Revised hazard assessment for Afulilo Dam, Samoa

Abstract Afulilo Dam was built as part of a hydroelectric scheme to augment the power supply for the island of Upolu, Samoa. The 23 m high concrete gravity dam sits on the crest of a waterfall that once drained an intermontane basin. Initially, concerns were expressed about a possible active fault through the dam site linked with a larger fault across the island. This assertion was refuted but not tested by the owners, and the dam came into operation as planned. This issue was again reviewed in 2009–10 as part of an environmental and power augmentation study. The opportunity was also taken to test the compliance of the dam with accepted international practices. Additional regional geological assessments, a review of the seismic data and further drilling at the dam site provided data to improve the geological model for the dam site. It is concluded and confirmed that there is no clear evidence for the existence of such faults. If they do exist, they are not active and therefore not significant for the safety of the dam.