Committee hears bill to resolve septic "mixing zone" conflict, grandfather existing permits

Representative Courtney Sprunger, sponsor of House Bill 180, told the House Local Government Committee the bill aims to fix a longstanding conflict between two sections of Montana law that can force property owners to remove or replace legally permitted septic systems when they divide land. "This is a common sense bill that will grandfather existing septic system mixing zones that were legally permitted and installed if a property owner wants to divide their property," Sprunger said in opening remarks.

Rachel Clark, engineering bureau chief for the Montana Department of Environmental Quality’s Water Quality Division, described how mixing zones function: wastewater percolates through soil until it reaches groundwater and is diluted within a defined mixing zone. Clark said most mixing zones are site-specific but commonly range on the order of tens to a few hundred feet and that, under the 2011 Sanitation Act change, parcels undergoing sanitation-act review are required to keep mixing zones inside subdivision boundaries. "This has led to a situation where someone might have gotten a drain field and a mixing zone approved by their county because their lot was greater than 20 acres," Clark said. "When they then try to split that property, DEQ can't approve the mixing zone because it's outside the subdivision boundaries. House Bill 180 will correct this issue." She told the committee the department recommends a due pass.

Professional engineers who work on DEQ submittals also supported the bill. Jeff Larson, vice president of the Montana Environmental Consultants Association, said HB 180 "will correct the conflict in the regulations and it'll protect legally permitted drain fields, from having to be replaced," and emphasized the bill requires systems to be legally permitted, not a path for unpermitted installations.

Key features of the bill described to the committee include: clarifying local board-of-health permitting requirements (referring to a modification of 50-2-116, MCA), accepting previously county-approved mixing zones for property divisions up to the bill’s effective date, and ensuring future septic permits require mixing zones to remain inside parcel boundaries to avoid conflicts with subdivision review under Title 76. Clark said mixing zones approved by counties before the bill’s effective date (committee discussion cited October 1 as the relevant cutoff in the bill text) would be honored and would not require new easements.

Committee members asked how many instances the conflict has caused problems; Clark said the department was aware of "probably several dozen" cases and that many owners avoid submitting proposals to DEQ because they expect denial under current rules. Members also asked how easements function as a cure; Clark said easements between neighbors can satisfy the requirement but are often difficult to obtain without compensation.

No opponents appeared. After questions and discussion, Sprunger closed by reiterating the bill would protect families who lawfully invested in systems and reduce regulatory friction when properties are divided.

The committee record shows the discussion focused on: (1) resolving a statutory conflict between Title 50 (local health/septic permitting) and Title 76 (subdivision law); (2) grandfathering preexisting county-approved mixing zones up to the bill’s effective date; and (3) requiring future mixing zones to remain inside parcel boundaries as a condition of local septic permits. The hearing record contains DEQ recommendations and endorsements from the engineering community but no formal opposition.