Heavy rains and flooding prompted the evacuation of dozens of residences in southwestern Virginia on Thursday, including 13 homes near an earthen dam in Roanoke.
The dam-related evacuations were done “out of an abundance of caution” and the structure was never under imminent threat of failure, Trevor Shannon, Roanoke’s battalion chief of emergency management, said at news conferences.
Rain and flooding of the Roanoke River and its tributaries also led to rescues of people in vehicles as well as evacuations of other homes and a hotel in the city.
Five to 10 inches (12.5 to 25 centimeters) of rain has fallen in that region of the Blue Ridge Mountains, said Patrick Wilson, a National Weather Service meteorologist in Blacksburg.
Wilson said the Roanoke River swelled to just shy of major flood stage Thursday and was predicted to rise slightly above it Thursday night.
“We’ve just been getting almost endless rain for the last three days,” he said.
Officials had become concerned about the Spring Valley Lake Dam because pipes under the structure had begun filling with water.
People living downstream received phone calls from the city early Thursday morning and Roanoke firefighters went door to door to inform residents.
Shannon, the city’s battalion chief, said they followed an emergency action plan for the privately owned structure. The order to evacuate came during the plan’s third phase, when water in pipes running under the dam reached a level of roughly 12 inches (30 centimeters), Shannon said. The pipes are 36 inches (91 centimeters) in diameter.
Shannon said residents and officials continue to monitor the structure. A dam safety engineer conducted an inspection Thursday morning and was “very confident in how it was holding up and running water through it,” he said.
An online database maintained by the U.S. Army Corps of Engineers says the dam is made of earth and has a high hazard potential.
A 2006 inspection of the dam maintained by a homeowner’s association found that it was in “good condition” overall, according to documents released by Virginia’s Department of Recreation & Conservation. The inspection report also said the embankment of the dam, which was built in 1960, showed no signs of erosion.
The evacuations in Virginia came after rapidly rising water in central Michigan overtook dams and forced the evacuation of about 10,000 people.
Concerns have been growing over dams in the U.S. that are in poor condition and located near homes, businesses and highways. An Associated Press review of federal data and reports obtained under state open records laws identified 1,688 high-hazard dams rated in poor or unsatisfactory condition as of last year in 44 states and Puerto Rico.