Key Project Facts

The objective of this project is to reduce the damages and risks associated with flooding in the Ala Wai Watershed. Flash-flooding conditions can materialize within an hour in the upper portion of the Ala Wai watershed.

The U.S. Army Corps of Engineers estimates a major flood in the watershed could damage 3,000 structures and cost more than $1.14 billion.

The project was developed to minimize the impact to private lands and maximize the use of public lands, but some impacts to private lands are unavoidable.

Acquisition of private lands is highly regulated under Federal law and is the responsibility of the non-Federal partner.

The U.S. Army Corps of Engineers has been authorized to move forward from the Feasibility Phase to the Design and Construction Phase, meaning the project is economically justified and environmentally compliant and has received authorization from Congress for construction.

In July 2018, Congress appropriated $345 million is an emergency appropriation to invest in projects located in areas prone to flooding that were determined to be economically justified and environmentally compliant. There is no expiration of funds provided under PL 115-123, for the Long Term Disaster Recovery Investment Program.

Non-federal sponsor cost share is approximately $125M. The benefit-cost ratio is approximately 3.68 to 1.

Federal Sponsor: U.S. Army Corps of Engineers (Local: Honolulu District)

Non-Federal Sponsor: Potential non-Federal sponsor are the State of Hawai’i DLNR, (Engineering Division) and the City & County of Honolulu (Department of Environmental Services)

Because the designs for the project are not complete, it is inappropriate to speculate on the exact location and size of the project features. USACE and our partners will complete data collection at specific project sites to further inform the design.

Project features include six debris/detention basins in upper reaches of Makiki, Manoa, and Palolo streams; one in-stream debris catchment structure; three multi-purpose detention basins; flood control elements along the Ala Wai Canal; flood warning system (non-structural); and fish and wildlife mitigation (non-structural).

Design development includes safety assurance reviews by the USACE Dam Safety Center and technical reviews to ensure a level of safety and operability.  The structures will also be constructed to meet Hawaii Dam Safety requirements so that the non-Federal Partner can maintain the project features in a way that will ensure the safety of the community and the project.

USACE is on the forefront of federal construction agencies in integrating climate change (including sea level change) into project planning and climate change adaptation into project design, construction and repair.

Concerned citizens are encouraged to communicate with their locally elected leaders, City & County of Honolulu, and the State of Hawaii. The Honolulu District welcomes your specific questions about this project. Once a project partnership agreement is in place between USACE and our non-Federal partners, additional formal channels will be established for the public to communicate questions or concerns.

Contact Information

Civil & Public Works Branch
Building 230
Fort Shafter, HI  96858-5440
(808) 835-4026