Cobra Hydraulic Infrastructures to undertake the repair of the Changuinola Hydroelectric Tunnel in Panama

In September Cobra Hydraulic Infrastructures starts the execution of repairs to the tunnel that forms part of the Changuinola 75 Hydroelectric Project, in the province of Boca de Toro, Panama.

AES is among the largest companies in the field of electricity generation and enjoys annual revenues of billion. The project will be undertaken as a joint venture in which CIH holds an 80% stake.

The Changuinola Hydroelectric Project includes a 4,200 metre tunnel with a flow rate of 221m3. The plant has a total installed capacity of 223 MW, generated by two Francis turbines and has a net head of 96 metres.

The work schedule for project execution is twelve and a half months, of which eight and a half will be employed in the completion of all planned works. Additionally, four months of preliminary work will be undertaken to speed up execution times.

Prior to commencing the repair work, the tunnel must first be emptied. This is one of the most complex procedures involved in the project, requiring extremely precise calculations and procedures, due to the possible loss of pressure that can occur in the case of excessively fast draining. The emptying process will be carried out mainly through gravity, using two 250 mm diameter pipes with net drainage volumes of 440,000 m3. Additionally, the final metres will be pumped dry through the Surge ADIT with net volumes of 46,000 m3.

The works to be undertaken in the HRT will encompass over 1,600 metres of the total 4,252 metre length, with a diameter of 10 metres and a hydraulic section of 100 m2, to be lined with reinforced concrete. In the Surge Adit, which will be the access point for the works, the installation of 300 metres of cladding is planned. In addition to these works and depending on the client's requirements, an additional 300mtres of the HRT may be subject to repair.

Finally, filling and functional tests will be carried out to ensure that all repairs have been completed correctly. The project will involve the placing of 7,000 tons of steel and 40,000 m3 of concrete.