Cirata Hydropower is the biggest hydropower plant in Indonesia. It has 8 x 125-Megawatt electrical power capacities. The assessment is conducted to ensure the tunnel safety to support the plant operation. The tailrace tunnel has vital function as final outlet to waste the water from penstock pipe. 

On this assessment works, we use CETU or Centre d’Études des Tunnels guidance book. CETU guide to assess the tunnel based on the following parameters: tunnel center line missalignment, tunnel deterioration, material degradation and seepage water quality. When meets the deterioration, degradation or seepage, we write it on inspection log and rate it based on IQOA rating guidance. After that, from the IQOA rate value, we rank the deteriorationinto 3 classes of IQOA Rank. 

For Tunnel missalignment test, we use Total Laser Scanner. From the TLS, we can describe the geometry change of tunnel such as Necking, Bulging, or lateral and vertical movement. In some case, TLS can be used to measure scouring rate of tunnel lining. Beside TLS test, we also conduct water quality test of seepage for the following parameters: pH, Electric conductivity, and major ion. The water test is used to determine water aggresiveness and dissolving or alteration process of surrounding soil/rock.