The Quitaracsa hydroelectric power plant now being built in the province of Huaylas, central Peru will add a further 112 MW of installed capacity to the country’s national grid.
Located 500 km northeast of Lima at a height of 1 800 m above sea level, this project is a major feat of engineering involving a 5.7 hectare reservoir and a 5 800 m long headrace tunnel installed inside the mountain at a steep incline of 16 percent.
The headrace tunnel reaches the underground powerhouse at the lowest point and connects a network of various tunnels including the tailrace tunnel, cable tunnel and access tunnel.
JME SAC, the consortium consisting of Peruvian contractor JJC and Mas Errazuriz of Chile, is responsible for the work. Adan Nanquen, Construction Equipment Manager at JME, explains that the challenges are considerable. “Hydropower projects usually have a slope of about one percent that reaches a penstock of about 500 meters long. This project is extreme because the slope of the tunnel is 16 percent and does not have a penstock tunnel.”
An Atlas Copco Boomer 282 drill rig is used to drill the blastholes but the extreme slope of the tunnel makes it difficult to ventilate and to evacuate the dust and fumes after each blast.
Water spray solution
Santiago Arenas, Underground Excavation Manager at Atlas Copco Peruana, says the project planners needed to create an efficient, clean and safe construction environment inside the tunnel and found the answer in the Häggloader 7HR-B. This continuous, front end loading system from Atlas Copco employs a special water spray system to keep the working area clear at the face.
The cross section of the tunnel is 3.6 m x 3.8 m and the Häggloader is specially designed for small-to-medium sized tunnels of this type. It uses a front digging bucket to backhoe the blasted rock fragments onto its built-in conveyor which continuously feeds a dump truck at the rear. Julio Salazar, Development Manager at JME, emphasizes the environmental and health benefits and says the Boomer and Häggloader are “ideal partners”. “It is in the most adverse of situations such as these that the Häggloader really shines,” he says “The Häggloader also works perfectly together with the 42-tonne capacity dump truck and the water spray system gives very effective dust control.”
Nisan Martinez Cuenca, who operates the Häggloader 7HR-B, comments: “The water spray system enables the smoke and dust to be removed faster and this means that the working environment at the face is much better.
“Inside the tunnel the Häggloader 7HR is working in front of us in a temperature of 30– 40°C without any problems.” Victor Mercado, specialist at Atlas Copco, says the performance of the Boomer– Häggloader combination has exceeded all expectations. In addition, maintenance of the Häggloader is easy, requiring just periodical replacement of certain parts.
The Häggloader solution
Häggloader is an electro-hydraulic loader providing continuous loading while maintaining good air quality. It is also equipped with a diesel-hydraulic system which is used for transportation and for smaller digging work.
The machine’s front arms or backhoe bucket loads material onto a conveyor belt which continuously fills a dump truck at the rear. The conveyor can also be raised and lowered to suit the loading height of different vehicles. Suitable for galleries and tunnels with a cross section of 7 m² and upwards, the loader’s front and rear axle also gives excellent agility and the ability to move sideways in confined spaces. In addition, the operator works in a compartment with a protective roof, door and comfortable backrest.