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Montana Statewide Rule

Montana Stormwater Discharge Permits Under the Water Quality Act

Some RestrictionsApplies statewide across Montana (2026)

Key Facts

Governing statute
MCA 75-5-401; 75-5-605
Enforcing agency
Dept. of Environmental Quality (MPDES)
Max civil penalty
$25,000 per day
Construction filing
Notice of intent plus prevention plan
Program
Montana Pollutant Discharge Elimination System
Last verified: July 31, 2026

Summary

Montana requires a Montana Pollutant Discharge Elimination System permit before stormwater reaches state waters. Under MCA 75-5-401, construction-site operators discharge under a general permit by filing a notice of intent and a signed pollution prevention plan with the Department of Environmental Quality.

governing authorization to discharge under a general permit for storm water associated with construction activity. These rules must allow an owner or operator to notify the department of the intent to be covered under the general permit. This notice of intent must include a signed pollution prevention plan that requires the applicant to implement best management practices in accordance with the general permit.

Full Breakdown

The Department of Environmental Quality runs the MPDES stormwater program under the Montana Water Quality Act. Rules adopted under MCA 75-5-401(1)(c) let a construction owner or operator discharge stormwater under DEQ's general permit once the department receives a notice of intent and a signed pollution prevention plan requiring best management practices. Municipal separate storm sewer systems and industrial sites obtain their own MPDES general permits. No one may operate a disposal system that discharges into state waters without a current permit under MCA 75-5-605.

Violations & Penalties

Discharging into state waters without a current MPDES permit is unlawful under MCA 75-5-605. DEQ can seek civil penalties up to $25,000 per day under MCA 75-5-631, with each day counting as a separate violation, plus injunctive relief.

Frequently Asked Questions

Do I need a permit for construction stormwater in Montana?
Yes. Under MCA 75-5-401, file a notice of intent and a signed pollution prevention plan with DEQ to discharge under the construction general permit before land-disturbing work begins.
What is the penalty for discharging without a permit?
MCA 75-5-631 allows civil penalties up to $25,000 per day, and each day of violation counts as separate. DEQ may also seek injunctions to stop the discharge.

Sources

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