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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(Corps) through contracts with private dredging operators. From October 1986 through June 2016, the job was 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. In 1986, the Port District began operating the dredging program under the Memorandum of Agreement with the Corps.

In 2016, the Port District acquired a new dredge Twin Lakes, built by Dredge Supply Company of Reserve, Louisiana at a cost of $4.9 million . Twin Lakes will be put into service with the 2016-17 dredge season starting November 7, 2016. Twin Lakes is fully compliant with the State of California Air Toxic Control Measure which sets emissions standards for diesel particulate matter. She is a modern, state-of-the-art dredge and is expected to render reliable and productive service maintaining Santa Cruz Harbor for decades to come.

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. Strong storms with accompanying movement of sand can close the entrance within a matter of hours and preclude safe passage of vessels.

About the Dredge Twin Lakes

SeabrightThe dredge Twin Lakes operates in much the same manner as a common vacuum cleaner. It employs an eighteen-inch diameter nozzle (taken from the Port District's previous dredge Seabright) which utilizes a suction head assisted by water jets which is lowered to the bottom where the sand is agitated into a slurry. The mixture is then sucked up by means of a 803 horsepower Tier III Caterpillar diesel engine 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 Facilities Maintenance and Engineering Manager oversees and directs the entire dredging operation. The dredge supervisor is responsible for daily activities and monitors the placement and total operation of the dredge, dredge tender and all other equipment, and serves as leverman, boat operator or in other positions. 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. Other positions on the crew include the tractor operator who positions the disposal pipe and grades sand deposited at the beach, and a deckhand who assists with boat operations, anchoring and equipment maintenance.

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 dredge is moved to that location by the dredge tender Dauntless, through new anchor placement.

About the Dredge Tender Dauntless

Tender DauntlessThe Dauntless is a very powerful and versatile tugboat which operates as a tender to the dredge Twin Lakes. 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 former 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.

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