Special Waters and Impaired Waters
NPDES/SDS permits for construction sites near specially-protected and impaired waters require additional controls, conditions or an individual permit:
- Sites that discharge near waters with qualities that warrant extra protection (special waters) must use additional best management practices and enhanced runoff controls.
- Sites within one mile (aerial radius measurement) of and that discharge to a water impaired for phosphorus, turbidity, dissolved oxygen, and biotic impairment, must meet special conditions (Appendix A, Section B.10). There are no additional requirements for waters impaired for other pollutants.
- Sites that discharge to calcareous fens, need a letter of approval from the Department of Natural Resources.
The MPCA has several documents and an interactive map called Special Waters Search to help project planners identify those waters near their site that may require extra protections or an individual permit. The specific requirements are outlined in the General Stormwater Permit.