The country's dams have become significantly safer since Sept. 11, 2001, but the gates holding back the nation's largest reservoirs, including Glen Canyon Dam, remain vulnerable to terrorist attack, a new federally commissioned study said.

Nationwide, water managers at the U.S. Bureau of Reclamation who monitor water and power flow at the dams are disconnected from the security teams and law enforcement officials protecting them, according to the National Research Institute study released this week.

Better communication is crucial, the study said.

"The cultures of two ends of that pipeline are very different," said John Christian, a consulting engineer from Massachusetts who supervised the Bureau of Reclamation-commissioned study.

Better security plans are needed to meet realistic, site-specific threats at the Bureau of Reclamation's 479 dams and dikes, the study says.

Although roads have been closed, cameras powered up and fences erected since Sept. 11, the dams' security appeared "brittle" and "lacking in depth," with officials having planned only for a certain amount of "threat scenarios," the study found.

For example, there were no plans for the possibility of an employee attacking a dam.

The chain of command during an attack also is unclear, and what security procedures that are in place are not well understood by Reclamation officials, the study found.

Christian said there also is confusion about who is authorized to use deadly force during an attack, since many of the dams are protected by private security teams.

Few specifics were given about problems at each of the five "critical infrastructure" dams — Hoover, Grand Coulee, Folsom, Shasta, and Glen Canyon — that were surveyed by the researchers earlier in the year.

Christian said that was done intentionally to prevent anyone with "malicious intent" from gaining information that could be used to damage the dams.

Bureau spokesman Peter Soeth said many of the issues brought up in the study already have been addressed.

He said that since Sept. 11, the Bureau of Reclamation has spent $84 million on security at dams.

And half of the $50 million budgeted this year for the bureau's security has gone to pay for guards at the facilities, Soeth said.

"With this commitment, we feel we're in position to recognize the findings and merge them into our efforts," he said.