This paper describes the repair of a cast-in-place reinforced concrete pipe at the El Encanto power plant outside San Josee, Costa Rica. The penstock that is 5742 feet (1750 m) long with a diameter of 7 ft (2.1 m) brings water from an upstream reservoir along mountainous terrain to the plant. While the water in the pipe is not pressurized, the change in elevation from the reservoir to the turbine complex introduces some pressure in the penstock.In spring 2009, when the construction of the plant was completed, the pipe was filled with water and thousands of small and large leaking holes were observed. As a first attempt, the holes and cracks were sealed with various chemicals and mortars; but when the pipe was filled with water, the cracks opened up again and leaking continued.The repair that was successfully implemented included applying Glass Fiber Reinforced Polymer (GFRP) fabrics on the entire inner surface of the pipe; nearly 150,000 ft~2 (14,000 m~2) of FRP lining was installed, making this the largest reported FRP pipeline retrofit project to date. Among the challenges were the sloping terrain along the mountain and the limited access to the pipeline which consisted of 4 small square ports each 2 ft × 2 ft (600 mm × 600 mm).To save time, all materials were shipped while the design was being finalized. A team of 2 engineers and 4 supervisors were sent to the job site to oversee the installation and train the local crew which consisted of some 40 laborers. The installation of FRP lining and the application of a top coat took only a record 15 days. The repaired pipe was successfully tested in July 2009 and no leaks were observed.
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