The state Environment Department on Thursday questioned Public Service Company of New Mexico's claims on how much a plan to meet federally required air-pollution reductions would cost ratepayers.

PNM says a government plan for the company's coal-fired San Juan Generating Station to reduce haze in national parks and wilderness areas would cost the average residential customer about $90 a year for the next two decades, and business costs would be even higher.

However, the state agency challenged claims by PNM in a news release and legal filing this week that a proposed rule to reduce nitrogen oxides emissions would cost up to $1 billion.

Environment Secretary Ron Curry said he is disappointed with PNM's "shortsightedness in failing to plan to reduce its emissions in accordance with longstanding federal requirements. Now because PNM neglected to plan for a rule that will protect air quality, the company threatens that its customers will have to pay for it."

However, the Environment Department said it doesn't object to PNM's request to delay a planned Oct. 4 public hearing until next year.

The utility has filed a motion with the New Mexico Environmental Improvement Board seeking more time to respond to the Environment Department plan, which would involve installing anti-pollution equipment.

"The current schedule does give the company adequate time to address the complicated issues raised in the proposal," a PNM statement said.

In addition, "PNM strongly believes that the selective catalytic reduction technology would not have a significant impact on improving visibility in the targeted national parks and wilderness areas," the company's statement said.

The proposed plan for new emissions control in New Mexico would only affect the San Juan Generating Station, which produces about half the power PNM uses to serve its 500,000 New Mexico customers.

PNM pointed out that nearby states, including Utah and Nevada, have reached "less expensive conclusions" in preparing their plans to meet Environmental Protection Agency rules for reducing haze.

The state says the 1977 Clean Air Act specifically requires "some of the oldest and dirtiest pollution sources, such as the San Juan Generating Station, to be retrofitted to reduce pollution."