Unknown substance in Sunapee Harbor prompts multi-agency response

A large sheen spread across part of Sunapee Harbor Sunday evening, and containment booms closed off a section near 71 Main Street, temporarily blocking some boats and leaving public docks inside the boomed area out of reach. Sunapee Fire Department, state environmental crews and local police moved fast to keep the substance from spreading farther while officials worked to identify what was in the water.

Sunapee Fire was dispatched at 5:16 p.m. after a report of an unknown substance in the harbor. Lieutenant Timothy White was already in the area and arrived on scene at 5:18 p.m., where he confirmed that the sheen covered part of the harbor. Fire personnel then worked with the New Hampshire Department of Environmental Services, the Midwestern New Hampshire Hazardous Materials Team and the Sunapee Police Department to contain the spill and limit its spread through the waterfront.

DES collected samples of the substance and planned testing for the next day to determine both the source and the composition of the spill. Until those results come back, officials do not know what entered the harbor or how far it may have traveled before crews boxed it in. The town said containment booms would remain in place overnight, and boat owners were told not to move, disturb or try to route around them.

The response had immediate effects on harbor use. Some boats were temporarily blocked in, and public docks inside the boomed-off section were not accessible as usual. Crews were expected to return Monday morning to keep monitoring conditions and maintain the containment area, as the town urged cooperation during the busy summer boating season. Questions were directed to the Sunapee Fire Department public information officer as the response moved into the testing and cleanup phase.

The state’s spill-response section, part of the New Hampshire Department of Environmental Services, handles emergency responses to petroleum and hazardous waste spills and operates 24 hours a day, seven days a week. That capability underscores why state help arrived quickly in Sunapee, where even a small release can affect a crowded harbor and the broader waterfront.

Sunapee has dealt with similar incidents before. On May 6, a fuel spill in Georges Mills Harbor was contained, with the launch expected to reopen within an hour and containment left in place for 24 to 48 hours. In October 2025, a Sunapee Harbor oil spill spread into a reported 700-foot-wide slick around several docks and was later described as posing no risk to the town water supply. In June 2023, a spill involving about 70 gallons of fuel oil from the Lake Queen dinner cruise boat created a slick stretching more than 600 feet before crews from Sunapee, New London and Newbury used absorbent booms, pads and a vacuum truck to clean up the water. Those incidents have made clear that Sunapee Harbor remains a tightly watched summer waterfront, where a fast-moving response can quickly determine how much of the harbor stays open.