State DOT selects final route for Honoapiʻilani Highway realignment

A roadway alignment for a six-mile segment of Honoapiʻilani Highway at risk of eroding into the ocean has been determined in a final environmental impact statement issued this month by the Hawaiʻi Department of Transportation, in coordination with the Federal Highway Administration.

The decision and completed environmental impact statement advance the project in a design-build process to reduce the highway’s vulnerability to erosion, sea-level rise and high-wave flooding. Now, the ocean is only a stone’s throw away from portions of the highway that provide a vital link between Central Maui and resort areas in Lahaina, Kāʻanapali and Kapalua.

The extent of the highway realignment is from approximately Milepost 11, in the vicinity of Pāpalaua Wayside Park to Launiupoko, at Milepost 17, the existing southern terminus of the Lahaina bypass.

In late June and early July, state highways officials designated a portion of Honoapiʻilani Highway near Milepost 14 (Olowalu) as a “traffic emergency zone” because of severe erosion under the road that threatened to cut off access to West Maui. Concrete barriers in the area were seen “floating” due to erosion undermining the highway.

The primary goal of the highway realignment project is to establish “reliable and resilient” transportation for the region.

The selected route — now referred to as the “preferred alternative” — is a combination of two previously identified options: “Build Alternative 2” in Olowalu and “Build Alternative 1” in Ukumehame.

The draft EIS, released Dec. 20, had identified this combination as the “preferred alternative.”

The final route selection incorporates refinements based on public input and continued consultation with cooperating and participating agencies. The substantive changes to the design of the selected alternative include:

• Shared-use pathway: Adding a shared-use pathway along the makai edge of the right-of-way.
• Second intersection: Adding a second signalized intersection at Ehehene Street in Ukumehame.
• Stream crossing: Using a bridge crossing over the intermittent Awalua Stream instead of a culvert.
• Alignment shifts: Modest shifts to the alignment’s location or configuration to “optimize design and to avoid and minimize disturbance of archaeological resources.”

The final EIS also includes the executed programmatic agreement for historic preservation, a determination of minimal impacts on the Ukumehame Firing Range and completion of a biological opinion by the US Fish and Wildlife Service.

The existing Honoapiʻilani Highway has been repaired three times in the past 10 years due to storm damage. The state Transportation Department’s analysis confirms that disruptions will increase due to climate change and sea-level rise. Much of the existing highway (51% in Olowalu and 73% in Ukumehame) are within the projected 3.2-foot sea-level rise exposure area, as defined by the Hawaiʻi Climate Change Mitigation and Adaptation Commission and the Hawaiʻi Department of Land and Natural Resources.

Relocating the highway is intended to strengthen its reliability for residents, businesses and visitors, and to provide a more dependable evacuation route during disasters like wildfires.

The project began its environmental review in November 2022 with an official notice, followed by three public scoping meetings. The public review period ran from Dec. 20 to Feb. 24.

The next step in the government review process will be the governor’s acceptance of the final EIS. For the federal process, the Federal Highways Administration will issue a record of decision, which “memorializes the findings of the EIS, affirms the selected alternative and delineates the environmental commitments and mitigation measures identified in the assessment.”

Next, the state DOT will conduct a design-build process to procure a contractor who will complete the project’s final design, obtain necessary permits and construct the realigned highway.

The new highway will be built as a two-lane, limited-access road (one lane in each direction) with an average right-of-way of approximately 140 feet. The existing Honoapiʻilani Highway will become a local Maui County road, maintaining access to homes, businesses and the publicly accessible shoreline.

The estimated construction cost of the project with the changes is estimated at $298 million and is expected to begin in 2028.