This part and parts 7050.0250 to 7050.0335 establish the antidegradation standards and implementation procedures for surface waters of the state in the Lake Superior basin. For the purposes of this part and parts 7052.0310 to 7052.0330, lowering of water quality means a new or expanded point source discharge of a BSIC to an outstanding international resource water, or a new or expanded point or nonpoint source discharge, for which there is a control document, of a BCC to a high quality water. The antidegradation standards established in this part and parts 7050.0250 to 7050.0335 for surface waters of the state in the Lake Superior basin apply as follows:
new and expanded point source discharges of BSICs to waters designated as outstanding international resource waters (OIRWs) under subpart 3; and
new and expanded point and nonpoint source discharges of BCCs to waters designated as high quality waters under subpart 4.
For discharges of BCCs directly to ORVWs or upstream of ORVWs in the Lake Superior basin, the actions or activities that may trigger an antidegradation demonstration are listed in part 7052.0310, subpart 4, and actions or activities that are exempt from antidegradation requirements are listed in part 7052.0310, subpart 5.
Parts 7050.0250 to 7050.0335 also apply to the discharge of pollutants to class 7 waters, except that any new or expanded discharge to a class 7 water upstream of an OIRW or a high quality water must meet the requirements of parts 7052.0310 to 7052.0330 as necessary to ensure compliance with the standards established in subparts 3 and 4.
Existing water uses under parts 7050.0250 to 7050.0335 and the level of water quality necessary to protect existing uses must be maintained and protected. Where designated uses of the water body are impaired, there must be no lowering of the water quality with respect to the GLI pollutants causing the impairment.
All surface waters of the state in the Lake Superior basin, other than class 7 waters and designated ORVWs as described in parts 7050.0460 and 7050.0470, are designated as OIRWs. Any new or expanding point source discharge of a BSIC to an OIRW must comply with the implementation requirements of part 7052.0310 and the demonstration requirements of part 7052.0320, subparts 2 and 3.
Where, for any individual BCC, the water quality of an OIRW is better than the quality necessary to support the propagation of fish, shellfish, and wildlife and recreation in and on the water, that water shall be considered high quality for that BCC and the quality must be maintained and protected under the implementation and demonstration requirements of parts 7052.0310 and 7052.0320. On a pollutant-specific basis, the agency shall allow a lowering of water quality if it determines the lowering of water quality is necessary to accommodate important economic or social development in the area in which the water is located, in accordance with part 7052.0310, subpart 3. If a lowering of water quality is allowed, existing and designated uses must be fully protected.
The agency's antidegradation determination associated with a potential lowering of water quality due to a thermal discharge must be consistent with section 316 of the Clean Water Act, United States Code, title 33, section 1326.
22 SR 1466; 41 SR 545
November 29, 2017