Published on: Thursday, September 09, 2010

By Spencer Broughten

What lies beneath the murky surface of Rock Creek Regional Park’s Lake Needwood?

The Montgomery County Department of Parks knows: 20 years of sediment buildup due to storms and stream erosion, the removal of which is set to begin in early to mid-October, parks department officials said Friday.

“The sediment’s accumulated so much that there are actually dry spots in the middle of the water,” said project manager Steve Reid, of the Park Development Division.

The objectives of the upcoming Lake Needwood modifications include improving future sediment control measures and dredging the forebay to remove 100,000 cubic yards of sediment from the lake. The dredging should also help future flood-control efforts by increasing the volume of water that the lake can hold. About 2,200 residents were evacuated from the downstream area in June 2006 after heavy rains caused the lake’s water level to rise quickly, and Lake Needwood Dam seeped ominously for three days before waters subsided.

Reid said the silt removal should result in a noticeable improvement in the water quality of the lake, and project engineers are aiming to provide a four-foot minimum depth through the upper areas of the lake. County reports attest that the dredging should result in a more operable and enjoyable recreational area around the lake.

The stacks of sediment and still-present danger of the Microcystin toxin from the blue-green algae that crowds the lake did not dampen the spirits of the lake’s patrons over Labor Day weekend, which marked the end of the 2010 recreational boating season for the Lake Needwood Boat House. Dozens of kayaks, rowboats and paddle boats dotted the lake’s shores Monday afternoon.

Boat house manager Ian Garvie noted that the boating season came to an early close this year because of the dredging — it usually lasts through the weekends of September, but time is needed to drain the lake level and allow the sediment to dry out before excavation begins.

“The north end of the lake is completely filled in with sediment, and it needs to be dug out,” Garvie said.

Aquatic biologist Doug Redmond said that even though the lake will be lowered about six feet to facilitate sediment removal, the operation should bear minimal impact on the habitats and ecological balance within Lake Needwood.

“Because the lake has to be drawn down slowly, the fish have plenty of time to move,” said Redmond, who works in the Park Planning and Stewardship Division of the Department of Parks.

The dredging will take about six months, and Reid said the county hopes to wrap up all in-stream work by the end of February 2011. By March, Reid said work on the modifications “will be more confined to the disposal site,” which sits one-quarter mile east of the lake at a treeless clearing next to Needwood Road.

This will be Lake Needwood’s first dredging since 1990, and Department of Parks spokeswoman Kelli Holsendolph said the dredging of Lake Needwood used to take place more regularly until “funding restraints became a problem” in the early 1990s.

County documents show that preliminary planning for the dredging stretches back to 2000, when a sediment study of the lake gave county officials an idea of how much silt existed under the lake’s surface and how high the costs would be to remove it. Holsendolph said the Montgomery County Planning Board approved the introductory plans for the $4.1 million dredging project in December 2007.

Reid stressed that the dredging project should not interfere with the beginning of the 2011 boating season and that the Department of Parks has no intention of shutting down any park roads or setting up any detours around the lake due to the dredging.