Manchester Waterworks staff told the Board on Aug. 28, 2025, that the utility is switching its distribution disinfectant from chloramines to free chlorine to address nitrification and depressed chlorine residuals detected in recent tank and distribution sampling.

Director Mia and operations staff reported that tank samples showed signs of nitrification, including loss of chlorine residual and depressed pH. To remove ammonia (the food source for nitrifying bacteria) and restore normal disinfectant residuals in the distribution system, staff scheduled a temporary switch to free chlorine beginning the Tuesday after the meeting and expected the program to run roughly six weeks, with continued sampling. Staff notified downstream customers, nearby Southern New Hampshire communities, the mayor’s office and the state. The utility cautioned customers that taste and odor changes are normal during the switch and provided a lab phone number for questions: (603) 792‑2855.

Staff updates: The board received a series of operational and capital updates. The city is preparing ARPA‑funded work to increase conveyance to southern communities affected by contamination: improvements at the Cohass Pump Station include upgrading a pump, providing an emergency generator, designing a new pump station on South Willow Street to allow pumping from both low and high systems, and parallel piping on Cohass Avenue. Design qualifications were due the day after the meeting; staff expected to contract an engineer soon and begin construction in the coming year, with a spending deadline tied to ARPA obligations (spend obligation through Oct. 2026).

At the water treatment plant the board heard that two factory‑tested raw water pumps are expected for delivery in September and installation soon after, and one remaining raw water pump remains in production. Filter media sampling for the Greensand filters is being coordinated with a vendor who will perform core sampling and off‑site analysis. Staff also reported a successful DES inspection of a lagoon discharge permit in Hooksett and said they expected a follow‑up letter with recommendations.

Watershed and maintenance: Watershed staff said Lake Massabesic levels were lower than normal but within expected ranges for the season; Tower Hill Pond and other source‑area monitoring continue. The watershed team is preparing invasive plant surveys (to assess milfoil and fanwort) and planned fall brush cutting, culvert work and timber harvests into the fall/winter. Staff also noted continued routine work on pipe breaks and valve boxes and the meter department’s ongoing 10‑year meter testing program.

No formal board action was taken on the disinfectant switch at the meeting; staff described the measure as a maintenance response and noted ongoing sampling and notification efforts.