WASHINGTON (AP) _ Replacing old water and sewer pipes and upgrading aging treatment plants around the country could cost $1 trillion over the next two decades, federal officials say. Lawmakers are trying to get attention for the problem _ and a lot more money for upgrades.

``There are significant unmet needs that require the federal government's immediate attention,'' Sen. George Voinovich, R-Ohio, said Tuesday. He introduced legislation to let the government provide more money for wastewater discharge pipes and treatment facilities.

Last year, Congress created a $1.5 billion, two-year grant program to help municipalities deal with part of the infrastructure problem: combined systems that use the same conduits for sewage and rainwater.

Voinovich's bill would allow the Environmental Protection Agency to give states up to $3 billion a year to deal with other wastewater infrastructure improvements.

That may be just a drop in the bucket.

A study commissioned by a group comprising sewer and water authorities, contractors, the U.S. Conference of Mayors and others estimated the overall cost of infrastructure needs _ improvements to wastewater pipes, storm sewer pipes, the lines that carry clean water from plants to homes, the water plants themselves _ at $1 trillion by 2020. A study by the Environmental Protection Agency used different methodology but reached the same conclusion.

Steve Allbee, the author of the EPA forecast, said there will be a gap of $23 billion a year over the next 20 years between what's spent on drinking water and wastewater systems and what's needed.

He estimated that if customers alone pay the cost, their bills would increase an average of 6 percent a year over the two decades. That would pose a particular hardship in cities with both old pipes and declining populations, which will mean fewer taxpayers to share the burden.

``It's more dramatic in the Rust Belt because of the financing issue and because of the aging of the systems,'' Allbee said.

Many of the nation's wastewater treatment plants were built at roughly the same time, in the 1970s and early 1980s, and have roughly the same 30- to 40-year life span, he said.

Those plants connect to underground pipes whose 50- to 75-year average life spans are ending or, in the oldest cities, to cast iron or brick pipes laid at the turn of the century, with a life span of 100 or 125 years.

When those oldest pipes were designed, office buildings were shorter, water pressure was lower and roads carried lighter loads.

Replacing pipes has been difficult for municipal systems that work hard just to service new customers and comply with new regulations that cover radon, arsenic, radionuclides, microbes and more.

``In the last 30 years, the nature of the investment was to serve more and more people and to provide higher and higher treatment levels to make sure that the public health and environmental objectives were met,'' Allbee said.

``If the present situation persists, the financial solvency of many drinking and wastewater systems will be in doubt,'' he said.

House members last year organized themselves into a Water Infrastructure Caucus to work jointly on finding more federal funds to help communities pay for the looming repair and replacement bills.

They got a good case study when a cast-iron pipe _ parts of which had been carrying drinking water since 1895 _ gave out in downtown Cleveland, crushing an antique section of brick sewer.

The break sent 25 million gallons of water cascading through the business district, closing some of the city's busiest streets for a week.

``The expense to our environment and the taxpayers will only increase the longer we procrastinate in addressing these needs,'' said Rep. Sue Kelly, R-N.Y.

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On the Net: Text of Voinovich's bill: http://voinovich.senate.gov/pr-010206.html

Environmental Protection Agency: http://www.epa.gov