In 1921, the construction of a tunnel and three weirs commenced.
Construction of weirs on the Orongorongo River, Big Huia Creek, and Little Huia Creek began in the year 1921. Simultaneously, a 3.2km tunnel cutting through the Orongorongo range was initiated to connect the Orongorongo River and valley to the Wainuiomata River and valley. Known as the Orongorongo Tunnel or Semples Tunnel, it was complemented by a small railway and a pipeline that facilitated the conveyance of water into the main pipeline system that led to Karori. This system is still in use today and provides around 5% of the Wellington region’s water supply.
During construction, one of the major challenges encountered in the project was accessibility. A 6.5km pack track, ascending to 300 meters into the Orongorongo Valley, was established to transport lighter materials. For heavier materials, trucks were utilized to transport them from the mouth of the Orongorongo Stream, covering a distance of 45km. From this point, horse teams pulled the materials an additional 22km up the riverbed to reach the entrance of the tunnel. This route streamlined the transportation of approximately 600 tons of steel water pipes, cement, timber, and compressing plant equipment.
The project reached its culmination in 1926, representing a significant enhancement in Wellington’s water supply by 27 million litres per day.
