In this month’s edition of Wright-Pierce’s 2025 Calendar Series, we look at the Influent Screw Pump Project in Concord, NH.
Project Overview
Influent screw pumps play an important role in wastewater treatment, helping to move raw wastewater to the head of the treatment process. To help the City of Concord optimize the performance of its screw pumps, Wright-Pierce provided engineering design, bidding, and construction-phase services to replace Screw Pump 1C.
The Concord Hall Street Wastewater Treatment Facility (WWTF) was originally designed to treat an average flow of 10.1 million gallons per day (mgd) and a peak hourly flow of 24.8 mgd. Incoming flows are directed to a shared concrete influent wet well, and the facility used three manually operated cast-iron sluice gates to control flow between three screw pump channels. The existing pumps consisted of Pump 1A (Lakeside, 72-inch diameter, c. 2010), Pump 1B (Epic, 58-inch diameter, c. 2017), and Pump 1C (FMC, 72-inch diameter, c. 1979). Although Pumps 1A and 1C were a similar size with a conveyance capacity of 12.5 mgd, Pump 1C was operating at about 40 to 50% less capacity than its original condition due to flight deformation and wear as well as grout degradation.
After visiting the site and evaluating the pumps, concrete channel, grout clearances, and related infrastructure, we recommended a full replacement of Pump 1C. At the beginning of construction, the City also encountered a failure of parts of Screw Pump 1A. Wright-Pierce provided responsive support to identify an immediate solution as well as a plan for temporary emergency bypass pumping to be implemented until repairs were successfully completed. The project also included select concrete repairs, replacing the cast-iron isolation gate and its hardware, and removing and reinstalling the influent pump station fiberglass enclosure.
About the Photo
Senior Project Manager Michael Theriault, PE, managed this project and shared a few thoughts about the work represented in this month’s calendar photo: “Wright-Pierce provided immediate engineering support for the evaluation and fast-tracked design of the existing screw pump, working in close collaboration with the City of Concord given the critical nature of the influent screw pump to the Hall Street Wastewater Treatment Facility’s influent pumping capacity. Wright-Pierce, the City of Concord, and Northeast Earth Mechanics worked closely together to expedite construction and minimize downtime of Pump 1C, as well as pivoting as needed to provide a remedy and an emergency bypass pumping solution for Pump 1A amidst construction. The installation of the 52-foot-long, 72-inch-diameter Archimedes-type screw required careful coordination and planning during construction to retrofit the pump into its existing concrete channel.”
Project Impact
Making sure all screw pumps are working as intended is essential for the wastewater treatment process. If a pump isn’t functioning properly, it can affect how wastewater is conveyed, which can impact the entire treatment system. Replacing Pump 1C and repairing Pump 1A restored the conveyance capacity at the Hall Street Wastewater Treatment Facility, allowing the City to maintain sustainable and reliable treatment to influent flows.
Contact us today if you’d like to learn more about the project or our wastewater or general engineering services.
Wright-Pierce’s Jason Gallant entering the influent trough for structural inspection.