Lake Accotink is being drained for an evaluation of the dam
Part of the lakebed at Lake Accotink is exposed, as the water level is being lowered to facilitate a study of the dam structure.
The lake drawdown is expected to lower the water level by as much as five feet. The Park Authority urges residents to keep off the lakebed to avoid getting stuck in the mud.
The dam study is aimed at determining whether the structure is safe and strong enough to continue supporting the lake. The evaluation of the dam is expected to be completed by Thanksgiving, but water levels may to take up to two months to return to their normal levels depending on precipitation.
Because the dam is owned by the Fairfax County Park Authority, they are leading the assessment of the dam with support from the Department of Public Works and Environmental Services.
Currently, the water level has drawn down approximately 2 feet with the removal of a large amount of debris along the top of the dam, said Park Authority spokesperson Ben Boxer. This is about halfway to the target water level necessary to complete the total assessment of the dam.
The next step is opening the sluice gates that control the flow of water from the lake into the creek below the dam. When those gates open, the Park Authority will monitor the water flow to ensure there are no negative downstream impacts on Accotink Creek.
The dam study is one of three efforts initiated by the Board of Supervisors last winter to determine whether the preservation of a smaller lake – 20 to 40 acres – is feasible.
In February 2023, DPWES determined that continual dredging to maintain Lake Accotink at its current size would be too expensive and too disruptive to adjacent communities.
The Board of Supervisors in late 2023 created the Task Force on the Future of Lake Accotink to explore alternative options. The task force suggested that a smaller lake would “present significant environmental benefits” and “meet significant community and social goals.”
Another effort underway is the Smaller Lake Accotink Preservation Feasibility Study.
That study is expected to identify what actions might be feasible to maintain a smaller lake 20 to 40 acres and 4 to 8 feet deep in a sustainable, equitable, and cost-effective manner.
Residents are encouraged to take a survey on the draft scope of work for that study which was developed by DPWES and Wetland Studies and Solutions Inc. The survey is open through Oct. 30.
The feasibility study will consider the best options for maintaining a smaller lake, including maintenance dredging intervals, which areas of the lake should be transformed into managed wetlands or islands, and where the dredged materials should be deposited.
Related story: Lake Accotink task force presents its findings to the BoS
Another study underway is a sedimentation analysis by the U.S. Geological Survey. That study is looking at how much sediment is coming into the lake from Accotink Creek and how much is flowing downstream from the lake.
The USGS collected sediment samples from Long Branch and Accotink Creek, conducted pebble counts, began processing data, and initiated reviews of existing data and hydraulic modeling.
They also installed a stream gage and water quality monitoring station on Accotink Creek at Old Keene Mill Road.
14 responses to “Lake Accotink is being drained for an evaluation of the dam”
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Hopefully if they find anything faulty with the dam, repairs can be made that won’t damage the work recently completed at the toe of the dam. Seems like maybe they should have looked at the two issues together.
I look forward to seeing what the USGS has from their sedimentary report. I’ve always maintained that the County (and the Commonwealth) needs to address upstream storm runoff. In the meantime as the lake empties, get some excavators in there and dig out the lakebed, it’s cheaper than dredging, and likely more efficient.
The cost is probably more in the disposal of the sediment, rather than the excavation of it.
Some time ago, they were talking about deepening the lake by pumping the sediment. This seems like it would be more efficient than dredging or excavating. With excavation, you still have to move the spoils somewhere by truck. I think the hitch for the pumping idea was that there was no nearby place that would accept the spoils. This seems ridiculous to me.
With all the angst and anger I’ve read about Lake Accotink and it’s repeated filling with sediment, this is the *first* comment I’ve ever read that addresses the root cause: upstream land use.
Remove the dam, let the stream of storm water run. Let it fill in naturally over time and then cart in a gizzillon tons of fill dirt. Build a baseball field , a few soccer fields and maybe pickle board courts. Upgrade the snack bar with a decent assortment of snack foods and that would probably cover operational expenses. Paying 65 million every 10 years or so for lake maintenance is just too much reoccurring expense to continue with this poorly conceived man made lake.
That’s a bs number.
Good thing the fish don’t need water to survive!
The County needs to know how changing the lake will affect the ecosystems downstream. Will flooding increase from the run off?
Perhaps they will unearth a proofreader.
How will that affect the beavers at Lake Accotink? They prepare dens underwater where they spend the winter. I hope their habitat won’t be destroyed by draining part of the lake at this time of year.
There are many environmental and financial considerations to be taken into account in deciding whether or in what manner to try to preserve some of Lake Accotink. My concern is that any dredging or pumping of the accumulation of silt and pollutants that have accumulated at the lake bottom will inevitably pollute downstream sites. It is often better to let sleeping dogs lie in the case of accumulated pollutants. This was found to be the case in remediating asbestos in homes and buildings. More asbestos was put into the environment by remediation than would have ever gotten into the environment had the asbestos been left alone. This has also been proven true of lead remediation . There was a recent article in the Washington Post about a woman whose child was permanently disabled by the dust from the lead paint that she was removing by sanding it off . I wonder if the same paradigm applies to the sediment on the bottom of the lake. I have no doubt that pollutants have accumulated over the years. I believe that other urban streams in the area have been found to have heavy and dangerous concentrations of PCB’s.
Finally after many replies someone comes up with the right response.
Thankyou.
-Signed,
A teacher.
I won’t comment on the environmetal issues. But I will say I appreciate that lake and it’s surounding trails. I truly hope it can be saved. I thank FDR and the Civilian Conservation Corp for developing it.