Posted: 2021-06-07 06:45:29
The NSW government has so far publicly backed raising the dam wall at Warragamba but documents show cabinet has been given alternatives.

The NSW government has so far publicly backed raising the dam wall at Warragamba but documents show cabinet has been given alternatives.Credit:James Brickwood

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In a document dated September 2014, a workshop by Infrastructure NSW examined a separate range of alternatives including lowering the full-supply level of Lake Burragorang behind the wall by 5-12 metres, or the release of between 40-130 billion litres over three days before a forecast deluge.

The workshop concluded the full-supply level be permanently lowered by 5 metres, upgrading the dam gates and further consideration of the 40 billion litre early release of water.

Minister for Western Sydney Stuart Ayres said raising the wall by 14 metres “outperforms all other options. It protects Sydney’s drinking water supply and delivers better flood mitigation than other options”.

“When modelled against the March floods the 14-metre wall would have lowered the flood peak by 3.5 metres at Windsor,” he said. “[That’s] significantly more than the other options.”

Independent MP Justin Field, who chaired an inquiry on Monday into last March’s floods, said the government “was putting all of its eggs in the one basket and saying lifting the dam wall would solve all the problems. That’s simply not true”.

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The inquiry heard from a range of stakeholders including the insurance industry, which earlier this year withdrew its support for the wall-raising plan. On Monday, the insurers called for a roundtable to work with the government to find a solution that would consider evacuation options, planning restrictions and other ways to manage the dam to reduce the threat of floods.

“I think at the end of the day, we’re often asked for opinion on something we aren’t the experts in, necessarily,” Andrew Hall, head of the Insurance Council of Australia, told the inquiry.

“It’s a bit difficult to back one idea if the work hasn’t been done for the full range of impacts.”

Harry Burkitt, campaign manager at the Colong Foundation for Wilderness, said without the insurance industry’s support, “it’s going to be very difficult for the NSW cabinet to simply rubber stamp the multibillion-dollar project”.

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