Hazards mitigation plan
Different solutions to this hazard have been investigated by the Jack Lockwood American team:
The HSF proposal
The following proposal is still an indicative draft as no field investigation has yet been carried out by any expert from HSF. The idea is to consolidate the lower unit and to protect the upper unit as detailed below.
1) Consolidating the lower unit and preventing the leakage (Figure 1)
In order to prevent the leakage, one, two, or three rows of concrete columns could be put in place using the "jet-grouting" technique. The jet grouting consist in drilling vertical holes inside of the structure and injecting an extremely high pressure (2000 bars) pure cement jet. This high speed jet (500 km/h) violently mixes the surrounding granular material and naturally results in a well-proportioned concrete.
The columns would be drilled next to one another to result in a concrete seal on the upstream side of the dam, and therefore prevent leakage. Steel bars have to reinforce these concrete columns.
On the down stream side of the dam, concrete columns would be drilled several meters apart in order to allow the drainage of the residual leaking.
2) Protecting the upper unit (Figure 2)
A concrete spillway would be laid over the upper unit. It would be anchored to the upper unit and to the bedrock through the reinforced concrete columns. This spillway would prevent the upper unit from superficial erosion when the stream floods during the rainy season.