Lewis and Clark County officials are proposing sweeping changes to the county's interim zoning regulations, though the alterations may not stay in place long.

The amendments, if approved, would:

- free most of the Helena Valley from requirements to install advanced septic systems;

- delineate areas within the central valley where standard, Level I-b and Level II septic systems would be required; and

- set up a process for landowners to challenge those distinctions with evidence, potentially changing the type of system they're required to install.

The amendments would yet again change the regulatory landscape in the Helena Valley, and county officials say they've responded to public requests for more scientific information about the valley's groundwater resources.

While some critics of the county's past work praised the proposal and said it should have come sooner, they questioned how the amendments fit into the county's ongoing efforts to develop comprehensive zoning regulations.

One critic claimed the proposal was a public-relations move in the months leading up to Election Day, an allegation that was dismissed by county officials.

Interim regulations

The new rules would be a departure from the county's policy just 15 months ago, when commissioners approved the first permutation of their interim zoning regulations, which required all new or replacement septic systems to be Level II systems. Those cost $10,000 and up, more than twice the price of a standard system.

Officials were criticized for the broad policy move, which opponents claimed unnecessarily burdened Helena Valley residents and potential homebuyers with large, unexpected costs. Critics also questioned the scientific basis of the rules.

A few months ago, commissioners responded in part by grandfathering existing systems and residents who had secured septic permits prior to May 2007.

This latest round of amendments grew out of an engineering study that rated areas of the Helena Valley based on the land's ability to protect groundwater from contamination, using data on soils, precipitation, geology and hydrogeology.

Commission Chairman Ed Tinsley said in a press release the commission has attempted to respond to the public's concerns.

"We've been asked to provide relief to owners of existing systems, and we did. We've been asked to provide economic relief to struggling residents, and we did. We've been asked to use scientific evidence and study the problem more, and we are. We've been asked to protect water quality, and we will continue doing so," he said.

"It's what we promised the people we would do when we got additional information, and it is the right thing to do," Commissioner Mike Murray said.

County commissioners will hold a public hearing Sept. 9 to consider the amendments, which are posted online and available for review in room 330 of the City-County Building. Follow the link at the end of this story to view the rules.

Officials are still working through a comprehensive zoning proposal that could erase the interim rules, which themselves expire next May and cannot be renewed. If the amendments are approved, the rules may stay in effect for about eight months at the most.

But County Administrator Ron Alles hopes to have a proposal for comprehensive zoning regulations, which would address development density, uses and other issues, to the commission in the coming months. Pressed for a timeline, he said the document might come forward by the end of the year, but likely not before the Nov. 4 election, when Tinsley is up for re-election.

Septic requirements

Earlier this summer, an engineering firm hired by the county created a groundwater sensitivity map for an 81-square-mile area on the valley floor. The firm compiled a variety of existing data to develop the map, which rates the lands in the study area based on their inherent strength or weakness in preventing groundwater contamination.

County officials are proposing to use this map to determine the required level of septic treatment within the study area. They're also proposing to use the map's boundaries to exempt any landowners outside the study area from requirements for advanced septic systems.

The map's ratings and the proposed regulations are based on 40-acre increments. Follow the links at the end of this story to view the groundwater study and the map.

Across the rest of the roughly 400-square-mile Helena Valley Zoning Area, folks looking to install new septic systems on newly permitted property may use standard systems if the amendments are approved.

The map is bounded generally north of Lincoln Road, near Spokane Creek Road, the Jefferson County line, and west of Green Meadow Drive. Lands outside the boundaries would be allowed to use standard systems, while newly permitted properties inside the boundaries would be required to install septic systems based on the groundwater map's ratings.

About 25 percent of the lands within the study area were considered at medium-high risk. Those areas would be required to install Level II septic systems for new homes that didn't have permits before May 2007 -- older homes will still be grandfathered and allowed to maintain or replace standard septic systems.

Another 28 percent of the land area was at medium risk, which under the proposal would carry a requirement for a Level I-b system, though the grandfathering clause is still in effect for existing systems. Level I-b systems cost about $7,500 and remove more nitrates from wastewater than a standard system but less than a Level II system.

And about 41 percent of the land was medium-low or low risk, allowing standard systems to be installed on new properties.

About 5 percent of the land, generally alongside streams, is considered high-risk, and septic systems would be prohibited in those areas. County sanitation and subdivision regulations already restrict development in riparian areas and in floodplains.

Officials also are proposing a process through which landowners can challenge the treatment requirements in their area. Property owners, if the amendments are approved, would be able to bring soil and water data to the county to challenge the rating established by the engineering firm's groundwater sensitivity study.

But landowners will have to live with the results, and the requirements for their properties could be upgraded or downgraded based on the evidence.

Scientific analysis

Alles said officials proposed using the groundwater-sensitivity study as a basis for more stringent septic requirements because the area has the highest densities of residential development. Other areas are still a concern, he said, but more data is available through the study to support higher levels of treatment within the map's boundaries.

Commissioner Andy Hunthausen said the proposed changes represent what he and other commissioners have been searching for: the ability to focus on areas of the valley that are most fragile.

"I wanted to focus our efforts on the places that were deemed the most vulnerable and in the most need of protection," he said. "I think these amendments will move us in that direction."

Alles and other officials said the county will continue to expand the scope of the sensitivity study as funding and resources become available.

The study used existing data from the county, the U.S. Geological Survey, the Natural Resources Conservation Service and other agencies, and is accurate to 40 acres.

Released earlier this summer, the study used a 20-year-old U.S. Environmental Protection Agency model to rate the landscape's sensitivity to groundwater contamination. It doesn't take into account the types or sources of contaminants and doesn't include information about current human impact on the aquifer. Rather, the study is a scientific attempt to rate the land's inherent strength or weakness in preventing contaminants from reaching groundwater resources.

Marjorie Bedessem, a senior environmental engineer with Laramie, Wyo.-based Trihydro Corp., told county officials the map is a good tool to use in planning decisions, but further study is needed to make more refined policy choices.

"Caution should be used when applying this information to particular land parcels, since the scale of data used to generate the mapping may not be sufficient to base site-specific zoning or land-use decisions without corroboration with site-specific data," the report said.

Alles, when asked to respond to those cautioning statements, said the county is basing the new proposed policy on the best information it has available, and Bedessem's study is not the end-all report on the matter.

He noted the amendments use the same 40-acre scale as the study's data and stressed that individual landowners can challenge the policy with site-specific information.

"We can't go out and test every one-acre parcel in a study ... so we take the best information we have available."

Click here to view the zoning amendments.

Click here to view the groundwater study and map.

Reporter Larry Kline: 447-4075 or larry.kline@helenair.com