The Londonderry mine shaft, located at Londonderry Reserve near the corner of Myrtle Street and Creek Street North, opened in late July and has been excavated and reinforced with a concrete foundation. City of Greater Bendigo Manager Works Rachelle Quattrocchi said it was not uncommon for old mine shafts to open up in the colder, wetter months.

She said the $10,000 project on the Garden Gully Line shaft, which starts under the Quarry Hill Golf Course and continues right through to Eaglehawk North, was one of several works required on old mine shafts each year.

"On average the City of Greater Bendigo is spending up to $50,000 a year to reinstate mine shafts that appear on land that is managed by the city," Ms Quattrocchi said.

She said while there were a large number of recognised historical mining sites, there were a lot of unknown mine shafts on city land.