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Fairfax County staff recommends Lake Accotink not be dredged

Posted on February 27, 2023

Based on a new analysis, Fairfax County staff are recommending against the proposed dredging of Lake Accotink.

“The excessive cost combined with significant environmental impacts from deforestation and social impacts from large numbers of trucks, noise, visual impacts and potential impacts to recreation [led to the recommendation not to dredge],” said Charles Smith, Fairfax County Department of Public Works’ chief of watershed projects implementation.

The lake has been dredged three times since the 1960s to prevent it from being filled in by sediment loads from Accotink Creek. A community engagement process from 2016 to 2018 resulted in a decision to implement a permanent dredging program to maintain a boatable lake, but studies conducted since 2021 led to County staff recommending against this course of action.

These studies revealed that more than 40% more sediment would need to be dredged than had been previously estimated. Because of this larger amount of sediment, costs related to the project would also be increased. The first dredge would cost $95 million, with maintenance dredges costing $300 million over the next 20 years.

Questions about the environmental impact of not dredging are still to be addressed. In the meeting Feb. 15, members of the public brought up concerns regarding the mussel populations living in Accotink Creek below the dam. According to county staff, conditions may not change too drastically.

“The lake has a tremendous amount of sediment in it now and has been this way multiple times in the past,” said Smith. “It is likely that large amounts of sediment have been flowing through and downstream of the dam since the 1960s. As such, although there may be more sediment flowing downstream as more sediment accumulates, it may not be much different from how it is now.”

According to studies released by Fairfax County’s Department of Public Works, an average of 20,000 cubic yards of sediment is deposited into Lake Accotink every year. Projects to mitigate the sediment and improve water quality are being implemented.

“Fairfax County has implemented numerous projects in the Accotink Creek watershed upstream of Lake Accotink to reduce the sediment and improve water quality,” said Smith. “We have three additional projects in construction now and about 25 additional projects being planned.”

An alternative project to divert Accotink Creek and create a separate, offline lake was also proposed, but similarly not recommended after studies revealed it would result in a significant impact on the environment and community.

If the lake is not dredged, its four-foot depth will steadily decrease over time until it becomes a wetland.

“Managing the lake as-is could result in a diverse nature park with a combination of open water and wetlands which could not only improve wildlife habitat but provide nature observation and continued aesthetic benefits for the community,” said Smith. “Another option could be to remove Lake Accotink Dam which could open up 68 miles of stream to fish passage and provide a diverse park setting with new trails and interaction with dynamic water features.”

The Fairfax County Board of Supervisors is expected to make a decision on Lake Accotink in spring. A public comment period is open until April 1.


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