KOPS II Hydropower Project

Project Overview

The KOPS II Hydropower project is located inside the Alps Mountains, drawing from the same reservoir as the KOPS I hydropower station, commissioned in 1969. The stations are supplied by the Rifa balancing reservoir, located between the tourist centers of Gaschurn and Partenen.  The KOPS II pump station and headrace tunnel was built to supply power to the grid during peak demand and to ensure long-term network stability. Being that KOPS II uses the same reservoirs, no additional water was needed compared to KOPS I. Also, KOPS II uses an existing high-voltage line currently used by KOPS I.

Construction began at Kops II in 2004/2005, after Swietelsky Tunnelbau GmbH, Torno SA and Torno Int. S.p.A JV signed the contract for a 5.54 m (18.0 ft) Robbins Double Shield TBM. Construction of not only the tunnel, but the entire hydropower plant, was under strict watch as an Environmental Impact Assessment (EIA) was initiated. More than 500 regulations had to be followed assuring that construction would be done in an environmentally friendly way and in a tight time frame of 42 months.

The completed KOPS II plant provides an additional 450 MW in turbine mode and pump mode to the already existing 247 MW hydropower plant.

 Geology

Geology on the tunnel alignment consisted of schist gneiss, migmatite gneiss, mica-schist, amphibolite gneiss, hornblende gneiss, granite-gneiss and aplite gneiss ranging from 30 to150 MPa (4,000 to 22,000 psi) UCS.

TBM Design and Tunnel Excavation

The Robbins TBM used 483 mm (19 in) back-loading cutters to bore through the very challenging and mixed geology. The cutterhead was designed with 9,074 kN (2,040,000 lb) of thrust and 2,159,424 N-m (1,591,300 lb-ft) of torque.  The TBM power was 1,575 kW (2,112 hp).

Boring commenced on the headrace tunnel on July 20, 2006.   The TBM was one of the first machines to use a back-loading 19 inch cutterhead. The resulting cutter blockage percentage ratio was very low—only 2% over the duration of the project, compared to the more typical rate of 10-15%. The KOPS II pump storage plant went into operation in 2008.