The second concrete floor platform was poured on Tuesday.
The two buildings will be completed early in November.
The Wakatipu area office will move there in March.
Rangers are moving from leased premises above Shotover St, in Queenstown, to the majority of the first floor of the Cavells building, near the Shotover Jet operation, on the Morning Star Recreation Reserve.
Doc capital works project manager Richard Struthers said the new depot would be 25m long, 8.5m wide and 4.2m high.
The adjacent rural firefighting equipment store would be 7.8m deep, 9.8m wide and 4m high.
Both gained consent on a non-notified basis and were compliant with the rural general zone.
The low-reflective steel buildings would have brown-grey walls, roofs and brick-red doors.
The new facilities will replace the department's existing workshop, on Industrial Pl, in Queenstown.
Doc announced it had bought Cavells from a private owner for $1.9 million in September 2008 after six months of negotiation.
The area office was originally expected to be established by April this year, but tendering and due diligence processes had protracted the timetable, Mr Struthers said.
"Doc has undertaken to clear some wilding pines and weeds from the Morning Star Recreation Reserve.
"There is a 900m public walking track being completed . . . from the new car park at the entrance to the reserve, across the terraces and down to the Morning Star beach and Shotover River, where gold was first discovered in the Wakatipu.
"Interpretation panels will be provided in due course."
