Wailuku River levee repair plan advances
County Department of Public Works finds ‘no significant environmental impact’ on the $20 million project
The county Department of Public Works has issued a finding of no significant environmental impact for a $20 million, federal-Maui County project to repair storm-damaged levees in the Wailuku River to protect Wailuku town.
Heavy rains in mid-September inflicted “significant damages to the existing levees,” according to a final environmental assessment that Honolulu consultant GSI Pacific completed in July for the U.S. Army Corps of Engineers.
An inspection by the Corps and Public Works Department found erosion of earthen levees and other drainage channel damage on the right bank of the river downstream of Imi Kala Bridge. At the time of the inspection, the county was making emergency repairs.
The assessment report says that the flood-control project was designed to provide protection against severe flooding, but now “the 33-year-old flood-control system no longer has the ability to provide the original level of protection to the town of Wailuku due to the recurring damages that have occurred since its original construction.”
“Wailuku River is in danger of reverting to a flood-hazard zone due to deterioration/scour of the right bank and undermining of the levee toe resulting from changes in the streambed dynamic and upstream watershed use/development that have occurred in the past 30 years,” it says. “In order to preserve the reliability of the existing flood-control systems, additional structures are needed to protect the Wailuku community.”
Project plans call for reconnecting the main stream channel with the floodplain to reduce damaging flooding along the main channel and right bank levees.
“The reconnection would be accomplished by lowering the left bank, grading the overflow area to disperse flow into the floodplain, and constructing the main channel with a concrete diversion weir to force flood flows to leave the main channel and enter the existing floodplain on the left bank of the stream,” the assessment says.
A portion of the river’s left bank would be lowered to allow the return of overflow into the main channel, it says.
Other work would include stabilizing riverbanks to prevent further erosion, and an existing revetment would be reconstructed.
The project would be located on a 0.4-mile stretch of the river from slightly downstream of Waena Street and upstream of Imi Kala Street. The repair work would be done in the vicinity of Papohaku Park, Iao Parkside and the Millyard. Piihana Road is on the other side of the river.
The project is designed to slow floodwaters by diverting them to an existing floodplain and by allowing them to be controlled and redirected.
The repair work “is needed to protect the many adjoining residences and commercial properties from flood damage during major storm events,” the assessment says.
Earthjustice attorney Summer Kupau-Odo said one of the major concerns of proponents of restoring natural stream flows in the Wailuku River and other Central Maui streams has been the negative impacts of the Corps’ flood-control structures on native stream life, such as ‘o’opu.
The Corps has recognized a resurgence of ‘o’opu, freshwater stream gobbies, since the initial return of stream flows to the Wailuku River in 2014, she said in an email.
“We’re disappointed the Corps dismissed our proposals for restoring habitats to facilitate upstream migration, which these species need to survive, by claiming it’s not the project’s purpose,” Kupau-Odo said. “The Corps’ own policies require it to consider potential for such restoration.”
She called the levee-repair project a “golden opportunity to not only reduce flood risk but also begin rectifying the ecological and cultural harm of its channelization of the Wailuku River.”
“It’s a shame the federal agency refuses to lend a helping hand to Na Wai ‘Eha communities who have fought long and hard to restore the ecological health of this river,” she said.
Earthjustice has represented Hui o Na Wai ‘Eha and Maui Tomorrow in legal battles over Na Wai ‘Eha stream flows. Na Wai ‘Eha includes the Wailuku and Waihee rivers, and the Waiehu and Waikapu streams.
Since the project was originally built for what was formerly called Iao Stream, the flood-control system has prevented an estimated $49.6 million in flood damage as of fiscal 2013, the environmental assessment report says.
“The flood-control system has instilled a sense of security in the growing community of Wailuku,” it says. However, “a failure in the deteriorating levees would cause floodwaters to inundate the Wailuku River drainage basin and loss of life and extensive property damage would be inevitable.”
Estimated future damage without the project was put at about $2.6 million, compared with $7,000 if proposed repairs are completed, the report says.
Dino Buchanan, chief of public affairs for the Army Corps of Engineers, Honolulu District, said in an email that the preferred alternative’s estimated cost is nearly $20.5 million. The project would be funded by a split between the federal government (65 percent) and Maui County (35 percent).
The Corps has proposed implementing engineering designs to address existing flood hazards and to provide the authorized level of reduced flood risk, he said.
“The final environmental assessment was prepared to give systematic consideration to the environmental, social and economic consequences of the proposed project,” Buchanan said.
The report says the preferred alternative was considered “the most economically feasible and beneficial.”
The finding of no significant environmental impact was published Tuesday in the state Office of Environmental Quality Control’s “The Environmental Notice.” It can be found at health.hawaii.gov/oeqc/.
* Brian Perry can be reached at firstname.lastname@example.org.