Water Quality Standards
Antidegradation requirements are consistent with 40 Code of Federal Regulation 131.12 that outlines methods used to assess activities that may impact the integrity of a water and protect existing uses. This policy may compel the state to maintain a level of water quality above those mandated by criteria.
Antidegradation language in Missouri's rules are available on the Secretary of State's website at http://s1.sos.mo.gov/cmsimages/adrules/csr/current/10csr/10c20-7.pdf, page 12, beginning middle of right-hand column. This rule references the May 7, 2008, Missouri Antidegradation Rule and Implementation Procedure.
Missouri Tiers in Summary:
Tier 1 - 10
For waters that just maintain a level of water quality that protect public health and existing in-stream water uses there will be no impairment or loss of existing uses.
Tier 2 - 10
For waters that maintain a level of water quality better than applicable water quality criteria. Existing levels of water quality shall be fully maintained and protected unless lowered water quality is necessary to allow important economic and social development in the area.
Tier 3 - 10
There shall be no lowering of water quality in outstanding state or national resource waters as designated in Tables D and E.