UPDATES TO OCTOBER 31, 2019
The work accomplished since the last update has been impressive.
About half of the dam is now complete:
Excavated area behind the north wing wall has been partially backfilled
The control infrastructure and gate control mechanism for the sluiceway is installed
Rip rap, large irregular stones, was permanently installed below the north section of the dam and at the foot of the sluiceway
A new bypass was installed in the coffer dam that allows the flow to be diverted through the sluiceway during the completion of the south wing wall and southern section of the dam
Next steps include extension of the coffer dam to properties at the south side of the pond. This will then allow removal of the bypass that was installed at the beginning of the project. Excavation for the south wing wall footing and the wall can then proceed. The riverbed will be cleared of the materials used for the earlier phase of dam construction.
The project team at Perras has recovered the original timetable that had been delayed at the early stages by unanticipated issues. Project onsite manager expects that the essential work will be complete by the planned date. That will leave minor items and site remediation to be done in spring 2020.
Update to October 11, 2019
Progress on building the new dam includes lots of steel and concrete
The sluiceway walls are formed, poured and await installation of the control gate later in the project
Footings for the spillways are excavated, rebar structure and forms built, concrete poured
Preparations have begun to change the location of the outflow to enable construction of the south wing wall and completion of the spillway
The next couple of weeks will include some significant shifts in the layout of the project: the conduits that have carried the river around the construction site will be moved so that water flows through the sluiceway. This step also includes the placement of stone ‘rip rap’ at the foot of the north sections of the completed spillway that will remain as a permanent feature of the project. Backfill of the excavation behind the north wing wall will also be taking place. The coming onset of winter weather is on the mind of the project manager who is confident the major work can be completed before winter arrives to stay.
UPDATE TO AUGUST 24, 2019
The Slurry Wall is setting up!
Uncontrollable underflow below the dam structure in the old dam was a constant problem.
For the Mountain View dam project, a slurry wall is a key design element included to minimize the potential for water to flow under the new dam.
The below-grade slurry wall, using bentonite, cement, and slag will restrict flow of groundwater, support excavation, and prepare the site for new concrete work and associated earthwork to build the new dam.
The start of excavation of the trench and pumping the slurry started on Thursday morning, August 22. The process is scheduled to be complete during the week of August 26.
For the Mountain View Dam project a vertical slurry wall was specified. This slurry wall is a hydraulic barrier, that when complete, will be three feet wide, 33 feet deep and will be under the more than 120 foot length of the dam. This video show the equipment beginning the digging of the 33 foot deep trench on the northeast footings for the wing walls of the dam will tie into the slurry wall at both ends. The forms for the concrete dam will be built on top of the slurry wall. Finishing the concrete phase of the dam and removal of the coffer dam is targeted to be complete by mid-December 2019, with some landscaping work to be done in the spring of 2020 on the northern edge of the dam site.