CLEANING UP DIRTY JOB IS IN THE (MESH) BAG

Marina owner Scott Kauffman was faced with having a big pile of dirt on his property for who knows how long from a dredging project. He decided instead to pump the dredged material into giant mesh bags.

The tiny holes in the bags allow water to filter out and flow cleanly back into a cove at Regent Point Marina on the Rappahannock River.

The dredged silt and sand remain in the bags. In as little as a week or two, the soil in the bags will be dry. He’ll cover the bags with more soil and then put grasses and other plants on what will become an attractive landscaping berm.

It's believed to be the first time the mesh bags have been used in Virginia in a dredging project such as this, and the bags may offer a viable option for others, said Adrian Jennings, an environmental scientist with the Army Corps of Engineers.

"One of the most difficult aspects of a dredging project is what to do with the dredged material," Jennings said.

The big tubes have been used on a few shoreline stabilization and beach replenishment projects. For instance, several years ago Hampton filled bags with dredged material to build artificial dunes at the Salt Ponds.

The bags then were covered with sand and plants. The city's Tom Daniel said the bags have done a good job of protecting the public beach, and in turn the houses behind it, by dissipating powerful waves.

More recently, at a neighborhood on the Potomac River, three bags were filled with dredged material and left in the river to form a jetty and to protect a beach, said Trina Sobotka, whose company did the dredging there and at Regent Point.

Kauffman became interested in the bag technology as a way to avoid what he did last time: the traditional disposal of the dredged material.

In that method, an earthen berm is constructed on a flat, dry space so the dredged material and water can be pumped in. The solids, such as silt and sand, settle to the bottom, and the filtered water flows out of the enclosure.

The remaining solids can take months to dry. If the material is being held only temporarily, it later must be hauled away, which can be expensive and time-consuming. Kauffman said getting ready for the dredging using the new method was more difficult, but he believes it will be worth it in the long term.

For this project, about 1,700 cubic yards of material will be removed to accommodate more boat slips. The area of the project is about 230 feet by 110 feet.

He has five bags on the ground: two are 200 feet long and three are 150 feet long. They are all 30 feet in circumference.

While Kauffman will leave the bags in place, another option would be to cut open the bags and haul the material away.

James Koontz, wastewater administrator for the City of Newport News, said the concept is new to him but he's eager to learn more.

The city, with assistance from contractors, cleans out three neighborhood lakes a year. It takes a lot of space to dry out the dredged materials, he said. About three acres at the former landfill are allocated for this purpose, although not all of the land is used every year.

Solving the drying/storage dilemma also might be helpful to small communities, although two in this region don't see a need right now.

In Poquoson, the Corps will dredge a section of the Back River at Messick Point this fall. The material will be pumped about a mile to a privately owned disposal site in Hampton, said Jeff Bliemel, director of engineering and utilities for the city.

On Corps projects, the storage site has to be available for 50 years. With the town's limited amount of dry land, "we hate to just use that as a place to store unsuitable materials," said Bliemel.

Smithfield Town Manager Peter Stephenson said the Corps handles all aspects of dredging the Pagan River, so town officials don't have to provide a dredge material site. "It does sound like a good opportunity" for citizens or businesses that might need to have dredging done, he said.

Tina McCloud can be reached at (804) 642-1746 or by e-mail at [email protected]

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