Five days after Hurricane Ana caused 20 million gallons of raw sewage and rainwater to spill into the basement of the Sand Island Wastewater Treatment Plant, crews brought a third clarifier back online and resumed normal plant operations, city officials said Saturday.
Power was restored to the No. 4 clarifier about 10 p.m. Friday, but one more clarifier needs to be repaired to be used as a backup and that should be finished Monday, said Wayne Salas, the metro wastewater treatment plant superintendent, during a short media tour of the state’s largest sewage plant.
The plant has eight clarifiers with four under repair.
"We feel pretty confident that we’re back into full operation again," said Mayor Kirk Caldwell. "We’re going to continue to look at what happened."
He said the city has yet to reckon the cost of overtime and equipment damage from the incident, but said the city has an insurance policy with a $75,000 deductible and it wasn’t immediately known whether that threshold had been reached.
The heavy downpour from Hurricane Ana on Oct. 19 inundated the plant with about 240 million gallons of water and sewage in about 15 minutes. About 5,000 gallons of sewage spilled into Honolulu Harbor.
The plant, which usually processes about 70 million gallons of sewage a day, can handle a spike of about 130 million gallons.
For the past five months, one of the plant’s two channels that direct wastewater into the clarifiers had been down for repairs. The rush of water overflowed the working channel, sending water into the other channel, through holes in the bottom of the empty clarifiers and into the plant’s basement.
In the end, the basement was flooded by about 20 million gallons of water — roughly enough water to cover by one foot the entire block where Ala Moana Center sits.
Water and sewage rose higher than 6 feet and submerged electrical equipment and pumps, shorting out the equipment that controls the clarifiers.
Salas said the clarifiers are the second to last step in the treatment process, where heavy solids and lighter materials are separated from the water before it is treated with ultraviolet radiation then piped 260 feet down into the ocean.
He said crews have been using portable pumps to remove sludge from the clarifier and send it to the Synagro Bioconversion Facility next door, where the sludge is turned into pellets.
When crews completed electrical repairs on Friday, the portable pumps were turned off and the clarifier started running on plant-controlled pumps.
Salas said the plant is currently undergoing a $50 million upgrade and the electrical equipment, which was installed in the 1970s, was supposed to be replaced in about eight months.
He said the latest misadventure prompted officials to look into erecting a platform to keep the new electrical equipment about 10 feet above ground level, protecting it from future flooding.
Caldwell said the city has taken other temporary measures to prevent flooding, such as plugging the holes that allowed sewage to run into the basement in the first place.
