Ahead of schedule, pumps used to drain water in January from a 5km section of the 26.5km-long canal between Lakes Tekapo and Pukaki were utilised again to pump water back in to the newly sealed portion .
Genesis public affairs manager Richard Gordon said re-watering of the first section started on April 3 and section 2 on April 5.
''Once the water levels were the same within the previously de-watered sections and the rest of the canal, long-reach excavators removed the temporary coffer dams, taking care to ensure the sides of the canal were not touched,'' he said.
All four dams were removed by April 10 and the canal brought back into service for generation on April 12.
Silt was expected to move down the canal and be visible in Lake Pukaki, but settle quickly. Silt barriers were installed along the canal to mitigate the effects, and water quality monitored during the removal of the coffer dams to ensure it remained within resource consent conditions.
Genesis warned about the possibility of having to release water from Lake Tekapo if there was heavy rain in the catchment during the process.
The Tekapo B power station on the edge of Lake Pukaki was now generating using water flowing through the canal from Lake Tekapo, where the Tekapo A power station was.
Work started on January 9. Settled weather meant it was completed ahead of schedule and the canal is expected back in service on Sunday.
The $150 million project by European specialist contractors is to stop leaks, some dating back to the 1970s when the upper Waitaki project was built.
Further work over 14 weeks in January next year will reline 2km of the canal at the Maryburn fill and improve earthquake resistance of the Maryburn earth dam structure.
Some preparatory work on that section will be done between now and July, including external earthworks on the canal batters and adjacent canal roads.
A section of the canal road used by heavy trucks will be closed to the public for health and safety reasons, with a gate at the Tekapo B head pond to provide pedestrian access as far as the third farm bridge.
Bridges crossing the canal will also be strengthened.
The work is expected to future-proof the canal for at least 50 years.
