NYC Wastewater Resiliency Plan: Climate Risk Assessment and Adaptation Study
Posted byKathryn Braddock
The New York City Department of Environmental Protection (DEP) owns and operates one of the largest waste- water collection and treatment systems in the world, with 14 wastewater treatment plants and 96 pumping stations that convey stormwater and wastewater. The City’s wastewater treatment plants (WWTP) utilize advanced biological and chemical processes to treat on average 1.3 billion gallons of wastewater per day, using state-of-the-art technology that removes between 85 and 95 percent of pollutants before discharging the treated water into the city’s waterways. During wet weather, these treatment plants can disinfect two times their dry weather capacity. This immense system protects the environment and the health of more than eight million New Yorkers, and DEP is committed to ensuring its continued performance and reliability.
Many of the City’s wastewater treatment plants and pumping stations are low-lying and necessarily located close to the waterfront in order to discharge treated wastewater and for efficient sludge handling. This waterfront dependency creates challenges that were plainly evident when a number of facilities experienced extensive damage during Hurricane Sandy. Flooding risk is likely to increase over time, as climate change brings more extreme storm surge events and continued sea level rise in the next several decades.
As such, DEP has taken a proactive stance in assessing its infrastructure risks and setting forth a framework to implement protective measures. Since 2008, DEP has been investigating the impacts of climate change on its infrastructure, not only for wastewater facilities, but also for drinking water supply and stormwater management.
Building upon previous studies, this climate risk assessment and adaptation study sets forth cost-effective strategies for reducing flooding damage to wastewater infrastructure and safeguarding public health and the environment. This comprehensive study examined buildings and infrastructure at DEP’s 96 pumping stations and 14 wastewater treatment plants, identifying and prioritizing infrastructure that is most at risk of flood damage. Through the study, DEP developed a set of recommended design standards and cost-effective protective measures tailored to each facility to improve resiliency in the face of future flood events.
The study produced a number of key results: All 14 wastewater treatment plants and 60 percent of pumping stations (58 out of 96) are at risk of flood damage. The study estimates that equipment valued at more than $1 billion is at risk and requires additional protection. It is unlikely that this high damage cost would be incurred during a single storm surge event, as flood heights tend to vary across New York City depending on storm characteristics; however, some at-risk equipment may incur repetitive damage from multiple storm surge events over time. Considering the entire range of surge heights up to and including the 100-year flood with 30 inches of sea level rise, the cumulative damages over the next 50 years may exceed $2 billion if no protective measures are put in place.
The recommended protective measures, totaling $315 million in improvements, are costly but critical. Increased resiliency not only reduces damage to DEP’s assets, but also enables rapid recovery of full service to the community following a flood event, reduces risk of sewer backup into homes, and reduces the likelihood of the release of un- treated sewage into the environment. DEP will prioritize these measures as part of planned capital projects and with an eye toward other proposals for engineered barriers or wetlands as part of the broader coastal protection initiatives described in A Stronger, More Resilient New York.