The Upper Ragged Mountain Dam and Lower Ragged Mountain Dam were originally constructed in 1887 and 1908, respectively. The older of the two dams, was approximately 45 feet high and 470 feet long, consisting of earth fill and a stacked masonry core. Lower Ragged Mountain Dam was 67 feet high and 400 feet long, originally built as a monolithic cyclopean concrete dam, with an earth buttress added in 1934. Before the expansion of Ragged Mountain, the two dams received rainfall from a 1.8 square mile watershed and were capable of storing a total of 514 million gallons of water, of which 463 million gallons is considered “useable” for water supply.With the construction of the new earthen dam, the upper and lower were partially dismantled and are now underwater.
In 1978 and 1979, as part of a national dam safety inventory, the U.S. Army Corp of Engineers identified both of these dams as having an “unsafe condition” because of inadequate spillway capacity. In the mid 1980’s the original spillway on the Upper Ragged Mountain Dam was altered to improve its capacity.
In the 1990’s and early 2000’s the state and national standards for dam spillway capacity increased, requiring an even greater ability to pass storm events. Current standards require a dam, such as Ragged Mountain, to pass the Probable Maximum Precipitation (PMP) safely through the spillway.
In 2003, the Rivanna Water and Sewer Authority began engineering investigations to identify and pursue an alteration/upgrade to the Ragged Mountain Dams facility to address the outstanding dam safety concerns. In 2006, and again in 2011, City and County officials approved the pursuit of the new water supply at the Ragged Mountain Dam site. Construction of the newly expanded Ragged Mountain Dam began in 2012 and concluded in 2014. Ragged Mountain reservoir has reached capacity in February of 2016.