A discharger-specific variance is a time-limited designated use and water quality criterion that provides a less stringent pollutant target for a permitted discharge where it is not economically feasible to meet an effluent limitation based on the water quality standards. Each variance includes:

• A comprehensive alternatives analysis that demonstrates the most cost-effective alternative capable of achieving the effluent limitation derived from the water quality standards would result in substantial and widespread economic and social impacts;
• An interim effluent limitation that represents the greatest pollutant reduction achievable given the circumstances; and
• A pollutant minimization plan.

Each variance is pollutant- and waterbody-specific and reflects the highest attainable condition in the receiving water for a set period of time. All proposed variances require formal rulemaking to amend Wyoming’s Surface Water Quality Standards (Chapter 1, Wyoming Water Quality Rules). Once adopted, each variance must be reviewed at least once every five years. 

The document “Options to Modify Water Quality Standards”, available in the Standards Resources and Guidance tab above, describes considerations for when a discharger-specific variance may be appropriate. For more information contact Eric Hargett (eric.hargett@wyo.gov) or 307-777-7079.