The controversy over the multibillion dollar plan to lift the Warragamba Dam wall may not be over, with incoming ministers in the Minns New South Wales government briefed that safety issues might necessitate work on the giant dam wall.
Labor went to the March election vowing to dump the Coalition government’s plan to raise the wall at Sydney’s main reservoir by at least 14 metres. In the pre-election review of promises, the Parliamentary Budget Office (PBO) noted scrapping the project would save $3.9m in 2022-23, implying further funds had not been earmarked for the project.
Guardian Australia understands department officials told the relevant ministers last month that the wall may need to be raised for safety reasons. One person familiar with the briefings said the connection was a surprise, as safety issues “had never been raised before” as a reason for lifting Warragamba’s wall.
Government officials, though, declined to detail the nature of the safety concerns and whether lifting the wall would be required. A spokesperson for water minister, Rose Jackson, said “we’re still working through our response on the matter” and would provide more information when it became available.
Premier Chris Minns, asked about the issues at media conference on Tuesday, confirmed that the dam may require “remediation works” due to “geotechnical risks”.
“There are other geotechnical risks associated with the dam wall which means that Water NSW and the board of Water NSW may have to take action in relation to remediating the structure from an engineering point of view,” he said.
Minns said Water NSW engineers had briefed the government “about next steps”, but he declined to detail the concerns nor the likely action needed to address them.
Geotechnical risks imply an issue that may not require changes to the 142m wall, but rather changes to the ground that the dam sits one, one expert told Guardian Australia.
Cate Faehrmann, the Greens water spokesperson, said matters of dam integrity or safety had not featured in previous arguments put forward by WaterNSW or the government to justify lifting the wall’s height.
“If there are in fact safety and integrity issues it is up to the new government to seek comprehensive advice and, once fully briefed, be transparent with the public about this,” Faehrmann said, adding that such advice would imply the need for “an entirely new development application and environmental assessment”.
“This would be an entirely different basis for works to those that were put forward by the former government, which was ultimately for flood mitigation,” she said.
The cost of lifting the wall 14 metres would be $1.95bn, the PBO reported, citing Infrastructure NSW data. That sum, though, excluded the cost of biodiversity offsets to compensate for the environmental impacts in the world heritage-listed Blue Mountains region.
Warragamba, along with other major dams, has a high-capacity spillway to allow water discharges in cases of extreme inflows in order to prevent water overflowing and causing erosion. The spillway was designed to cope with events projected to happen in the order of just one in a half-million years compared with the one-in-20 or one-in-50 year events endured by the dam in the past couple of wet years.
Guardian Australia understands environment staff working on the offsets program linked to raising the dam wall asked management after the election whether they should continue the work. They were told to await further advice.
Guardian Australia approached environment minister Penny Sharpe for comment. Her office diverted questions to minister Jackson’s office.
Harry Burkitt, one of the environmental campaigners who had led opposition to the dam-wall raising, questioned whether safety issues might reflect a rearguard effort by “dam-obsessed bureaucrats in the NSW public service” to keep the project alive.
“Throughout the 10 years of this proposal, dam safety was never cited as justification for raising or altering the dam wall, as the safety of the dam was guaranteed in 2000 by the Carr Labor government’s $200m investment in an auxiliary spillway,” Burkitt said.
“Unfortunately it seems not even the new Labor government’s policy will get between these fixated bureaucrats and raising Warragamba Dam,” he said.
Steph Cooke, the shadow minister for water, said the Labor government’s opposition to raising the dam wall meant it had “abandoned flood-mitigation efforts in the Hawkesbury-Nepean” valley.
“Labor must explain to flood-exposed communities how they intend to better protect them from flood risk,” Cooke said.
The NSW dam safety committee referred questions to WaterNSW.
