International Dredging Review

International Dredging Review

After four years of drought followed by an El Nin˜o season Santa Cruz Small Craft Harbor in Santa Cruz California had a federal entrance channel that had completely shoaled in through the winter. To compound the problem the harbor’s dredge Seabright which had been working to clear the harbor for 30 years was nearing the end of its life. In June DSC delivered a new dredge Twin Lakes to the harbor just in time.

“In the Santa Cruz Harbor the inlet can sand in with just one storm closing off the harbor and creating the worst conditions imaginable for dredging” said Charles Johnson director of domestic sales for DSC Dredge. “The channel should have a depth of 20 feet at low tide. There were times this winter when the depth was only a foot or foot-and-a-half. The Seabright which also was built by DSC 30 years ago was struggling to keep the channel clear but it really was at the end of its useful life.”

Winter shoaling has been an issue for the harbor since it was dedicated in 1964. It resides in an area of the California coastline where there are no natural features to protect a deep entrance. For a number of years the harbor relied on contract dredging supported by the federal government and the port district. With uncertainties surrounding funding each year the district began setting aside money to help purchase a dredge for the harbor. The district took delivery of the Seabright in 1986 sharing the cost of a new dredge with the federal government.

The Twin Lakes commissioned from DSC in April 2015 was christened on July 20 this year. It is a custom-built 16-inch by 16-inch dredge with a hull-mounted pump. It features a PLC operating system with color touch-screen controls Global Positioning System (GPS) electro-proportional hydraulic circuits high-capacity service water system and an inline direct marine-style transmission for dredge pump gear ratio reduction. A planetary winch provides the swing operation. A magnetic flow meter shows the operator the velocity of the material being moved providing information on the dredge’s efficiency. With two engines – a Caterpillar C32 dredge pump marine diesel engine and a Caterpillar C18 marine diesel-powered electric generator – the dredge fully complies with federal EPA and California CARB environmental standards.

Area beaches at Twin Lakes State Beach will also benefit from the sand dredged from the harbor. Dredging at the harbor typically begins in November and concludes in March or April.