Ala Wai Canal Flood Project Cost Increases

A Cost and Schedule Risk Analysis (CSRA) workshop conducted with the City and County of Honolulu in Oct. 2020 determined an increase to the cost for the Ala Wai Flood Risk Management project. The U.S. Army Corps of Engineers (USACE) is in discussions with city, state, and federal leaders to determine the next steps for the project.

The CSRA and cost estimate were developed based on roughly 10% design concepts from the Engineer Documentation Report signed in Aug. 2020. Conservative, worst-case scenario costs and risk assumptions were applied to the CSRA across all features of the project. The draft estimate then underwent a series of reviews at the USACE Walla Walla District Cost Engineering Mandatory Center of Expertise (Cost MCX), resulting in a certified cost estimate of $651 million.

The most significant changes in design and cost include the removal of debris and detention basins in the upper watersheds, addition of bypass structures at Woodlawn Bridge and at the Makiki Stream confluence, alterations to floodwalls/levees (including an extension along the Manoa-Palolo Channel to Date Street and addition of floodwalls in Manoa and along Koali Road), and a consolidated pump station at the confluence of the Manoa-Palolo and Ala Wai Canal. The debris and detention basins ultimately had a much lower cost than the added conveyance features. However, advanced modelling proved that the detention features were not suitable for mitigating damages at the 1% probability (or 100-year) annual exceedance level of storm event. 

The certified cost of $651 million (fully funded) nearly doubles the Bipartisan Budget Act of 2018 authorized project cost of $345 million. USACE leadership has been in close communications with City, State, and elected officials since the new costs came to light.  The project is currently under review by Headquarters USACE for continued federal interest in funding.

A fully reviewed economic analysis is currently scheduled for completion in Feb. 2021. USACE will summarize the certified costs, economic analysis, supplemental National Environmental Policy Act efforts, and recommendation for path forward in a report, due for completion in March 2021.