Summary Update - 5/20/2025

Summary of NH DES Update on Dolloff Dam – Spring 2025:

• Pawtuckaway Lake is now full, and the sinkhole at Dolloff Dam has not grown since it was first noticed in the spring.
• Leakage has stabilized, but monitoring continues twice weekly along with real-time sensor data.
• There's concern about ongoing minor sediment loss, which could affect the dam's integrity over time. This issue is being closely watched and will require remediation.
• Diving inspections are scheduled for next week, and test borings are planned for later this summer to better understand the sinkhole and develop a potential solution.
• A larger rehabilitation of the dam will likely be needed in the future to address broader safety concerns.
• The removal of Burnhams Marsh Dike is complete, and the area has been restored to its natural state.
• If the sinkhole worsens or dam stability is threatened, lake levels may be lowered again as a precaution. Stakeholders will be notified promptly if this occurs.
• The situation will be discussed further at the Pawtuckaway Lake Improvement Association meeting on June 14 at 9:30 AM at the State Park Pavilion.

Dolloff Dam Update - 4/9/2025

The New Hampshire Dam Bureau has made significant progress addressing concerns at Dolloff Dam following the discovery of a sinkhole. Since the last update, key measures have been completed, including lowering the lake by over 5 feet, installing around-the-clock monitoring equipment, patching concrete voids, and beginning a cautious refill of the lake.

As the lake is slowly refilled, engineers are closely monitoring for any signs of increased sinkhole activity or structural instability. If conditions worsen, water levels will be lowered again to reduce risk. Upcoming actions include a dive inspection, drilling for potential repairs, and continued data analysis to guide future decisions.

Public safety remains a top priority, and residents are urged to avoid approaching the dam area. Regular updates will be provided as the situation evolves.

Notice - 3/20/2025

The NH Department of Environmental Services (NHDES) has identified a sinkhole on the crest of Dolloff Dam at Pawtuckaway Lake. To address potential risks, NHDES will lower the lake level over 1-2 weeks and conduct concrete repairs, which will take about a week. Further investigation is required to assess structural stability before refilling the lake. If risks persist, the water level may remain lower than usual. NHDES is collaborating with an engineering consultant for further analysis.

For questions, please contact NHDES.