Royal Lake Spillway

AMT designed training dikes and auxiliary spillway armoring using articulated concrete blocks, which are blocks that lock together and form a concrete mat to contain and move floodwater to a safe location past the dam.  Open cell blocks were used to increase permeability and a grass cover crop was used to hide the armoring system within the park property.

Project Details:

Royal Lake Dam was the first of several dams within the Pohick Watershed that needed attention due to safety concerns.  While well maintained, the dam failed to comply with new state regulations enacted in 2010, since it did not convey the Probable Maximum Flood (PMF).  Located in environmentally sensitive parklands, the dam is surrounded by suburban and residential development requiring stringent safety measures to protect county residents.

AMT designed earthen training dikes with an auxiliary spillway improvement to convey the floodwaters safely beyond the dam without overtopping.   Articulated concrete blocks, or ACB armoring, was used to prevent erosion by forming a protective mat in the spillway.  Once built, the armoring system was covered with a topsoil/peat mix and permanently stabilized to hide the armoring system and restore the natural environment of the dam site.  This template was then used to develop similar dam rehabilitation projects at Woodglen Lake, Lake Braddock, and Huntsman Lake in recent years.

The project earned a Merit Award from the American Council of Engineering Companies of Virginia in 2010, mostly for its success in dealing with a sensitive environment, and the design was featured in the July/August 2010 edition of Erosion Control Magazine.