Early works in the $40 million expansion of Newcastle Art Gallery are set to kick off after a tender was awarded for remediation of the site.
Council on Tuesday awarded the tender to remediate the site which sits above the Borehole Coal Seam, about 75 metres below ground, and Dudley Coal Seam, about 27 metres down.
The remediation is set to start in June and will require about 15,000 cubic metres of grout deployed into the seams via more than 100 individual bores.
Lord Mayor Nuatali Nelmes said the remediation was a crucial part of early work to prepare the site ahead of the main construction.
"An interesting and little-known fact about Newcastle Art Gallery is that it sits atop abandoned mine workings, so it's important that we ensure the site is safe for construction of the expanded gallery to commence later this year," Cr Nelmes said.
"Work continues inside the gallery to decant and prepare the extensive collection for offsite storage."
The gallery closed in January for the expansion, which will add 1,600 square metres of exhibition space.