No one knows yet whether Salt Lake City will build a water treatment plant in the mouth of Mill Creek Canyon. But opponents of the idea and one local mayor aren't content to sit back and wait for construction to begin.

"We don't need a water treatment plant in Mill Creek Canyon," said Dan Miller, secretary of the Save Mill Creek Committee, whose opposition to the plant is expressed in 4,000 petition signatures. "They have got all the others; we want this one left alone."Salt Lake City Public Utilities Director LeRoy W. Hooton Jr. said the city has purchased a Utah Power & Light Co. generating station in Mill Creek Canyon and has held a public hearing and gathered data on the pros and cons of a treatment plant. But the city still is about a year and a half away from deciding what to do.

The issue is complicated by water-rights contracts dating to the 1920s, by low stream flows and by the fact the city has been subsidizing water to residents of the canyon for 70 years, at a combined cost of about $20 million.

"There are a lot of issues to be resolved," Hooton said. "We just don't have the answers right now. I believe the Mill Creek folks are pushing this now because they just want to put the issue away.

"Our commitment is that if we do it, it will be environmentally sound. Otherwise, we won't do it."

The possibility of a treatment plant has caught the attention of South Salt Lake Mayor Jim Davis, who Thursday sent a letter expressing his concerns to Salt Lake Mayor Palmer DePaulis.

Davis worries a plant, if built, may affect a new housing project downstream, in his city - one that borders an inner-city arboretum.

"Our main concern in seeing the plant built is the possible reduction of water flow and the degradation of the quality of the water in Mill Creek Stream where it runs through South Salt Lake," Davis said.

In his letter, Davis said South Salt Lake has just spent more than $1 million of flood control and other funds building a flood retention pond and a nature park between 3300 South and 3100 South between 700 East and 500 East.

In that same area more than 50 new homes are being built.

"If the stream flow is restricted anymore than it currently flows, it will definitely affect the areas we have been working so hard to create and preserve in South Salt Lake," he said.

Echoing the sentiments of other county and city officials, Davis calls Mill Creek Stream a precious resource.

Miller said every canyon in Salt Lake County has water shed controls except Mill Creek. Salt Lake County recently decided to begin charging people $2 per carload to enter the canyon. If water shed controls are in place, those people will have to stay 50 feet back of the creek, he said.

He also cites environmental concerns.

"Many of the trees that align the creek will die because of the restricted flow of water from the plant. Fish will also die," he said. "Yet Mill Creek provides less than 2 percent of the Salt Lake Valley water supply."

Hooton said the concerns may be valid, but they are premature. The city hasn't decided what to do.

Davis acknowledges that a decision on the proposed plant will not be made for possibly more than a year.

"The issue is important enough to my city that we go on record now," he told DePaulis.