|About 100 people attend a meeting at Kings Glen Elementary School in Springfield on the future of Lake Accotink.|
Dozens of people attended a community meeting May 16 on the future of the lake as part of the Fairfax County Park Authority’s efforts to develop a new Master Plan for Lake Accotink Park.
Sedimentation, caused by storm water runoff is a huge problem. As the areas upstream have been developed – what used to be forest and farmland is now covered in impervious surfaces – stream banks have eroded and a huge amount of silt flows into the lake.
That has led to a sharp declines in water volume. The lake’s depth averaged 20 feet when the dam was built in 1940; it’s now just four feet, said Gayle Hooper, a landscape architect in the park planning branch. The lake was dredged in 2007-08, which temporarily improved water volume, but dredging has to be done periodically.
As a result, the sustainability of the lake is the major element in the Master Plan revision. “The most sustainable solution will be at the intersection of environmental, social, and financial goals,” Hooper said.
Since 2011, about 91,000 cubic yards of silt has been deposited into the lake, said Frank Graziano, the director of engineering at Wetlands Studies and Solutions Inc. (WSSI), the consulting company that developed the alternatives.
Graziano described five options in the draft study, although he cautioned there are “missing pieces” that need to be resolved before a clear picture emerges and the county can make a decision. The options are:
A – Continue the current practice of dredging the lake every 15 to 20 years. Each dredging operation would remove 350,000 cubic yards of material, and the county would have to find an offsite location to dump it. The lake could still be used for recreation but would have to be shut down for two or more years every time dredging is done.
B – Create a “sediment forebay” upstream. This calls for digging a 13-acre bay eight feet deep to trap the sediment and a deeper hole upstream to temporarily deposit the sediment. This would require a full lake dredge first, with 500,000 cubic yards of sediment removed. The forebay would need to be regularly dredged but the dredging lifecycle for the lake would be extended to 30 or 40 years. Recreational use of the lake would not be disrupted.
C – Set up four “in-line beaver dams” within the channel leading into Lake Accotink to encourage sediment deposits. This area would gradually turn into a meadow. The lake would have to be fully dredged first, then no more maintenance dredging would be needed. This would be a short-term band-aid, however, rather than a permanent solution.
Options A, B, and C would all require many truckloads of dredged materials to be deposited somewhere off site.
D – Remove the dam, which would transform the lake into a narrow channel. Sediment would no longer be captured, and no more dredging would be needed. The area would remain a natural park, but there would be no more recreational use of the lake.
E – Create a “single thread channel” to carry sediment downstream and a new smaller lake – 18.5 acres and eight feet deep – not connected to the channel so it wouldn’t fill up with sediment. Dredging wouldn’t be necessary, and there wouldn’t be a need for maintenance once the stream channel is stabilized. (The lake is currently 55 acres; the park is 493 acres.)
Whether options D and E are feasible depends on new state regulations on TDML (total maximum daily load) requirements aimed at protecting water quality in the Chesapeake Bay. The regulations should be issued by the end of the year.
Neither Graziano nor any of the county officials at the meeting would discuss how much the different options would cost.
“Some options are more expensive than others. We’re not putting a price tag on any options,” said Edward Batten, who represents the Lee District on the Park Authority Board.
“If we put out the numbers, people would focus on that,” said Park Authority Board member Anthony Vellucci (Braddock). “We don’t want people to feel constrained by the numbers. We want a free flow of ideas.”
The last time the lake was dredged, the cost was $10 million, which included $8 million for the dredging operation and $2 million for the project design, permitting, and other costs.
Members of the public discussed the various options in small groups, then a representative from each group reported back to the entire audience. Here’s a sampling of their feedback and questions:
- Why not carry out stream restoration projects upstream to curb erosion and minimize silt coming into the lake?
- There should be a study analyzing the impact on wildlife.
- What can be learned from similar projects carried out in other areas?
- What would be impact on other recreational uses besides boating?
- If the lake is gone, would people still come to the park, and how would that affect other lakes in Fairfax County?
- Maybe Lake Accotink could it be more like Huntley Meadows, a wetlands park with lots of wildlife, boardwalks, and hiking trails.
- One group said option D seems like the best long-term solution.
- Another group didn’t like D, because they feared the park would “become another Wakefield Park with ball fields.” They preferred option B, with some beaver dam construction.
- What would be the impact on biodiversity?
- Since there are train tracks by the dam, couldn’t a train be used to move the dredge materials instead of trucks?
- Could the dredging material be sold or used to build dams upstream?
- Why does the sediment need to be removed anyway? Pile it up and create a mountain.
- The public needs more information about the cost and where the money will come from.
- The lake needs to be preserved even if it’s smaller.
- Closing the lake for two years during dredging is a hardship.
- Option B, with dredging done every 30 years, is less disruptive than option A.
- Why not use dredging to make the lake deeper than eight feet?
- If nothing is done, would the lake become a wetlands?