Construction Stormwater Update 

Winter Season Considerations

Winter Is Here…. Are You Prepared? 

Project’s that extend more than one season or will still be active during winter months need to take special considerations when planning for winter shutdown or an active winter construction season. Consult with your SWPPP Designer to develop a specific winter construction plan and SWPPP. 

The University of Minnesota has prepared short AMA presentations including winter site preparation available here: Ask Me Anything | Erosion and Stormwater Management Certification Program

Common Questions:

1. Can I remove inlet protection over winter?

No, inlet protection needs to remain in place unless a specific safety concern is noted for the inlet protection device location and the SWPPP is amended to note this. Inlet protection needs to be replaced upon snowmelt or prior to a rain event. The contractor may need to remove and replace inlet protection several times throughout a project. 

For example, inlet protection freezing up in a catch basin at a low-lying road sags or intersections with little or no overflow relief is a safety concern.  The SWPPP must be amended to include the reason for removal. Inlet protection within project sites must remain in place.

2. Do I need to continue weekly inspections & maintenance?

Yes, if the construction site is active (including interior and exterior work), all inspections and maintenance continue as normal. Minnesota Department of Transportation (MNDOT) has created helpful Winter Inspections Protocol that breaks down the NDPES CSW General Permit Inspection Requirements during winter months. 

3. When can inspections be reduced?

Only after the site is inactive/shutdown for winter. BMPs should be inspected periodically during the winter months to ensure their function. If inspections are suspended during frozen ground condition, they must resume within 24 hours of runoff occurring on the site or when construction resumes, whichever comes first (CGP Section 11.10).

Regardless of site activity, the permit requires you to continue to inspect BMPs within 24 hours of a rain event over ½ inch in 24 hours or when runoff occurs because of snowmelt conditions.

4. What are acceptable stabilization practices during winter months?

As winter construction progresses, additional stabilization needs cannot be addressed with traditional methods of stabilization. Dormant seeding, mulching on frozen soil or short depths of snow, and placing erosion control blanket using heavy anchors are all acceptable practices during winter months.

Visit MN Stormwater Manual: Winter Practices for additional information.

Owner/Operator Roles & Responsibilities

Project owners are ultimately responsible for ensuring NPDES coverage is obtained and the SWPPP is developed. See below links for additional MPCA information regarding roles and responsibilities. 

MPCA Guidance Document: Owner vs. operator

MPCA Guidance Document: Owner Responsibilities 

Importance of Lot Grading & Drainage

Proper lot grading and drainage play a crucial role in protecting buildings and properties from potential issues caused by stormwater. By shaping the land to properly convey surface water and prevent water accumulation, structure flooding, soil erosion, and basement or foundation damage. 

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Stay Tuned! 

We have made a few modifications to the permit application to make the process easier and are working through some more. We will also be releasing a “Developers Guide to Stormwater Management” in 2025. This document will summarize stormwater, construction, and grading permit requirements and help guide your team with planning for construction and development projects. 

Our Construction Stormwater webpage is the best resource for information specific to Owatonna’s Grading Permit and stormwater management requirements for construction projects. We have recently reorganized, updated, and expanded our guidance documents available for use.