The next phase of paving the Derry Rail Trail will be put off till autumn while the town revamps a portion of the Hood Pond Dam per orders of the New Hampshire Department of Environmental Services (DES).
Michael Fowler, head of Derry’s Department of Public Works, confirmed this week that the DES has changed the hazard classification of the dam.
“The Hood Pond Dam was built years ago,” Fowler said in a phone interview March 31. “It is owned by the Town of Derry, and the DES requires all dam owners to provide updated hydraulic classifications to determine whether the dam can meet the standard of passing 2.5 times the flow of a 100-year storm.”
While the dam endured four “100-year-storms” in the past 15 years, the standard has changed and the dam is required to resist 2.5 times the flow of such a storm, Fowler said.
Fowler emphasized that nothing has changed with the dam, and there is no imminent threat of failure.
“We’ve had four 100-year-storms and the dam has held up fine,” he said.
But the last time the calculations were done was in 1991, and it was time for an update, according to Fowler.
“Some of the regulations have changed since then, and what used to be okay has been updated,” Fowler said.
Approval of the dam plan will affect the paving of the Derry Rail Trail, Fowler said. The Rail Trail was scheduled to have another 1,800 feet paved this summer, from Hood Park to North High Street, to bring it closer to the Londonderry line, but “that is not in the cards,” Fowler said.
At the time the paving was authorized, it looked like a relatively simple job, Fowler said.
However, he said, new plans call for paving the section of the trail concurrently with the dam work, which will most likely take place this fall.
Fowler further detailed the project in a press release, stating, “The Town of Derry will be contracting with a consulting engineer to provide NHDES with a proposed dam modification plan. Once approved, the Town of Derry will seek to proceed with construction within the time frames allowed by NHDES. The design and approval process may take up to six months to complete. Preliminarily, the dam modification design will likely feature added fill on the northern side of the dam and removal of several feet of fill closest to the parking lot at Hood Park.”
Fowler added that as the work will most likely be scheduled for fall, it will have little effect on summer activities at Hood Park. The park has a public swimming beach and is home to several of Derry’s summer recreation programs. But the work will be done in the fall and on the other side of the pond, Fowler said, away from the area where most recreation takes place.
No impact is expected on the water quality, he said.
In January the Town Council voted to appropriate $125,000 to expand the paved trail. The money was to come from the Land and Building Capital Reserve Fund, with no cost to taxpayers. Paving the last segment, North High Street to the Derry-Londonderry town line, was estimated to cost from $275,000 to $300,000, would involve replacement of a culvert and repairing of a bridge, and dealing with private property owners. The then-Council deemed that Phase II was too expensive at that point. It would also involve the proposed Exit 4A off Interstate 93.
For more information, contact the DPW office at 432-6144.
