Harbor deepening study almost two thirds complete

Washprobing is used to try to determine the type of material on the harbor floor (Scott Garrand/WCIV)

By Sonya

MCCLELLANVILLE, S.C. (WCIV) -- The Charleston Harbor study continues, and is actually getting more funding.

The president recently set aside more than $1 million to support the Army Corps of Engineers as they study what it will take to deepen the harbor.

There are three phases and the project is almost two-thirds of the way complete. Phase two is all about washprobing -- shooting a concentrated jet of water through loose material on the harbor floor until it hits something hard.

"What we will do is actually turn on the jet pump, run the pipe until it hits refusal -- whatever that material is -- and then we disconnect the pump," said Adam Freeze, a geologist with Athena Technologies. "With this size pump, three inch pump like that, it will bypass almost all unconsolidated sediments so far from what we can tell."

The process itself only takes about two minutes, but it must be done on 150 high-priority spots throughout the harbor. There are 23 more high-priority sites and 53 low-priority sites to be tested.

The rough conditions offshore have made it difficult to get the work done on time, so the company resorted to using a shrimp boat.

"Shrimp boats are designed for operating in the ocean conditions," said Brian Williams, the Army Corps project manager. "Smaller vessels more square shaped hulls and may not be -- it's just a great opportunity to use something that is non conventional but that it working really great."

Once the washprobing is complete, the data will then be analyzed by the Army Corps.

"They are going to give us elevations of where their probe basically stopped, where they couldn't go any farther because the material was too hard to get there," said Williams. "It's really used for our cost estimating purposes. Rock is more expensive to dredge than sands or silts, so we need to know that information when we are putting together our cost estimates, which ultimately get compared to the benefits we'll be calculating for potential deepening alternatives."

Phase two is expected to be complete by Friday, April 19. Phase three, which will include taking samples from the harbor floor, should begin this summer.

"We expect to collect about 10 samples. Basically, after we have the information here from the guys at Athena," said Williams. "We'll plan where those ten samples need to be taken and then they will be tested in a laboratory, tested and broken, and all kinds of data analyzed on those and we'll get that information."

The Army Corps expects to have a better handle on the types of material on the harbor floor by the end of the 2013.

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