up dam reservoir filling schedule

their producer statement (PS3), means that specialist dam consulting engineers Damwatch Engineering Limited cannot complete reviewing the contractor’s work and issue the PS4, which confirms that construction has been carried out in accordance with the consented plans, building codes and manufacturers’ installation instructions. Council, however, requires both compliance statements to be completed before it grants final consent. “TDC will not sign off until the PS3 and PS4 are completed, so we can’t fill the dam until then,” says Mike.

Explaining that the contractor’s delay is “entirely their problem”, Mike points out that some of the missing paperwork dates back to work carried out two years ago.

The management deficiency raises the question of whether such a large infrastructure project is beyond the capability of New Zealand contractors. The Waimea Dam is the first major dam to be built in New Zealand since Clyde in 1992 and, in the intervening decades, swathes of specialist expertise and capacity has been lost.

The challenges won’t end with construction. Once the dam is completed and signed off, there will still be ongoing operational risks to deal with. Among the key concerns are resilience to serious seismic events and major floods, both of which the dam is designed to withstand, says Mike.

Another, very topical, concern is the potential impact of forestry slash. The reservoir basin is surrounded by steep hillsides currently used for commercial forestry, which will at some time be harvested. To prevent debris reaching the dam and causing damage, a flexible floating boom will be deployed laterally across the reservoir surface, attached at either end to concrete anchor points located a few hundred meters back from the dam’s upper face. However, Mike is particularly concerned about the potential impacts from the future harvesting of a forestry block sited on a steep slope dam-side of the protective boom. This is something that he suggests could be addressed by TDC through its harvest consenting requirements.

Despite the latest delay, Mike hopes to be able to close the reservoir and begin filling in May, with commissioning penciled in for later this year.