No through traffic on Route 127 in Hopkinton while dam is upgraded

  • Construction worker Dave Parris controls the flow of traffic at the intersection of Mechanic and Mascoma Streets in Lebanon, N.H., on Tuesday, June 5, 2018. Nearby businesses Dairy Twirl and Phnom Penh Sandwich Station have seen a decrease in customers around lunchtime due to the construction. (Valley News - August Frank) Copyright Valley News. May not be reprinted or used online without permission. Send requests to August Frank

Monitor staff
Published: 8/13/2018 11:41:16 PM

Upgrading a small hydropower dam in Hopkinton will give drivers something of a headache through the fall.

A portion of Route 127, Maple Street, will be closed to through traffic starting Monday, Aug. 20, for about 10 weeks while an underground tunnel known as a penstock can be dug up and replaced, said the state Department of Transportation.

The road will be closed just east of the Rowell Covered Bridge. The generation station is near where Maple Street makes a sharp turn away from the bridge; the penstock goes underneath the road and back into the river.

There’s no easy way for traffic to get around this site while work is going on, probably through the end of October.

The Department of Transportation will set up a detour that uses Interstate 89 and U.S. Route 202. Route 127 will still be accessible from both sides, but you won’t be able to drive through.

During this period, the 1-megawatt power plant that uses the penstock will get an upgrade, said Kristin Kelly, director of communications for Green Mountain Power, which bought the plant last year.

“We bought it knowing that it would need an upgrade,” Kelly said. “The generating facility has two turbines which combined have 1 megawatt. One of those turbines, 0.4 megawatts, has been operational, but the other hasn’t been operating for some period of time. It needs a tune-up, which we will do while it is offline.”

The dam in question is a small, run-of-the-river dam located downstream, or north, of a large flood-control dam owned and operated by the U.S. Army Corps of Engineers. It diverts water north into a canal alongside Maple Street that goes underneath the road through the penstock and turns the generators in a small power plant. The water then flows east through a canal and re-enters the river.

Vermont-based Green Mountain Power owns more than 30 small- to medium-sized hydropower dams, including 14 that it bought last year as part of its effort to use non-fossil-fuel-based electricity supplies.

In New Hampshire, it also owns dams in Manchester, Rollinsford, Somersworth, Claremont, West Lebanon and Woodsville, Kelly said.

(David Brooks can be reached at 369-3313 or or on Twitter @GraniteGeek.)

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