The Daguan Power Station’s penstock is composed of 50m deep, 6m diameter shafts and two long 80m horizontal water chambers.Due to an earthquake causing serious damage to the RC lining, repair was needed.The repair work had to be carried out deep inside the shafts and each water hamber, and the rapid change in head pressure in the penstock had to be taken into consideration, so the work was difficult and had to be performed under high quality requirements.The owners were on a tight schedule, so the work was proceeded at a peak of continuous 24 hours with 6 teams on rotating shifts. The main repairs included Epoxy cracks resin grouting, polyurethane resin grouting, repair using resin mortar and cement consolidation grouting. A total of about 4,400 tons of cement mortar was used to repair cracks over 2,300 meters. The work was successfully completed in February 2001, and on completion, the penstock had been restored to its normal functioning condition.The Daguan Power Station’s penstock is composed of 50m deep, 6m diameter shafts and two long 80m horizontal water chambers.Due to an earthquake causing serious damage to the RC lining, repair was needed.The repair work had to be carried out deep inside the shafts and each water hamber, and the rapid change in head pressure in the penstock had to be taken into consideration, so the work was difficult and had to be performed under high quality requirements.The owners were on a tight schedule, so the work was proceeded at a peak of continuous 24 hours with 6 teams on rotating shifts. The main repairs included Epoxy cracks resin grouting, polyurethane resin grouting, repair using resin mortar and cement consolidation grouting. A total of about 4,400 tons of cement mortar was used to repair cracks over 2,300 meters. The work was successfully completed in February 2001, and on completion, the penstock had been restored to its normal functioning condition.