Long submerged tunnel inspections: the Mantaro headrace tunnel, Central Andes Mountains, Peru

Located in the central Andes mountains in Peru, the 900 megawatt C.H. Antunez de Mayolo hydroelectric facility (Mantaro) generates approximately 70% of the region's power, which includes the capital city of Lima (population 7 million). In a remote region approximately 350 kilometres east of Lima, at an altitude of over 2500 meters above sea level, the Mantaro facility (named after the river upon which it is situated) is a major engineering feat in itself. The headrace tunnel servicing the plant, 4.8 metres (15 feet) in diameter, has been bored through the Andes mountains and extends for an extraordinary distance of 19.8 kilometres (66000 linear feet). Since its construction in the early 1970s this facility has been unable to meet its maximum generating capacity due to a gradual loss of head pressure. The purpose of the inspection is to determine the cause of this problem and to identify possible solutions. The paper describes the ROV developed to carry out the inspection. The ROV incorporates an application designed sensor package, multiple camera suite, dual sonar, NDT probe, five function manipulator and a concrete coring drill.