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The U.S. Army Corps of Engineers has started a detailed survey of conditions around the Harbor of Refuge Lighthouse’s underwater base and the breakwater securing it.
The survey is a first step in determining what needs to be done, and how much it might cost to do it, if money is made available to make repairs that would help stabilize the 82-year-old landmark.
Throughout the week beginning Monday, March 17, Army Corps engineers used side-scan radar to determine how much of the lighthouse’s foundation has been disturbed after years of exposure to scouring wave action of the Atlantic Ocean and Delaware Bay.
“We’ve first tried to accomplish a multibeam, high-resolution survey of the riverbed around the structure and provide a picture of the side of the breakwater structure,” said Army Corps engineer and Project Manager Charlie Myers.
He said side-scan sonar imaging has also been used to provide a full picture of the breakwater’s underwater condition, obtain views of the riverbed and see where capstones have been dislodged by wave action.
“Some of those stones weigh 10 to 12 tons, and they’ve been knocked off. Our initial survey, done several years ago, detected some of the stones laying at the base of the breakwater structure,” Myers said.
He said engineers also used a boat-based laser scanner to look at the structures.
“As the vessel runs alongside the breakwater and the lighthouse, we’re able to measure and retain actual pictures in a database of all the voids in the breakwater structure and any voids in the concrete ring that surrounds the historic lighthouse,” Myers said.
He said there are significant voids under the lighthouse’s protective concrete ring, and there are also areas where the structure’s foundation has deteriorated.
“We’ll be able to figure out how much concrete would be needed to fill the voids, and we’ll also be able to figure out how many rows of protective stone would be needed if we decided to use that repair method,” Myers said.
He said protection of the lighthouse’s concrete ring could involve using a double-layer of stone with each stone weighing 8 to 12-tons. Myers said the Army Corps received $343,000 to investigate conditions of the breakwater and lighthouse.
“The survey is pretty sophisticated and detailed. After we have all the data we’re going to need about 30 days to analyze it. Then we’ll begin work on repair designs and cost estimates,” he said.
He said if all went perfectly, work on the project could start before the end of this fiscal year in September.
Earlier underwater surveys of the breakwater and lighthouse conducted a few years ago discovered a large, 120-foot deep hole located southwest of the structure’s southernmost point.
The hole was also noted following a 1930s survey. Meyers said the most recent data captured, but not yet analyzed, would yield the most accurate information about the hole.
“Our hope is that the hole has not migrated, has not gotten any deeper and is having no direct impact on the structurally stability of the breakwater,” he said.
He said until data analysis is complete, an assessment of the breakwater’s stability or an estimate of repair costs isn’t possible. He said a preliminary design and initial cost estimate could be available by mid-May.
Myers said the Army Corps has worked closely on the project with Judith Roales, Delaware River & Bay Lighthouse Foundation president. In 2004 through the National Historic Lighthouse Preservation Act the structure was donated to the foundation for public use.
“She’s been a real help in sharing information with the Army Corps,” Myers said of Roales’ assistance.
The federal government completed the 1.5-mile long stone National Harbor of Refuge Breakwater in 1901. The structure’s purpose is to safeguard ships from northeast gale force winds.
In 1902 the U.S. Lighthouse Service set up a beacon and fog bell at the south end of the breakwater, but the devices lasted only a year before storms swept them into the sea.
According to the book “Lighthouses of New Jersey and Delaware,” by Bob Trapani Jr., the original Harbor of Refuge Lighthouse was completed and activated in November 1908.
But by April 1926, after sustaining damage caused by years of pounding storms, the process of dismantling the 52-foot lighthouse, then considered no longer usable, had begun.
In November 1926, the existing Harbor of Refuge Lighthouse was completed.
Contact Henry Evans at hevans@capegazette.com
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