Utilities nationwide are bringing plants out of mothballs, but its in the West were the need is most acutely felt. Arizona's largest utilities-Arizona Public Service, Salt River Project and Tucson Electric Power Co.-have been readying seldom used urban plants for operation in the next few weeks.

Four of the plants are located in the Valley, three in the Tucson area, one in Yuma, near the southwest corner of the state, and the other lies in a rural area between Phoenix and Tucson. The plants will burn either natural gas or oil, depending on the reliability of supplies and overall demand. In Phoenix, APS is re-starting two electrical generation plants that were first operated in the 1940s and which haven't been in operation since 1989.

Environmentalist are concerned that the plants, which predate the federal Clean Air Act ad have few or no anti-pollution modifications, could spew pollutants-like nitrogen oxides, carbon monoxide, and sulfur dioxide-into the air all summer. The permits that allow the plants to operate were issued in the 1970s, and have little relation to restrictions common today.

The plants could do even great damage to the environment if they resort to burning oil rather than natural gas, say environmentalist. Some of the plants already have burned oil. In December, two utilities said they had to burn oil when their supply of natural gas was cut off as a result of an explosion of an interstate pipeline between Phoenix and El Paso, Texas. Utility spokespersons say that they are confident that the plants won't have to burn oil this summer.

The plants, the utilities say, are being taken out of mothballs so that Arizona residents will have plenty of power during the summer, when air conditioners are running round the clock. But the power companies must also have an eye on California and the lucrative power market that has been created as a result of the energy crunch there. Several energy companies, including APS and TEP, have reported big spikes in their first-quarter profits this year, due in large part to out of state power sales.