The goal for water quality standards is protecting water uses through applying criteria. A water quality standards variance is a time-limited designated use and criterion change for a specific pollutant, allowing deviation from meeting a water quality-based effluent limit for dischargers. For information about water quality standards reviews, when the standards are reviewed and, as appropriate, modified and adopted, visit Water Quality Standards Review.
Federal and state regulations allow the flexibility to adopt a variance based on one of the following factors:
- Naturally occurring pollutant concentrations
- Natural, ephemeral, intermittent or low flow conditions
- Human caused conditions cannot be remedied or would cause more environmental damage to correct than to leave in place
- Dams, diversions or other hydrologic modifications
- Physical conditions related to natural features preclude aquatic life uses
- Controls more stringent than needed to meet technology-based limits cause substantial and widespread economic and social impact
- Actions needed to facilitate lake, wetland or stream restoration through dam removal or other significant reconfiguration activities preclude attaining the designated use and criterion while the actions are being implemented
A variance must meet the federal requirements in Code of Federal Regulations 40 C.F.R. § 131.14 and state requirements in Code of State Regulations 10 CSR 20-7.031(12). A variance serves as the applicable water quality criteria for implementing the National Pollution Discharge Elimination System permit program or when issuing Clean Water Act Section 401 Water Quality Certifications. Current water quality must not be adversely affected during the term of the variance.