The US EPA Multi-sector General Permit promulgated in 2008 (“MSGP-2008”) includes antidegradation requirements that apply to new and/or expanded discharges of stormwater from regulated industrial sites.
[What is an Antidegradation Policy?]
Regulation of discharges is based on three categories of waters:
Tier 2 Waters – Tier 2 waters are characterized as having water quality that exceeds the levels necessary to support propagation of fish, shellfish, and wildlife and recreation in and on the water.
Tier 2.5 Waters – For antidegradation purposes, Tier 2.5 waters are those waters designated by States or Tribes as neither Tier 2 nor Tier 3. States have special requirements for these waters. These waters are given a level of protection equal to and above that given to Tier 2 waters, but less than that given Tier 3 waters.
Tier 3 Waters – For antidegradation purposes, Tier 3 waters are identified by states as having high quality waters constituting an Outstanding Natural Resource Water (ONRW), such as waters of National Parks and State Parks, wildlife refuges, and waters of exceptional recreational or ecological significance.
Regardless of these general descriptions, the water bodies regulated under each tier must be LISTED by US EPA. The list of effected waters can change overtime. Currently, the States with listed waters include:
Tier 2 or 2.5: Massachusetts, New Hampshire, District of Columbia, Minnesota
Tier 3: New Hampshire, Puerto Rico, Minnesota, Wisconsin, New Mexico
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