New homes within an 81 square-mile study area in the Helena Valley may require more advanced and expensive septic systems, after the Lewis and Clark County Commission on Tuesday unanimously approved amendments to the county's controversial interim zoning regulations.

Not everyone within the 81 square miles, which run roughly from the city limits into the North Hills, will be required to install premium septics. The area has been divided into 40-acre increments, and officials estimate a quarter of the lands will require Level II septics, 28 percent will need Level I-b systems and 41 percent can still have standard septics.

Around 5 percent of the land, mostly near waterways, is considered high-risk and is off limits to any kind of septic system.

See Wednesday's Independent Record for more details.