Summary of Current and Future Wet Weather Regulations in the United States

Since the passage of the Clean Water Act of 1972 (CWA), significant progress has been made in improving the quality of the waters in the United States (US). Over the past 25 years, a significant portion of these efforts focused on reducing pollutants in wet weather discharges, such as combined sewer overflows (CSOs), sanitary sewer overflows (SSOs), and municipal separated storm sewer systems (MS4s), in addition to the reductions in pollutants accomplished from wastewater treatment plants (WWTPs) over the nearly 45 years since the CWA was enacted. The policies and regulations surrounding wet weather discharges are complicated and time consuming to understand. This manuscript provides an overview of the current state of these requirements, as well as offering some thoughts on the futures direction of these requirements. An understanding of wet weather requirements is a key component in being able to effectively and efficiently manage these systems while reducing the adverse impacts of these discharges.The CWA of 1972 and its subsequent amendments is the primary federal law that drives water pollution control activities in the United States, including those targeted towards wet weather discharges. As described in the CWA §101.(a), “The objective of this Act is to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” The CWA sets the lofty goal of completely eliminating the discharge of pollutants into navigable waters, and further stipulates that “the discharge of any pollutant by any person shall be unlawful,” unless the discharge is authorized under a permit in accordance with the CWA. The far-reaching and comprehensive CWA is the enabling statute for all federal wet weather requirements and establishes the goal towards which all wet weather programs must strive—namely, the control of all pollutant discharges into US waters.A number of regulations, policies, and guidance addressing wet weather discharges have been established following the passage of the CWA. This manuscript provides an overview of these regulations, which include the:CSO Control Policy (1994)Stormwater Phase I and Phase II RulesBlending and bypass requirementsSSO requirements, including the proposed SSO rule in 2001In addition to discussing requirements, this manuscript discusses the various enforcement actions that have been undertaken by the United States Environmental Protection Agency (EPA) related primarily to CSO and SSO discharges, but expanding more recently to address discharges from MS4s. The background, current state, and trends in these enforcement actions, such as requirements to consider environmental justice and green infrastructure in alternatives analysis, are discussed.Lastly, this manuscript discusses potential future regulations or regulatory activities that may shape the future of wet weather requirements. Examples include increasing attention being given to enforcement actions against MS4 dischargers, and efforts to increase the affordability of implementing wet weather programs through integrated wastewater and stormwater planning and renegotiation of CSO and SSO consent decrees. Several case studies are presented on how municipalities, both within the US and internationally, have applied unique wet weather planning approaches such as integrated planning to comply with regulatory requirements.