Volcanic and geotechnical challenges at the Belisama pumped-storage scheme, Philippines

Belisama Hydropower Corporation intends to develop the 800 MW Belisama pumped-storage plant at Laguna de Bay, approximately 50 km southeast of Manila. The rated gross head of the scheme will be 466 m and the mean annual generation is expected to be 1523 GWh. The main geotechnical construction challenges for the project include the stability of the foundations, construction of the pressure shaft, powerhouse and transformer caverns in heterogeneous volcanic deposits, and excavation of the outlet/intake foundations in soft sediments. The paper provides details regarding these challenges as well as the planned mitigation measures, planned further investigations, layout and construction methodology.