NZ Dam Safety Depends on ‘Blind Faith’

The Clutha River Forum, an alliance of environmental groups opposed to further dams on the Clutha River, is concerned that New Zealand’s long-awaited Dam Safety Scheme has been deferred.

The scheme was due to come into effect on 1 July 2010, but the Minister of Building and Construction, Maurice Williamson, says it will be delayed for two years following a report earlier this year which found that the scheme imposed rules and compliance costs on dam owners ‘out of proportion to the risks’ imposed on New Zealanders.

“Unlike most other developed countries, New Zealand does not have a ‘Dam Safety Authority’, says Lewis Verduyn, Forum Spokesperson, and Chairperson of the Clutha Mata-Au River Parkway Group. “Thousands of people live and work in the hazard paths of dams, and yet dam safety in New Zealand depends on the public having blind faith in dam owners.”

The report, which was released by the Department of Building and Housing, recommends a number of changes to the scheme, which would regulate the safety of an estimated 1150 dams. But the Clutha River Forum believes that some critical issues have not been addressed.

“The report doesn’t acknowledge that overtopping events are a leading cause of dam failures,” says Dr. Richard Kohler, Chair of the Central Otago Environmental Society. “When it comes to dam safety, reservoir-related risks such as landslide areas and active fault-lines are just as important as the dams themselves. Rainfall and earthquakes can trigger catastrophic landslides and overtopping waves, and sediment-filled reservoirs can cause devastating floods. Both Clutha dams have reservoir risk factors, however the report recommends that all reference to ‘earthquake-prone and flood-prone dams’ be removed from the Act.”

There are two large concrete dams on the Clutha River. The Roxburgh dam was commissioned in 1956, and has been blamed for serious floods in Alexandra because of reservoir sedimentation. It was re-consented in 2007 for a further 35 years. The Clyde dam was commissioned in 1992 after years of controversy arising from complex fault-line and landslide mitigation issues.

Mr. Verduyn says “Although the review acknowledges that dams degrade over time, there is no mention of criteria to establish when and how dams and reservoirs are decommissioned, when the risks they impose become unacceptable and cannot be fully mitigated. Large concrete dams have a design life of 80-100yrs, but reservoirs trap sediment from eroding catchments, usually reducing this lifespan. Dams older than 50 years with known issues, like the Roxburgh dam, should have decommissioning timetables. Forward planning is needed because the impacts and costs are substantial.”

According to a report by SPX Consultants, ‘Reversibility of Renewable Energy Developments’, released in 2008, decommissioning and river restoration costs for a large dam, as a proportion of construction costs, are between 35% and 150%.

Last year, Contact Energy, the owner of the Clutha dams, dusted off historic plans for four more large dams on the Clutha River.

“The Clutha River Forum,” says Lewis Verduyn, “is firmly opposed to further dams on the Clutha River. Large dams are a gamble and it’s time that we recognised the serious risks that they impose on communities. New Zealand needs a credible ‘Dam Safety Authority’ that can enforce safety baselines and hold dam owners accountable for the impacts of their dams.”

ENDS.

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