Ragged Mountain Dam
The Ragged Mountain Dam system has provided a valuable source of raw water supply for Charlottesville, Virginia, and surrounding Albemarle County for over 125 years. In the early 2000s, however, it became apparent the previous two-dam system required an upgrade and an increase to raw water supply.
The primary purpose of the project was to increase raw water supply volume and upgrade the appurtenant structures, as well as provide a new dam and spillway system that met current dam safety design and construction requirements. In 2009, Schnabel was approached by the Rivanna Water and Sewer Authority (RWSA, client/owner) to provide value engineering review of another consultant’s new dam alternative: a new roller-compacted concrete dam. Our preliminary geotechnical investigation and analyses determined an earthfill dam alternative could provide a cost savings to RWSA of more than $20 million versus the roller-compacted concrete alternative. Because of this ingenuity and cost savings potential, RWSA selected us to continue with the final design for the project.
We planned and oversaw detailed geotechnical field explorations to define subsurface conditions at the dam site and to assess on-site soil borrow sources. The final design consisted of a 125-ft tall zoned earthen embankment, a drill-and-blast tunnel through the right abutment that houses the 36-inch raw water line and a channel to convey principal spillway discharges, the structural design of the 92-ft tall reinforced-concrete intake structure, a 125-foot-deep double-row grout curtain through the fractured foundation bedrock, a soil-cement-bentonite cutoff wall, mechanical and electrical upgrades of raw water supply components, and the construction of rock-cut auxiliary spillway channel located in the right abutment.
All critical schedule milestones were met, and the Virginia Department of Conservation and Recreation’s (DCR) Dam Safety Program issued a permit for construction with no comments. The project team interacted extensively with local citizens, environmental activist groups, and local government entities to identify concerns, and integrated solutions to those concerns into the design of the final project to reduce community impacts. The Ragged Mountain Dam natural area once again provides a great spot for fishing, hiking, kayaking, and other outdoor activities in addition to serving as a vital infrastructure project for the Charlottesville community.