Catwalk Pix and Other Shots Highlight Dam Construction Progress

Freedom—September 22, 2020—The following is the latest report on the dam construction by Tim Otterbach.

1. New catwalk and drop block beams installed, looking upstream from the new dam. The catwalk is accessed by the stairs on the right, which are adjacent to the new headhouse. There will be a total of 224 drop blocks, which can be lowered into the beams to provide a temporary dam when the steel gates require servicing. This backup feature is similar to the drop block design utilized in the old dam. When not in place, the drop blocks are stored in the north section of the headhouse. When installed, the drop blocks are manually lowered into the channels of the steel beams by two people using poles.

2. This is the view looking across the top of the catwalk from the new headhouse. The catwalk installation is in progress, and once the catwalk baseplate welding is complete, the decking (walking surface) will be installed. The catwalk and the access stairs are bolted together, and they look like a giant erector set! The final step will be to install all the railings not already in place. The railings on the upstream side of the catwalk are removable to facilitate the installation of the drop blocks, when required.

3. View of the gate in the lowered position from the catwalk. Grouting of the end plate recesses, seen at the end of the gate, will occur next week. The next time the gates will be raised will be with the hydraulic actuators, one seen in the foreground.

4. Looking into the headhouse from the catwalk, where the drop blocks will be stored. The left side of the headhouse, which is separated by an interior partition, houses the emergency generator and associated equipment. The generator will provide power to the hydraulic pump, as well as to the gate end plate heaters to prevent ice buildup on the ends of the gates during winter, restricting movement of the gates when required.

 

5. Looking upstream towards the dam, showing both gates in the lowered position and the relationship of the catwalk to the headhouse. The electrical conduit and the hydraulic lines, to be installed, will run along the downstream side of the catwalk supplying power to the heaters and hydraulics to the gate actuators. The fill in the foreground will be removed, and the large rip-rap stones placed downstream from the dam base once access for construction equipment is no longer required.

6. Looking downstream from the dam, at the dry riverbed. It won’t look like this much longer.

7. View of the west gate and headhouse, and the propane tank platform to the left. Once the catwalk installation is completed, the actuators will be connected to the gates and, utilizing the hydraulic equipment in the headhouse, the gate operation will be tested.

 

8. View of the west facade of the headhouse. The roof work was completed during this visit. An additional stairway will be installed on the right side of the Headhouse to access the Generator Room. The two utility masts (conduits) will receive the data lines (left) and power lines (right) from service on the street. The area around the foundation of the headhouse will receive loam and  be seeded with grass to prevent any erosion from rainwater runoff.


9. Upstream view of the new dam and the old dam, to the right, from the east side. Again, the fill material upstream from the base of the new dam will be removed following the demolition of the old dam after access for construction equipment is no longer required. Large rip-rap stone will also be placed at this location. Temporary large sand bags will be placed upstream from the old dam to allow safe access during its demolition, then removed.

10. A close-up photo of the west wingwall adjacent to, and upstream from, the headhouse, showing the dam graphics donated by the concrete contractor. It reads: BERRY BAY  2020! This was formed and cast into the concrete wall.

 

11. Upstream view looking back at the old dam and the new dam. The large sandbags, similar to those in the foreground will be utilized to temporarily hold back the lake waters from the old dam during its demolition. The area to the left of the east wingwall, with the low concrete wall extending to the left, will be the overflow spillway for water runoff during an extreme storm event. The grade on both north and south side of the low wall will receive erosion mats to prevent any erosion of the soil in this area when water runs over this overflow spillway. The excess water will flow past the end of the dam and will be channeled back into the downstream river bed, flowing over large rip-rap stones.

 

12. Looking downstream at the spillway from the existing west headhouse, showing the very small amount of water flowing out of the lake and bays.

Only one control gate is currently slightly open. We are currently experiencing a drought condition in approximately 70% of the state, and lake levels, including on Ossipee Lake, are lower than normal and continue to drop. Some boaters may have difficulties hauling out their boats this fall, given the low water levels on certain bodies of water.

My next visit to the site will most likely occur after the new dam work has been completed and the demolition of the old dam is underway. A brief mention is in order for the great work being performed by Charter Construction and their project team and subcontractors!

Timothy Otterbach is an Ossipee resident and a member of the Ossipee Lake Alliance board of directors.

3 Comments

  1. Richard Lover 2 months ago September 23, 2020

    These pictures and the descriptions are just the very best for people who really do not get to see the actual project itself. Thank you so much, stay safe, stay socially distant and let’s all get through the coming winter season healthy and be able to get back on the big lake in the Spring.

    REPLY
  2. EDMUND Corcoran 2 months ago September 23, 2020

    Thanks again, great up date. just a thought, any chance of a video of the gates moving when they test them?

    REPLY
  3. Bill Winter 2 months ago September 23, 2020

    Great job on the update.
    Thank you

    REPLY

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