Renourishing
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It is finally happening. There is an interesting clamor of earth moving equipment and large piles of pipe have appeared at a couple of places on the beach. On April 3 renourishing actually began near Edings Street with a gusher of sand and water and two frenetic bulldozers struggling to corral it. The project really began much earlier when the town of Edisto Beach contracted with Coastal Science and Engineering (CSE) to design the project. |
Great Lakes Dredge and Dock Company (GLDD) is the contractor that actually moves the sand. When they are done approximately 850,000 cubic yards of sand will have been moved onto the beach.
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One of the strangest sites puzzling onlookers is the Coastal Research Amphibious Buggy (CRAB) although some just call it the "giant tripod". It is a topography survey instrument. The CRAB blazes along at up to 2 mph, in and out of the water, using differential GPS to precisely map the existing topography. It will do the same again after renourishing is completed to assess the amount of sand deposited. |
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The new sand comes from the shoal that is often visible by a strip of offshore breakers near the south end of the beach. A dredging barge there works night and day pumping a slurry of sand and water through a submerged pipe that comes onto shore near Edings Street. |
Sand was built up there, and then the pipe was connected through valves to two branches that pipe slurry both north and south from that location. Pipe is being laid on the beach, piece by piece to advance the area of sand deposition. They will add sand southward for about 3,000 feet to just beyond Neptune Street. The same process is advancing northward. After the south stretch is completed, renourishing will continue to advance northward. Twice during the process the submerged pipe will have to be moved further northward on the beach as renourishing proceeds to its completion at a point north of the pavilion on the State Park beach. Approximately 18,000 feet or 3.5 miles of beach will be renourished.
At each location where sand is being deposited, about 1500 feet of beach will be ribboned off for public safety. This restricted area will move as the work proceeds along the beach. At the moving point of deposition, bulldozers will maintain a temporary impoundment to allow the slurry flow to slow so the sand can settle out before the water flows back to the ocean. GLDD expects to proceed along the beach at between 500 feet and 1500 feet per day.
How long will the new wide beach last? That is not certain. Some say ten year renourishing intervals are typical. The last time it was done at Edisto Beach was eleven years ago. CSE is aiming for it to last 15 years this time. About five times more sand is being deposited than was deposited in 1995. The next renourishing occurrence will of course be subject to the vagaries of weather, politics, and perhaps ultimately to global climate change.
After May 1 when turtle crawls may begin, CSE will coordinate closely with members of the Edisto Beach Loggerhead Turtle Project to hopefully avoid interfering with any early nesting turtles. The renourishment contract requires all work to be ended and all equipment and materials removed from the beach by May 15, whether or not the project is finished. Last year the first turtle crawl was on May 20. Work has begun a little later than expected but crews report that they are currently on target to finish by May 15. Contingencies like bad weather can always impact the schedule of marine projects.
What about the turtles? Will they like it? In 2005 half the nests had to be relocated because of erosion. At least one mother turtle headed out onto Palmetto Blvd instead of returning to the ocean. Babies emerging near houses sometimes headed west toward the house and street lights. Renourishing increases available nesting area and widens the space between the high tide line and houses. However, there is not much time for it to stabilize and take on a natural slope before nesting begins.
The sand itself should be good. CSE reports that the shoal sand is of excellent quality, resembling the natural beach sand. They believe it is likely to stay in place much better than sand obtained from land or marsh such as was used in a recent renourishing on the state park beach and in a 1954 major renourishing at Edisto. That sand packed harder, and disappeared sooner, probably because of grain size issues.
Last summer many Folly Beach turtle nests had to be moved to make way for the advancing renourishment there. Some nests were relocated into new sand where renourishment had just been completed. The Folly beach sand was also of good quality but it did have some differences from natural beach sand in terms of light refraction and grain size that caused it to retain water more and compact a little tighter. This seemed to have been beneficial for protecting relocated nests when unusually hot weather occurred. Folly Beach volunteers have some concern for this nesting season because the renourished area is quite flat. That means that when a turtle crawls out it has further to go to reach an area sufficiently high to be safe from washout in the highest tides. An unpopulated beach would clearly be the best environment for nesting turtles, but a beach properly renourished with good sand is probably a better situation for a turtle than running into a house or bulkhead.
We would like to remind everyone to keep the beach dark---no artifical lights on the beach. It would also be most helpful if beach visitors would fill in the large holes that they make when they are playing on the beach. These holes can be devastating to our turtles. Remember. All dogs must be leashed from May to October. This is a Town of Edisto Beach ordinance.
