Subdivisions|Circular DEQ-8 Montana Standards for Subdivision Storm Water Adoption|September 20, 2024
The adoption notice for the Circular DEQ-8 Montana Standards for Subdivision Storm Water Drainage went into effect today, September 20, 2024. The notice was published in Issue 18 of the Montana Administrative Register as Notice No. 17-444
The department adopted a new version of Department Circular DEQ-8 (Circular), which provides design standards for subdivision storm water drainage facilities. The Circular was last updated in 2018. The department worked collaboratively with stakeholders to develop the changes to the department storm water regulations with the express intent to make them clearer and more functional.
These changes include but are not limited to defining “Storm Water Facility”, clarifying submittal requirements for Simple versus Standard Storm Water Plans, defining Pre- and Post-Development Conditions and clarifying how they are calculated, setting standards for computer aided modeling instead of calling out which models are approved, clarifying the requirements for the initial storm water facility, and increasing allowances for Best Management Practices (BMPs) to meet storm drainage criteria.
The updates also present increased flexibility for post-development conditions when the extent and location of impervious area is unknown at the time of application by introducing the concept of building location area and storm water facility construction area.
Additionally, consistent with Senate Bill 285, the department added a new method for determining the minimum retention pond size under a Simplified Plan. The minimum size of a retention pond must be 250 cubic feet of volume per every 1,000 square feet of impervious area (buildings, driveways, parking lots, etc.), with the minimum size of the retention facility being 750 cubic feet. This change is meant to simplify the application process for applicants, simplify the review process, and ultimately reduce review times.
Associated Materials and Links:
Adoption Notice: Montana Administrative Record Issue No.18 September, 2024 (Pages 2191-2200)
Proposal Notice: Montana Administrative Record Issue No.11 June 7, 2024 (Pages 1259-1277)
Program Contact:
Hannah Monday
406-444-1801
hannah.monday@mt.gov
Tags: Water and Public Notice