Waterproofing of the head pond and canal was essential to stop water leakage and had to be carried out during the 10-week shutdown period of the project.

A patented tensioning system to increase the water flow and speed up the installation, and careful preparation on a 1:1 scale replica of the canal built before the start of the work: these were the two keys to the success of this huge project which allowed 160,000 m2 to be waterproofed in record time and improved the hydraulic efficiency of the installation by 12,5%.

  • Name of the Owner and Client
    PT VALE Indonesia
  • Delivery date of the project
    April 2019
  • Partners of the project
    Main contractor: Leighton Contractors
    Waterproofing contractor: Carpi

Key figures

The Larona Canal, located on the island of Sulawesi in Indonesia, supplies water from a lake to a hydroelectric power plant, which provides electricity to a nickel processing plant.

The Larona Canal is 7 km long and ends in a headpond that feeds the Larona power plant.

On February 2018, Larona canal was dewatered to install a Carpi waterproofing membrane, the Sibelon® CNT 4400.

In order to meet the strict contractual deadlines, a 1:1 scale 100m long canal replica was constructed several months before the start of the work.

It was used to develop and validate procedures to minimise installation times and maximise safety, and to organise extensive training sessions for a large number of workers.

  • 160 000
    Waterproofed surface, in sq.metres
  • 7.4
    Weeks of work, instead of 10 weeks allowed
  • 1200
    Number of workers on site, speaking 9 different languages
  • 12.5 %
    Increase of power achieved

Restore watertightness and improve hydraulic efficiency

The Larona head pond in Indonesia, located at the downstream end of a 6.7 km long hydroelectric canal, is a storage reservoir for turbine start-up and automatic overload shutdown. Most of the time, the plant is operated at full capacity to generate as much power as possible for a major mining company.

The main objectives of the waterproofing project were to stop leaks to prevent loss of structural integrity, to increase water flow, and to install the waterproofing solution within the 10 weeks of planned shutdown. The solution must also be able to withstand seismic events, as Larona is located in a seismic zone.

Tensioning anchorage

Tensioning anchorage

The watertight geomembrane lining the entire head pond was kept taut at the surface in areas of high turbulence by means of tensioning profiles, so that the water flow could be increased.

Preparatory work

The preparatory work consisted of removing previous unstable repairs with hydro-jetting and checking the position and depth of the reinforcement bars where the anchorage profiles would be installed, to avoid the anchors intercepting the concrete reinforcement.

Larona headpond-preparatory work for waterproofing-Carpi
Waterproofing works-Preparatory works with support at joints-Carpi

Support at joints

A strip of geomembrane identical to the waterproofing liner was then laid to support it over the joint.

Placement of the waterproofing liner

The geomembrane liner was installed directly over the existing rough concrete and support geomembrane strips at the joints.

Placement-waterproofing liner_Carpi
Title* Put the title in the TeFace anchorage-perimeter sealing-Carpi

Face anchorage and perimeter sealing

The face anchorage was made by stainless steel flat profiles and stainless steel tensioning profiles, specially designed to insert anchors without intercepting the reinforcement. The perimeter seals are mechanical and watertight under pressure.

Restored watertightness and improved hydraulic efficiency

Static filling showed that leakage had stopped. Flow testing of the canal at full production showed lower water levels, and an increase in production from 160 MW to 180 MW.

Restored watertightness-Carpi