Safeguarding Vital Wastewater Infrastructure

Authors:

  • A. Luck, L. Bendernagel, T. Groninger - Hazen and Sawyer
  • P. Balci, A. Cohn - New York City Department of Environmental Protection
  • V. Rubino - CH2M Hill

The New York City Wastewater Resiliency Plan presents an assessment of the facilities identified as at-risk for flooding, potential costs of future damages, and suggested protective measures.

The New York City Department of Environmental Protection (DEP) owns and operates 7,500 miles of sewers, 96 pumping stations, and 14 wastewater treatment plants that employ advanced biological and chemical processes to treat more than 1.3 billion gallons of wastewater every day. During Hurricane Sandy, multiple feet of storm surge inundated many of the facilities with sea water that damaged pumps and electrical equipment. DEP staff worked around the clock to maintain or restore service and enacted a number of emergency preparedness and response plans prior to the storm to protect its facilities. Those measures prevented much higher costs and significantly longer service disruptions. In total, 10 of the City’s 14 treatment plants, and 42 of the City’s 96 pumping stations, were damaged during Hurricane Sandy and nearly $50 million has already been spent on repairs. When completed, DEP estimates that the immediate damages from Sandy will top $100 million. This event, combined with projected increases in the frequency of extreme future flood events due to climate change, further enforced the need to develop a plan to harden the City’s wastewater infrastructure to reduce the likelihood of damage, service disruptions, and environmental impacts from future surge events.

Since it is difficult to predict when these events will happen and to what degree, DEP developed a detailed risk assessment framework, including evaluations of vulnerabilities, likelihoods of failure, impacts of failure, and appropriate mitigation strategies. The protective measures were recommended based on a triple bottom line approach, accounting for feasibility, cost of implementation, value and criticality of equipment being protected, the population and critical facilities in the service areas, and potential impacts on beaches. The findings of this risk assessment were published in the NYC Wastewater Resiliency Plan, which provides valuable insight to guide capital planning and operations modifications which ultimately increase the resiliency of the system.
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STUDY STATUS:The NYC Wastewater Resiliency Plan, initiated in 2011 and expanded after Hurricane Sandy, was based on an asset-by-asset analysis of the risks from storm surge under new 2013 FEMA flood maps at all 14 treatment plants and 96 pumping stations. The plan resulted in the development of a set of recommended design guidelines and cost-effective protective measures tailored to each facility to improve resilience in the face of future flood events. The NYC Wastewater Resiliency Plan was released to the public on October 29, 2013 and puts into action initiatives laid out in Mayor Bloomberg’s A Stronger, More Resilient New York report to mitigate and adapt to a changing climate.?

OBJECTIVE:The objective of this presentation is to walk-through the key components of the risk assessment framework developed for the NYC Wastewater Resiliency Plan, including the climate, vulnerability, and adaptation assessments. The presentation will provide sample case studies on how a triple bottom line analysis was conducted to help prioritize capital projects; walk-through key assumptions and equations used to develop asset estimates, damage costs, implementation estimates, and cost-benefit ratios; discuss lessons learned; and illustrate how other agencies can use this adaptable risk management framework to perform their own assessments, building stronger, more resilient communities against future climate risks.?

For more information, please contact the author at aluck@hazenandsawyer.com.

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Horizons Fall 2017 (pdf)

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