Down in Alleghany County, just west of Covington, stands
a structure unique in the U.S. -- the Humpback
Covered Bridge. Built in 1857, it is so-named because
the bridge is about four feet taller in the middle than
at either end and is the only design of its type in the
country. The extra height, as well as the decking, was
designed to protect it from flooding and help it last
longer.
Bridges were covered to protect the truss, the interconnected
side timbers of wooden bridges, not the flooring, as many
believe because the truss was the most expensive part
of the structure. An unprotected bridge would last only
10 years, but covered, it could last for centuries barring
natural or manmade disasters.
At one time there were hundreds of covered bridges in
the commonwealth, but fire and flood took their toll.
By 1900, metal had replaced timber as the material of
choice, and was soon superseded by reinforced concrete
in the early 20th century.
Today, the Virginia Department of Transportation lists
eight
surviving covered bridges in the Old Dominion. In
addition to the Humpback structure that spans the James
River, there is Meem's
Bottom Bridge over the North Fork of the Shenandoah
River in Shenandoah County; the
Bob White Bridge and the
Jack's Creek Bridge over the Smith River in Patrick
County; and the Sinking
Creek Bridge on Sinking Creek in Giles County. Three
other decked bridges – one in Rockingham County
and two in Giles County -- sit on private property.
Wooden, roofed bridges aren’t the only spans of
historical interest in the state. Back in 2000, VDOT published
“A Survey of Masonry and Concrete Arch Bridges in
Virginia” to determine which stone bridges were
eligible for preservation with the National Register of
Historic Places.
In the early years of the commonwealth, stone bridges
were not built as often as wooden bridges. Masonry structures
were expensive and required a certain engineering skill.
Also, the sources for stone and mortar weren’t always
available.
The VDOT study identified 21 of 127 masonry arched bridges
as eligible for the National Register of Historic Places
list. Nine were built before 1900 and served as canal,
turnpike and railroad bridges. You can see an example
of a turnpike bridge, built circa 1823, in the Falling
Creek Wayside Park in Chesterfield County.
A number of the early 20th-century masonry bridges are
the work of civil engineer Daniel Luten, who by 1927 had
received 50 patents for reinforced-concrete designs related
to bridges. His goal: to reduce cost, without reducing
strength. A typical Luten bridge – more than 10,000
were built according to his designs from 1900-1932 in
the U.S. -- is found crossing the Dan River on Route 29
in Danville.
Arched masonry bridges became less popular in the heyday
of road and bridge construction in the 1940s and 1950s,
when design standardization was the goal. Today, there
are more than 21,000 bridges in Virginia. Among the most
noteworthy are the 23-mile Chesapeake
Bay Bridge Tunnel, which connects Virginia Beach to
Cape Charles, and the 4.6-mile Monitor-Merrimac
Memorial Bridge-Tunnel, which crosses I-664 in Hampton
Roads. The latter opened in 1992 and 3.2 miles are a double
trestle bridge.
Virginia’s tallest bridge is the recently constructed
175-foot-high Wilson Creek Bridge, also known as the Smart
Road Bridge. The
Smart Road is a short, limited-access road in Montgomery
County maintained by the Virginia Tech Transportation
Institute and used to test transportation technologies.
Power and communication lines run its length, equipping
it for research.
Engineers are not the only people studying bridges. It
seems the Old Dominion’s spans are habitat for creatures
great and small. Wildlife biologists with the Virginia
Department of Game and Inland Fisheries have launched
a "Wildlife
and Bridges" project to document the birds, mammals
and even a reptile or two that call the state’s
bridges home. So far, they have found seven species of
birds, eight species of mammals and one reptile. Among
the birds are various types of swallows, osprey and peregrine
falcons. The mammals include six species of bats, woodrats
and gray fox. A black snake feeding on a bat was the lone
reptile the researchers found.
Biologists believe many species are opportunistic and
when natural habitat is destroyed due to flooding, overgrowth
or man-made development, various bridge structures offer
alternative housing. Tall bridges provide niches for swallows;
small bridges with I-beams create a ledge for phoebes
to nest; or the expansion joints in an overpass provide
a tight crevice for bats raising their young.
The density of wildlife living on the commonwealth’s
bridges varies according to geographic region. The Piedmont
Region, in the center of the state, boasts the most occupants.
Fifty percent of bridges in that area host five species
of birds, three species of mammals and that lone reptile.
The mountain regions come in next with 34.4 percent of
their bridges occupied. The coastal plain, which stretches
along the Atlantic and extends 100 miles inland is the
least attractive to wild creatures. Only 18.4 percent
of its bridges host wildlife.
It seems Virginia’s high technology, as well as
its fauna can co-exist. Who knows what creatures will
soon grace the Smart Road Bridge?
May 30, 2006
Nice & Curious
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Last Modified:
Friday, June 27, 2008
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