Strabag-led team takes over GKI challenge 02 Mar 2017

A Strabag-led JV is taking on the tunnelling challenge of the 22km long Gemeinschaftskraftwerk Inn (GKI) hydro headrace in Austria after agreed termination in early January of the previous contract between the client, lead by TIWAG-Tiroler Wasserkraft AG of Austria, and Hochtief Infrastructure Austria.

Two Robbins TBMs progressing 22km long headrace from mid-point adit

The key part of the project is the 22km long headrace which is being excavated by two 6.53m diameter hard rock Robbins double shield TBMs progressing in opposite directions from the mid-alignment adit and erecting a precast concrete segmental lining as they go to provide a final i.d. of 5.8m.

Hydro developer GKI GmbH said earlier this year that tunnelling on the project had been experiencing geological problems. After launching the two TBMs in mid-October 2015 and January 2016, there remains approximately 19km of a total 22km to be constructed.

In a telephone connection with the client organisation, Johann Herdina, a Project Director with project owner partner TIWAG, told TunnelTalk that the TBM in the south-bound heading and is ready to resume boring, while the TBM in the north-bound heading is being maintained and prepare to restart after becoming stuck in early November.

“The plan is to restart the southern TBM heading at the beginning of April and to complete maintenance on the freed north-bound TBM to resume boring not before late May or early June. The south-bound heading is the longest drive at 11km - about 2km longer than the north bound heading - and is on the project’s critical path.”

Construction on the project began in late 2014 with early preparatory works and completion was then anticipated by mid-2018. Main tunnelling was underway by early 2016. The plant is now scheduled to be operational by late 2019/early 2020, said Herdina.

When TunnelTalk visited the project in late 2015, Hochtief reported that the geology comprises mainly hard schist with the possibilities of fault zones and squeezing conditions. Overburden reaches up to 1,200m

First Robbins double shield TBM launch in October 2015

Strabag AG confirmed it would be teaming with Jager Bau and G Hinteregger & Sohne Baugesellschaft for a contract that is based on the Australian alliance and partnering contract model.

“We adopted the Alliance procurement model for the take over contract as the change was negotiated at short notice and this offered the best terms for restarting the project as soon as possible,” said Herdina. “GKI became the owner of the two TBMs for the continuation of the project and has made them available to the new contractor for the remainder of the drives. It is the first time that the Australian Alliance contract concept is to be used in Austria.”

Other specific details of the termination agreement, as full and final resolution of all issues between the two parties, and finalised during intense negotiations between December 23 and January 2, are mutually agreed as confidential.

In selecting a replacement contractor, Herdina explained that the second and third bidders of the original project contract in 2014 were invited to enter negotiations with the owner and for the Alliance-based completion contract.

GKI confirmed in February that the Hochtief workers on site would be taken on by the new JV contractor and confirmed there would be no transfers of any obligations, liabilities or business as part of the process of the new contractor taking on the construction work.

Gemeinschaftskraftwerk Inn GmbH is a JV of three Austrian power companies led by TIWAG-Tiroler Wasserkraft AG (76%) with Engadiner Kraftwerke AG (14%) and Verbund (10%), respectively.

The plant is located on the upper reaches of the River Inn, close to the border with Switzerland, and will generate 414 GWh of electricity annually.