Los Angeles officials said Tuesday they would stop buying power from the coal-fired Navajo Generating Station in northern Arizona by 2015, and replace its other source of coal-fired power, a Utah plant, by 2025. Bloomberg News reported that this move, which has been expected for some time, makes L.A. the nation's biggest coal-free city. City officials say they will invest more in renewable energy and energy efficiency, and build a natural gas-fired plant.

This is a big victory for environmentalists in their effort to reduce this country's dependence on coal, which they blame for both conventional and greenhouse gas pollution. It doesn't end the impending struggle over Navajo's future, however. The plant's operator, Salt River Project, has already said it is negotiating to buy Los Angeles' 21 percent share of the plant's power.

The Environmental Protection Agency has ordered the Navajo plant to reduce nitrogen oxide emissions by more than 80 percent in a decade. That worries many Arizona officials who fear this will trigger a spike in water prices because Navajo pumps most of the Central Arizona Project water uphill from the Colorado River to Phoenix and Tucson.