Piilani Hwy, Maui

Makai Slope Repair below Alelele Slope along Piilani Highway (Route 360) on Maui addresses critical erosion and rockfall risks at Alelele Point near Mile Marker 38 in East Maui's rugged coastal section, where the highway hugs steep cliffs overlooking the ocean. This remote stretch serves as the main route connecting Central Maui to Hana, handling both local traffic and tourists heading to scenic spots like the Pools of 'Ohe'o (Seven Sacred Pools), but frequent heavy rains and seismic activity have caused repeated slope failures threatening roadway stability. Emergency work here stabilizes the makai (ocean-side) slope below the mauka (mountain-side) repairs already done by Prometheus Construction after 2023 rockfalls, ensuring safer passage through one of Maui's most dramatic and vulnerable highway segments.​

The project builds on prior interventions like the nearby Nuanualoa Gulch slope stabilization, which repaired landslide damage with soil nails and shotcrete, by focusing on the lower slope's loose material and debris accumulation to prevent further incursions onto the pavement. It supports Maui County's ongoing infrastructure resilience efforts post-wildfires and amid climate challenges, keeping this vital East Maui lifeline open year-round without major detours.​

From a technical standpoint, the repairs involve scaling loose rocks from the basalt cliff faces, installing wire mesh or rockfall netting anchored into the slope, and applying shotcrete or grouted soil nails for reinforcement, similar to the Nuanualoa Gulch approach just upslope. Earthwork clears debris buildup, with erosion control measures like hydromulch seeding, mechanical anchors, and BMPs (best management practices) to manage runoff into the ocean and protect sensitive marine habitats. Guardrail upgrades, shoulder reconstruction, and traffic control during work phases ensure minimal disruption on the narrow two-lane highway, with phased execution typical of Maui Public Works' emergency slope projects costing in the $200,000–$1.5 million range.