Drone use canceled for stormwater inflow identification project

posted on 5/16/2026; updated 5/21/2026

Drone flights over private property to identify potential areas of stormwater connections into the sanitary sewer system will not occur as previously announced. The city has been made aware and shares privacy concerns related to drone use. The city has instructed the contracted vendor to use other methods to identify areas of stormwater inflow and infiltration (I/I) into the sewer system.

The use of drones for identification work was only a very small part of the overall contract. Instead of using drones, the vendor, Wright-Pierce, will contact property owners to request permission to inspect roof drains and other potential sources of I/I that may be entering the sewer system during storm events without their knowledge. Other work for the project includes maintenance hole inspections, video inspections of more than 60,000 feet of sewer pipe, dye-testing and smoke-testing.

The need to identify and remove stormwater connections from the sewer system remains an ongoing obligation for the city in complying with state and federal permit requirements, as well as ensuring the health of our vital natural resources like the Great Bay Estuary.

When excessive stormwater or groundwater enters the sanitary sewer system during rain events, it strains the wastewater treatment facility operations. Since 2000, the city has been working to identify and correct inflow and infiltration into the system.

The greatest flow-reductions have been by reducing illegal, direct connections into the sewer system, known as the “inflow” of the I/I acronym. These include roof drains, catch basins, and residential sump pumps. “Infiltration” is the other part of the acronym which refers to water seeping through cracked pipes, broken maintenance holes, or utility cover access hatch openings.

A comprehensive follow-up I/I flow study in 2019 identified areas of high-flow inputs in various sub-drainage sheds of the sanitary sewer system, including in and around Bellamy Road, Knox Marsh Road, and Mount Vernon Street. This remains the focus of the vendor's contracted work.

For more information, contact Community Services at 603-516-6450.

Original Post on May 16, 2026:

City to use drone to identify areas of stormwater inflow/infiltration into sewer system

As part of an ongoing effort to reduce stormwater flow into the sanitary sewer system, the city will be working with consultant Wright-Pierce to fly a drone over areas of the city to help identify potential direct connections to the wastewater collection system. Common sources include roof drains on flat roofs and roof gutters. The Wright-Pierce drone operator is a federally-licensed operator.

Weather and conditions permitting, the drone flyover is anticipated to occur Wednesday, May 20 through Friday, May 22.

The camera-equipped drone is expected to remain over any individual rooftop for no more than 5 to 10 minutes, depending on roof size, before moving on. Wright-Pierce is the contractor. Wright-Pierce is also doing video camera work of the sewer system in the Broadway area.

The city will be evaluating three areas for this phase of the drone flyover: Bellamy Road/Old Littleworth Road, the Broadway neighborhood, and the Mount Vernon/Grove/Maple neighborhood.

• View maps of the flyover area

For more information, contact Community Services at 603-516-6450.