Members are adamant a prisoner transfer tunnel exists between the old courthouse, now the Young High School, and old jail, now the Young TAFE, despite the state government insisting they have found no evidence of tunnels after "comprehensive investigations", including use of ground penetrating radar.

The state significant development application was approved in May.

Shadow Minister for Rural Affairs Mick Veitch MLC earlier this month successfully requested the government to table all documents relating the Young High School joint use facility. YCRA member and heritage professional Joe Kinsela says they have eye-witness evidence a prisoner transfer tunnel exists.

"Hilltops residents have described in detail a typical prisoner transfer passage running between the jail and courthouse. Detailed statements and affidavits describe the Young courthouse tunnel. This is eye-witness evidence," he said.

Mr Kinsela believes a tunnel will be found and the new joint use facility will have to be redesigned because the tunnel will protrude along the ground floor of the facility.

"This will be very expensive if construction has already begun. To avoid a waste of ratepayers and taxpayers money, public money, your money, the Young Community and Residents Association calls on the Planning Minister, Schools Infrastructure NSW, the NSW Department of Education and the Hilltops Council to arrange an urgent archaeological investigation, or a small dig, to establish the position of the prisoner transfer tunnel before any contracts are issued or work commences."

The state government has previously stated that the Department of Education used "radar scanning in the relevant areas and also physical investigation of the sub floor areas", and investigated records.

Mr Kinsela says he met the project manager on site late last year and advised them of the probable route of the tunnel, and arranged to be present when a second scan took place.

Mr Kinsela says this was done when the project manager was on leave and he was unable to ensure the scans were thorough.

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