Waipiʻo Valley Road Closed for County Survey and Geotechnical Assessment

Waipiʻo Valley Road will be closed to all traffic between 8:30 a.m. and 3 p.m. each day from Tuesday, Feb. 24 through Friday, Feb. 27 between the Waipiʻo Valley lookout and the beach access road while Geolabs, Inc. conducts a geophysical survey of the roadway’s subsurface. The county says the work is part of the Waipiʻo Valley Road Safety Improvement project.

"The survey, which will look at the subsurface conditions of the road, is being done by Geolabs, Inc. as part of the Waipiʻo Valley Road Safety Improvement project," county communications and local reporting state. Phase 1 of the safety improvement work was completed in 2023 and "consisted of removing hazards along the upper portions of the road," and the County says it has moved into planning and design for phases two and three to "involve removing additional hazards and installing rockfall mitigation along the slope." The remaining work is "expected to be completed in 2027."

Technical background for the survey traces to a Hart Crowser geotechnical evaluation the County hired in 2020. Hart Crowser field crews performed an initial reconnaissance with County staff on April 29, 2020, followed by a detailed field reconnaissance on June 1-2, 2020, and on-rope rappels of slopes from August 27 through September 4, 2020 to assess rockfall and slide hazards. "Based on our observations, there is one primary slide location, referred to as the March 2019 primary slide described in this report," the consultant wrote, and the "primary slide is approximately 500 feet tall and 70 feet wide and extends from the downslope road edge towards the Wailoa Stream valley below."

County records and the geotechnical report note prior instability on the south valley wall: "Steep exposed residual soil slopes on the upslope side of the road have been susceptible to instability as indicated by past failures, the most recent of which were landslides in April 2018 and February 2019." The County’s proclamation connects the March 2019 slope failure to heavy rainfall and high streamflow associated with Hurricane Lane and records that Waipiʻo Valley Road "can experience significant amounts of runoff, particularly after heavy rains."

Legal and emergency measures remain in place as the County advances work. The Amended Traffic Emergency Zone Declaration for Waipiʻo Valley Road "remains effective September 19, 2022, continuing thereon until February 25, 2027," and the mayor issued a proclamation declaring an emergency "effective January 2, 2026, and continuing through March 3, 2026." The County document also emphasizes that Waipiʻo Valley Road "is the only vehicular ingress and egress for Waipiʻo Valley" and that the road is "used by residents of Waipiʻo Valley, farmers who transport agricultural products grown and harvested in Waipiʻo Valley, Hawai‘i County residents, visitors, and authorized tour operators."

Hart Crowser also outlined long-term options that could inform the survey’s outcomes, saying the County "could also consider building a new road alignment to join the hairpin turn at the base of the slope in the Upper Section of the road," noting advantages such as wider travel lanes, engineered drainage, and separate foot and vehicle traffic, while warning a new alignment "would require several switchbacks to navigate the elevation change" and that installed costs may be higher.

For project details and questions about the Feb. 24–27 closures, contact Civil Engineer Preston Vierra at 808-961-8787 or Preston.Vierra@hawaiicounty.gov.