Lewis and Clark County commissioners on Tuesday approved controversial interim zoning regulations, while at the same time asking a group of builders, Realtors and smart-growth advocates to continue working on its own proposal to manage growth in the Helena Valley.

Each of the three commissioners told residents they believe a water-quality problem exists in the valley. If the Development Standards Working Group brings forward an acceptable proposal, commissioners said, its measure could supplant the interim zoning rules.

"The operative word is 'interim,' " Commission Chair Mike Murray said.

"I'm begging for your help," he said to the audience, which included members of the development-standards group. "With your help, we can ... deal with areas of the valley that have problems."

Helena Building Industry Association President Mike Hughes, who has worked with the ad-hoc group, said he didn't like the commission's decision, although he expected it. The HBIA had asked for a 90-day delay to allow the working group to finalize a proposal.

"We would have wished that they would have waited, let the group finish," Hughes said. "And we're still looking forward to being part of the process."

The working group will hold the first of four community listening sessions tonight at 7 p.m. at Jim Darcy School. The meetings are being used to gather public comments on managing growth in the Helena Valley, group members have said.

Commissioners Ed Tinsley and Andy Hunthausen agreed with Murray. They said they believe a water-quality problem exists in the valley, and they said they're willing to consider a community-based zoning proposal.

"Please keep working on it," Hunthausen said. "Bring it before us."

The interim zoning regulations for the Helena Valley Planning Area set height and building setback restrictions, define uses and require one use per lot, and set a five-acre minimum lot size for newly subdivided parcels with on-site septic systems. Smaller lots are required to connect to community systems.

Proposed developments with "complete and sufficient" subdivision applications, as defined by state law, filed with the county are not subject to the regulations, County Administrator Ron Alles said.

County officials' assertion of a water-quality problem in the Helena Valley has been the largest source of controversy. Water Quality Protection District Administrator Kathy Moore, after Tuesday's meeting, said her analysis of several studies performed by the U.S. Geological Survey and others shows nitrate levels have increased eightfold over the past three decades.

Nitrate levels in some areas have exceeded federal standards, though those rules don't apply to private wells. Moore said some areas of the valley have problems, while others do not show increased levels of contaminants.

Moore and other officials also have pointed to a study completed last year, which showed trace amounts of pharmaceuticals, personal-care products and other chemicals in well water.

Hydro geologist Patrick Faber, of Aqua Bona Consulting, in written comments to the county commission, disputed Moore's conclusions and said the county's zoning efforts would increase water-quality issues by encouraging higher-density development.

"I greatly dispute the claim that there is a 'state of emergency' with respect to nitrate levels in the Helena Valley," Faber wrote.

He said he sampled 98 wells over a seven-year time span and those wells had average nitrate amounts of about 1 part per million, similar to amounts found by the USGS in the 1970s. Moore said the average nitrate level of well samples she used was about 4 ppm.

Faber said Moore had erred. Her numbers, Faber said, were skewed because she used data from wells with high nitrate levels -- wells that had been tested again and again. Wells with lower nitrate levels aren't often retested, he said.

"This 'ambulance chaser' mentality results in a skewed average," Faber wrote.

Moore said she had included data from WQPD well tests in her summary report to county commissioners, but the 4 ppm figure came from six studies by the USGS and others -- studies in which researchers had retested randomly chosen Helena Valley wells over the past three decades.

Some of those wells are within developed areas, others are not, Moore said. She said Faber's tests sampled wells solely on undeveloped land, where contaminant levels are much lower. Faber could not be reached for comment Tuesday afternoon.

"The argument he makes is really not, in my opinion, legitimate," Moore said.

"In a way, Pat's right," she added. "It's a matter of where you sample."

Public session

The Development Standards Working Group will hold its first public session on Helena Valley growth tonight at 7 p.m. at Jim Darcy School.

Larry Kline can be reached at 447-4075 or larry.kline@helenair.com.