Evaluations underway on Lake Accotink dredging project options

Lake Accotink is filling up with sediment.

Options under consideration for drying out the sediment dredged out of Lake Accotink have been narrowed down to Wakefield Park near the maintenance facility, the Dominion Energy right of way, the upper lake settling basin, and the lake island.

Several alternative sites – Howrey Park, the Wakefield Park ballfields, and the Vulcan concrete plant – have been eliminated.

County officials presented an update on the dredging project at a community meeting at Annandale High School July 29. There will be a virtual meeting on Aug. 5 at 7 p.m. The public can submit comments online.

Meanwhile, the Board of Supervisors agreed to pursue an additional $30 million loan from the Virginia Clean Water Revolving Loan Fund. That’s on top of a $30.5 million loan from that fund approved in December 2020.

The additional funds are needed because the amount of sediment that must be removed from the lake has increased 43 percent since the previous cost estimate. The earlier estimate was based on the need to remove 350,000 cubic yards of sediment.

Related story: Lake Accotink dredging sites could disrupt the Howrey memorial, youth sports, and wildlife habitats

The amount of sediment buildup is accelerating. Now, 500,000 cubic yards of sediment have to be removed to restore the lake to an average depth of eight feet, said project manager Charles Smith of the Fairfax County Department of Public Works and Environmental Services.

Braddock Supervisor James Walkinshaw defended the additional funds as necessary to retain Lake Accotink as a recreational and environmental asset. “In 2019, this community spoke with a very clear voice and said ‘we want to save the lake,’” he said.

The following sites for dewatering the dredged material are viable options, said Amanda Kohler, an environmental engineer at Arcadis, the engineering consulting company hired by the county. Each site, however, has challenges.

An area near the maintenance facility in Wakefield Park would require at least 7.7 acres within a floodplain.

Transporting the dredged material to that site via a pipeline along the Cross County Trail would require temporary closures of the trail, and pipeline construction would be noisy for nearby residents. A pipeline in that location, however, could stay in place for future dredging.

An alternative pipeline route along Flag Run and Port Royal Road would minimize trail closures but would have an impact on traffic. Another option is running the pipeline along the I-495 right of way.

Having the dewatering site in the Dominion right of way would disturb up to 10 acres. This site would also be in a floodplain and would be less accessible to trucks hauling the material away. Running the pipeline north of Braddock Road would mean the potential temporary destruction of parts of the trail.

The upper settling basin, on the west side of the lake next to the Danbury Forest subdivision and close to Danbury Forest Elementary School, would require 6.7 acres and would be outside the floodplain.

On the negative side, there would be a noise impact for residents, part of the trail would have to be closed, recreation on the lake would be curtailed, and trucks accessing the site from Rolling Road would go through the neighborhood.

Using the Lake Accotink island as a dewatering site would have the least land disturbance – just 3.3 acres. The sediment would be transported via barge, so a pipeline won’t be needed. The challenges include the difficulty of getting equipment to the island via barge, harm to wetlands, and increased truck traffic and noise.

Another option calls for expanding the footprint of the Lake Accotink island to form a peninsula to allow for a 10-acre dewatering site. This option would reduce the size of the lake and would also mean trucks and noise in neighborhoods.

Related story: Studies underway to prepare for Lake Accotink dredging project

“It’s hard to nail it down to one alternative,” Smith said. Staff wants to maintain flexibility as the evaluations continue.

“All of these options have high costs and significant environmental impacts,” said Phil Latasa of Friends of Accotink Creek. “Had this information been available earlier, we could have taken a different course.” He suggested using the dredge spoils to reconstruct the berm near the dam – and create a smaller but deeper lake.

A North Springfield resident asked whether there will be dredging every few years and urged the county to focus on sustaining the natural environment rather than saving a manmade lake.

Walkinshaw said the project calls for a major dredging operation as a permanent solution and would be followed up with short-term dredges every few years.

“We need better stormwater management but it’s not feasible to retrofit neighborhoods built decades ago” before stormwater controls were required, he said. A major project underway to restore Long Branch Stream would reduce some of the sediment entering Lake Accotink.

Other stream restoration projects in the works for Accotink Creek and other areas farther upstream will also reduce sediment in the lake, Smith added.

Arcadis also evaluated dredging and dewatering methods. Mechanical dredging is noisy and has a negative impact on floodplains, Kohler said, while hydraulic dredging is less able to handle debris. Both are feasible though.

Mechanical dewatering is more expensive than passive dewatering, but passive dewatering requires a larger area.

The project timeline:

• May 2022 – concept design and engineering study completed.
• May 2023 – final design and permitting.
• Fall 2023 – dredging starts.
• 2026 – dredging completed.
• 2026-31 – post-construction monitoring.