Mill Falls dam replacement will cost $6-$8 million through grant, private funds

MEREDITH — The Lake Waukewan Dam, which runs through Mill Falls Marketplace and its hotel and its adjacent waterfall, needs vital repairs.

The dam is owned by Hampshire Hospitality Holdings, which was purchased, in 2019, by Procaccianti Companies. Vice President Ralph Izzi Jr. said repairs are expected to cost between $6 million and $8 million, to be paid for privately, and through a grant.

Project Engineer John Lavigne, of The Turner Group, said the project will be completed in three phases, by 2029.

Words from the owners

Representatives of the Turner Group, hired by Hampshire Hospitality Holdings to engineer the project, gave a presentation to the selectboard July 27, to walk the public through the issues, and how they will tend to them.

Izzi was not present, but wrote in an email before the meeting his team has been working with the Dam Bureau since it issued a letter of deficiency in May 2021.

Repairs relate to the system of pipes, tanks and waterways that convey water from Lake Waukewan to Lake Winnipesaukee.

“The current equipment dates back many years and upgrades are needed to keep the system functioning as intended,” Izzi wrote in an email July 24. “Some interim measures are already in place to stabilize the system and facilitate the reconstruction work.”

The project is supported by a cost-sharing grant through the Federal Emergency Management Agency, and the town is also participating as an administrator of the funds, he said. The town is not obligated to pay toward the project.

The expected cost is a projection until a contractor is hired.

“The total project will cost something on the order of six to eight million dollars, though precise costs will not be known until the project goes out for contractor bids later this summer and into the fall,” Izzi wrote.

Background

Lavigne has been involved since 2021, and gave the presentation to explain what is going wrong, what needs to be fixed, the schedule, and how it will affect the area.

He said July 27 that most people think of a dam as something with a pond, embankment, and a spillway, with water heading into a stream. This is not the case here.

“This is different,” Lavigne said. “This is a channel that has been fed by the lake. Historically, the water was used for old hydropower in the mills, the millworks. All the components were designed and put around the fact of delivering power to the mill.”

Over the years, this has become the major outlet of the lake, Lavigne said. The original outlet that existed about 100 years ago has been filled.

“A big aspect about looking at these facilities is not what we have to do to repair them today, but how can we enlarge them, and make them big enough to take the spillway design required today,” Lavigne said.

Lavigne said more rain and snow have made it so flood discharges for dams are increasing. The whole system can only control 5 or 6 feet of the lake itself, and the rest is below grade. He said they can only control the lake to the depth of the channel seen at the intake, and noted the lake is much deeper.

Lavigne said water comes off the lake and a channel moves it down to the parking lot by High Street. The channel has stone walls on either side.

Lavigne showed a picture of Frog Rock Tavern on Main Street, as well as a pedestrian bridge, and said as a temporary measure, there were two iron trash racks installed at both spots. One problem, he said, is all the debris that ends up in Lake Waukewan finds its way into the canal, and plugs up the pipe. Dam owners routinely have divers go in and pull material out.

Part of the permanent solution is installing a concrete structure with better racks which are easier to maintain.

Lavigne said underneath that area currently is a 6x6-foot concrete box culvert built in the 1930s. Since it has always been underwater, divers inspecting it have found it in good condition.

“This is one component of the system that doesn’t have to be changed in order to accommodate the new design floods the state is asking us to accommodate,” Lavigne said.

There is a tricky part. The flow goes across the street, under the property of Hermit Woods Winery & Eatery, at 62 Main St. Lavigne said the penstock piping there is 6 feet in diameter, made with joints that fit neatly but are not waterproof. Lavigne suspects that over the years, there have been leaks.

Just before the pipe goes under the parking lot adjacent to Mill Falls Marketplace, the pipe shrinks from 6 feet to 4 feet. Lavigne said at some point, inspections found the pipe was coming apart, and to prevent that, a 4-foot diameter insert was installed. However, that pipe is now corroding and collapsing.

“So, one of the things we’re going to be doing with this project is take the penstock out of service, and put in a brand new one.”

Lavigne said when talking to town staff, they made it a goal to minimize disruption, and stay on private property. He said Hermit Woods Winery has given continued permission and an easement to continue the penstock piping, and bring it back down on the hotel property.

In the past, there was a gatehouse with a wooden gate that controlled the lake and the amount of water needed to run the old hydropower mill. When engineers looked at this, they found it was all made of wood, and rotted. Divers went down and removed the pieces.

From the gatehouse, the pipe underneath is still 6 feet in diameter, and flows into a concrete surge tank, designed to equalize the water. The tank is leaking and corroding.

“This system is archaic and needs to be replaced,” Lavigne said. “Part of building a brand new tank will be a new control system.”

Another area where things get tricky is the waterfall, which flows down next to Giuseppe's Pizzeria & Ristorante.

He said the waterfall was made of a series of stones embedded, then smeared with a layer of concrete. The channel bottom has eroded, and water can get underneath, into the restaurant. The intention is to reline the channel, remove and replace stones that will be pinned down with dowels. A supporting wall will be built to ensure stability.

The project

The project will be done in three phases, the first two occurring simultaneously to minimize impact. It will start at the bottom in the waterfront, then move on to fixing the flume, then embankment work.

The next step will be taking care of penstock piping. Lavigne said when they are finished installing the new penstock, the old one will not be dug up. Instead, a “flowable fill” of loose concrete, will be pumped in. That will fill the voids and leave it solid underground to ensure there is no leak, and eliminates the need for further excavation.

The gatehouse will also stay in place. The surge tank will be cut down to the level of the parking area, then loaded with flowable fill, and topped with pavement.

The final phase involves going across Main Street and building the new trash rack structure. The plan is to extend a 6x6-foot concrete box with a precast concrete culvert, and use flowable fill on both sides to keep it stable.

Lavigne said 65% of project costs will be covered by the FEMA grant, and the rest by Procaccianti Companies. The project needs to be started and finished as soon as possible, and he expects it to be completed in two to three years.

For the grant, the project will go out to bid in September, and aim to start between Thanksgiving and Christmas this year. Winter construction will take place until the beginning of May, and crews will take the summer off during the area’s busiest months. Crews will return in the fall, after Columbus Day, and finish the first two phases during the winter. The third and final phase of the project is expected to take place in late 2028, into 2029.

Resident Anne Sprague was amazed at what a “huge project” this was, and had question about the aesthetics. She said it is so beautiful right now, and hopes it will be when it's done. Lavigne said all the engineering is underground, and he knows in the end, the project will be judged with how it looks from the outside.

“The goal is to make it look like it is today, or better,” Lavigne said.

Another presentation about the project will take place at the selectboard meeting on Monday, Aug. 10.