Water Quality Standards Variances
A water quality standards (WQS) 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 either a specific or multiple dischargers. A WQS variance must meet the federal requirements in 40 CFR Section 131.14 and state requirements in 10 CSR 20-7.031(12). A WQS variance serves as the applicable water quality standard for implementing the National Pollution Discharge Elimination System permit program or when issuing Clean Water Act 401 certifications. Current water quality shall not be adversely affected during the term of the variance.
WQS Variances on Public Notice
None at this time.
Federal and state regulations allow the flexibility to adopt a variance based upon 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 attainment of the designated use and criterion while the actions are being implemented.