Under Section 316(a) of the CWA, thermal effluent, such as cooling water , is considered a pollutant, and facilities wishing to discharge thermal effluent into a water source must apply for a NPDES permit. CWA Section 316(a) allows a thermal discharger to obtain a thermal effluent variance by demonstrating that less stringent thermal effluent limitations would still protect aquatic life. To receive a Section 316(a) variance, a discharger must demonstrate to the appropriate regulatory agency that alternative thermal limits will not cause significant harm to the aquatic life in the receiving waters. The effort required to make this case varies greatly, depending on state requirements and the site-specific potential for impacts. In nearly all cases, however, the demonstration involves extensive evaluation of potential impacts and characterization of local aquatic populations. A regulatory agency can reject a demonstration or ask the discharger to study certain issues in more detail. A permit applicant may apply for a variance from otherwise applicable thermal discharge limitations.
It is this type of thermal variance request that was the subject of the permit amendment before the Vermont Supreme Court. The Court’s decision supports the view that State water quality standards apply even under a Section 316(a) thermal variance process. States may impose thermal effluent requirements stricter than would be required under the federal CWA Section 316(a) standard alone. However, the court also held that States may also waive those requirements, and held that Vermont had properly done so.
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