1920s-era Amoskeag Dam 1 of 8 in Eversource hydroelectric dealBy MARK HAYWARD
New Hampshire Union Leader
May 29. 2018 3:43AM
A secret passage.
A horizontal dungeon.
Call it what you want, but an underground — rather, an underwater — tunnel exists to take brave souls from one side of Manchester to the other.
And as Eversource prepares to divest itself of its hydroelectric power assets, the utility has been conducting selected tours of the Amoskeag Dam, which is located in the heart of Manchester on the Merrimack River. The tour ends with a trek through the 400-foot tunnel.
The arched passageway is a mere 6 feet high at the crest. One walks on wooden planks, while carefully eyeing the concrete walls, their dampness, the cracks, the drips, and the small stalactite-like structures that form along the arch.
The passage is illuminated by incandescent bulbs whose shine seems beaten back and hemmed in by the darkness.
The dam holds back a 15-foot-deep pool of water.
“Passing through a small concrete tunnel built in the 1920s while hearing the power of the Merrimack River rushing overhead was an experience I won’t forget,” said Mayor Joyce Craig, who took the tour recently. Craig said her grandfather worked for Eversource in the 1920s, when the dam was being built.
William Smagula, Eversource’s vice president for New Hampshire generation, said the dam is made of steel-reinforced concrete, so there is little to worry about while walking through its hollow core.
“There’s a little bit of natural leakage in a concrete structure. It’s natural,” he said.
Last year, Eversource divested itself of its coal-burning power plants. As early as next month, Eversource could complete the $83 million deal involving its eight Eversource hydroelectric dams. In total, they have 65 megawatts of generating capacity.
The Amoskeag is the second-largest dam in the package, behind the Smith Hydro Dam in Berlin with 17 megawatts of energy. Only one of the other dams — Ayers Island Hydro in Bristol — has a tunnel.
“This is a dam that is hollow,” said Smagula. “You can buy different kinds of cars, different kinds of houses. This is a different kind of dam.”
In February, the Federal Energy Regulatory Commission issued a general approval for transfer of assets between Eversource and Hull Street Energy, a Maryland-based private equity company that specializes in energy generation.
The company is now awaiting FERC approval to transfer the licenses of the hydroelectric dams. Eversource spokesman Kaitlyn Woods said that final step could take place next month.
The Amoskeag Hydro facility was placed into service in the early 1920s and involves three turbines. At high water times when all three are spinning, two million gallons of water flow through them every minute. It generates enough electricity to power about 12,000 homes.
According to Manchester Historic Association Director John Clayton, the dam played an essential part in the rescue of the Millyard. In 1936, the Millyard, bankrupt and flood-damaged, seemed destined to be carved into pieces and sold to the highest bidder.
But civic leaders raised $5 million in 1936 to obtain control of the Millyard. Key to their efforts was the agreement of Public Service of New Hampshire to pay $2.25 million for the dam. The utility has owned the dam ever since.