The hammer, a steel tube filled with lead, will be used by Christchurch engineering firm March Construction to drive piles for both hospital buildings.
It will be hoisted into position using a Liebherr heavy duty crawler crane.
"It is probably the biggest hammer of its kind in New Zealand, given these will be the largest bottom driven steel tubes ever done here," March Construction operations manager Andrew March said.
"The hammer has been manufactured solely for use at the new Dunedin Hospital, which is a pretty unique job in terms of the size of the bottom driven steel tubes and the size of the hammer."
Consent documents for the hospital groundworks reveal how challenging the site, which is largely on reclaimed land, will be.
Five different layers of materials have been identified, including clay, silt, gravel and, at the bottom, volcanic rock.
There will also be tidal groundwater on site, as close as half a metre to the surface, and there are also expected to be patches of contaminated soil due to the numerous former industrial uses of the site.
Some piles are likely to have to be drilled as deep as 20m, and engineers expect boulders could cause obstructions in some areas.
Piling work was given fast-track consent last year and is expected to begin soon.
Conditions imposed by the independent panel which assessed the application included mitigation for noise and vibration.