The Kaloko dam in Hawaii stood 116 years – until last year when it collapsed after heavy rains, killing seven.

Potential disaster was averted in April in Hollis, N.H., when a dozen families were evacuated and engineers made a controlled breach of an old pond dam to keep it from failing .

Such incidents are warning signs that many of the nation's more than 87,000 dams are in need of repair. Last month's high-profile collapse of the I-35 bridge in Minneapolis focused America's attention on bridge problems. The nation's dams are worse off.

In 2005, the last time the American Society of Civil Engineers rated America's infrastructure, bridges received a "C" grade; dams earned a "D."

Even that rating may be generous, a Monitor analysis of dam-inspection data shows. Since 1999, the number of "high-hazard" dams rated "deficient" has more than doubled, according to data from the Association of State Dam Safety Officials (ASDSO) in Lexington, Ky. High-hazard dams are those whose failures could cause fatalities. In 1999, the US had 546 such dams rated deficient. By last year, it had 1,333.

A second category of "significant-hazard" dams (so-called because they threaten substantial property loss) saw a rise from 339 to 949 deficient dams over the same period. In all, 2.6 percent of the nation's dams are deficient, according to the ASDSO.

"The growth of deficient high-hazard dams in this country is a major issue," says Brad Larossi, legislative chairman for the ASDSO, which represents dam-safety inspectors in all states. "The trend is rising at such a steep slope, much faster than states can do [dam] rehabilitation. Without question the overall trends are clear."

Several factors are behind the rise. Old dams continue to deteriorate or may fail suddenly because of inadequate spillways and trees growing on dams. Many states don't have enough dam engineers to keep up proper maintenance, causing the repair backlog to grow. And as more homes and businesses are built closer to dams, the hazards increase, a phenomenon dam-safety experts call "hazard creep."

Some experts claim that some of the rise is due to better reporting, an encouraging sign. "To be frank, there's been in the past a reluctance in some quarters to identify too many dams as deficient," says Mark Ogden, administrator for dam-safety engineering at the Ohio Department of Natural Resources in Columbus. "But there's also been a strong effort by our association to increase awareness of this problem. We all are realizing we need an honest assessment."

Some states are seeing a faster rise in deficient dams than others. Pennsylvania leads the pack with 215 deficient high-hazard dams, 172 more than in 1999. Not far behind is Ohio, with an increase of 158 . Other states, such as Colorado, New Jersey, and California have seen declines. Some of that is due to better funding, experts say. All three have boosted dam budgets by a third or more since 1999.

Those increases are in contrast to federal dam spending. The nation's dam-safety program, which helps fund safety inspector and engineer training, has not been fully funded in at least five years, Mr. Larossi says. Actual funding is about $5.9 million, well below the $9 million budgeted, he says.

As a result, the number of full-time inspectors has not increased since 1997 (excluding Florida, which claims to have hired 45 inspectors). That leaves each inspector responsible for about 195 dams on average; the ASDSO recommends no more than 50.

"We have seen increased awareness over the importance of adequate funding for state inspectors, but these offices are still understaffed," says Stephanie Lindloff, of American Rivers, an environmental group.