Work on repairing the Tekapo canals is under way, as Genesis Energy begins to ramp-up staff numbers on site.
Chief executive Albert Brantley said about two dozen workers would be on site over the next month in the lead up to the canal shut-down in January.
"The construction management site is being established and this includes an aggregate crushing area and the excavation of borrow pits for material suitable for canal repairs," Mr Brantley said.
"We'll be continuing to provide irrigation water from the canal and pipe-work is being constructed to assist the transfer of water around sections that will be de-watered."
Genesis would be lowering Lake Tekapo to its minimum operating level for remedial work before its planned shutdown of the canal from January 14 to April 21.
This would be followed by a similarly long shutdown in the summer of 2013-14. Mr Brantley said at its peak, there would be 150 workers on site.
The work is expected to cost about $125 million. It includes the building of temporary coffer dams, bridge repairs, and the repair of the canal surface and installation of a new liner material from European firm Carpi Tech. Fulton Hogan received the site establishment contract and external works contract.
The Government directed Genesis to purchase the Tekapo power stations from rival state-owned generator Meridian last year.
Mr Brantley said in the lead-up to January, there would be a large site office comprising seven Portacom modules.
"An additional three modules will be for site workers comprising a lunch room, ablution block and a drying room. Long term, there will be approximately 15 buildings," he said.
Mt Cook Alpine Salmon, which farms on the hydro canals, is in the process of moving hundreds of thousands of fish in preparation for Genesis's repair work.
The salmon company's chief executive Geoff Matthews said it had received consents to build six rafts to store some of the fish near the Lake Ruataniwha canals.
"We've known about Genesis' work months in advance, and we have already begun the process of re-homing some of the fish," Mr Matthews said.
"We will be doing a lot of our major shifting [of fish] around Christmas time."
Once the canal closes, Lake Tekapo will gradually fill to its maximum control level.
"Once spill begins, it will continue until the outage ends on April 21. This means there will be higher flows in the Tekapo River."
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