The Association of Metropolitan Water Agencies, which serves 160 million people, also wants $155 million - a 62-fold increase - for the Environmental Protection Agency for security planning.
Lawmakers on Wednesday were exploring whether the nation's water supplies - its web of reservoirs, rivers, dams, wastewater treatment plants, chemical operations and power plants - are at risk from terrorism.
"The answer can only be a reluctant, sobering, 'Yes,"' said Army Corps of Engineers chief Mike Parker.
Despite the potential for harm, FBI intelligence and other information sources have turned up "no specific credible threats to major waterways or distribution networks at this time," said Ronald L. Dick, director of the FBI's National Infrastructure Protection Center.
A bipartisan group of 11 senators on the Environment and Public Works Committee sent Senate leaders a letter Tuesday also proposing the $5 billion among other billions of dollars in spending to boost U.S. security and to help revive the ailing economy further weakened by the Sept. 11 hijackings.
Major worries include concern that an explosion at a sewage plant along a river could contaminate the drinking water of millions downstream or that the catastrophic loss of major dams could wreak havoc on cities in the flow's path.
"The safety and security of the water infrastructure has not been a high priority in the past," said Rep. John Duncan, R-Tenn., chairman of the House Transportation subcommittee. "We hope to get some of the cities and water agencies to look more seriously at this."
However, he added, "Even if we spent the entire federal budget on security, we still couldn't make the country 100 percent safe from every danger or every nut that's out there. We want to do what we should be doing, but we don't want to do things that are totally unnecessary."
In a 1998 presidential directive by then-President Clinton, the EPA gained responsibility for protecting the nation's water supply from terrorist attack, including biological contamination.
The agency received $2.5 million to combat bioterrorism this year.
Before that it received as little as $10,000 to protect water supply infrastructure in 1998, no funding for that purpose in 1999 and $100,000 in 2000 - money that mostly went toward assessing vulnerability and conducting a water protection workshop, according to EPA figures.
Water system operators say the EPA could use $100 million more to assess the vulnerability of the nation's largest water supply systems and $55 million more to improve an emergency response plan, developed mainly to handle natural disasters like floods and earthquakes and accidents such as hazardous waste spills.
"There is no higher priority than ensuring that EPA's mission ... extends to homeland security," said Marianne Horinko, EPA's asistant administrator for solid waste and emergency response.
Among the critical links identified by the subcommittee were dams overseen by the Corps and nuclear, coal-fired and hydroelectric power plants operated by the Tennessee Valley Authority, the nation's largest producer of public power.
On Sept. 11, TVA's emergency procedures - most of which remain in effect today - included dispatching 24-hour guards, helicopters fueled and put on standby, police boats next to cooling-water pumping stations and troops posted at the Army's Fort Campbell, Ky., power substation, TVA's chairman, Glenn McCullough, said.
© MMI The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed