sixteen-inch diameter plastic pipe. Under ideal conditions, the dredge can move up to 600 cubic yards of material per hour.

While in operation, the dredge and dredge tender "Dauntless" are manned by five individuals. The dredge supervisor is in control of all activities and monitors the placement and total operation of the dredge, dredge tender and all other equipment. The leverman controls the depth and action of the nozzle, the pressures required for pumping, and the "sweep" of the nozzle across the bottom of the channel. The watch engineer is in charge of the engines, generators, and other mechanical equipment involved in the dredging process. The boatman and mate required to operate the Dauntless fill out the remaining two positions on the five person crew.

The dredge is capable of some limited movement on its own by reeling in and out on cables attached to five, 3000 lb. anchors. These anchors are strategically placed and moved as directed by the dredge supervisor. The precise placement of these anchors allows the dredge to sweep the bottom and to create a uniform depth under the selected area. If an entire new area is to be deepened, the Seabright is moved to that location by the dredge tender Dauntless, through new anchor placement.

About the Dredge Tender Dauntless

The Dauntless is a very powerful and versatile tugboat which operates as a tender to the dredge Seabright. Its purpose is to deliver crew and equipment to the dredge, set anchors, tow and position the heavy discharge pipes as required, and to move the dredge to different locations within the harbor and entrance channel. The Dauntless is equipped with a frame and winch which allows it to raise the heavy anchors which control the movement of the dredge.

Powered by twin diesel engines, the "Dauntless" is extremely maneuverable, thus an ideal craft for operation within the limited confines of the harbor.

In this photograph, the Dauntless is in the process of changing the position of one of the anchors controlling the movement of the dredge Seabright. The large yellow hemispheres are floats that mark the position of the five anchors to which the dredge is attached by cables. Strategic placement of these anchors permits the dredge to "sweep" and deepen a selected harbor area.