The project is designed to increase climate change resilience, water supply security and renewable energy penetration. The main works are expected to be delivered under a single-responsibility Design-Build arrangement, and will comprise a large roller-compacted-concrete gravity dam approximately 59.6 m high from deepest foundation to crest and approximately 320 meters long, as well as associated hydraulic structures, together with a small surface hydropower plant, electrical substation, grid interconnection and ancillary facilities.
The proposed reservoir will have an indicative total storage volume of approximately 4 x 106 m3, of which approximately 3 x 106 m3 for flood retention, 0.5 x 106 m3 for seasonal water supply and 0.5 x 106 m3 of dead storage for sediment management. Reservoir operation will be supported by an ungated overflow spillway, low-level outlet, mid-level outlet and power intake.
The Design-Build contractor will complete the detailed design of the dam and all associated permanent and temporary works. The design scope is expected to include civil, structural, geotechnical, hydraulic, hydromechanical, mechanical, electrical, control, instrumentation, environmental and dam-safety disciplines.
The site preparation, debris and vegetation clearance, and the design and construction of the principal access-road and bridge works are being undertaken separately. The works are to be financed by the Asian Development Bank (ADB) and as such the eligibility rules and procedures of the ADB will govern the prequalification and the bidding process.
No more than three of the highest ranked eligible applicants will be shortlisted. It is expected that the Invitation for Bids will be issued in Q2 2027.
The Alaoa Multipurpose Dam Project is located where the eastern and central branches of the Vaisigano River meet on the Samoa island of Upolu. The proposed dam site is situated upstream of the existing 1.05 MW Alaoa power station and the Alaoa Water Treatment Plant, within the upper Vaisigano River catchment and upstream of the urban area of Apia, the capital of Samoa.
The location is strategically important because the Vaisigano River is a major contributor to flooding in Apia, while the same river system supports existing water supply and hydropower infrastructure. The proposed multipurpose dam is therefore intended to address interrelated flood-management, Apia water supply security and renewable-energy needs through a single integrated scheme.
The primary objective is to reduce flood risk to Apia, downstream communities and critical infrastructure. The reservoir and outlet arrangements are intended to attenuate flood peaks and enable the flood-retention volume to be re-established following a flood event. The project will also provide approximately 0.5 x 106 m3 of seasonal raw water-supply storage to improve supply reliability during low-flow periods and reduce the vulnerability of Apia’s water supply to seasonal variability and high-turbidity river conditions. In addition, it will incorporate a surface hydropower station with an installed capacity of approximately 0.6 MW with an expected annual clean energy generation of approximately 2.12 GWh. The hydropower component will contribute to Samoa’s renewable-energy target and reduce dependence on imported fuel.
In addition to the physical work, the wider project supports capacity development for dam operation and maintenance, project management, non-structural flood management and biodiversity conservation and monitoring. gender equality, community engagement and environmental and social safeguards.
Project preparation has included feasibility-level topographic, geological, geotechnical, hydrological, climate-change, environmental and social studies. An Independent Panel of Experts has also reviewed the project, and additional geotechnical, seismic-hazard and hydrological investigations have been progressed to strengthen the basis for detailed design.
The Prequalification Document has been advertised through the Government of Samoa e-Tendering Portal https://portal.tenderlink.com/mof_samoa/. Eligible applicants wishing to participate in the prequalification process shall download the Prequalification Document from the portal.
Bidders shall submit their applications electronically through the Government of Samoa e-Tendering Portal https://portal.tenderlink.com/mof_samoa/ on or before the deadline for bid submission.
The employer will notify all bidders in writing of the names of the prequalified applicants.
To obtain further information and inspect the Prequalification Document, interested eligible applicants should contact: Fui Tupai Mau Simanu, Chief Executive Officer, Ministry of Works, Transport and Infrastructure (MWTI), Level 4, Tui Atua Tupua Tamasese Efi (TATTE) Building, Sogi City, Apia, Samoa; Tel.: +685 21858 / 21611 ext. 202 / 21990; E-mail: mau.simanu@mwti.gov.ws
