While the Northeast is not plagued with the severe drought conditions the West Coast is experiencing, communities across the country are being pressed to consider resiliency in the face of widespread climate change impacts. Building off the concept of mutual aid, one of Massachusetts’ largest cities spearheaded a regional interconnectivity study to determine if neighboring water districts could provide each other with additional supply during periods of critical need.
The communities involved in the Regional Emergency Water System Interconnectivity Analysis, including Fall River, Somerset, Swansea, and Dighton, cover 86 square miles. Each distinctly different community presents unique challenges in emergency scenarios, but the analysis seeks to identify possible opportunities for interconnections and support.
Fall River is situated in southern Massachusetts at the mouth of the Taunton River. The city’s water division supplies approximately 100,000 residents, sourcing water from North Watuppa Pond, and sells drinking water to neighboring Tiverton, Westport, and Freetown. Fall River also has two emergency water supplies: the Copicut Reservoir and the South Watuppa Pond.
Across the Taunton River sits the town of Somerset, with a year-round population of approximately 18,100. Drinking water for the community is sourced from a combination of groundwater and surface water supplies. The town’s water supply is recharged by rainfall and flow from the Labor in Vain Brook, which is susceptible to dryer than average weather. Somerset also serves as an emergency water supply for Swansea.
Swansea’s population of nearly 17,000 is served by three water treatment plants with source water derived from 12 wells (two are currently inactive). The well water is supplemented by a desalination facility that converts saltwater from the Palmer River into fresh, potable water. Swansea’s water supply is extremely susceptible to drought.
The town of Dighton, north of Somerset, is home to a much smaller population of approximately 8,000. The Dighton Water District provides potable water to its residents from five active gravel-packed wells with connections to Somerset and Taunton’s distribution system for extreme emergencies. The well supply, however, is insufficient for the community’s current and projected demand.
With communities already struggling with capital improvements and maintenance programs, we brought our funding team in at the start of this project to identify financial opportunities for the municipalities involved. One state source we have worked with frequently since its establishment in 2017 is the Massachusetts Municipal Vulnerability Preparedness (MVP) grant program designed to assist with planning for climate change resiliency and implementing priority projects. The grants are awarded to communities seeking to conduct vulnerability assessments and develop action-oriented resiliency plans, which aligned with Fall River’s intention for the analysis. We worked with our clients to submit a grant application and secure MVP funds with a community match to execute the study. The study was focused on how the communities could work together to provide water in a drought scenario, as well as considerations for the future.
The communities hired Woodard & Curran to:
The study assessed existing interconnections and the possibility of future interconnections in areas where water infrastructure from neighboring communities were within proximity to each other. Of the three existing interconnections, two interconnections were in adequate condition to be brought into service. Our team assisted Fall River and Somerset in conducting pressure tests to confirm the condition of the subaqueous interconnection between the two communities under the Taunton River. The pressure testing found that the subaqueous main, constructed in the 1950s, maintained integrity and could be used in the future. Woodard & Curran recommended some optimization of valves, hydrants, and metering if the communities wanted to bring the interconnection back into more regular use. There are isolated gravity pit connections from Somerset and Swansea’s distribution system and from Dighton to Somerset. These buried, unmetered connections have valves on either system’s piping to control the gravity flow. The isolated gravity pit between Somerset and Swansea was used last in 2021 and deemed still functional. However, the isolated gravity pit between Dighton and Somerset is nonfunctional.
Sharing water resources between the communities is limited by both water treatment capacity and demand, as well as water quality. The analysis took the average and maximum daily demand to determine the excess water available in each community. This process helped determine that Fall River has the largest excess capacity – between 14 to 16 million gallons per day (MGD), which could provide the total maximum daily demands for the other three communities combined. With approximately 2 to 3 MGD of remaining supply in Somerset, the town could receive or supply emergency water. Dighton and Swansea, on the other hand, treat little to no excess water, which means these communities could not provide backup water resources to the neighboring towns.
Woodard & Curran developed a regional hydraulic model to assess the conditions at each existing interconnection and identify potential new points of interconnection. Utilizing hydraulic modeling software, the team combined hydraulic models from each system into one combined system with average and maximum demands for analysis. The team worked with the communities to troubleshoot things such as with execution of flow testing. Most of the flow test results from the field matched the predictive computer modeling, however, field testing identified two potential interconnections between Somerset and Swansea where the hydraulic model likely underestimated the flow in some locations. The modeling tools allowed the team to create different scenarios to assess and model regional supply assistance based on water supply emergencies in each community. This process helped the team identify five potential new interconnection locations based on proximity to existing mains, pipe diameters, and water sources. Each potential connection identified would provide the greatest flow between the communities by gravity or pumping depending on the direction of flow.
The project team further evaluated two interconnections, providing conceptual designs that would improve piped interconnections from Swansea to Somerset and Fall River to Somerset. For Swansea and Somerset to provide supplemental and emergency water, a new 8-inch gravity-driven interconnection was designed. This would allow Somerset to supply all of Swansea’s water demand if a well pump failed, or contamination occurred. In an emergency, the interconnection would also help Swansea maintain tank levels.
The existing subaqueous 12-inch steel water main connecting Fall River and Somerset’s water distribution systems under the Taunton River has maintained integrity and is functional. Modeling and preliminary testing show that Fall River could supply water to Somerset in an emergency for at least 36 hours under maximum demand conditions. Somerset could also supply Fall River for a few hours, but would require a pump to push flow in the opposite direction.
The communities all utilize slightly different treatment with differing finished water quality. An initial evaluation of water quality indicated that this would be the biggest challenge in providing water aid to neighboring communities. The team also recommended further assessing water compatibility across the individual systems, including a detailed corrosion control, disinfection byproduct, and solubility study. In emergency cases, the risk of blending water sources could be acceptable over a short period of time. However, for continuous sharing of water resources, it poses risks such as exceeding lead and copper action levels, increased levels of disinfection byproduct, and scaling. The aforementioned studies would help the communities understand the differences and treatment changes necessary to achieve a similar water chemistry and reduce risk in sharing water resources.
In addition to providing a final report to the clients, Woodard & Curran supported the communities in developing a public-facing website to communicate the benefits of sharing resources. While the four municipalities are currently meeting the domestic water needs of their residents and businesses, this study helps prepare for potential water shortages in the future. The website helps explain to the public how this regional support works, the findings of the analysis, and potential impacts. The team also produced an animation to simulate flow conditions assessed using the regional hydraulic model under various emergency conditions and an educational video on the benefits of intermunicipal support. The website also provides water conservation and drought fact sheets to inform the public about water preservation and scarcity.