Dredging up savings

About 4,000 truckloads of sediment were hauled from the lake to a landfill 10 miles away. The savings realized from hauling and disposing sediment locally allowed the project to excavate deeper than originally planned, which added more capacity to the lake.

The I-95 Landfill Complex overlooks Belmont Bay on the Potomac River. Sediment dredged from Woodglen Lake was used to fill areas that had settled and provide topsoil for grassy cover. The grassy slopes are bright green during the summer months and didn’t require any seeding. department’s willingness to share resources allowed the project to proceed at the full dredge quantity and optimize environmental and recreational benefits such as restored streams and shoreline, new fish habitat for the restocked fish population, restored wetlands, reforested buffer areas, improved water quality, and new features that provide long-term maintenance improvements.

Concrete blocks at the dumping area. When trucks from the lake began arriving at the landfill, drier material was applied directly to the slopes around construction areas.

The I-95 Landfill Complex overlooks Belmont Bay on the Potomac River. Sediment dredged from Woodglen Lake was used to fill areas that had settled and provide topsoil for grassy cover. The grassy slopes are bright green during the summer months and didn’t require any seeding. Because dredging is a stormwater-management activity, the project was funded primarily by a stormwater service district created by the county’s board of supervisors in 2010. The solid waste division charged the project a flat fee of $150,000.

Woodglen Lake was mechanically dredged in the dry. This was necessary to construct the new forebay. The draw down took about one month. Dam safety regulations only allow the lake to come down 6 inches per day.

About 80% of the sediment in Woodglen Lake came from bank erosion upstream, threatening an access road and sanitary sewer line. Fairfax County’s dredging project included restoring the stream.

A berm was installed to create a forebay that improves the lake’s ability to trap sediment by 10% to 15% and serves as the primary settling pond. The berm is submerged when the pool is at full depth. Future dredging will be on a much smaller scale, only in the forebay, and performed by public works employees instead of contractors.

About 4,000 truckloads of sediment were hauled from the lake to a landfill 10 miles away. The savings realized from hauling and disposing sediment locally allowed the project to excavate deeper than originally planned, which added more capacity to the lake. Sediment needs to be controlled during dredging projects. To keep clean water clean, a diversion channel was built to move bypass the construction site. Temporary sediment ponds were created to slow down and capture additional suspended dirt. Sediment is full of seeds, so with the lake drained and the dirt exposed to the sun, grasses quickly formed a carpet of green across the site.

A two-stage rise with baffles was installed at the lake. A mid-level sluice gate will allow future maintenance crews to draw down the water without draining the entire lake. Only the new forebay will be emptied. The permanent pool will continue to support wildlife.

About 4,000 truckloads of sediment were hauled from the lake to a landfill 10 miles away. The savings realized from hauling and disposing sediment locally allowed the project to excavate deeper than originally planned, which added more capacity to the lake. As development marched westward, infrastructure was built to prevent flooding and reduce sediment flow downstream to the Potomac River and eventually the extremely sensitive and economically important Chesapeake Bay.

From left: Paul Taylor; Dipmani Kumar; Travis Roach; Tristan Proffet, Jacob Edwards, and Joel Lum of ASI Constructors Inc.; Rick Blankenship; and Mark Katrina at the I-95 Landfill Complex. The team worked together to find a home for 40,000 cubic yards of dredged sediment.

About 12,000 cubic yards of wet sediment was placed in a rehabilitated dewatering pit. Crews used heavy equipment to mix and stir the wet sediment until it was dry enough to scoop up and spread on nearby slopes.

Crews used old steel pipes and large concrete blocks found onsite to secure the perimeter of the dewatering pit. Trucks were able to back up to the edge and dump their loads.

The I-95 Landfill Complex overlooks Belmont Bay on the Potomac River. Sediment dredged from Woodglen Lake was used to fill areas that had settled and provide topsoil for grassy cover. The grassy slopes are bright green during the summer months and didn’t require any seeding.

Woodglen Lake refilled naturally following construction. At full pool, the water level will just reach the bottom of the inverted triangle of the riser. The Woodglen Lake project also prepared the landfill to accept sediment from the next dredging project. Royal Lake is expected to yield up to 100,000 cubic yards.

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