Seismic improvement work is under way on Benmore’s massive, 130m-long penstocks, which funnel water from the top of the dam down to its turbines.
Meridian Energy generation general manager Tania Palmer said unlike in most dams around the world, Benmore’s penstocks were made of concrete and with the probability increasing of a large earthquake along the South Island’s Alpine Fault, it was time to enhance their performance.
"Benmore will be critical to recovering from a large quake as it’s from here that the high-voltage DC [direct current] link runs between the South and North Islands.
"With Benmore generating enough power for around 300,000 Kiwi homes, the country can’t afford to have it out of action for long.
"There’s a 75% chance of a significant earthquake along the Alpine Fault in the next 50 years, so we’re investing now to make sure the penstocks have very little, if any, damage when it does inevitably happen."
Dams in the Waitaki Valley hydro-electric system were designed to withstand much greater ground shaking than they would experience from a magnitude8 earthquake on the Alpine Fault, she said.
In a large earthquake, infrastructure damage was likely, but catastrophic failures or uncontrolled release of water downstream were not expected.
The seismic strengthening work, being carried out over the next four years will involve modifying the joint at the top of each penstock to allow it to move freely in an earthquake.
The project would also install fluid viscous dampers (a form of shock absorber) to dissipate the energy caused during an earthquake and reduce the likelihood of cracks appearing in the penstocks.
During the works, the western side of Loch Laird Rd would be down to one lane for about four weeks in March and April.
Part of the Benmore Dam top carpark would be closed for the duration of the works, she said.
