Subdivisions | Nondegradation Rules | Adoption Notice
The adoption notice for the Nondegradation of Water Quality and Mixing Zones in Surface and Ground Water Rule Updates went into effect today, July 5, 2024. The notice was published in Issue 13 of the Montana Administrative Register as Notice No. 17-439. The adoption notice also includes a minor change to Circular DEQ-20 regarding Source Specific Well Isolation Zones.
Nondegradation of Water Quality and Mixing Zones in Surface and Ground Water Rules
These rule updates incorporate changes adopted by the 2023 Legislative Session under Senate Bill 285.
- SB 285 directed the department to adopt criteria for crediting nitrogen attenuation at the drainfield and riparian zone based on soil type in making nonsignificance determinations for non-permitted septic system discharges.
- SB 285 required the department to adopt new criteria to determine when septic system discharges that are not subject to permit requirements result in nonsignificant changes in water quality.
- SB 285 required the department to consider elevation and the horizontal distance between the discharge and the surface water in the direction of ground water flow and that nondegradation analysis for surface water impacts must be limited to a maximum of 1/2 mile.
The rule update also includes changes to replace inconsistent standard groundwater mixing zone lengths that were based on wastewater treatment system size, lot size, subdivision size, and type of water system, which results in widely different standard mixing zones for wastewater treatment systems designed for the same use and the same design wastewater flow. The changes are necessary to provide flexible and consistent standard mixing zone lengths that are based on the most important factors, design flow and the nature of the wastewater discharge.
Finally, the department updated rules regarding the requirements for classifying wastewater treatment systems as level 2 treatment and the long-term operation and maintenance requirements for those treatment systems.
CIRCULAR DEQ-20 STANDARDS FOR NONPUBLIC WATER SYSTEMS
Senate Bill 327 from the 2023 legislative session directed the department to allow source-specific well isolation zones that are smaller than 100 feet. Amendments were made to ARM 17.36.323, 17.36.918, and Circular DEQ 20 in MAR Notice No. 17-430. The amendments to ARM 17.36.323, 17.36.918, and Circular DEQ 20 were intended to be applied to both individual and shared wells. However, during the drafting of DEQ 20, Section 1.8, "Shared Wells" were mistakenly omitted as being eligible for the SSWIZ. This change ensures there is no conflict between department rules, local health rules, and the design circular.
Upcoming Training
Training regarding these rule and circular updates will be provided by the department in the upcoming month. A notice regarding this training will go out in a separate notification.
Associated Materials and Links:
Adoption Notice: Montana Administrative Record Issue No.13 July 5, 2024 (Pages 1581-1627)
Proposal Notice: Montana Administrative Record Issue No.5 March 8, 2024 (Pages 361-390)
Circular DEQ-20 (July 2024 Edition)
Tags: Water, Public Notice and Rule Making