The 1972 Clean Water Act required States to develop and implement an antidegradation policy that sets thresholds beyond which additional evaluations of potential water quality impacts are required to obtain a discharge permit and sets additional control requirements. The antidegradation policy is intended to preserve the benefited uses of water bodies that current meet their water quality standards.

Minnesota adopted its first antidegradation policy in 1984 (referred to as “nondegradation policy) which applied to listed Outstanding Value Resources. A revision was made in 1988 which applied the requirements to all waters of the State, any identified requirements for new and expanded discharges. Other States have used a tiered system and apply their antidegradation policy differently to different waters

MPCA has been attempting to revise the Minnesota Nondegradation Policy for several years. Major issue has been how rule will apply to stormwater discharges, because the existing policy was developed to apply to traditional point source discharges.

In September 2012, MPCA released its proposed revision to the State Nondegradation Policy. Under the proposed rule, MPCA will address future nondegradation requirements for stormwater discharges as new permits are issued. For new, reissued, or modified stormwater permits, agency will conduct nondegradation review. This review will include an analysis of prudent and feasible alternatives that avoid and minimize net increases in loading or other causes of degradation. The agency will then select the least degrading prudent and feasible alternatives shall be identified.

Therefore, with the final revision of the Nondegradation Policy, as currently proposed, the requirements for new or expanded stormwater discharges will not be clarified. These requirements will be incorporated into various permits issued in the future.

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