Water Quality-Based Effluent Limitations (WQBELs)
Water quality-based effluent limitations are calculated in order to insure that discharges to waters of the state are in compliance with water quality standards. Water quality standards include water quality criteria (such as those in chs. NR 102 , 104 , and 105 , Wis. Adm. Code), use designations or classifications of the state's waters (examples include fish and aquatic life uses, public water supplies, recreational uses, outstanding or exceptional resource waters), and antidegradation provisions to address new or increased discharges to waters of the state. All of these standards are considered together in order to protect Wisconsin’s aquatic life, wildlife and human health from the effects associated with the discharge of toxic (poisonous) and organoleptic (adverse impacts on sensory organs) substances to the state's surface waters.
Water quality-based effluent limitations may take the forms of limits on specific pollutants, calculated to make sure the discharges are in compliance with criteria for a particular use designation after mixing with an appropriate streamflow rate or dilution factor in a lake. These limitations are normally expressed as a concentration (such as milligrams or micrograms per liter), a mass (pounds or grams per day), or both, or in other units as appropriate for parameters such as temperature or pH. Limitations may also take the form of a regulation on combinations of pollutants, otherwise known as whole effluent toxicity, when it is necessary to insure that the combination of pollutants do not violate water quality standards.
Chapter NR 106 , Wis. Adm. Code, addresses how to calculate water quality-based effluent limitations, and also includes the procedures for determining when it is necessary to include those limitations in permits for discharges to rivers, lakes, drainageways, wetlands or other surface waters in the state of Wisconsin.