Section 250-RICR-150-05-1.20 - Antidegradation of Water Quality StandardsA. Purpose - The State Antidegradation Regulations are based on the federal Antidegradation Policy requirements, Antidegradation Policy and Implementation Methods, 40 C.F.R. § 131.12 and have as their objective the maintenance and protection of various levels of surface water quality and uses. Antidegradation applies to all projects or activities subject to these regulations which will likely lower water quality or affect existing or designated water uses, including but not limited to all Water Quality Certification reviews and any new or modified RIPDES permits. For the disposal of dredged or fill material into the waters of the State, Guidelines for Specification of Disposal Sites for Dredged or Fill Material, 40 C.F.R. § 404(b)(1), incorporated above in § 1.3(C) of this Part, guidelines shall be followed in the evaluation of 40 C.F.R. § 131.12(a)(1), incorporated above in § 1.3(F) of this Part, and the State's Antidegradation Policy. The Antidegradation regulations consist of four (4) tiers of water quality protection.B. Tier 1 - Protection of Existing Uses - Any existing in situ water uses and level of surface water quality necessary to protect the existing uses, shall be maintained and protected.C. Tier 2 - Protection of Water Quality in High Quality Waters - With the exception of Outstanding National Resource Waters, in surface waters where the existing water quality exceeds levels necessary to support propagation of fish and wildlife and recreation in and on the water, that quality shall be maintained and protected, except for insignificant changes in water quality as determined by the Director and in accordance with § 1.27 of this Part. An exception to this level of protection may only be allowed if it can be proven to the Director by a preponderance of clear and scientifically valid evidence having a probative value, and the Director finds, after full satisfaction of the intergovernmental coordination and public participation provisions of the RI Continuing Planning Process, that allowing significant water quality degradation is necessary to accommodate important economic and social benefit in the area in which the receiving waters are located. In allowing such significant degradation or lower water quality, the Director shall assure water quality adequate to fully protect existing and designated uses. In allowing a change in water quality, significant or insignificant, all reasonable measures to minimize the change shall be implemented. Adequate scientifically valid documentation shall be provided to the Director demonstrating that designated and existing uses, water quality to protect those uses, and all applicable water quality standards, will be fully protected. Further, the highest statutory and regulating requirements for all new and existing point sources and all cost-effective and reasonable best management practices for nonpoint source control shall apply.D. Tier 21/2 - Protection of Water Quality for SRPWs - Where high quality waters constitute a SRPW, there shall be no measurable degradation of the existing water quality necessary to protect the characteristic(s) which cause the waterbody to be designated as an SRPW. Notwithstanding that all public drinking water supplies are SRPWs, public drinking water suppliers may undertake temporary and short term activities within the boundary perimeter of a public drinking water supply impoundment for essential maintenance or to address emergency conditions in order to prevent adverse effects on public health or safety, provided that these activities comply with the requirements set forth in § 1.20(B) of this Part (Tier 1 Protection of Existing Uses) and § 1.20(C) of this Part (Tier 2 Protection of Water Quality in High Quality Waters).E. Tier 3 - Protection of Water Quality for ONRWs - Where high quality waters constitute an Outstanding National Resource, as defined in § 1.7 of this Part, that water quality shall be maintained and protected. The State may allow some limited activities that result in temporary and short-term changes in the water quality of an ONRW. Such activities must not permanently degrade water quality or result in water quality lower than that necessary to protect the existing uses in the ONRW.F. Implementation - The Antidegradation provisions shall be implemented in accordance with the Antidegradation Implementation Policy § 1.27 of this Part.250 R.I. Code R. 250-RICR-150-05-1.20
Amended effective 12/28/2023