A bit of history…
In the 80’s a big project came to light in this small town of Clyde. For about 10 years inhabitants of Clyde/Cromwell saw a big changes in the scenery with the building of a new, challenging and controversial dam. Before the building, along the state highway between Cromwell and Clyde were stone fruit orchards. A part of the main street of Cromwell, some buildings and an old bridge have been drowned to allow this new hydro-electric dam to be born. If you have the chance to dive you still would see some old ruins, a car on the bridge and maybe even some trunk from old apricots orchard tree.
Here is a bit of history with some pictures.
The dam was constructed between 1982 and 1993. Filling it was done in four controlled stages beginning in April 1992, and completed the following year, creating Lake Dunstan. The power station has a capacity of four 120 MVA (116 MW) francis turbines(for a total of 464 MW), but was only allowed to run 432 MW due to resource consent conditions. The dam is built such that two further penstocks and turbines can be installed, but if they were installed there will not be enough water to keep them running.. The resource consent was changed in 2005 to allow the full 464 MW to be produced.
During construction, the adjacent rock was discovered to be microfractured, because of an earthquake fault running underneath the dam site. The dam was redesigned, losing a sluice channel and cutting its generation capacity from 612 MW to 464 MW. A slip joint was built into the dam to accommodate 1–2 metres of potential ground movement, and a large amount of slurry cement was pumped into the rock to stop water leaks. This additional work was one reason for a major project cost overrun, which made the dam the most expensive in New Zealand. The other areas of overrun were due to stabilisation of landslides in the Cromwell Gorge.There are over 18 km of tunnels throughout the gorge for draining purposes. Because of all this extra work it overran the budget by nearly an extra 50% and delayed the filling of Lake Dunstan by a few years.
Maintenance workers accidentally activated fire alarms in the dam on 15 December 2008. The alarms triggered the release of a large bank of CO2 cylinders at the generators, flooding the equipment with the gas. Extractor fans to clear the CO2 then activated, and firefighters with breathing apparatus and gas detectors checked through the dam to ensure it had cleared.