City provides details on wastewater spills during Tropical Storm Lala

HONOLULU– The City and County of Honolulu Department of Environmental Services (ENV) is providing additional details on four wastewater spills that occurred during Tropical Storm Lala on Aug. 16, 2026. The spills were caused by a combination of heavy rainfall, significantly increased wastewater flows, and power-related equipment failures.

“We want the public to understand what happened, how our crews responded and what we are doing to reduce the risk of this happening again,” ENV Director Roger Babcock said. “Our teams worked through extremely difficult conditions to stop these spills, protect the public and restore normal operations as quickly as possible.”

Sand Island Wastewater Treatment Plant

At the Sand Island Wastewater Treatment Plant, screens designed to remove rags and other debris from incoming wastewater became overwhelmed by debris during the high-flow conditions caused by Lala. The accumulated debris restricted wastewater flow, causing it to back up and overflow from the screening area.

Approximately 26.1 million gallons of mixed wastewater and stormwater overflowed. Approximately 650,000 gallons were recovered, while 25.45 million gallons entered storm drains that discharge into Honolulu Harbor.

Once conditions were safe, operators isolated one screen and removed the accumulated debris. This reduced pressure on the remaining screens, allowing crews to clean them and return all four screens to normal operation. Restoring flow through the screens stopped the spill.

ENV has engaged a consultant to evaluate the screening system’s capacity and performance during extreme high-flow events involving large amounts of rags and debris and to recommend potential corrective measures.

ENV posted warning signs and conducted water-quality sampling, with results provided daily to the State Department of Health (DOH). Warning signs and sampling were discontinued on Aug. 24 after DOH determined they were no longer necessary.

Atkinson Drive and Ala Moana Boulevard

Power outages during Lala affected the Ala Moana No. 1 and No. 2 Wastewater Pump Stations, causing pumps to shut down. At the same time, heavy rainfall increased wastewater flows and overwhelmed available storage capacity, resulting in overflows from four sewer manholes.

Approximately 700,000 gallons overflowed. About 150,000 gallons were recovered, 150,000 gallons dissipated into the ground, and 400,000 gallons entered the Ala Wai Canal and were not recovered.

The Ala Moana No. 2 Wastewater Pump Station automatically switched to emergency backup power, but a critical gasket failed, making the generator inoperable. Operators redirected flows to the Ala Moana No. 1 Wastewater Pump Station. Recurring power interruptions repeatedly shut down pumps at that station, prompting crews to activate an onsite portable generator.

Crews secured the area and used two Vactor trucks to recover wastewater and transport it to a downstream sewer manhole with available capacity. Once power was restored, operators ran pumps at both stations and regulated flows until the spill was stopped. The affected area was cleaned, disinfected, and deodorized by Aug. 17.

ENV posted warning signs and conducted water-quality sampling, with results provided daily to DOH. Sampling and warning signs were discontinued in stages at the direction of DOH, with all warning signs removed by Aug. 29.

425 South Street

Power outages affecting the Ala Moana No. 1 and No. 2 Wastewater Pump Stations also caused wastewater to back up into the basement of a building at 425 South Street. Building management pumped wastewater from the basement onto Auahi Street to protect the building’s electrical system.

Approximately 16,422 gallons entered a storm drain that discharges into Honolulu Harbor. None of the wastewater was recovered.

After power was restored, operators ran pumps at both stations and regulated flows, stopping the backup. The affected area was cleaned, disinfected and deodorized by Aug. 17.

ENV posted warning signs and conducted water-quality sampling, with results provided daily to DOH. Warning signs and sampling were discontinued on Aug. 24 after DOH determined they were no longer necessary.

2702 Lowrey Avenue

Heavy rainfall caused wastewater levels to rise in the sewer system near 2702 Lowrey Avenue, resulting in an overflow from a sewer manhole.

Approximately 100 gallons overflowed. Sixty gallons were recovered, 20 gallons dissipated into the ground, and 20 gallons entered a storm drain and were not recovered.

Before the storm, ENV positioned crews and a wastewater truck on Lowrey Avenue. Crews removed wastewater from sewer manholes and transported it to a downstream manhole with available capacity. Despite those measures, the intensity of the rainfall caused the manhole to overflow.

Crews secured the area, continued controlling wastewater levels, and cleaned, disinfected, and deodorized the spill site on Aug. 16.

DOH waived warning signs and water-quality sampling for the Lowrey Avenue spill. ENV will continue positioning crews and equipment at this location in advance of anticipated wet-weather events.

Tropical Storm Lala brought significant rainfall and widespread power outages that placed extraordinary pressure on Oʻahu’s wastewater system. ENV continues to review the four incidents, identify lessons learned, and evaluate improvements that can strengthen the system’s resilience during future severe weather events.

About the Department of Environmental ServicesThe City and County of Honolulu’s Department of Environmental Services (ENV) manages wastewater and solid waste systems that serve the island of Oʻahu, which include 2,100 miles of sewer lines, 72 wastewater pump stations, nine wastewater treatment plants, three solid waste transfer stations, seven refuse and recycling convenience centers, seven solid waste collection base yards, one active landfill, and one waste-to-energy facility (H-POWER). ENV is dedicated to protecting public health, preserving the environment, and ensuring the sustainable management of Honolulu’s essential infrastructure through innovation, efficiency, and community partnership.

—PAU—

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