The mystery of the noises and rumbles coming from the Portsmouth Naval Shipyard has been solved.

Members of the public Facebook group Portsmouth NH posted about an "intense" noise coming from the Shipyard several nights.

"Most of the time it doesn’t disturb me, but for a while there was distressing pulsating drone sound that really made it hard to sleep," Dixie McLean wrote.

"The other morning around 4 a.m. it sounded like incredibly loud fog horns, do they still use those? Scary sounds to wake up to," Kyle Reilly wrote.

The noise is being created by a stepped up schedule on two dry docks as part of the Navy’s $1.7 billion Shipyard Infrastructure Optimization Program.

"Portsmouth Naval Shipyard is constructing once-in-a-century investments to reconfigure, modernize and optimize the shipyard’s industrial infrastructure. There are multiple construction projects on-going from utility improvements, waterfront support facilities, production consolidation facilities, dry-dock caissons, and the Multi-Mission Dry Dock," Congressional and Public Affairs Officer Danna Eddy told Seacoast Current.

Eddy said the work on the two dry docks has been extended to around-the-clock shift work for the next few weeks.

"During this time, the same noises heard during the day, which consist of drilling and pile installation, will extend periodically into the overnight hours," Eddy said. "We apologize for the impact this may have on our surrounding neighbors."

The two new Dry Docks are being built over the next seven years. They are intended to provide service for Virginia-class attack submarines to support future submarine maintenance workload at Portsmouth Naval Shipyard.

Contact reporter Dan Alexander at or via Twitter @DanAlexanderNH

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