Maui County is proposing a $1.29 million slope protection project along the Wailuku River to protect foundations, commercial buildings and preventing flooding in the Wailuku Millyard.

The project would take place on about 5,000 square feet of the existing riverbank behind buildings along Wili Pa Loop, according to a draft environmental assessment for the project.

High flow within the stream and severe storms have contributed to the erosion along the steep, unprotected slope along the right bank of the river, according to the assessment. The bank is subject to increased velocity and scour due to a bend in the channel immediately upstream.

The earthen embankment within Maui County’s property also has eroded, exposing the foundation of an adjacent commercial building, the assessment said.

Continued degradation of the embankment may cause loss of property and flooding in the light industrial subdivision.

The county’s Department of Public Works is proposing excavation, regrading and reinforcement of the riverbank slope using grouted rip-rap consisting of cobbles and boulders with concrete infill, according to the assessment, which was published Thursday in the Office of Environmental Quality Control’s “The Environmental Notice.”

A line of large boulders will be placed at the toe of the lined slope.

During construction, a temporary diversion berm will be used to divert stream flow around the active grading area.

Project activities will also be limited to one half of the river cross-section at a time to allow a migratory pathway and maintain streamflow so animals can use the stream during construction.

Ideally, work will take place in the low-rainfall months of May to October, the assessment said.

Temporary construction measures will be removed and the parcels restored to their pre-construction conditions following completion of the project.

The assessment said that no aquatic species protected by the state, or federally endangered or threatened species were observed in the Wailuku River within the project area.

No traditional or cultural practices have been identified within the project area and the project is not anticipated to impact cultural practices at the project site, the assessment added.

The county has consulted with Hui o Na Wai ‘Eha, a local nonprofit that advocates for the protection of the streams, and will continue the consultation throughout the design phases.

According to the nonprofit, the aquatic biological resources of the Wailuku River are considered cultural resources as well, due to their role in traditional Hawaiian diet and practices.

The current proposed work would only involve half of the river channel directly adjacent to the project site, in order to preserve uninterrupted mauka-to-makai flow and limit any disruption to movement and migration of aquatic species.

A program of archaeological monitoring will be carried out during ground-disturbing activities in order to minimize impact to cultural resources if they are present in the project area, the assessment said.

A 30-day public review and comment period has begun. Comments are due by Aug. 9 and can be sent to the proposing/determining agency: County of Maui, Department of Public Works, 200 S. High St., 4th floor, Wailuku, HI 96793. Kristi Ono is the contact and can be reached at (808) 270-7745 or at public.works@ co.maui.hi.us.

Comments should be copied to the consultant: Munekiyo Hiraga, 305 High St., Suite 104, Wailuku, HI 96793. Gwendolyn Rivera is the contact and can be reached at (808) 244-2015 or at planning@ munekiyohiraga.com

The full assessment can be found at oeqc2.doh.hawaii.gov/The_Environmental_Notice/2021-07-08-TEN.pdf.

* Melissa Tanji can be reached at mtanji@mauinews.com.