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Wailuku River levee repairs slated for spring

$1.8M project aims to protect town from flooding, address erosion

A proposed levee repair project in the Wailuku River aimed to protect Wailuku town from future flooding and to prevent further erosion is expected to move forward in the spring after the county issued a finding of no significant impact for the project’s plans.

After years of repeated flooding and the undermining of infrastructure within the river, the Iao Stream Levee 27 Repair Project is proposing to repair a 240-foot long section of the stream bank, located downstream from the Imi Kala Street bridge and upstream of Levee 27.

“The proposed action will prevent further erosion of the bank, protect the downstream levee and provide reduced flood risk in Wailuku,” according to the final environmental assessment published earlier this month in the Office of Environmental Quality Control’s “The Environmental Notice.”

The plan calls for removing an existing concrete boulder fill slope and grading the slope; excavation to deepen the protection along the toe of the slope to be below the scour depth; and constructing a new revetment system consisting of a reinforced soil slope, grouted riprap face slope, use of under-drain pipes and placing dumped riprap at the toe of the slope to protect against scour, which can cause erosion.

The project area covers about 1.39 acres and is not a part of the Iao Stream Levee System.

The estimated costs for repairs in the project area is $1.8 million, with construction slated to begin in the spring at the end of the wet season and anticipated to last between six to eight months.

Exact construction dates will be available when a contractor has been selected for the project, according to the environmental assessment. Dates are subject to change based on permitting and design and the scheduling of work in the dry season.

From an upstream sediment basin to Kahului Bay, Wailuku River is about 12,000 feet long and is located within the Na Wai ‘Eha Watershed.

Projects over the years have sought to stabilize the river and protect against flooding. The Iao Stream Flood Control Project, which dates back to the 1980s, was implemented to reduce flood damage to the town of Wailuku. The completed project consists of a debris basin, channel improvements, a drop structure, levees along the right bank, floodplain management along the left bank and stream realignment with channel improvements.

Still, intermittent heavy rains have caused minor to severe flooding in Central Maui and erosion to the river bank’s walls for the past 40 years despite emergency repairs.

According to the environmental assessment, Wailuku River in the project site area is “in danger of reverting to a flood hazard zone due to erosion/deterioration/scour of the right bank and undermining of the bank toe.”

In order to “preserve the reliability of the stream bank,” protect the downstream levee and reduce flood risks for the Wailuku community, the county Department of Public Works said that repairs are needed.

“In the long term, the proposed action is expected to have beneficial environmental and social impacts as it will prevent further erosion of the bank, protect the downstream Iao Stream Levee 27, and provide reduced flood risk to the town of Wailuku caused by design deficiencies and long-term damage to the existing bank stabilization structure suffered during repeated floods since its original construction and subsequent repairs,” according to the environmental assessment.

* Dakota Grossman can be reached at dgrossman@mauinews.com.

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