Ala Wai Project Designs Presented

The U.S. Army Corps of Engineers, Honolulu District, recently completed a three-day Ala Wai Flood Risk Mitigation Project Design Charrette in Honolulu.

USACE together with stakeholders from the governor’s office, mayor’s office, State of Hawaii Department of Land and Natural Resources discussed proposals for the construction of this $345 million project.

“An opportunity to execute a project of this magnitude does not occur every day, so it’s important for us to have everyone gain a common understanding of the project, from Congressional authorization and funding through local real estate policies,” said Ala Wai Flood Risk Mitigation Project Manager Jeff Herzog.

During the charrette participants were given tours of upper and lower watershed locations where retention basins and debris catchment areas are planned and also areas along the Ala Wai Canal where flood control features are planned.

Enterprise personnel from USACE’s Seattle District, New Orleans District, USACE Contracting Enterprise, and Risk Management Center identified best practices, lessons learned and suggestions for how to execute the project.

“Having the Enterprise participate was invaluable,” Herzog said. “New Orleans District executed $14.6 billion in constructing the Hurricane Storm Damage Reduction System while working with the State of Louisiana from 2005 to 2011. Similarly, we are negotiating with the stakeholders to construct a Flood Control System here in Honolulu.”

“These are not just separate projects throughout Honolulu but are all integral pieces to an overall system which will reduce the risk to life, safety, and property for the communities in the Project Area. New Orleans District didn’t accomplish that work alone – they used Engineers without Borders, engaged other USACE Districts. Honolulu District is planning to engage in a similar manner,” Herzog added.

The Ala Wai Watershed encompasses a drainage area of 16.2 square miles and is located on the southeastern side of the island of Oahu in urbanized Honolulu. The three major streams within the watershed include the Makiki, Manoa, and Palolo streams, all of which drains into the Ala Wai Canal. The Canal is a two-mile-long waterway constructed during the 1920s to drain extensive coastal wetlands, thus allowing development of the Waikiki district.

Honolulu District is currently negotiating particular terms of the Partnership Agreement with the stakeholders. The project is being funded under the Fiscal Year 2018 Emergency Supplemental and allocated $345 million for Pre-Construction Engineering & Design and construction to be cost-shared proportionately.

Project features include the following eleven individual structural elements and two non-structural components:

• Six debris/detention basins in upper reaches of Maikiki, 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);
• Fish and wildlife mitigation (non-structural).