Wet Weather and Water Quality: The Regulatory Puzzle Keeps Getting More Complicated

Climate change has been a subject of intense discussion for many years. One part of the discussion is the effect on precipitation. EPA notes, 'In recent years, a higher percentage of precipitation in the United States has come in the form of intense single-day events. The prevalence of extreme single-day precipitation events remained fairly steady between 1910 and the 1980s but has risen substantially since then. Nationwide, nine of the top 10 years for extreme one-day precipitation events have occurred since 1996. The occurrence of abnormally high annual precipitation totals (as defined by the National Oceanic and Atmospheric Administration) has also increased.' (USEPA 2024). Moving this into the regulatory context it is important to note that wet weather discharges are often cited as being a cause of (or contributing to) water bodies not attaining water quality standards. Wet weather discharges include municipal separate storm sewer systems (MS4s), combined sewer overflows (CSOs), sanitary sewer overflows (SSOs), increased flows at wastewater treatment plants and nonpoint sources. All of these sources except for nonpoint sources require a National Pollutant Discharge Elimination System (NPDES) permit in order to discharge pollutants. The presentation and accompanying manuscript will summarize the different NPDES program areas addressing wet weather discharges and the complexity inherent in controlling these discharges and how this has led to confusion and variability of implementation across the different states and EPA regional offices. The presentation and manuscript will also discuss options for reducing the burden of these different approaches and the potential for integrating approaches to increase the environmental benefit of controlling wet weather discharges. As noted, all of these regulated sources are impacted by precipitation and it is pretty clear precipitation has changed significantly over the past few decades, however there have been only minimal changes to the regulatory requirements for these sources during that same time. Also, when one looks at the list of sources impacted by precipitation there is very little regulatory coordination. Under the NPDES program, MS4s are required to develop, implement, and enforce storm water management programs designed to reduce the discharge of pollutants from the MS4 to the maximum extent practicable (MEP). Compliance with water quality standards (WQS) is not explicitly required as part of CWA section 402(p)(3) for MS4 discharges. Communities with combined sewer systems, must obtain coverage under an NPDES permit for discharges from the overflow points, and these permits must be written to conform with the CSO Control Policy (see CWA section 402(q)). CSO Permits must include technology-based limits, which under the Policy are the Nine Minimum Controls (NMCs). Unlike MS4s, CSO Permits must also include water quality-based limits if the technology-based limits are not stringent enough to achieve water quality standards (see CWA section 301(b)(1)(c)). Sanitary Sewer Overflows (SSOs) that result in the release of pollutants to waters of the United States are point source discharges. In many states, the discharges from SSOs are considered to be 'prohibited' without any regulatory basis. This is often supported by federal enforcement actions and Consent Decrees that require the 'elimination' of SSOs without any mechanism for achieving the requirement. In 1999, EPA published a draft proposed regulation to provide a strategy for addressing SSOs, but the regulation never went forward. In 2010, EPA published a request for stakeholder input in the Federal Register (see 75 FR 30395) and noted that even 'municipal collection systems that are operated in an exemplary fashion may experience unauthorized discharges under exceptional circumstances'. Despite this longstanding discussion and the recognition SSOs will occur, very few states have developed a strategy for addressing SSOs. During the first twenty years of the NPDES program, the major emphasis for POTWs was to provide treatment to comply with the statutory requirements and compliance deadlines in the CWA. There was very little attention placed on the management of peak flows at POTW treatment plants. EPA issued two draft policies, one in 2003 and one in 2005, addressing treatment of peak flows at POTWs. The 2003 Policy allowed peak flows to be blended and discharged with certain constraints while the 2005 draft Policy deemed the blended discharge as a bypass covered by 40 CFR 122.41(m). Ultimately this led to litigation and was eventually ruled on by the 8th Circuit Court of Appeals. Even after the 8th Circuit ruling, there is little clarity about this issue. More recently, the Biden-Harris Administration released, 'FACT SHEET: Biden-Harris Administration Announces Roadmap for Nature-Based Solutions to Fight Climate Change, Strengthen Communities, and Support Local Economies.' Included in this release there was also the report, 'Opportunities for Accelerating Nature-Based Solutions: A Roadmap for Climate Progress, Thriving Nature, Equity, and Prosperity.' There has been no additional information regarding how to implement these within the current regulatory framework. These unresolved issues and many other requirements under the NPDES program will be explored in detail in the paper and presentation.