Uncanoonuc Lake Dam Rehabilitation

August 22, 2018

Last week the Town had our final walkthrough with Busby, Stantec, and the NH Dam Bureau. Besides final punch list items, the project is complete.

We are asking residents to please stay off the grass until it is fully established - at which point Busby will remove the orange construction fence. 

This is a State regulated Dam structure. We are asking everyone to please keep off the grate. Boaters please use caution, there are underwater structures around the grate that could be damaged. Parents, please keep children from climbing on the grate or throwing things into the structure. We are in the process of ordering signs to put on the grate and we will be monitoring the structure throughout the year. 

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August 2, 2018

This week Busby removed the remaining bypass pipe and backfilled the trench with embankment material up to finish grade. The crew placed all the remaining embankment material, made adjustments to final grade, and shaped the downhill side slopes. The crew started hauling and spreading loam.

During the rain events, Busby covered the entire embankment area with poly sheeting to keep the embankment protected from the rain. 

The crew will continue working to remove all excess materials from the stockyard area. This area, along with all other disturbed areas, will be seeded before the project is complete. Once 4 inches of loam have been spread throughout the embankment, the area will be hydroseeded. The site will remain fenced until vegetation is established. It is very important that residents remain out of the project area for their safety and to allow the grass to grow.

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July 27, 2018

This week Busby completed placing the stone along the shoreline. The Port-a-dam was removed Wednesday and Thursday and the frames were taken off site today. The water level is approximately 10-12 inches below the principle spillway, which is approximately equal to the water elevation after the 1-foot drawdown. As we get more rain events, the lake should return to its natural elevation.

The principle spillway riser was designed with a 2 inch orifice to continually let water flow through the structure. This was a NHDES requirement to protect the health of aquatic species downstream. This means that you will hear running water moving through the structure even when water is not spilling over the top.

Next week, the crew will adjust the embankment to final grade, and shape the downhill side slopes. Once completed, the area will be loamed and hydro seeding is scheduled for the end of the week.

As the crew has time, all excess materials will be removed from the stockyard area and safety fencing removed from around the home below the dam. The safety fencing along the road will remain until vegetation is established. It is very important that residents remain out of the project area for their safety and to allow the grass to grow.

It is our hope that the project will be completed by the end of next week.

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July 23, 2018

Busby is working on placing stone along the shoreline today and tomorrow. The stone will help prevent any erosion of the dam that might result from wave action in the lake. Once the stone has been placed, Busby will work on bringing the water level back up within the work area. The Port-a-dam is scheduled to be removed Wednesday, July 25th. There could be delays as the trucks move in and out of the area to load up the frames. Please allow extra time for traveling along Mountain Base Road. Busby will work to keep traffic moving as efficiently as possible. 

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July 19, 2018

Last week Busby successfully poured the concrete cradle and the forms were removed Wednesday. Busby continued to import and place additional embankment material around the cradle. Placement of lifts embankment material on top of the concrete cradle and outlet pipe could not take place until the concrete reached 75% strength. A concrete cylinder was tested on Friday, however it did not meet the 75% threshold.

On Monday, another concrete cylinder was tested by Contest Consulting and the break was successful (3,230 lbs). Throughout the week Busby worked on bringing up the elevation of the embankment over the concrete cradle and throughout the site. Over the weekend, Busby will be shutting off the dewater pump and allowing water weeping through the Portadam to start filling the work area. They will maintain the water level at the invert of the 12” low-level intake pipe while they continue working.

Next week, Busby is hopeful that they will be able to place stone material at the shoreline on Monday and Tuesday so that the water level can be brought up as they finalize construction. The work area will be filled at a rate no faster than 1 foot per day.

Busby will be paying close attention to the site over the weekend and next week as we are expecting significant rain fall.

It is my hope that by next week I will be able to give you all a date that the Port-a-dam will be removed.

We are in the home stretch of the project and I just want to thank all of you for your patience and cooperation.

