Meridian Energy will invest more than $40 million on a four-year project to refurbish the Waitaki dam and power station.
The Waitaki is the oldest power station in the Waitaki hydro system and was built by manual labour as a "make-work" programme during the 1930s Depression.
The power station has six operational 15 megawatt generating units and generates enough electricity each year for about 62,000 average New Zealand homes.
Meridian general manager markets and production Neal Barclay said Waitaki was a "historic part of New Zealand's electricity network and, despite it being almost 80 years old and with the work that we are planning, it will continue to provide reliable and sustainable electricity for many generations to come.
"Meridian will carry out a range of work to ensure the old powerhouse building remains strong and usable.
"This work includes earthquake strengthening, but the architectural look of the building will be retained.
"The four-year project starts in April and involves reinstating the site's seventh generation unit, which hasn't operated for a number of years."
Mr Barclay says work will include upgrading the protection for the existing units so Meridian can identify and rectify faults as early as possible.
"We are also making the intersection to the site safer and carrying out erosion, seismic and flood protection work around the site," he said. "This is business as usual maintenance that will give us increased flexibility.
"We will continue to operate within our water consents and will continue to generate a similar amount of power as we always have."
The project work should have little impact on the community, according to Meridian and there are likely to be long periods where locals will not notice any additional activity on the site.
"One of the first things people might notice is that we'll be limiting access to the site," Mr Barclay said.
"At the moment people can, and do, drive right up to the powerhouse.
"The dam and powerhouse are going to be the site of some major maintenance and we'll be securing the site for health and safety reasons, but locals and visitors will still be able to stop at the viewing area above the powerhouse."
Mr Barclay says at times during the project there will be an increase in the amount of traffic coming in and out of the site.
"At any one time, there will be a couple of dozen extra people on site and, as a result, there will be increased traffic with some significant loads accessing the site," he said. "A traffic management plan will help us minimise any disruption to the local community and we will keep the community informed."
The flow-on effects of the work should not affect users of the Waitaki River or Lake Waitaki. Mr Barclay said: "We are also developing a database of interested locals who would like to be kept up-to-date during the project and if anyone would like to be added to the list and receive emails when there's a development, please email firstname.lastname@example.org."
Meridian Energy is the largest energy generator in New Zealand and, with its online subsidiary Powershop, supplies retail electricity to 290,000 connections - homes, farms and businesses throughout New Zealand.
The company owns and operates seven hydro stations, six within the Waitaki Hydro Scheme, and four wind farms throughout New Zealand.