FLAGSTAFF - The U.S. Environmental Protection Agency wants haze-causing nitrogen oxide emissions reduced by 84 percent at a coal-fired power plant on the Navajo Nation, but a group that includes the plant's operator says it can do better.

An alternative plan submitted Friday to the EPA would shut down one of three 750-megawatt units at the Navajo Generating Station near Page by 2020, cutting pollution beyond what the EPA has proposed. The plant's operator, the Salt River Project, said the plan takes into account potential ownership changes and pushes back the implementation of expensive pollution controls.

It also sets a firm deadline for shutting down the largest coal-fired power plant in the West by 2044, unless the Navajo Nation opts to run it itself.

"We believe as the owners that operating two units in the future is a good outcome," said Mike Hummel of SRP. "We believe that's a better outcome than putting us in a position where we may not have any units running."

Should the plan fall through, the group has a backup plan to reduce emissions that would be equivalent to shutting one unit.

The EPA's proposal gives the power plant's owners 10 years to install technology that would improve visibility at the Grand Canyon and other places. The alternative proposal brought forth by SRP, tribal and federal officials, environmental groups and the Central Arizona Water Conservation District, would give the power plant's owners an additional five years to make decisions on major investments in pollution controls.

The National Parks Conservation Association, which wasn't involved in crafting the alternative, isn't endorsing it because it doesn't provide as much assurance as the EPA's proposal in improving air quality.

"We stand ready to work with the stakeholders to refine some of the plan's deficiencies and its unfortunate 'escape ramps' that result in more years of dirty air at the Grand Canyon and the other 11 national parks and wilderness areas in the region," said Kevin Dahl, the association's program manager in Arizona.

Dahl also said he believes the emissions under the alternative proposal would be worse than what the EPA proposed.

Navajo President Ben Shelly said shutting down one unit isn't favorable for the tribe's economy, which relies heavily on natural resources for revenue. But he said it is better than a complete shutdown of the plant that would result in the loss of hundreds of jobs at the power plant and associated coal mine.

A 25-year lease extension for the power plant that Shelly is expected to sign next week also gives the tribe the option of purchasing a share of Navajo Generating Station.

Two of the plant's owners, the Los Angeles Department of Water and Power, and NV Energy Inc., have signaled their intent to cut ties with Navajo Generating Station by 2019.

Together, those two owners' shares in the plant add up to nearly the equivalent of one of the plant's three units. So shutting down one unit would leave intact the amount of electricity now received by the other owners.

SRP, the U.S. Bureau of Reclamation, Tucson Electric Power Co. and Arizona Public Service Co. also own shares of the power generated at the plant.

The EPA will consider the alternative proposal along with any other comments submitted on the EPA's own proposal before issuing a final rule for pollution controls. The deadline for public comments is Oct. 4.

The Sierra Club said the alternative proposal "contributes to the discussion" of how to protect health and improve visibility but lacks a "clear, enforceable path to end coal's dirty legacy in the region."

The EPA has embraced similar proposals. When it issued a final rule for the 2,040-megawatt Four Corners Power Plant in northwestern New Mexico, it gave the plant's owners the option of upgrading the five units or shutting down three units and installing pollution controls at the two others.

New Mexico also had brokered an agreement with federal regulators and the state's largest utility to shut down two units at the nearby 1,800-megawatt San Juan Generating Station by the end of 2017 and replace them with a new natural-gas-fired plant.

The Navajo Generating Station is more complex in that it meets power demands in the West but also sends water through a series of canals to Arizona's most populous cities and helps fulfill water-rights settlements with American Indian tribes.

Did you know?

Tucson Electric Power Co. has a 7.5 percent ownership stake in the Navajo Generating Station.