HONOLULU — Recent outages that left thousands of East Honolulu households without power may have been caused by overgrown albizia trees choking critical transmission line corridors that run along the base of the Koolau mountains, Hawaii Electric reported on Thursday.

The overgrowth was detected during recent helicopter inspections conducted by HECO.

What You Need To Know

  • Recent outages that left thousands of East Honolulu households without power may have been caused by overgrown albizia trees choking critical transmission line corridors

  • As HECO noted, East Honolulu relies on power lines that carry electricity from Windward Oahu

  • Follow-up aerial inspections found albizia trees encroaching on long sections of the lines, according to HECO

  • Introduced to Hawaii from Indonesia more than a century ago to help control erosion, Albizia trees are a particular hazard to power lines because of their rapid growth—up to 15 feet per year—and brittle branches, which are prone to breaking during high-wind or storm conditions

As HECO noted, East Honolulu relies on power lines that carry electricity from Windward Oahu. These lines run along the base of the Koolau range near Waimanalo and into East Honolulu.

Last weekend, portions of Hawaii Kai lost power when an albizia tree fell across one of the lines. Follow-up aerial inspections found albizia trees encroaching on long sections of the lines, according to HECO.

“We have schedules we follow to cut back vegetation from critical areas but invasive albizia are especially challenging because they grow so quickly and have branches that can break off easily, especially in heavy rains,” said Jim Alberts, HECO senior vice president and chief operations officer. “We’re developing action plans to clear this area to ensure reliable service to the area.” 

Introduced to Hawaii from Indonesia more than a century ago to help control erosion, Albizia trees are a particular hazard to power lines because of their rapid growth—up to 15 feet per year—and brittle branches, which are prone to breaking during high-wind or storm conditions.

Recurring, prolonged outages in Hawaii Kai and East Honolulu over the last few months have drawn the scrutiny of local lawmakers who last month called for the Public Utilities Commission to investigate HECO reliability issues.

In a letter to the PUC dated April 16, state Sens. Glenn Wakai, chair of the Senate Committee on Public Safety and Intergovernmental and Military Affairs; Jarrett Keohokalole, chair of the Senate Committee on Commerce and Consumer Protection; and Lynn DeCoite, chair of the Senate Committee on Energy, Economic Development and Tourism, called on the commission to exercise its investigative powers to protect the public interest.

The lawmakers cited the April 14 outage that knocked out power to more than 13,000 HECO customers, prompted the closure of five East Oahu schools and triggered the release of 237,500 gallons of sewage into the ocean when the East Honolulu Treatment Plant lost electricity.

In that instance, HECO said heavy rains and severe weather caused about 4,000 feet of 46-kilovolt line to fall across a second transmission line, taking both lines out of service. Repair efforts were hampered by steep terrain and the inability to use a helicopter due to continued bad weather.