Muddy floodwaters smothered vast stretches of Oʻahu's North Shore on Friday, lifting homes and cars, and prompting evacuation orders for 5,500 people.
Meanwhile, authorities were cautioning that a 120-year-old dam upstream in Central Oʻahu could fail. With the immediate risk appearing to have subsided for the time being, here's why the dam has been a concern for many years.
Eyes on an aging dam
Officials were closely watching the Wahiawā Dam, which has been vulnerable for decades, saying it was “at risk of imminent failure.”
Water levels in the dam about 17 miles northwest of Honolulu receded by late Friday and then went up again slightly with overnight rain.
Overnight into Friday, the water level went from 79 feet to 84 feet — just 6 feet shy of what the dam can handle, authorities said. After peaking at more than 85 feet, the water level had dropped Saturday to about 81.5 feet, according to the U.S. Geological Survey.
During last weekend's storm, Green said, "When that dam water gets past 83 feet, we start getting concerned. At 85 feet, we tend to evacuate, and at 88 to 90 feet, it becomes a deep concern."
Kathleen Pahinui evacuated her Waialua home early Friday because of the dam danger.
“Hopefully if we make it through today, then tomorrow will dawn bright and sunny,” she said Saturday. “And then everyone can start moving slowly back in, and we can start to resume normal and start cleaning up and helping our neighbors.”
The history
The dam, an earthen structure, was built in 1906 to increase sugar production for the Waialua Agricultural Company, which eventually became a subsidiary of Dole Food Company. It was reconstructed following a collapse in 1921.
The state has said the dam has “high hazard potential” and a failure “will result in probable loss of human life.”
It has sent Dole four notices of deficiency about the dam since 2009, and five years ago it fined the company $20,000 for failing to address safety deficiencies on time, according to records.
Afterward, Dole proposed to donate the dam, reservoir and ditch system to the state in exchange for an agreement to repair the spillway to meet and maintain dam safety standards.
The state passed legislation in 2023 authorizing the dam’s acquisition. It also provided $5 million to buy the spillway and $21 million to repair and expand it to comply with dam safety requirements. But the transfer has not been completed. A state board is due to vote on the acquisition next week.
“The dam continues to operate as designed with no indications of damage,” Dole said in a statement.
The state regulates over 100 dams across Hawaiʻi, most of them built as part of irrigation systems for the sugar cane industry, according to a 2019 infrastructure report by the American Society of Civil Engineers.
Sign up for emergency alerts from your county:
- City and County of Honolulu (Oʻahu) | Shelters and assembly areas
- Hawaiʻi County
- Maui County | Shelters
- Kauaʻi County
The Associated Press contributed to this report.
