There is no longer a danger of flooding or a need for possible evacuations near a 21-million-gallon Nuuanu reservoir that filled close to capacity with the recent heavy rain from Tropical Storm Olivia, city officials said Thursday afternoon.

Earlier there had been speculation that 10,000 people might need to be evacuated, but that is no longer the case, Ernest Lau, manager and chief engineer for the Honolulu Board of Water Supply, said at a press conference.

Dam No. 1, an earthen dam built in 1905, filled with rainwater to about 1.5 feet below the dam’s spillway. A mandatory evacuation would only be necessary if the water actually breached the dam’s spillway.

City workers pump water from a near-capacity reservoir in Nuuanu on Thursday morning.

Marcel Honore/Civil Beat

In an earlier statement the BWS said it “has been monitoring and siphoning the excess water from the reservoir since the beginning of the week to keep the water level below the spillway. However, with the passing of Olivia, the rain exceeded the siphoning capacity.”

The Honolulu Fire Department had about 16 firefighters at the scene with about three trucks and a helicopter to provide aerial surveillance Thursday morning. Fire and BWS crews parked their vehicles and worked along the reservoir’s makai bank, as police and city officials observed.

An enclave of houses lies on the other side of that bank.

By 11:30 a.m. those crews appeared to have the flood threat under control. The water had receded to about 5 feet below the dam spillway as the pumps sent it into nearby Waolani Street.

BWS will continue pumping water from the dam in anticipation of more rainfall this hurricane season.

Officials knew the reservoir was rising before Olivia even approached Oahu, Acting Mayor Roy Amemiya said. 

“This is not something that crept up on us,” he said. 

Board of Water Supply Ernest Lau holds evacuation diagram if dam is compromised or is damaged from too much water.

Ernest Lau of the Board of Water Supply displays an evacuation map based on a breaching of the dam.

Cory Lum/Civil Beat

BWS was in contact with the state Department of Land and Natural Resources, which requires all dam owners to report concerns to the department.

No other facilities or reservoirs are experiencing issues, the DLNR said in a press release.

Lau said the BWS will review its emergency processes.

If an evacuation had to occur, the evacuation area could stretch from lower Nuuanu near the dam all the way down to Honolulu Harbor, according to a map provided by BWS.

“We would actually start the evacuation before a failure occurs,” said Hiro Toiya, deputy director of Honolulu’s Department of Emergency Management.

Any such evacuation should be completed in an hour, Toiya said. A city incident management team was evaluating how to approach potential evacuation conditions in the future.

“There are opportunities to improve here in the (evacuation) process,” Lau said.

The Legislature has provided funding to plan for dam renovations, but there is no construction money available yet, Lau said.

This is a developing story. Check back for updates.

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