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.”
(VLWA
Dam Awards Program.)
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.
October 3, 2005
Nice & Curious
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