Cavico Corporation announced in May that Cavico Bridges and Tunnel Company, a wholly-owned subsidiary, signed an agreement valued at approximately USD20.7 million to construct a headrace tunnel, surge tank, and intake for the Thai An hydropower plant, 200 km north of Hanoi. The project includes a 3,800 m-long headrace tunnel, 5.2 m bored diameter and 4.5 m completed diameter. The surge tank is a 75 m, 11 m bored diameter and 10 m inner diameter vertical shaft. There is also a 133 m inclined penstock tunnel at 70 degree inclination. According to investigation data provided by the owner, the path is based in granite rock with highly hardness and massive, few location of weak zone anticipated at the geological faults crossing the headrace tunnel.Cavico B&U proposed to bore all the tunnel by drill and blast method with an Atlas Copco drill rig H282 or equivalent. The excavated rock will be mucked out by wheel loader and dumptruck. For the inclined penstock, the contractor proposes using a raise boring machine for reaming at 1.8 m diameter. The excavation then shall be carried out downward by drill and blast. During excavation stage, the tunnel will be temporary supported with shotcrete (with and without reinforced wiremesh), rockbolt and H beams where required. A sliding formwork carriage will be used for tunnel lining concreting and climbing formwork (jump form) for the surge tank. Construction is expected to commence very soon. The company estimates the project should be completed within 25 months. Visit www.cavicocorp.com and www.atlascopco.com 25/07.