Bozeman, MT Environmental Rules: Stormwater Management (2026)

Bozeman Municipal Code § 40.04.700 requires all new developments and redevelopment projects to submit a stormwater management plan or a comprehensive drainage plan to the city engineering department for approval, to control the quality, volume and rate of runoff to storm drains. A comprehensive drainage plan is required for all development larger than five acres. A stormwater management plan is required for developments of five acres or less that are designated a sketch plan or larger under chapter 38, article 19, or that sit within 50 feet of a watercourse. Plans must prevent any off-site direct discharge of untreated stormwater and non-stormwater, and minimize increased post-development discharge rates or volumes. They must also remove total suspended solids to meet the median concentration of the state general permit for MS4s, protect groundwater, and comply with section II of the city Design Standards. Drainage reports, peak flow rates, runoff volume calculations and grading plans must be certified by a state-licensed professional.

Section 40.04.710 sets the review rules. A plan is filed with a permit fee at the time a subdivision or site development application is submitted. No plan is approved if it increases the peak level of runoff from impervious surfaces above the level from the site in its natural, undeveloped condition. No final plat, final site plan or building permit issues without an approved plan. Approval can be revoked or suspended if a project is not completed within two years or development stops for more than two years, though a one-year extension can be granted on written request. An owner can appeal a revocation to the city board of appeals within ten business days, and can ask in writing for an engineering variance for undue hardship, though the cost of minimum BMPs does not count as hardship.

Ongoing duties follow. Under § 40.04.720 the owner keeps stormwater facilities working as designed and keeps installation, maintenance and repair records for the life of the development, and § 40.04.850 requires annual inspections. Section 40.04.200 makes it unlawful to discharge into the MS4 anything that causes a water quality violation, and § 40.04.560 requires a person responsible for a release to call 911 for an emergency, notify the city engineering department within 24 hours, and give written notice within five business days.