Durham, New Hampshire is home to the University of New Hampshire (UNH) and a bustling community with shops, restaurants, and several outdoor amenities. The Town is responsible for the water and sewer systems that serve both UNH and the Town, operating and maintaining over 21 miles of separate sanitary sewers ranging in size from 8” to 30” in diameter. All wastewater flow is conveyed by gravity to the 7.4 MGD Dover Road Pump Station and then through a 3,000’, 18” asbestos cement force main that traverses wetlands and private property, then runs along the Oyster River before discharging to the 2.5 MGD treatment facility.

The force main, which dated back to 1967, had the highest criticality rating of all Town pipelines due to the absence of any redundant pipe. In addition, the force main was not accessible by maintenance vehicles because of its location along Oyster River, within a marshy tideland area with poor soil conditions and high-water table. Based on a thorough evaluation of the force main, it was determined that a failure could be catastrophic, potentially impairing the river water quality. Due to its criticality, age, material, and inaccessibility, replacement of the existing force main was the recommended course of action.

With comprehensive foresight and close collaboration among public and private stakeholders, (which included the UNH, NHDOT and NHDES, Town of Durham, and a private developer) a cost saving, forward-thinking infrastructure upgrade project evolved which reaped broader benefits than originally anticipated. Following significant geotechnical evaluations, realignment alternative analyses, and extensive environmental permitting, a joint-trench design was adopted. This innovative design accommodated both a new force main and a new water main. The Town reaped substantial cost savings by constructing both utility upgrades simultaneously, gained improved accessibility and reliability for the most critical sewer pipeline within the Town’s wastewater collection system, and upgraded important water infrastructure resulting in the Town being well-positioned for future developments. This project’s success was accomplished by a team of stakeholders with a big-picture approach based on forward thinking, supported by engineering technical expertise, and empowered by close collaboration. 

Wright-Pierce was the recipient of a 2021 Engineering Excellence Honor Award from American Council of Engineering Companies (ACEC), New Hampshire Chapter, for our role in this project. Watch the video below to see the project evolution and contact us today to learn more.