Lake Accotink sedimentation study to start this fall

The U.S. Geological Survey has gotten the go-ahead to carry out a $1.14 million three-year sedimentation study of Lake Accotink.

Two other studies are in the works – an assessment of the dam and a feasibility study on the preservation of a smaller lake. Joni Calmbacher, director of the Stormwater Planning Division at the Department of Public Works and Environmental Services, presented an update on the studies to the Fairfax County Board of Supervisors’ Environmental Committee on July 23.

Those concurrent studies were authorized by the BoS after the Lake Accotink Task Force suggested in December 2023 that a smaller lake might be feasible as an alternative to a full-scale dredge or letting the lake fill in with sediment.

The USGS will begin work on the sedimentation study this fall. That analysis will determine the amount of sediment entering and exiting Lake Accotink and how fast the lake is filling up with sediment. The results will drive the decision on the future of the lake.

An interdisciplinary Lake Accotink Team is working on finalizing the scope of the preservation study. Once the scope is approved, DPWES will invite public comment.

Related story: Supervisors call for more studies on Lake Accotink

Recommendations on the preservation of a smaller lake – 20 to 40 acres – need not be held off until the three-year sedimentation study is completed. By 2027, the lake could be in a much worse condition.

A decision on the future of the lake could be based on the first-year results of the USGS study, Calmbacher said, which are expected to be published in late 2025. Continuing the study for another two years could provide insights on long-term preservation.

DPWES is coordinating with the Fairfax County Park Authority on developing the scope for the dam study, Calmbacher said. That study is expected to start this fall.

The county has also identified a consultant to carry out community engagement and outreach. According to Braddock Supervisor James Walkinshaw, it’s important to have a dialogue with the community throughout the effort to address the future of the lake.