Vol. 20 No. 3 March 14, 2012

WSSI Hydraulic Dredging Capability Solves Unique Challenges at Lake Anne


WSSI has expanded its suite of pond and lake maintenance capabilities through the acquisition of a floatable sediment removal system (hydraulic dredge). The hydraulic dredge is ideal for servicing forebays, smaller ponds and lake coves that many traditional dredging systems cannot access. In addition, WSSI's system allows for on-site dewatering - which saves money by greatly reducing the volume of material that must ultimately be disposed of and often can be reused as a highly organic top soil or planting media.

Hydraulic dredge operating in canal with bridge and turbidity curtain in background
Click on image to enlarge.
WSSI was recently able to assist the Reston Association (RA) with a unique dredging challenge at Lake Anne in Reston, VA. It was RA's desire to excavate approximately 850 cubic yards of sediment from a narrow canal that served as both a boating amenity to residents and a water intake for Aqua Virginia, owners of the Lake Anne Air Conditioning Company. This area had previously been inaccessible by dredging contractors, due to the townhomes that bordered the north side of the canal and a pedestrian bridge that blocked the entrance from Lake Anne. Over time, this allowed sediment to build and decreased the water depth, which was causing problems for the intake system and was limiting boating access for adjacent homeowners.
Minimizing the disruption of lake and outdoor amenities for the community is a high priority to RA. Thus, prior to work commencing, two turbidity curtains were installed – one at the entrance of the canal to maintain the aesthetics of the lake and a second in front of the water intake to decrease the amount of sediment being drawn to the plant during dredging operations. In addition, dewatering tubes were used to create a clean and contained work area, which allowed work to continue with no hazards or closures to the trail network surrounding the lake. This was possible by piping the material from the dredge within the confined canal to an isolated area where the dewatering bags were staged approximately 1000 feet from the furthest dredging area. This area also provided easy access for the on-road trucks to haul the material away once dewatered.
Removing sediment at water intake

Dewatering bags containing piped
dredge material

In the end, sediment was successfully excavated throughout the canal and from the concrete apron in front of water intake with no threat to the integrity of the canal retaining walls. Following the canal project, WSSI was contracted to perform additional dredging in West Cove at Lake Thoreau. "We were really impressed with WSSI's ability to remove sediment from confined and hard to access areas that we have not been able to dredge in the past. The success of these dredging projects ensures that our residents will be able to enjoy these lake features for many years to come" - Larry Butler, Director of Parks and Recreation for RA.

For more information on WSSI's hydraulic dredging or pond/lake maintenance operations, please contact John Connelly.