The Best Solution to Combined Sewer Overflow May be the Sustainable One

During a bad storm in the Detroit area in August, an estimated 4.5 billion gallons of sewage entered the water supply when the combined sewer systems overflowed. Such overflows can pose a risk to human health and aquatic life as they send chemicals and untreated sewage straight into the nearest body of water.

epa diagram

This diagram from the EPA shows how combined sewer systems can overflow during heavy rain

Traditionally, local governments and regulatory agencies have favored “gray infrastructure,” which includes sewer separation, storage tunnels, and additional treatment units. However, the cost of building an infrastructure with sufficient capacity to avoid CSO’s during unusually large storm events can exceed the point of commensurate benefits, such as the amount of risk reduction expected over a certain period.

Permeable pavement, which allows water to reach the ground beneath

As an alternative approach, the EPA is starting to encourage “green infrastructure” — methods such as constructed wetlands, rainwater harvesting, and pervious or porous pavements — to provide a wider range of benefits to the community and the environment. Green infrastructure can also help air pollution, energy use, habitat connectivity, and even the economy.

The recent NRC report Sustainability Concepts in Decision-Making examines scientific tools and approaches for incorporating sustainability concepts into assessments used to support EPA decision making. Committee Chair Mike Kavanaugh explains, “As discussed in the committee’s report, consideration of the benefits of green infrastructure as part of CSO control planning for the long-term is one of many ways in which EPA and other government agencies can incorporate sustainability concepts into decision-making.”

Further explore sustainability with these reports from the National Research Council. All are free to download.

Sustainability Concepts in Decision-Making: Tools and Approaches for the US Environmental Protection Agency

In its current strategic plan, the U.S. Environmental Protection Agency (EPA) describes a cross-agency strategy to advance sustainable environmental outcomes and optimize economic and social outcomes through Agency decisions and actions. Sustainability has evolved from an aspiration to a growing body of practices. The evolution includes a transition from the development of broad goals toward the implementation of specific policies and programs for achieving them and the use of indicators and …


Sustainability and the U.S. EPA

Sustainability is based on a simple and long-recognized factual premise: Everything that humans require for their survival and well-being depends, directly or indirectly, on the natural environment. The environment provides the air we breathe, the water we drink, and the food we eat.

Recognizing the importance of sustainability to its work, the U.S. Environmental Protection Agency (EPA) has been working to create programs and applications in a variety of areas to better incorporate …


Science for Environmental Protection: The Road Ahead

In anticipation of future environmental science and engineering challenges and technologic advances, EPA asked the National Research Council (NRC) to assess the overall capabilities of the agency to develop, obtain, and use the best available scientific and technologic information and tools to meet persistent, emerging, and future mission challenges and opportunities. Although the committee cannot predict with certainty what new environmental problems EPA will face in the next 10 years or …


Sustainability for the Nation: Resource Connection and Governance Linkages

A “sustainable society,” according to one definition, “is one that can persist over generations; one that is far-seeing enough, flexible enough, and wise enough not to undermine either its physical or its social system of support.” As the government sector works hard to ensure sufficient fresh water, food, energy, housing, health, and education for the nation without limiting resources for the future generations, it’s clear that there is no sufficient organization to deal with sustainability …


Science and Decisions: Advancing Risk Assessment

Risk assessment has become a dominant public policy tool for making choices, based on limited resources, to protect public health and the environment. It has been instrumental to the mission of the U.S. Environmental Protection Agency (EPA) as well as other federal agencies in evaluating public health concerns, informing regulatory and technological decisions, prioritizing research needs and funding, and in developing approaches for cost-benefit analysis.

However, risk assessment is …