The D.C. Water and Sewer Authority will replace more than 23,000 lead service pipes across the city by 2010 under an ambitious public works program aimed at eliminating the potentially toxic metal from the water supply.

The $350 million plan, unanimously approved by WASA's board of directors yesterday, means pipes will be replaced at a far more aggressive pace than mandated by federal regulators. Water rates, already expected to increase 5 percent per year because of other projects, could rise an additional 1 or 2 percent, the agency said.

Board Chairman Glenn S. Gerstell said eliminating lead service lines would largely remove the threat of the metal leaching into the water, as has occurred over the past few years. The agency set aside concerns from some city officials who said replacing the pipes should be a last-ditch effort after other, less expensive measures are tried.

"This is very much the right thing to do," Gerstell said. "These pipes have been in the ground over 100 years, and over the years, we've replaced some in fits and stops but never fully addressed it."

Some city leaders, including Mayor Anthony A. Williams (D), had urged the agency to hold off on a complete lead pipe replacement program until the utility was able to assess the effects of new chemicals added last month to the drinking water. The change in water treatment, made by the Army Corps of Engineers, which operates the Washington Aqueduct, is intended to coat the pipes with a film and prevent the lead from leaching.

Tony Bullock, spokesman for the mayor, warned yesterday that WASA's decision could cause unnecessary disruption to neighborhoods. Streets will be closed for weeks, and sidewalks and curbs will be excavated. Homeowners with lead service pipes will have to decide whether to pay hundreds or thousands of dollars to replace the portion of the pipes on their property.

"It's a laudable goal to want to rid the world of lead pipes," Bullock said. "At the same time, you have to have some evaluation and cost-benefit analysis of this. There is concern that WASA is moving a bit too quickly before having fully evaluated all of the consequences."

After WASA discovered excessive levels of lead in some tap water in 2002, federal rules required that the agency begin replacing 7 percent of its lead lines -- about 1,600 -- each year. This year, under pressure from city and federal leaders, WASA pledged to replace 1,800.

Under the new plan, to be funded through the agency's capital budget, WASA will replace about 2,500 pipes in each of the next two years, then ramp up the pace significantly in future years. It is the most ambitious lead pipe replacement plan attempted in the country, water quality experts said.

D.C. Council member Carol Schwartz (R-At Large) acknowledged the potential disruption in neighborhoods. But she said the city should not shy away from replacing the pipes simply because it is logistically difficult.

"A lot of public officials would like to pass these problems on to another generation so that they don't have to spend the money or have the disruption, but I'm worried about the next generations, too," Schwartz said.

Also yesterday, a WASA board committee recommended that the agency give a one-time credit of 1,000 free gallons of water to customers as a goodwill gesture to restore public trust. That would translate into a savings of about $6.15 per customer and cost the agency about $725,000, officials said. The full board will vote on the proposal in September.

WASA's lead pipe replacement program will dwarf similar efforts underway in Madison, Wis., and St. Paul, Minn., where officials are replacing 500 to 1,600 lines. It will require WASA to coordinate on a larger scale with other D.C. agencies, including the departments of transportation, health, and consumer and regulatory affairs.

Gerstell said he has talked to Williams, who appointed him, and other senior administration officials, who have told him that they will facilitate WASA's efforts. One idea would be to grant the agency a blanket work permit rather than require it to return to the regulatory affairs department for every job, Gerstell said. Also, WASA will seek an agreement with the city that sets out the roles and responsibilities of each agency, he added.

Council member Adrian M. Fenty (D-Ward 4), who supports replacing lead service pipes, cautioned against giving WASA crews free rein on city streets. Over the past few months, some residents have complained that WASA contractors have torn up yards, failed to clean up and returned to dig up the same streets two or three times.

"They need to prove they have their act together first," Fenty said. "I would be fearful of giving them a blanket permit to do anything, or we could find all types of problems."

WASA officials have disputed contentions by residents that crews have dug on private property without permission.

General Manager Jerry N. Johnson said that he will appoint a coordinator to oversee the replacement program and that customers will be notified according to a plan that includes sending letters to homeowners and placing fliers on doors.

He added that the agency has worked with a bank to offer low-interest loans to residents who elect to replace the private portion of the service pipes. In Madison, a law requires homeowners to replace their lead pipes at the same time the water utility is replacing the pipes in the public space. District leaders have not discussed such a plan.

Paul Schwartz, policy coordinator for Clean Water Action, an environmental group, said he supports removing lead service lines. But he noted that WASA is dealing simultaneously with several other massive environmental health programs, such as an effort to clean up sewage overflows into local rivers, that should not be compromised.

"We need to have a comprehensive, top-to-bottom overview of the water infrastructure needs and an adult discussion about the health impacts," Schwartz said. "We have an aging infrastructure, and the lead lines are a part of that."