Study Finds 11 Billion Gallons of Sewage Entered Rivers & Bays after Hurricane Sandy
More than six months ago, Hurricane Sandy swept through the mid-Atlantic leaving a path of destruction across New York, New Jersey, and surrounding states. With total damage estimates reaching $70 billion, communities across the region are still recovering from its impacts.
Hurricane Sandy revealed the vulnerability of our infrastructure, and particularly the vulnerability of our water systems, to extreme weather events that will likely become both more frequent and more severe in a changing climate. Since 1948, the number of storms with extreme precipitation has increased by 24 percent. Including Hurricane Sandy, eleven extreme weather events in 2012 [PDF] caused damage exceeding $1 billion.
A new report [PDF] by Climate Central released this month revealed that the combination of heavy precipitation, flooding from storm surges, and power loss during Hurricane Sandy resulted in 11 billion gallons of untreated and partially treated sewage overflowing into rivers, bays, and even city streets. Sewage overflows pose a significant risk to public health and safety. Bacteria, viruses, and parasites common in human waste enter the water during sewage overflows and can cause water-borne illness from contact with polluted water, ingestion of contaminated fish or shellfish, or contaminated drinking water supplies.
Many wastewater treatment plants are built in low-lying areas to take advantage of gravity, allowing wastewater to flow into the plant and treated water to flow back into local waters without significant pumping. While this can make wastewater treatment more efficient, it also places plants located in coastal communities in the front line of impacts from sea level rise, flooding, and storm surges.
While the report focused primarily on sewage overflows related to storm surges, overflows from urban communities with combined sewer systems also contributed to the problem. In a combined sewer system, rainwater that falls onto streets and parking lots flows into the same pipes that carry wastewater to the treatment plant. When too much rain falls, the capacity of the system is overwhelmed and untreated sewage and stormwater are released into local rivers and streams. In fact, here in Washington, DC the city’s combined sewer system was responsible for the sixth-largest overflow from Hurricane Sandy. Over five inches of rain falling in a 24-hour period sent 475 million gallons of raw sewage and polluted runoff into the Anacostia River.
With the vulnerabilities of our water infrastructure so starkly illuminated, there is an opportunity to reduce these catastrophic overflows that pose a threat to human health and the environment. American Rivers’ new report, Getting Climate Smart, offers strategies that communities can use to improve resiliency in the face of a changing climate. For example, evaluating opportunities to “flood-proof” vulnerable wastewater treatment plants, increasing emergency power backups, and integrating green infrastructure to reduce polluted runoff and alleviate stress on treatment systems are different approaches that communities can incorporate to improve their resiliency.
Unfortunately, extreme events like Hurricane Sandy also serve to highlight what is a common problem, although often on a much smaller scale. Combined sewer overflows (CSOs) are not unique to hurricane conditions. Even in places without combined systems, sanitary sewers can overflow due power loss or to blockages or breaks that allow stormwater or groundwater to enter and overwhelm the capacity of the system. Capturing and treating rainwater where it falls can reduce the volume of stormwater that overwhelms treatment systems, leading to overflows. Green infrastructure, such as green roofs or rain gardens, is one approach that communities are beginning to integrate that treats rain as a resource instead of a waste product to better protect clean water and public health.