"I wanted to go to the mountains"
For Julia Geist, summer is no time for sweet idleness: the construction site on the Grimsel is only snow-free for six months of the year, during which time around 100 people work in several shifts to build the new, double-curved arch dam block by block until 2025.
No fear of responsibility
As site foreman, Julia is responsible for materials management - a challenging task on this construction site. It is a special concrete with very high requirements. It contains aggregates of up to 125 mm in diameter and is produced in the site's own concrete plant directly on the installation site at the foot of the wall. It is tested several times a day in the construction site laboratory, which is installed in one of the wall's tunnels.
LET OUR TEAM SHOW YOU AROUND THE CONSTRUCTION SITE!
The material for the concrete production comes from the local area, as Julia emphasizes: "We extract the rock ourselves. At first, we recycled the rock excavated for the dam wall. We now use the material from an old legal landfill site from the last century, which was used for tunnel excavations and power station construction throughout the Grimsel system."
Before the rock can be used for concrete production, several work steps are necessary, which must be coordinated in terms of quality and timing, as Julia emphasizes: "Over the years, all kinds of waste has accumulated in the landfill. We not only remove plastic and wood, we also sometimes find old vehicles. In the search for material for the dam wall, we really clean up here to be able to guarantee a high-quality rock in the end."
The pre-crushed raw material arrives at the gravel plant, where it is further crushed, washed and screened to prepare it for the various aggregate components for the concrete. "We then drive it around 3 km with several trucks in different rotations up to the concrete plant and fill it into the appropriate silos and storage areas," says Julia. "Cement, fly ash and the concrete chemicals are the only things we have to bring up from the valley to make the concrete."
Construction of the Spitallamm replacement dam
Kraftwerke Oberhasli AG is replacing the existing dam wall with a new one between 2019 and 2025. The old wall is in need of renovation, but will be retained and flooded at a later date. By replacing the Spitallamm dam, KWO is ensuring that the water from Lake Grimsel can be used for electricity production without restriction in the long term.
