By Clare Boyle

Special to The Sentinel

After nearly two years of construction, repairs to the Lake Needwood dam in Derwood were officially completed June 2, and the entire park was open to visitors.

Located on the Northern end of Rock Creek Regional Park, Lake Needwood offers picnic areas, trails for biking and hiking and a 75-acre lake for water activities, including boating and fishing.

The park's Westside Trail, which has been closed since March 2007, was opened to the public and all boating activity on the lake resumed at the start of the season as usual.

''We are happy to welcome trail users back to the park this summer now that construction on the dam is complete," Rock Creek Regional Park Manager Jim Humerick said in a press release.

Despite recent hot weather, locals are taking advantage of the newly opened trail.

"I've biked around the trail twice since it opened," said Chris Hersman, of Chevy Chase, as he was unloading his bike from his car to go for a third ride around the trail.

Hersman also brought a kayak to the lake immediately after the season started.

"It was nice, since the lake was totally empty," he said.

Crews worked on repairing the dam since late June 2006, when a torrential downpour flooded the lake and exposed weaknesses in the dam. The rains caused a rapid rise of the water level to 25 feet above normal.

On June 27, 2006, leaks appeared on the left downstream slope and abutment of the dam.

Since the Lake Needwood dam is an earthen dam, and uncontrolled leaking can compromise an earthen dam, emergency procedures went into place. These included the evacuation of about 2,200 downstream residents, many in Aspen Hill, and the closure of areas of the park until the leaks were stabilized.

Three days later, the lake receded and leaking stopped.

To repair the damage, the County Council appropriated $3.8 million to the project in November 2006.

With a few minor repairs remaining, Andy Frank, the dam's project manager and construction manager, believes "we will be at or under budget."

Major repairs were completed in two phases. The first involved installing a grout curtain below the dam to stabilize the fractured bedrock that had been allowing water to leak through the dam.

"We drilled 250 holes through the dam into the bedrock, then injected those holes with grout to fill any fractures in the bedrock," said Frank.

Phase two, finished in May, involved installing a blanket drain that uses sand and gravel to intercept any residual seepage.

Frank called repairing the dam "a lengthy process, since everything has to be done sequentially and we can't do anything concurrently."

In addition to repairing the dam, preliminary work began in February as part of a project to dredge Lake Needwood. Dredging occurred regularly until about 1990, when funding constraints discontinued the practice.

The silt that has built up since then contributes to poor water quality and limits boating and fishing, parks officials said.

The County Council recently approved another $3.8 million for the dredging project.

Frank, who will most likely be the project manager for the dredging, said the park is working with the state highway administration so its timing can be coordinated with the completion of Intercounty Connector construction in the area.

"We're hoping to dredge the lake in the fall of 2010 into the winter of 2011, so we interrupt park activities as little as possible," Frank said.

Photo by Gavin Jackson