Lake Accotink Dredging and Dam Repair Projects - Status Update (Braddock District) - December 2007

Dredging

In September 2005 the Park Authority Board approved a contract award to Mobile Dredging and Pumping (MDP) to hydraulically dredge 161,000 cubic yards of silt from Lake Accotink, and pump the material to a property owned by Virginia Concrete for dewatering and disposal. The Department of Public Works and Environmental Services (DPWES) is overseeing the construction contract because of their past experience on other similar type projects.

MDP was given Notice to Proceed on the project in November 2005. The first phase of the work was to install a 2.8-mile long slurry pipeline along a Norfolk and Southern Railroad right-of-way from Lake Accotink to the Virginia Concrete disposal site. The pipeline was completed in June 2006, and hydraulic dredging operations began in July 2006. In order to transport the dredging equipment to the top end of the lake, DPWES authorized MDP to dredge 7,000 cubic yards outside of the contract limits to create an access way.

It has been 16 months since the dredging operation began, and approximately 136,600 cubic yards of silt, or 85 percent of the original contract amount has been dredged and pumped to the Virginia Concrete disposal site. During the contract period, MDP requested and was granted a no penalty four-month winter shutdown in 2006 that started the end of October. Due to the dry weather this fall, MDP has been able to dewater the slurry impoundment at an accelerated rate and received permission by DPWES to continue the dredging operations into November as long as the weather permits the operations to continue. It is anticipated that MDP will be granted a winter shutdown on or before November 30, 2007. MDP will then work throughout the winter to dewater and consolidate the impoundment in order to restart dredging operations the first week of April 2008.

At the Park Authority's request, DPWES performed a preliminary evaluation to determine if the Virginia Concrete disposal site could accommodate additional dredge material above the 161,000 cubic yards currently specified in the contract. Based on their review, up to 204,000 cubic yards of material can be disposed of at the Virginia Concrete site, and DPWES has agreed to provide $1,545,000 in additional funding to dredge and dispose of 43,000 additional cubic yards In June 2006 a major storm caused a significant amount of silt to flow into the marina area reducing water depth. In combination with the recent drought conditions boat access from the marina to the main lake channel has been limited. DPWES has agreed that a portion of the additional 43,000 cubic yards of dredge material (estimated at 10,000 cubic yards) could be reprogrammed for dredging in the vicinity of the marina. Reducing the dredge amount at the top end of the lake by 10,000 cubic yards.

Based on increasing the total dredge amount to 204,000 cubic yards and the historical production rates of MPD, we anticipate completing the dredging operations at Lake Accotink by fall 2008 and fully closing the Virginia Concrete disposal site by summer 2009.