The Press - Concerns continue over Waimakariri Irrigation Ltd dam plans

Opposition to a 13-metre high dam in the Waimakariri district continues, despite the idea being out of the limelight for a couple of years.

Catherine Ballinger, of the Eyre Community Environmental Safety Society (ECESS) residents' group, said although the matter had been before the Environment Court for the past two years, many people were unaware of the group's efforts, which was why she wanted to "ring the bell again" and rally the troops.

"We need the whole community behind us," she said. "We want to do some fundraising and get our voice heard again."

The group is opposing Waimakariri Irrigation Ltd's (WIL) plan to build a large dam, citing safety concerns. With about 1800 people now living downstream of the proposed dam, Ballinger said residents were concerned about the lack of a workable evacuation plan. 

"Nothing has been built like this before, with no natural water course for it to flow to if it breaks or floods," she said. "The only course of action we could take was to appeal, which we are doing now."

Ballinger said public meetings had been held with WIL and GNS scientists, attended by "lots of unhappy people".

Concerns were heightened after last year's North Canterbury earthquake, but there had been no change to the dam plans to take a potential natural disaster into account, despite building standards changing in recent years, she said.

"We are not anti-dairying, and we are not against water storage. It's just the safety issues. There are other alternatives – farmers could put their own ponds in, underground storage could be put in. By all means have your water, but store it safely."

WIL general manager Brent Walton said some farms already had on-farm storage, but the dam was necessary to protect against the ravages of drought. 

Farmers in the area had a 75 per cent reliability on being able to take water, but the Waimakariri River was too low and restrictions came into force the remaining 25 per cent of the time. 

With the dam, the reliability would be up between 92 and 95 per cent, he said.

Alternative sites had been researched, but there would always be people living beneath any proposed dam. 

As for the safety concerns, four flood scenarios had been modelled. While the ECESS group argued they would not hear warnings over loud speakers or sirens, the modelling showed there would be plenty of time for an evacuation.

The water would take at least two-and-a half-hours to reach Downs Rd, and a further two to five hours to reach Two Chain Rd. 

In the event of a major earthquake, which was the only realistic risk to the dam's structure, the quake itself would be the trigger for the area to evacuate, Walton said.

In terms of a fault with the structure, there was a three-tier emergency management plan with checks and balances in place, including weekly inspections, water level checks and seismic triggers.

The design of the dam, which would be built to the highest standard, had been extensively peer-reviewed.

He said it was also important to note there were shareholders in the irrigation scheme living in the flood path who would be unlikely to be investing if they believed it was going to burst in five years.

The next step was for the matter to take its course in court, with a hearing anticipated before Christmas, he said.

A construction contract and price would then be negotiated before it went to the shareholders for approval. Only then would construction go ahead, Walton said.