The two dams at Breivatn will be modified over the course of 2019 and 2020. The water level must be adjusted for the work, but will not significantly deviate from normal levels.
Breivatn dam consists of a rock-fill dam and a concrete dam. The dams were built in 1958 and the failure consequence class of both is class 3, which is the second highest class for dams. The dams will now be rehabilitated to meet the requirements of the current Regulations governing the safety and supervision of watercourse structures.
What will be done?
For the rock-fill dam, block stone will be used to clad the downstream face, crest and upper part of the upstream face. A seepage measurement system will also be established at the base of the dam. Rock for the dam construction will be taken from inside the reservoir. A boat ramp will be constructed here when the project is concluded.
The concrete dam will be partially filled with concrete and a gate will be installed. The gravity dams on either side of the spillway will be clad in concrete on the upstream face and top. The small windows on the downstream face will be replaced and metal cladding will be added to the pillars at the base of the dam.
Start-up in March 2019
Skanska Norge is the main contractor and will start rigging at the dam in March 2019. The work itself will start with extraction of rock to be used in the rock-fill dam. Since the rock will be extracted from inside the reservoir, the contractor is dependent on a low water level, which is normally the case in spring.
The concrete work on the end sections of the gravity dam will then commence. The concreting work inside the concrete dam must be carried out when the water level is high. This is planned after the summer holiday in 2019.
Most of the work will be carried out in 2019. Some minor remaining work will be carried out in the course of the spring/summer 2020. This work relates to the gate to be installed in the concrete dam and de-rigging of equipment and facilities used during the construction period.
Minor adjustment of water level
The highest regulated water level (HRV) at Breivatn is 749 metres above sea level and the lowest regulated water level (LRV) is 723 metres above sea level. The water level will stay within these regulated levels during the construction period. The HRV and LRV will remain unchanged after the work has been concluded.
During the construction period, the water level will be adjusted to the work being carried out, but not to the extent that it will significantly deviate from normal levels.
The water level will be kept low until the end of May 2019, and will then be raised to around 735 metres above sea level. From mid-July, the water level will be gradually raised. When the concreting work inside the dam is close to completion in late autumn 2019, the water level will be approaching HRV.
Before the snow melts in spring 2020, the water level will be kept low for a period in connection with the installation of the new gate in the concrete dam.