Replacement of the Spitallamm dam Grimsel


New double-curvature arch-gravity dam


Replacement of the existing dam which was originally built in 1932. The new double-curvature arch-gravity dam is built directly in front of the existing dam which is preserved and subsequently flooded while a tunnel next to the old dam wall will ensure that the water level is balanced hydraulically. The new structure has the same crest height as the existing arch-gravity dam and offers the possibility of a height increase at a later stage in order to enlarge Lake Grimsel.

The Grimsel Lake can continue to function throughout the construction period, practically without restrictions.

The construction site is on the road over the Grimsel Pass, at a height of between approx. 1,800 m and 1,950 m above sea level (Grimsel Hospice).

Key data

  • Max. dam height 113 m
  • Crest length 212 m
  • Crest width 8 m
  • Max. width of footing 20 m
  • Concrete volume 223’000 m3

Total cost

Construction costs: approx. CHF 125'000'000




Kraftwerke Oberhasli AG (KWO)

Services provided

  • Geology Consulting / Expertise
  • Grout curtain and drainage arrangement system: design, core logging & hydraulic conductivity assessment (Lugeon-tests) in grout holes, grout injection evaluations
  • Geology inspections & assessment of rock mass prior to concrete pouring
  • First impounding planning (geological and hydrogeological monitoring)



  • Construction (SIA 52)
  • Commissioning, completion (SIA 53)


Date: 20.11.2023