The tunnel between Burrawang and Avon proposal has come under fire from one Wingecarribee Shire councillor.
Councillor Larry Whipper said he was not aware of the proposal to construct a water transfer tunnel from Fitzroy Falls to Avon Dam.
"There are justifiable concerns being expressed about subsidence and potential impacts on groundwater," he said.
"As chair of the Environment Committee and also a previous board member of the Sydney Catchment Authority, I made enquiries to WaterNSW as to why we have not had any notification of the proposal.
"I was told that WaterNSW did meet with representatives of Wollondilly Council and Wingecarribee Council in early August, three months ago.
"Why have councillors been kept in the dark?
"Why as a local advocate for our environment was I not informed of this proposal when it has been know to council staff and executive since August this year?
"When I questioned council on this matter I was told we will have a briefing on the December 4, 2019. As an elected representative and environmental advocate, I do not believe this is good enough.
"From my conversations with potentially affected locals, there is considerable interest in the matter.
A spokesperson from Wingecarribee Shire Council said that key water infrastructure staff were briefed by representatives from WaterNSW.
"The meeting was a preliminary discussion whereby the WaterNSW outlined their broad plans. No details or specifics were entered into," they said.
"WaterNSW representatives will have discussions with councillors on Wednesday, December 4.
"We are sure that WaterNSW will keep council informed should this project progress. At this stage I'm not sure what Wingecarribee Shire Council's involvement would be should this occur."
WaterNSW were contacted for comment.
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