The upgrade could cost $45 million more than the original $80 million proposal for a traditional staged-aeration plant that residents feared would blanket 20 acres, spew smells and mar Jordan River views.

Meanwhile, general manager Craig White said the district is pushing legislation, backed by Rep. Steve Urquhart, R-St. George, that would allow water and sewer treatment facilities to be built with little or no oversight by municipalities.

Planning for the controversial Riverton facility began almost five years ago, but became snarled in litigation when residents opposed the original design. The upgraded plant would cut the footprint in half, reduce odors and produce water clean enough to be used in secondary-water systems, according to district officials.

Water emissions from a conventional facility - such as the one in West Jordan - only meet requirements for discharge into the Jordan River.

Wednesday's decision came on a 4-2 vote. The board then directed staff to study the option further before trustees make a final decision - expected early next year.

"It's a state-of-the-art technology that will take us into the future," board member and South Jordan Mayor Kent Money said after the meeting. "If you do have to change [to meet higher water quality standards] down the road, this system is more compatible."

With construction halted on a new plant, White said before the meeting that the agency is in "crisis" mode because rapid growth in the valley's south end is exceeding current capacity. In January, the trustees expect to hold a public hearing and vote on whether to impose a moratorium on new sewer connections.

"In essence, we'd be saying we're shutting down growth in the southern one-third of Salt Lake County," White said.

While technology has yet to be finalized, one thing is certain: Impact fees on new home and business construction will be raised, along with monthly sewer rates.

With an $80 million traditional plant, impact fees could go from $3,000 to $4,000. Rates could rise from $15 per month to between $16 and $22, according to projections by contract financial consultants from Lewis Young Robertson & Burningham Inc.

Construction of a $125 million membrane plant would boost impact fees by the same amount and bump rates to between $17 and $23 per month.

"If you weigh the cost of a moratorium versus the increased cost of going to this [membrane] system, I think it's going to be far cheaper," said Herriman Mayor Lynn Crane, a board member.

Former Riverton Mayor Mont Evans and board chair Wayne Ballard were the only two trustees to vote against the proposal.

Evans said he needs more information, but Ballard, after the meeting, said he would back the plan "now that the board has voted to lean that way." He said he voted against it because of the additional cost to homeowners, particularly young couples and people living on fixed incomes.

rwinters@sltrib.com