He said yesterday the board expected to get agreement in principle from the Ministry of Education on July 21 to proceed to the detailed design phase.
It was hoped the tender process would start about October and construction might start during the Christmas holidays, if not before.
Waitaki Valley School opened in 2004 on the Kurow Area School site following the merger of the Hakataramea Valley, Otematata and Kurow schools.
As it was previously an area school, many of the buildings were designed to suit the needs of secondary school pupils.
The main block, housing classrooms and the administration area, was built in 1940 and was outdated.
The new school, comprising five classrooms and an administration area, will cover 833sq m.
In keeping with the board's vision of a community campus, a building of 527sq m, built in 1981, will be retained and it is hoped the Kurow preschool will use part of it.
The remaining part will be used for the adult education programme.
The existing community library building will be retained, along with the Centennial Sports Complex, which has been leased from the ministry by the Upper Waitaki Community Trust and is used primarily for school activities.
A concept design report was being peer reviewed and Mr Watherston was confident it would meet all the required specifications.
Mr Watherston praised principal Helen Blick for maintaining an excellent teaching environment in such demanding conditions.
It had been very difficult for her and staff, he said.
Since a project manager was appointed in December last year, the board had been concerned the time line had become increasingly drawn out, with "bureaucratic procrastination" holding it up, and Mr Watherston was looking forward to work starting.
Both Mr Watherston and Mrs Blick said the initial design drawings had been well received at a community consultation meeting last week.
Mrs Blick was excited about the plans, saying it would be a "wonderful" environment for teaching and learning.
The school has a roll of 106 pupils and they will be relocated into the old secondary school block during construction.
