Wilson Contractors, on behalf of Doc Wakatipu, has used a half-tonne digger, rock drillers and explosives since late October in a $500,000 realignment of the section which descends from McKellar Saddle to the Greenstone Valley floor.
Contracts and programme management ranger Richard Struthers said this week the existing section was an old New Zealand Forest Service track, which dated back to the 1970s, and was used for deer control.
The old section was "poor and difficult", as it descended in a straight line then sidled around the shores of Lake McKellar, Mr Struthers said.
"The new track takes a sidling gradient, avoiding most of the difficult terrain, through steep Fiordland granite rock country and some beech forest, to join up with with 30m of new boardwalk across a swampy section on the valley floor."
Contractors were expected to finish the section in April this year.
The existing route remains open to the public but its signs will be removed and it will be allowed to revegetate.
Mr Struthers said Doc Wakatipu was in the process of calling for tenders for the renovation and extension of the nearby McKellar Hut, from an 11-bunk to a 22-bunk facility.
"It's a reasonably old structure. I think it was [built in] 1986, and it's too small for current usage.
"It's quite a popular circuit and attracts people coming off the Routeburn Track and perhaps people who don't want to pay Great Walk fees."
The size of the hut will be doubled, the toilets will be upgraded and warden's quarters built, which will be occupied during the summer tramping season of October to April.
Mr Struthers said the hut improvement was scheduled to be completed during winter this year. The finished facility would be a typical Doc hut design, similar to the Greenstone Hut, with fireplace and mattress bunks.
The McKellar Saddle Track is found on the three- or four-day Greenstone-Caples Track and accessed via Glenorchy
