As Duke Energy prepares to plead guilty to violating the federal Clean Water Act, it has started delivering bottled water to people with tainted wells close to its North Carolina coal ash pits.

Duke has long denied its 32 dumps in the state have contaminated the drinking water of its neighbors. But recent state-mandated tests found that more than 150 residential wells tested near Duke's dumps have failed to meet state groundwater standards.

Company spokeswoman Erin Culbert says any homeowner who gets a letter warning of a tainted well will get safe bottled water from Duke, if they request it.

Duke is scheduled to plead guilty Thursday to nine environmental crimes as part of a negotiated settlement with federal prosecutors requiring it to pay $102 million in fines and restitution.