After two weeks that saw evacuations near Oroville, Calif., and flooding in Elko County, Nev., America’s dams are showing their age.
Nearly 2,000 state-regulated high-hazard dams in the United States were listed as being in need of repair in 2015, according to the Association of State Dam Safety Officials. A dam is considered “high hazard” based on the potential for the loss of life as a result of failure.
By 2020, 70 percent of the dams in the United States will be more than 50 years old, according to the American Society of Civil Engineers.
“It’s not like an expiration date for your milk, but the components that make up that dam do have a lifespan.” said Mark Ogden, a project manager with the Association of State Dam Safety Officials.
The United States Army Corps of Engineers keeps an inventory of 90,000 dams across the country, and more than 8,000 are classified as major dams by height or storage capacity, according to guidelines established by the United States Geological Survey.
Two weeks ago, heavy rains caused the Twentyone Mile Dam in Nevada to burst, resulting in flooding, damaged property and closed roads throughout the region.
The earthen dam, built in the early 1900s and less than 50 feet tall, is one of more than 60,000 “low hazard” dams, according to the Army Corps of Engineers. Typically, failure of a low hazard dam would cause property damage, but it would most likely not kill anyone.
Last week, 180,000 people downstream from Oroville Dam in California were evacuated after an emergency spillway showed signs of failing.
Built in the 1960s and more than 16 times the height of the Nevada dam, Oroville was listed as a high hazard dam. Had it not been for the speed of the response last week, there could have been severe flooding of the surrounding area.
“The larger dams are being watched very carefully. The smaller dams don’t enjoy that level of scrutiny,” Mr. Ogden said.
In 2016, the Association of State Dam Safety Officials estimated that it would cost $60 billion to rehabilitate all the dams that needed to be brought up to safe condition, with nearly $20 billion of that sum going toward repair of dams with a high potential for hazard.
In 2015, Representative Sean Patrick Maloney, Democrat of New York, introduced the Dam Rehabilitation and Repair Act to provide grant assistance to rehabilitate publicly owned dams that fail to meet minimum safety standards. A version of the legislation that covered private dams — which account for more than half of the dams in the United States — was incorporated into a larger water infrastructure bill and signed into law by President Barack Obama in December.
Oroville Dam is owned by the state of California, but the Twentyone Mile Dam is owned by Winecup Gamble Ranch, a cattle operation in northeastern Nevada.
While most legislation involves inspection and rehabilitation, hazardous dams that have outlived their usefulness can also be removed.
“The very fact that you are blocking a river and allowing a reservoir to fill up with millions of gallons of water presents a risk,” said Bob Irvin, the president of American Rivers, an environmental conservation and advocacy organization. The group has partnered with the State of Maryland to remove the Bloede Dam, built in 1907, where several people have drowned over the years.
Nationwide, 1,384 dams had been removed from 1912 through 2016, according to the nonprofit American Rivers. A majority of those dams were removed within the last two decades, with 72 removed in 2016.
Article by: Troy Griggs, Gregor Aisch, and Sarah Almukhtar
Published: February 23, 2017 by The New York Times
Read original here.