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July 9, 2018

Placement of concrete has been scheduled for Monday July 9th at 2:00pm. Redimix and Contest Consulting have both committed to this time. The crew will finish up forming and bracing the forms this morning.
Once the concrete has been poured, Busby will work on the installation of the 12” pipe and valve. Removal of the forms will be done first thing Wednesday morning and backfilling with embankment and sand filter will start and continue until completed.
As Busby moves away from the pipe and precast concrete structures, the remaining area will be sub graded, sand filter trench re-excavated (area of concrete core removal) and sand filter material will be placed and compacted.

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July 2, 2018

Busby completed the riprap apron for the outlet pipe.

This week Busby will install the 30” outlet pipe. The crew is working on excavating a trench from the riser structure to the headwall.

The pipe and riser structure grate were delivered to the site this morning.

The concrete pouring for the pipe cradle will likely take place on Thursday, July 5th or Friday, July 6th.

As a reminder, the crew will be taking Wednesday, July 4th off.

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June 29, 2018

The headwall and riser structure were placed yesterday. Today, the crew started backfilling around the precast concrete headwall up to the pipe cradle elevation.

The crew also installed the remaining rip rap apron at the pipe outlet.

Next week, Busby will install the 30” outlet pipe. The crew will place the rebar for the form work for the concrete pipe cradle. The concrete pouring for the pipe cradle will likely take place on Thursday, July 5th.

Installation of the inlet pipe and valve will be done by the end of the week. Next, Busby will start backfilling around the spillway structure.

The crew will be taking Wednesday, July 4th off.

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June 26, 2018

The Goffstown Department of Public Works announces delivery of the precast structures for the Uncanoonuc Lake Dam rehabilitation project. A crane and large trailer will be present on site the morning of Thursday, June 28th. Alternating one-way traffic and temporary closures will be necessary at times and delays should be expected.

Please contact the Goffstown Engineering office at (603) 497-3617 ext.250 with any questions. 

Able Crane and Scituate Precast will be on site first thing Thursday morning June 28th for installation of the spillway and headwall structures. Since the crane will take some time to set up and knock down, we don’t expect any long delays before 8:00 am. There will be some minor delays as the crane moves in and out of position. When the precast structures are off loaded it will be necessary to close the road for everyone’s safety. We estimate that any closures could be up to 15 minutes long, hopefully shorter. Police and Fire are aware of the temporary road closure. Should an emergency arise, we will open the road as quickly as possible to let emergency vehicles through. Residents should plan extra time on Thursday (June 28th) morning if driving by the site on Mountain Base Road is unavoidable. Flaggers will be positioned at each end of the work area and no unauthorized personnel will be allowed beyond the flaggers until it is safe.

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June 22, 2018

This week Busby completed the excavation of the embankment area and removal of existing concrete core. They excavated the areas for the 30” DI outlet pipe, spillway and headwall structures. During the excavation, all unsuitable material was removed and replaced with new material. During inspections by the NH Dam Bureau and Stantec, it was discovered that the concrete core wall was significantly deteriorated and needed to be completely removed. The wall was removed and was backfilled with embankment material.

Busby prepared the spillway and headwall footing areas for the placement of the concrete structures and started placement and compaction of the embankment material at the north end of the project site.

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Upcoming Schedule:

The morning of Thursday, June 28th a crane and additional trucks will be on site to deliver and place the precast concrete spillway and headwall structures. As we get closer, DPW will send out updates with more specific information on timing. Delays and temporary lane closures should be expected.

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June 19, 2018

The Portadam was unaffected by the storm and work will continue as planned.

June 18, 2018

Last week, Busby started excavation of the embankment area and concrete core wall starting at the north end of the project. Two test pits were excavated along the left embankment that exposed the concrete corewall. The test pits showed that a portion of the existing concrete corewall is essentially crumbling below the design grade line. The Town is working with the NHDES Dam Bureau and Stantec to determine how much of the existing wall needs to be removed.

