Michigan now has the country's strictest drinking water rules for lead.
The plan filed Thursday will eventually result in the replacement of all 500,000 lead service pipes statewide in the wake of the contamination of Flint's supply.
The rules will drop the "action level" for lead from 15 parts per billion, the federal limit, to 12 in 2025. Underground lead service lines connecting water mains to houses and other buildings under a broader plan to repair and replace buildings will be replaced by 2040, unless a utility can show regulators it will take its water infrastructure.
The plan could cost $2.5 billion over decades, money that is expected to largely come from water customers.
Gov. Rick Snyder says the federal lead rules do not do enough to protect public health.
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