Flint Mayor Karen Weaver speaks to the media regarding the current status of the Flint water crisis. (Brett Carlsen/Getty Images)

Flint Mayor Karen Weaver called Tuesday for immediate replacement of the lead service lines that run from water mains into the city’s homes, a large-scale repair effort that would eliminate one of the prime sources of lead that have poisoned this city’s water supply.

Weaver offered no cost estimate or source of funds for the project, but she touted an approach used in nearby Lansing over the past 11 years that does not require digging trenches. That city has spent $42 million, funded by water-rate increases, to replace 13,500 lead service lines, according to Randy Hannan, chief of staff to Lansing Mayor Virgil Bernero.

Weaver and Hannan estimated that 30 crews could replace 15,000 pipes in a year, at a cost of $2,000 to $3,000 per home.

Flint’s nearly 100,000 residents have been told not to drink unfiltered tap water until tests show it is free of lead, a potent neurotoxin that is especially dangerous to the developing brains and nervous systems of children younger than 6.

Such warnings have forced tens of thousands to rely on bottled water and water filters for weeks, creating a health, logistical and political crisis with no end in sight.

Take a look at the key moments that led up to Flint, a city of 90,000, getting stuck with contaminated water. (Claritza Jimenez/The Washington Post)

The situation began in April 2014, when Flint’s emergency manager switched the city’s water supply to the Flint River to save money and the state Department of Environmental Quality failed to ensure that anti-corrosion chemicals were added to the water. The more-acidic river water quickly began to leach lead from aging pipes into the city’s drinking water.

The city switched back to water furnished by the city of Detroit in October, but the tap water is still not considered safe to consume.

Also Tuesday, the Baltimore law firm that represents the family of Freddie Gray, who as a child suffered lead poisoning, announced that it had filed a federal lawsuit seeking a refund of water-bill payments for all 31,000 Flint households.

Attorney William “Billy” Murphy Jr. estimated that ratepayers are owed about $150 million for the costs of water they can’t drink, bottled water and water filters.

“The citizens of Flint got cheated by having to pay water bills for absolutely undrinkable and horribly dangerous water. They are entitled to an immediate refund,” he said.

Gray, a 25-year-old Baltimore man, died in April of spinal-cord injuries he had suffered in police custody a week earlier.

The new lawsuit is one of several that have been filed seeking remedies or damages for the Flint water crisis. In one, a coalition of environmental groups has asked a federal judge to order the immediate replacement of the lead pipes in the city’s water system.

Weaver said the city should first replace the service lines to the homes of residents who are most vulnerable to lead poisoning: young children, pregnant women, the elderly and people with compromised immune systems.

It’s not clear how many Flint homes have lead service lines or where they are. The administration of Gov. Rick Snyder (R) has estimated that it could cost $55 million to replace an estimated 15,000 lines. As part of this year’s federal budget, the Obama administration is sending $80 million to Michigan for infrastructure upgrades, but the amount headed to Flint has not been determined.

Hannan said Lansing crews have developed a technique that involves punching a hole in the street, threading a new pipe underground and bringing it up through another hole to connect to a home. That method eliminates the need for a trench and shortens the work time from 10 hours to four hours, he said.

Alexander reported from Washington.