Southern New Hampshire Regional Water Project

Design and Construction of the Southern New Hampshire Regional Water Project

The Southern New Hampshire Regional Water (SNHRW) project was conceived as a way to address contamination of private and public water supply wells by methyl tert-butyl ether (MTBE), a gasoline additive that had gotten into the groundwater from leaking underground storage tanks at gas stations. Looking for a long-term regional solution vs. a town-by-town solution, seven towns and cities (Manchester, Derry, Windham, Salem, Atkinson, Hampstead, and Plaistow) in southern New Hampshire banded together using previous MTBE court settlements to form the SNHRW project with support and funding from the New Hampshire Department of Environmental Services (NHDES). Weston & Sampson was asked by NHDES to assess the implementation of a regional water supply project that would connect the existing community water systems and improve access to drinking water for the regional stakeholders.

Initially working for NHDES, and later for individual stakeholders such as the Town of Salem and the Hampstead Area Water Company (HAWC), Weston & Sampson provided a broad range of services under this extremely ambitious project, including water quality assessments, water demand estimations, regional water system hydraulic modeling, and feasibility assessments. These focused the goals of the project for the stakeholders and established design criteria for the construction of the system. We conducted life cycle cost analysis to evaluate the full impact of multiple design decisions to better gauge the long-term viability of each design feature. We designed seven different construction contracts for public bidding including 26,500 linear feet of new 20, 16, and 12-inch diameter water mains, three pressure reducing valve facilities (two with chemical feed systems), a booster pump station with chemical feed systems, and assisted with the conversion of HAWC’s water disinfection process from chlorine to chloramines by upgrading nine well stations. The chloramine conversion allows HAWC’s water system to be compatible with the disinfection strategy of the other regional water supply partners.

The SNHRW project is the single largest water supply initiative ever undertaken in New Hampshire and included the creation and execution of a groundbreaking intermunicipal agreement between the seven regional partners. The project was performed under an aggressive timeline for completion and Weston & Sampson was integral in helping our clients meet that goal. The project could not have become the celebratory success it is without effective communication across all parties involved, which included the New Hampshire Department of Transportation, NHDES, other state agencies, and multiple towns and contractors.

Project attributes:

  • Largest water supply project in New Hampshire history
  • Regional water system hydraulic modeling
  • Upgrades to nine well stations for full system disinfection conversion from chlorine to chloramines
  • Over five miles of new water mains
  • Three pressure reducing valve facilities and a booster pump station
  • Chemical feed systems
  • Seven-community intermunicipal agreement created for the project
  • Significant public interaction and agency coordination


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American Council of Engineering Companies of New Hampshire Engineering Excellence Gold Award and "Overall Winner" 2021

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