State and federal regulators and an S.C. environmental group have asked the U.S. Army Corps Engineers in Charleston to withhold approval of plans to dredge Sea Pines waterways on Hilton Head Island, arguing the project is fraught with questionable assumptions and misleading conclusions.
The S.C. Department of Natural Resources, U.S. Environmental Protection Agency, U.S. Fish and Wildlife Service, and the S.C. Environmental Law Project also assert that more environmentally friendly options have not been thoroughly explored.
The South Island Dredging Association, composed of boat-slip owners and some Sea Pines residents, applied Sept. 10 with the Army Corps for permits to dredge creeks and marinas in Sea Pines, including the Harbour Town Yacht Basin. About 300,000 cubic yards of silt, clay and sand would be pumped into open water near the mouth of Calibogue Sound.
The association says the waterways provide valuable recreation and tourism revenue to the island's economy. Harbour Town Yacht Basin is only 4 1/2 to 5 feet deep at an average low tide -- too shallow for large yachts and some commercial sightseeing and charter vessels. At nearby South Beach Marina, smaller pontoon and motor boats sit in mud at low tide.
OCEANOGRAPHER QUESTIONS MODELS
State and federal regulators halted a 2003 effort to deepen the waterways after a contractor was accused of improperly dumping dredge spoil into the sound. About 75 percent of the 140,000 cubic yards of material dredged wound up in the sound, according to regulators.
The spoil from the SIDA project would be dumped on about 56 acres of sandy bottom near Barrett Shoals, a popular site for anglers and a spot where the town gets sand for beach renourishment.
SIDA members say the dredge spoil -- sediment pulled from the bottom during dredging operations -- is unlikely to harm marine life or habitat. They have cited nearly 500 pages of studies by Charleston-based GEL Engineering, which was hired by SIDA.
GEL principal Tom Hutto has said the dump site is desolate, with "low biological diversity," and that the tides would sweep the spoil out to sea.
But GEL used limited field measurements and incorrect tidal current calculations to establish its models, Coastal Carolina University oceanographer P. Ansley Wren contends.And in letters submitted to the Corps of Engineers during a public-comment period that ended last month, regulators and environmental groups assert material dumped in the sound could drift and harm water quality and marine life, including shrimp, flounder, cobia, Spanish mackerel and sharks.
DNR has asked the Corps to hire an independent expert to review the modeling.
All three agencies and the S.C. Environmental Law Project also object to SIDA's assertion that its plan to dredge hydraulically with inshore dumping is the "only feasible and practicable" solution.
After the problems in 2003, regulators set new requirements for monitoring the amount of sediment that overflows barges as they head to offshore dump sites. However, barge operators cannot guarantee spoil would not be spilled en route, according to the dredging association. Other sites in Sea Pines and on neighboring Daufuskie Island have been deemed unsuitable by GEL, and Calibogue Cay property owners last year denied a request from Harbour Town slip owners for one-time use of the community's disposal site, according to SIDA.Mechanical dredging is also more expensive and requires more careful handling of spoil, increasing the likelihood for spills and leaks, according to GEL. State regulations also deem hydraulic dredging the preferred method.
However, DNR, the EPA, and the Fish and Wildlife Service argue SIDA could make offshore, open-water and land disposal more viable by dredging in phases over two or three years, using a combination of hydraulic and mechanical dredging techniques and multiple disposal sites, and reducing the amount of sediment dredged.
The Fish and Wildlife Service maintains spoil could still be dumped at an approved offshore site if improved barges with tighter seals are used.
DNR also suggests SIDA use non-bottom-dumping barges, thickening agents and mechanical de-watering techniques to avoid leaks and spills. It says a clamshell dredge could be used to remove material from Harbour Town and be dumped offshore.
The EPA contends the 2003 dredging was halted because the barge malfunctioned, and one that operates properly could be used to dump material farther out to sea.
The S.C. Environmental Law Project proposed the association use "spray dredging" to bolster and restore surrounding marshes by spraying a layer of sediment over the marsh grass -- a technique it says prevents salt marshes from being submerged by rising sea levels.
BETTER MONITORING REQUESTED
SIDA's plan calls for an on-site monitor to file daily reports with the Army Corps to ensure requirements are met. Water-quality testing and habitat surveys also will be conducted before, during and after dredging, according to SIDA.
The agencies and Coastal Conservation League, however, want assurances that if problems occur, an authority is assigned to stop or revise operations. They also say contingency and cleanup plans are needed should spoil wash up on island beaches, equipment fail, and water quality or marine habitat be damaged.The EPA, Fish and Wildlife Service, and Environmental Law Project also asked that dredging not be conducted around the clock, seven days a week for six months.
"We believe this intensive schedule may pose significant stress on dredging equipment, leading to failure and accidental spoil release," U.S. Fish and Wildlife Field supervisor Jay Herrington wrote in a letter to the Army Corps.
Mark Plowden, spokesman for the S.C. Department of Health and Environmental Control, which is charged with approving or denying the dredging application along with the Army Corps, said last month that officials were still reviewing comments received and working with SIDA to address concerns.
Attempts Thursday and Friday to reach Corps project manager Robin Coller-Socha were unsuccessful.