Supreme Court decision will make much more work for NPDES permit writers and others trying to protect water quality.

As a result of the recent Supreme Court decision in City and County of San Francisco v. EPA, (March 4, 2025) it is clear that U.S. EPA cannot require that permits regarding discharges from combined sewer overflows (CSOs) contain a provision stating that the permittee may not discharge so as to "cause or contribute" to a violation of water quality standards in the receiving water. This holding directly affects numerous CSO permits in many cities across the country. It may also affect non-CSO permits with "cause or contribute" limits. 

Read broadly, the Supreme Court decision may hold that National Pollutant Discharge Elimination System permit writers may not write limits that forbid a result in the receiving water (e.g. thou shall not kill aquatic life, raise the water temperature more that 3 degrees F or render the receiving water unsuitable for swimming or drinking) but must instead spell out specific numeric effluent limits that prevent violations of water quality standards (e.g thou shall not discharge concentrations of ammonia at a concentration greater than .5 mg/L, discharge at temperatures greater than 99 degrees F in March or discharge more than X.0 level of pathogens) or must spell out specific best management practices (e.g. thou shall clean the facility once a month or thou shall not place dirt within 50 feet of a stream bank). Justice Alito wrote that if permit writers did this it would be more clear for dischargers. By writing the permits with such specific requirements, permit writers could assure that water quality would not be harmed by the Court's holding. (easy for him to say).