This project was for the replacement of the external coating system on the three penstocks that feed into the Tuai powerstation in Waikaremoana.
Each pipe was 1.8m in diameter and 1300m in length, with a surface area of 30,000m2. Two of the pipes were built in the 1920’s and were riveted structures while the third was built in the 1950’s and was a welded structure. The work took close to 3 years to complete and specifically involved:
- The removal of the external lead based coating system initially via automated ultra high pressure (UHP) water jetting equipment and later via abrasive blasting
- The application of a modern coating system over all three penstocks.
The project had many challenges, including the removal and management of significant quantities of lead based paint, harsh environmental conditions and the added difficulties associated with personnel working in a remote area for an extended period of time.
The paint removal process initially began via the use of automated UHP water jetting equipment, however it could not remove the paint around the rivets on the two 80 year old pipes due to their unusual size. As a result, this process was changed to abrasive blasting. The contract required strict attention to the control and removal of discharges to the surrounding environment, therefore a full containment structure was built around the pipes to ensure no discharges were released.
The remote location and duration of the works added extra pressure, with staff spending extended periods of time away from their families and in fairly inhospitable conditions. This was largely managed through regular rotation of the project team so that staff could return home to their families and have some down time.
Despite the challenges faced during the works, the project was delivered successfully and to the standard required by the client specification.