Glendoe diversion

9 February 2010

Contractors were last month due on site to start works

on the new diversion tunnel at

the Glendoe hydroelectric

scheme in Scotland.

Bam Nuttall was awarded

the contract by the station’s owner Scottish and Southern Energy (SSE).

A rockfall blockage in the tunnel was realised last August, rendering the plant non-operational. SSE confirmed the rockfall as “very substantial”,

up to 20,000t according to

project sources.

SSE did not reveal the cause of the collapse, which happened in the upper third of a 6.2km headrace tunnel that carried water from the reservoir in the Monadhliath Mountains to the powerhouse close to Loch Ness.

Bam Nuttall declined to comment on the project, however a project source confirmed the contract award. The source told T&TI that the tunnel would be excavated by drill and blast.

The collapsed tunnel was excavated by TBM.

SSE said in November that the work needed to repair the tunnel was so extensive that it didn’t expect the power plant to be operational before 2011 (T&TI, December 2009, page 11).

A significant proportion of the funding for the repair project, thought to be £20M (US$32.4M), will be covered by contractual arrangements and insurance, according to SSE.

The ground conditions on

site comprise interbedded quartzites and schists with little

or no groundwater.

The headrace excavation was completed two years ago. The Queen formally opened Glendoe last June, just two months before the collapse.