Studies underway to prepare for Lake Accotink dredging project

Lake Accotink

Planning and analysis for the Lake Accotink dredging project is well underway. Construction is not expected to start until March 2023, however, as key decisions need to be made about how the dredging will work.

The project involves construction of a pipeline and a large clearing in Wakefield Park for drying out the sediment removed from the lake.  

When Fairfax County officials and consultants described the project at a community meeting on Dec. 10, representatives of environmental groups raised concerns about the impact of the project on the environment. 

“The dewatering site will very likely come at the expense of clearing five acres of woods in Wakefield Park, given the impracticality of other nearby sites. This was not part of the bargain when citizens advocated for saving the full lake,” said Philip Latasa of Friends of Accotink Creek. “How can we come together to avoid this environmental sacrifice?”

Braddock Supervisor James Walkinshaw said he would work to minimize the disruptions, but acknowledged that some disruptions will be necessary. 

The lake is filling up with sediment, and its average depth is just four feet. Without any action, the lake will eventually disappear. 

Related story: County proposes $30.5 million plan to save Lake Accotink

After years of studying various alternatives and numerous community meetings, Fairfax County officials announced a plan in September 2019 to save Lake Accotink by dredging out the sediment, dewatering it, and carrying it away by truck. 

The Board of Supervisors approved funding for the project in October 2019. The initial dredging will cost $30.5 million and the annual maintenance cost would be about $2 million. 

At the time, environmental groups and community residents applauded the effort to retain the lake at its current footprint, but now the project appears to be more disruptive than anticipated.

The dredging project would remove 350,000 cubic yards of sediment to restore the lake to an average depth of eight feet, said project manager Charles Smith of the stormwater division in the Fairfax County Department of Public Works and Environmental Services. 

Major decisions need to be made on where the dredging will take place, the location and design of the pipeline, where and how the dewatering will occur, and whether the dewatering will be mechanical or passive. 

The dewatering site would most likely be north of Braddock Road, but the exact location would depend on the results of sediment analyses, said Amanda Kohler, an environmental engineer at Arcadis, the engineering consulting company hired by the county. Mechanical dewatering would require a smaller area than passive dewatering. 

Another major issue is whether the pipeline would be permanent, so it could be used in future dredging operations. Walkinshaw said he would be concerned about a permanent pipeline. If the pipeline is permanent, it would most likely be buried, said Mike Wooden of Arcadis. 

Related story: Lake Accotink pipeline could threaten park’s habitat

An analysis of various alternatives will be conducted in summer 2021, said Smith. A concept design and engineering study are expected to be completed in April 2022, and the final design would be completed in late 2022. Dredging could start in March 2023. The project is scheduled to be completed in November 2025. 

The proposed project design would be presented to the community before the work begins. During the dredging, the lake could still be used for recreation, but there will be daily vehicle traffic within the park during the pipeline construction. The public can submit comments on the project here.

Between now and into spring 2021, the project is in the data collection phase. That involves an aerial survey of the ground surface and a hydrographic survey to determine how much sediment is in the lake and whether there are other objects in there. Dozens of sediment sample cores will be collected so the sediment composition in various areas can be analyzed.

Other studies will examine the soil composition and groundwater to determine the location of the pipeline. Environmental evaluations will help the engineers minimize the impact on trees, wetlands, and wildlife. 

The dredging would have a temporary negative impact on the Lake Accotink’s fish population, Smith noted, but the lake currently has “extremely poor water quality.” After the project is completed, the lake water will be significantly improved.  

Plans for a pedestrian bridge by the dam have been delayed, pending a decision on the dredging operation. Construction on that project is expected to start in 2021.