Wright-Pierce’s 2025 Calendar Series highlights projects featured in our yearly calendar. This month we take a look at the Wastewater Treatment Facility (WWTF) Phase III and Pump Station Upgrade project in Merrimack, NH.
WWTF Upgrade Overview
The Town of Merrimack, New Hampshire, owns, operates, and maintains a five-mgd WWTF, nine pump stations, and a compost facility. These facilities are integral for the conveyance and treatment of flow from a variety of commercial, residential, and industrial sources. The WWTF Phase III and Pump Station Upgrade project was developed to address three key goals: replace equipment well beyond its useful and recommended life, address safety concerns, and address code-related deficiencies.
The project, led by Project Managers Kattie Hartwell and Dave Cockburn and Lead Project Engineer Anna Smith, includes comprehensive upgrades to Thornton Ferry, Souhegan, and Main Pump Stations, and the construction of a new screenings building at the WWTF.
Additionally, the project included modifications to the headworks building, including roof replacement, and renovations to the locker room, restroom, laboratory, and offices. Furthermore, the project entails modifications to sludge storage tanks, the replacement of the return-activated sludge (RAS) pumping system, the replacement of one primary and three secondary clarifier mechanisms, and the upgrade of the compost facility ventilation system. Finally, Wright-Pierce will install new emergency generators, along with other electrical upgrades throughout the facility.
About the Photo
Project Manager Dave Cockburn captured the included image of the new screenings building at the WWTF. The screenings building houses a new climber-style mechanical bar screen with 3/8” bar spacing, a screenings washpress, and a roll-off container in the garage area for disposal.
When asked what made the picture calendar-worthy, Dave said, “The screenings building was the only new building on the project and acts as a nice showcase for an overall successful project.”
Project Impact
Since the original construction of the WWTF in Merrimack, the facility has relied on a channel-mounted comminutor ahead of the influent pumps to provide some protection for downstream equipment and to reduce the potential clogging of the influent pumps. To minimize costly and labor-intensive maintenance issues related to pump clogging and tank cleaning, the design included a new influent screenings facility as a key component of the project. The new facility provides better protection for the new influent pumps and downstream equipment and will reduce the cleaning required to remove rags from structures and equipment throughout the facility (especially the sludge holding tanks).
Contact us to learn more about the project or how we can provide similar services to your community, or if you’d like a copy of Wright-Pierce’s 2025 wall calendar.