Charleston Harbor Deepening Awaits Approval from Congress

Charleston Harbor waiting authorization from Congress for deepening.
3 minutes reading time (628 words)

ANAMAR’s Work in Charleston Harbor Profiled in "Dredging Today"

ANAMAR’s Work in Charleston Harbor Profiled in "Dredging Today"

(Pictured above is the cooper marl we frequently encountered while collecting core samples)

The Charleston Harbor Federal Navigation Channel covers an area of approximately 14 square miles and is formed by the confluence of the Ashley, Cooper, and Wando rivers. Maritime interests want the harbor channel deepened beyond 45 feet so the Port of Charleston can handle the larger container ships that will routinely call when the expanded Panama Canal opens in 2015. In response to this need to accommodate larger ships and increasing ship traffic, a feasibility study is being conducted for the Charleston Harbor Navigation Improvement Project to analyze and evaluate improvements to Charleston Harbor. The Post-45 feasibility study examines the economic benefits and environmental impacts of the deepening project and determines what depth would be recommended for construction. ANAMAR was contracted to conduct sediment evaluations to determine if the proposed dredge material is suitable for disposal in the Charleston Harbor ocean dredged material disposal site (ODMDS) and to help identify potential beneficial uses for dredged material such as habitat development, shore protection, or beach nourishment.

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ANAMAR managed all sampling operations and worked closely with subcontractors to coordinate logistics. The sampling plan included collection of vibracore samples at 105 sites, plus grab samples at the reference station, and site water samples at three locations for elutriate preparation. Due to the size of the project, the sampling effort took nearly 4 weeks to complete and presented some unique challenges. Inclement weather caused by Tropical Storm Sandy followed 2 days later by a winter storm resulted in minor delays in sampling operations. This area also experiences six-foot tidal fluctuations resulting in very strong currents during incoming and outgoing tides; therefore, the sampling team had to plan daily sampling operations during workable currents (i.e., slack tides). Since sampling was taking place within the shipping channel and berthing areas, the captain maintained regular communication with the ships so that sampling would not interfere with shipping traffic. The physical composition of the sediment itself also proved to be challenging. Most of the sediment in the areas of interest was highly consolidated Cooper Marl, which was difficult to penetrate and to remove from the core barrel. A method was developed in the field to pressurize the core barrel using compressed air to extrude sample material from the barrel. This “on-the-fly” innovation helped the field effort stay on schedule.

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Coordinating sample delivery with the chemistry and bioassay laboratories to meet holding times while field operations were ongoing required multiple sample shipments due to holding times and the amount of time required to collect all the samples. It was necessary to run the bioaccumulation tests in two batches due to holding times and the laboratory space required for such a large number of samples. Close coordination with the laboratories and couriers was critical.

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ANAMAR succeeded in collecting all the required sample material and processed and shipped the material to the laboratories within holding times. ANAMAR reviewed and evaluated all the laboratory data and produced a report summarizing the results of the physical, chemical, and toxicological analysis of sediment, elutriate, water, and tissue samples of the proposed dredge material collected from the project area.

Below is a quotation from the news article: Dredging Today (July 2, 2015) "Post 45 Project Gets Funding"

"The Charleston Harbor Post 45 Deepening Project is the first project in the U.S. Army Corps of Engineers to go through the Corps’ new Civil Works Planning Process from start to finish.

This has enabled the Charleston District to reduce the initial study timeline of five to eight years down to less than four years, and reduce the initial study budget from $20 million to less than $12 million dollars. This project will serve as a model for Corps civil works projects around the world."

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