Assessing the Vulnerability of a Wastewater Treatment Facility to Anticipated Climate Change Impacts

This presentation will describe the funding mechanism obtained for the assessment, the strategy employed for assessing the vulnerability of the WWTP and the recommended solutions from the assessment to increase the resilience of the facility. Wastewater treatment facilities are often sited in locations which give them high exposure to negative impacts of climate change. Understanding the potential impacts of that exposure to maintaining operations is a critical part of ensuring a reliable and dependable service to the public Located near the mouth of the Merrimack River, in northeast Massachusetts, the City of Newburyport's WWTP provides secondary treatment to domestic and commercial wastewater flow generated within the City and treats approximately 3.5 million gallons per day (MGD) of raw sewage.  The WWTP also lies within the current FEMA annual flood plain, making it vulnerable to flooding from significant precipitation events and storm surge. Given the its location, the City had significant concerns about the WWTP's exposure to anticipated climate change and sea level rise impacts, and potential impacts on the operations of the facility. During a king tide in 2019, water had encroached onto the WWTP site and the City urgently proceeded with an assessment of the vulnerability to the WWTP in the short and long term. Funding Massachusetts office of Coastal Zone Management (CZM) oversees a program of Municipal Vulnerability Preparedness (MVP) Grants to support municipalities to build resilience to climate change. Dewberry worked closely with the City to prepare a grant application for the MVP program for an assessment of the WWTP climate change exposure. The City was fortunate to be awarded $160,000 in June 2019 for the effort.
Vulnerability Assessment Strategy The strategy employed will be detailed during the presentation in the following phases of the vulnerability assessment:
SITE - A comprehensive program of data collection was undertaken to make sure that the available information necessary and useful to the assessment was gathered and presented in a beneficial manner. We created a GIS geodatabase of the site using this information which was used to track water intrusion. The database now allows the City to manage its assets for operations and maintenance.
RISK – We developed a climate risk assessment comparison tool to measure the effects of stressors including sea level rise, coastal storm surge, increased precipitation, wind intensity and increased heat. Data sources used to inform this assessment also included Massachusetts Climate Change Municipal Vulnerability, FEMA, NOAA and NOAA Hurricane Center, and National Weather Services.
FACILITY – Impact assessments were performed for critical components such as electrical power systems, headworks, influent wet well, influent pumps, clarifiers, aeration system, sludge pumping, disinfection system, effluent pumping, and structures. A loss of any of these systems would reduce or halt operations. This set of information allowed us to identify the intersection between the critical components of the WWTP and the anticipated impacts of climate change on the site. Assessment of this intersection allowed understanding of the key needs for protection and led to development of solutions to support protection.
Development of Recommended Solutions With a balanced focus on nature based and engineered solutions, a series of solutions were developed to provide the protection determined to be necessary for different climate change scenarios. These solutions included deployable barrier walls, green infrastructure, back check valves on drainage outfalls, submersible pumps and emergency effluent pumps; coastal Berm with recreation path, flood walls, stormwater pumping station on WWTP property, tide check valves on outfalls (sewer and storm). The proposed solutions were then presented to City leadership to support proposed investment for ensuring continuity of operations. This presentation is an excellent primer for those seeking to learn more about assessing climate change vulnerability risks, the types of solutions that can be applied to mitigate the risks, and a framework for selecting the most appropriate solutions. This approach can be applied to WWTPs and other critical infrastructure.