Surveying the Dam

Surveying the Dam

Supervisor and community tour Lake Royal dam.

A second community meeting on the rehabilitation of Lake Royal was a hands-on meeting, with Supervisor Sharon Bulova (D-Braddock) and county and state public works officials accompanying community members on a tour around the lake and dam.

"It's good to visually see what’s going on here," said Wade Biddix of the Natural Resources Conservation Service (NRCS).

Lake Royal was built in the 1970s as a means of flood control, along with Lake Braddock, Burke Lake and 150 other man-made lakes across the state. The "V"-shaped Lake Royal has a principal spillway: a drainpipe attached to a cement riser at the bottom point of the lake. The auxiliary spillway, a grassy ditch flanked by hills on either side, branches off the lake to the west of the riser. Any water the principal spillway could not handle would flow into the auxiliary spillway, instead of residents' yards and nearby Guinea Road.

A month ago, Bulova's office presented a meeting to tell the community about the problem with the dam: its auxiliary spillway is not strong enough to hold back flooding from a major storm.

A 1998 Gannett Fleming, Inc. study concluded that, for storms exceeding 18.5 inches in 24 hours, the auxiliary spillway might erode, causing water to flood the surrounding area. A probable maximum precipitation storm (PMP) is statistically unlikely to occur in any given year, according to the NRCS, but a dam like Lake Royal's must be able to handle a PMP of 27.5 inches of rainfall in six hours.

But the soil in the auxiliary spillway is not the only problem, said Biddix. The dam was built before many of the developments in Burke, so the auxiliary spillway was built pointing south, straight out from the lake. Since then, a parcel of townhouses went up directly in front of the spillway, and now the floodwaters are inadvertently directed right at the townhouses, said Biddix.

"We never would have built this dam pointing directly at the townhouses," he said.

THE COUNTY has several options for rehabilitating the spillway. It could "armor" the spillway, or line it with concrete and cover the concrete with soil and grass. This option would also raise the surface of the spillway to a more acceptable level, said Biddix. It could also redirect the spillway so that it curved eastward into an area with no houses.

Another option, said Don Lacquement of the Fairfax County Department of Public Works and Environmental Services (DPWES), is to shove an underground cutoff wall into the bedrock between the mouth of the spillway and the townhouses. No water or soil would go beyond the wall, said Lacquement, but the water would tear up everything between the wall and lake.

The county could also simply cover over the spillway at its present site and cut a new one in the center of the lake, said Biddix. This option would be far more expensive, he said.

On one extreme end of the spectrum, the county could do nothing, said Biddix; on the other, it could remove the townhouses altogether. These are unlikely options, said Bulova.

While redirecting the spillway would mean removing a swath of trees, this would be safer than building the cutoff wall and allowing Mother Nature to take out the trees herself during a large storm, said Lacquement.

"We have to look at the cost and the benefits, both human and environmental," said Biddix.

In late 2005 or early 2006, the supervisor's office will convene a task force to come up with a draft plan for the dam rehabilitation sometime in the spring, said Bulova.

"If I lived over there [in the townhouses], I would be concerned," said Phil Franklin, director of the Lakepointe Homeowner's Association. "I'm glad they are making some effort to keep the surroundings of the lake with some park-like atmosphere."

Franklin will serve on the task force when it begins meeting to discuss rehabilitation, he said.

But not all nearby residents agree with the project. Fred Staudenmayer, who likes to come to Lake Royal to fish for bass, said he does not see why the project has to be completed now.

"There are so many other projects that require safeguarding," he said. "This seems like a waste of money."

Bulova said she, too, was skeptical when she first learned of the rehabilitation project. But after learning about the project and seeing a video of a dam failure in Madison County, she was convinced, she said.

"We try to have zero chance of failure," said Biddix. "It's insurance for the future, and I think that's where we're at."

Still, said Staudenmayer, the highest he has ever seen the lake is just over a footpath which edges the water.

"We shouldn't be worrying about biblical events," he said. "That much water would cause bigger water management problems elsewhere in the county … it’s a solution looking for a problem."

Tom Franzinger, whose house overlooks the spillway, has never seen the water come up that far either. But he approves of the project.

"I think they are taking a good approach, with surveys, modeling, projections," said Franzinger.