MPCA Industrial Stormwater Permit - Draft Antidegradation Requirements

On December 18, 2008, the Minnesota Pollution Control Agency (MPCA) released a redraft of the Multisector Industrial General Permit (MSGP) currently being written. Similar to previous drafts, this version is incomplete. [Read about previous draft of MPCA permit]

One of the important elements of this draft is the proposed antidegradation requirements for stormwater [Read further information on Antidegradation Policies].

Two overall categories are presented to determine potential antidegradation policy status:

All waters of State (Statewide). Any facility that requires an NPDES permit for stormwater discharge AND after January 1, 1988 increased the area of industrial activities by more than 91 acres (by expansion or new construction) must implement specific additional stormwater controls listed in the permit. As currently drafted, this requirement appears to apply retroactively, meaning that a facility that expanded by more than 91 acres anytime after January 1, 1988 could be required to retrofit stormwater controls to meet the new requirements.

Sites Near “Special Waters”. This requirement applies to facilities located within 1-mile of listed special waters, including Lake Superior, upper Mississippi River, lake trout lakes and other outstanding resource value waters. This requirement, as currently drafted, applies to all facilities within 1-mile of these waters, regardless of a “new or expanded” discharge. Facilities currently permitted and in compliance with the MPCA general permit would need to meet all permit requirements, including the listed additional stormwater controls. These permittees could be required to retrofit existing stormwater controls to meet the new requirements.


The MPCA MSGP is a work in progress; revisions and additions to the permit continue to be made. Once a draft is completed, the permit will be issued for public comment. Because of the size and complexity of the draft permit (especially compared to the current permit, written in 1997), it is expected that there will be significant public comments.

Caltha LLP provides expert technical support to Minnesota facilities subject to stormwater permitting requirements. [More information on Minnesota Stormwater and SWPPP Services]

For further information, contact Caltha LLP at:
Email: info@calthacompany.com
Phone: (763) 208-6430
Website: www.calthacompany.com

Two Minnesota offices - Minneapolis and Pine River