Nice & Curious Questions

Edwin S. Clay III and Patricia Bangs


From Gristmill to Hydro Power:
Virginia's Dams


Virginia’s relationship with its dams has come full circle. While the 19th and 20th centuries saw a flurry of dam building in the Commonwealth, the 21st century is more likely to see a few dismantled.


In fact, on February 23, 2004, thousands watched as almost 650 pounds of explosives blew a 40-meter hole in the Embrey Dam on the Rappahannock River near Fredricksburg. Officials had decided the dam was too expensive to maintain and blocked fish migration to spawning grounds (“Tales of the Undamned, Removing Barriers Doesn’t Automatically Restore River Heath,” Science News, April 10, 2005.) The Embrey is just one of about 500 small dams that have been removed across the U.S. in the past three decades. Such structures are usually dismantled because of safety concerns, high maintenance costs or environmental issues.


Dam removal is a fairly recent trend in the U.S. and a far cry from the glory days of the controversial Tennessee Valley Authority. The federal agency began building dams in the 1930s and 1940s, for flood control and to bring electricity to the then-rural South. Two of the TVA’s 49 dams, Beaver Creek and Clear Creek, are located in the southwestern corner of our state. Both were built in the 1960s.


Dam building actually began in the Commonwealth in the early 1800s, according to George Mason University geography teacher, Charlie Grymes (Virginia Places). The structures provided waterpower for gristmills and factories. Such water-powered mills helped transform Richmond into a major exporter of flour in the Old Dominion’s early days. At one time, five major dams existed on the James River. As such structures developed, they served several different purposes. Dams created canals for transportation; harnessed hydropower for industries; or provided drinking water for towns, cities or counties.


Today, there are more than 1,300 state-regulated dams in Virginia, according to an April 2005 “Report of the Ad Hoc Dam Safety Study Committee” submitted to the Virginia Soil and Conservation Board. Most are small; many are on private land. This number does not include larger federal dams, such as the TVA projects or the John H. Kerr and Philpott dams, both run by the Southeastern Power Administration. The John H. Kerr Dam is located on the Roanoke River in Mecklenburg County and was built in 1952. The Philpott Dam, built one year later, is on the Smith River in Henry and Franklin counties. Both use turbines to transform their impounded water into electrical power.


Thanks to Hurricane Katrina, we’ve learned a lot about how water barriers are engineered and constructed. Just as the levees of New Orleans were built to withstand certain weather conditions (which unfortunately proved inadequate for Category IV Katrina), Virginia’s dams are judged on their ability to withstand damage from extreme weather and the dangers posed should they fail.


The benchmark in dam safety is “probable maximum storm,” which is a storm so intense it would happen only every 500 to 10,000 years. For example, Hurricane Floyd in 1999 created half of a “probable maximum storm” by dropping 24 inches of rain in 30 hours in the Franklin area. But even experts can’t predict the consequences of severe weather on dam structures. Katrina forced the Association of State Dam Safety Officials, those who inspect and certify the safety of our nation’s dams, to move its September national convention from flooded New Orleans to Orlando.


Virginia’s regulated dams fall into four categories based on their threat to surrounding communities should they fail. A Class I dam would cause probable loss of life and excessive economic loss downstream; a Class II, possible loss of life and appreciable economic loss; a Class III, no loss of life expected and minimal economic loss; a Class IV, no economic loss to others and no loss of life expected. As of a 2004 inventory, the bulk of the Commonwealth’s dams – over 900 –  were rated as Class III, although as rural areas become more populated, they may be reclassified Class II or Class I structures as more and more people choose to live in harm’s way.


Dam safety is serious business in Virginia. The Virginia Department of Conservation and Recreation administers a dam safety program mandated by the 1982 Virginia Dam Safety Act. It ensures that dams are designed, constructed and maintained safely. Another organization, the Virginia Lakes and Watersheds Association even offers a Dam Awards program in such categories as “Best Operated and Maintained” or “Best Rehabilitated.”


Still the state of Virginia’s state-regulated dams garnered national attention several years back. At the time, 40 dams needed repairs. According to an article in a professional journal, U.S. Water News, the director of Virginia’s dam safety program was concerned that many individuals did not know they were living or buying a home in dangerous locations below dams. He explained that individuals tend to adopt a “dry-weather mentality” and don’t realize how dangerous a flood can be. A probable maximum storm, he explained, “is a big storm, but it’s a very realizable storm, and that’s what worries me.” ("Virginia Dams in Distress and Need of Repair," January 2002.)


Three years later, a tsunami, hurricanes Katrina and Rita and mudslides in Guatemala and New Hampshire have proved the improbable does happen. Dismantling a dam doesn’t seem so odd anymore.


NEXT:  Breaking the Codes: Virginia’s Multiplying Numbers


-- October 3, 2005













About "Nice & Curious"


In 1691, a group of English wits, calling themselves the Athenian Society, founded a publication entitled, "The Athenian Gazette or Causical Mercury, Resolving All the Most Nice and Curious Questions proposed by the Ingenious." The editors accepted questions posed by readers on any and all topics, and sought the most ingenious answers.


Inspired by their example, Edwin S. Clay III, president of the Virginia Library Association and Director of the Fairfax County Public Library, created an occasional column on Virginia facts that may require "ingenious answers" of the type favored by those 17th-century wags.


If you have a query, e-mail him at


Fairfax County Public Library staff Patricia Bangs, Lois Kirkpatrick and MaryAnn Sheehan assist in the writing, editing and research of the column.