Comments sought on Iao Stream project

April 12, 2011

Comments can be submitted through May 9 to be included in an environmental impact statement being prepared for a project to correct a design deficiency that has led to major erosion in the Iao Stream flood control project in Wailuku.

The fixes in the project, designed to reduce flood risk to Wailuku, would cover 2 miles between Market Street and Waiehu Beach Road. It includes a debris basin, diversion levees and channel improvements.

No cost has been determined for the project, which is in the planning stage, said Nani Shimabuku, project manager with the U.S. Army Corps of Engineers in Honolulu. She said the planning would be followed by design, then construction, which would be years away.

The flood control project was designed to protect Wailuku against a 222-year flood, with a 0.5 percent chance of flooding in any given year. But over the years, numerous storms have sent rushing water through the steeply sloped channel, resulting in major erosion of the streambed, undermining banks and levees, according to the Army Corps of Engineers.

The storms included a flood that caused extensive erosion in January 1980 during initial construction of the project. Repairs were made, but shortly after the project was completed, high stream flows again caused extensive erosion requiring additional corrective work, according to the corps.

The corps estimates that the flood control project has prevented an estimated $50 million in flood damage since its completion in October 1981.

Without corrective action, there could be further damage that could result in levees collapsing or overflowing, according to the corps.

After the corps released a draft environmental assessment in March 2009, concerns were raised about the effect on native aquatic species and habitats and on groundwater recharge.

The evaluation of design alternatives will take into account minimizing adverse impacts, according to the corps.

Agency and public comments submitted as part of the draft environmental assessment will be considered as part of the environmental impact statement. Additional comments can be submitted by email to iaostreameis@usace. or at the project website,

Comments also can be mailed to the U.S. Army Corps of Engineers, Honolulu District; CEPOH-PP-C; Building 230, Room 307; Fort Shafter 96858-5440; Attention: Nani Shimabuku, project manager.

Copies of comments should be sent by email to or mailed to County of Maui; Department of Public Works; 200 S. High St.; Fourth Floor; Wailuku 96793; Attention: Ty Takeno, Design Section head.

A draft EIS is scheduled to be available for public review and comment in the summer of 2012.

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