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While outside of the original scope, the benefit of completely removing the concrete wall is to reduce the possibility of any established seepage pathways. The concrete core wall would be replaced with engineered filter and embankment material founded on an approved subgrade. It also reduces the introduction of another weak zone at the interface of the concrete and filter material.

Upcoming Schedule:

The crew is continuing to remove portions of the concrete core per plan for the outlet pipe. Busby is working to expose an obstruction (appears to be a very large boulder) in the way of the outlet pipe on the lake side of the concrete core.

The precast concrete spillway and headwall structures will be installed within the next week or two. The precast concrete structures will require the use of a crane and large truck, so traffic delays are to be expected. DPW will keep everyone informed as the schedule becomes more definitive.

June 8, 2018

This week, Busby completed the installation of the PortaDam. Busby will now begin pumping water out of the work area. The dewatering will be ongoing (24 hours a day, 7 days a week) throughout construction (at least 6 weeks).

There will be a sight hum of the generator running to power the pumps and Busby personnel will be monitoring the pumps and generator periodically (including over the weekend).

Upcoming Schedule:

Monday - The crew will work on removing any remaining water in the work area.

Tuesday - The crew will likely begin excavation of the existing dam starting on the north end working south. Dump trucks will be entering and exiting the work area daily. Portions of the concrete core will also be removed.

Please be aware the construction area will be fenced off and is off-limits to the public (including residents) for your safety.

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June 1, 2018

This week, Busby started the 1-foot drawdown. The drawdown involved installing a siphon pipe to pump the water out. They had to get creative as they were visited by some curious muskrats who decided to nibble through the siphon pipes. The holes created by the muskrats slowed down the drawdown. Today, Busby worked on switching over to a more rigid material siphon pipe that will hopefully not be chew through as easily.

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Busby started stockpiling materials for the port-a-dam. The A-frame beams and membrane bundles will be installed next week starting Monday. Divers will be used to place sandbags to hold the framing in place. Once the port-a-dam has been installed, Busby will start pumping the water out of the construction area.

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May 29, 2018

The siphon pipes to start the lake draw down are being installed. 

The remainder of the week Busby will be organizing material and delivering by-pass piping, sand bags, demarcation fencing, silt fencing and equipment etc. to the site. The crew will most likely start installing some of the orange fencing along Mountain Base Road to secure the area.

PortaDam is scheduled to deliver temporary coffer dam supplies to the site on Friday (6/1) at which time Busby crew will unload the supplies and stage them on the dam for installation next week.

May 24, 2018

Thank you to everyone who attended our Neighborhood Meeting on May 14th. 

Busby Construction will begin the 1-foot drawdown of the lake on Tuesday, May 29th. The drawdown will take approximately 4-6 days.  

Throughout the duration of the project DPW will post updates here and on our facebook page. If you would like project updates emailed to you directly, email This email address is being protected from spambots. You need JavaScript enabled to view it. and you will be added to the list. 

If you have any questions, please call our office at 497-3617. 

Uncanoonuc Lake Dam

April 23, 2018

The Department of Public Works is moving forward with plans to reconstruct the Uncanoonuc Lake Dam. Busby Construction Co. will be reconstructing the dam and Stantec will perform inspections throughout the construction. The work involved includes installation of a cofferdam system, drawing down of the lake by 1 foot, excavation of the existing concrete core, installation of a new headwall and filter material, installation of the riser, construction of the new embankment, and restoration of site surfaces.

The following is the scheduled date, time and location of the informational meeting.

            Date:    Monday – May 14, 2018 - 5:00 p.m.

            Place:   Uncanoonuc Lake Dam (next to 118 Mountain Base Road)

The public is invited to attend, ask questions and comment. Plans for this project will be available for your viewing at the Department of Public Works, 404 Elm Street.

If you have any questions, please call our office at 497-3617. If you would like to be added to the project update email list, send me a message at This email address is being protected from spambots. You need JavaScript enabled to view it..

Click here to view the Construction Plans.