Montana SWPPP inspection requirements
- Rain trigger
- 0.25″ storm event
- Post-rain deadline
- Within 24 hours
- Routine inspections
- Every 7 or 14 days
- Permit
- MTR100000 Construction General Permit
- Agency
- Montana Department of Environmental Quality (MT DEQ)
How Montana handles construction stormwater
Construction sites in Montana disturbing one acre or more need coverage under the MTR100000 Construction General Permit, administered by Montana Department of Environmental Quality. MTR100000 is effective January 1, 2023 – December 31, 2027. Choose weekly inspections with no storm trigger, or every 14 days plus within 24 hours of the end of a 0.25″ rainfall (and within 24 hours of any snowmelt runoff).
Inspector qualifications
Inspections must be performed by a certified SWPPP Administrator (DEQ-recognized course; 3-year certification).
Official sources
Common questions
What triggers a SWPPP inspection in Montana?
Under the MTR100000 Construction General Permit, a storm event of 0.25 inches or more triggers a post-storm inspection, within 24 hours (non-work days typically extend to the next work day; check your permit). Routine inspections: every 7 or 14 days.
Who can perform SWPPP inspections in Montana?
Inspections must be performed by a certified SWPPP Administrator (DEQ-recognized course; 3-year certification).
Who administers the construction stormwater program in Montana?
Montana Department of Environmental Quality (MT DEQ) administers the NPDES construction stormwater program in Montana under the MTR100000 Construction General Permit.
What are the penalties for SWPPP violations in Montana?
Federal Clean Water Act civil penalties can reach $68,445 per day per violation, and MT DEQ can issue administrative orders and state penalties on top. Missing rain-triggered inspections is among the most commonly cited violations in stormwater audits.
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