InfrastructureDanger building up behind aging, vulnerable dams

Published 24 February 2011

Of the U.S. 85,000 dams, more than 4,400 are considered susceptible to failure; a 2009 report put the cost of fixing the most critical dams — where failure could cause loss of life — at $16 billion over twelve years, with the total cost of rehabilitating all dams at $51 billion; those figures do not include dams among the approximately 3,000 that are owned by the federal government; the Army Corps of Engineers, for example, says that more than 300 of the roughly 700 dams it is responsible for need safety-related repairs, and estimates the total fix-up bill at about $20 billion

The fragile Lake Isabella Dam, on the slopes of the southern Sierra Nevada, is just one acute example of a widespread problem: Of the U.S. 85,000 dams, more than 4,400 are considered susceptible to failure, according to the Association of State Dam Safety Officials. Repairing all those dams, however, would cost billions of dollars, and it is far from clear who would provide all the money in a recessionary era.

The New York Times reports that the stakes are particularly high not just for the 4,000 residents of Lake Isabella, but for the 340,000 people who live in Bakersfield, forty miles down the Kern River Canyon on the edge of California’s vast agricultural heartland. The Army Corps of Engineers, which built and operates the 57-year-old dam, learned several years ago that it had three serious problems: it was in danger of eroding internally; water could flow over its top in the most extreme flood season; and a fault underneath it was not inactive after all but could produce a strong earthquake. In a worst case, a catastrophic failure could send as much as 180 billion gallons of water — along with mud, boulders, trees and other debris, including, presumably, the ruins of Nelda’s Diner — churning down the canyon and into Bakersfield. The floodwaters would turn the downtown and residential neighborhoods into a lake up to thirty feet deep and spread to industrial and agricultural areas.

The potential is for a twenty-first-century version of the Johnstown Flood, a calamitous dam failure that killed more than 2,200 people in western Pennsylvania in 1889. Corps and local government officials say, however, that the odds of such a disaster are extremely small, and that they have taken interim steps to reduce the risk, like preparing evacuation plans and limiting how much water can be stored behind the dam to less than two-thirds of the maximum.

Still, they acknowledge that the impact of a dam failure would be enormous. “It’s not just the loss of life, potentially,” said David C. Serafini, lead technical expert for the corps on the project. “It’s the economic damages and the environmental damage, too.”

NYT reports that corps engineers are preparing to propose fixes later this year. At best, repairs would not begin until 2014 and could cost $500 million or more, money that would have to be approved by Congress.

Nationwide, the potential repair costs are staggering. A 2009 report by the state