UPDATE: 3 p.m.

Board of Water Supply officials said this afternoon that there is no danger of Nuuanu Reservoir No. 1 failing and said they notified the public about the possibility of evacuations downstream in an abundance of caution to keep the community informed.

BWS Chief Engineer Ernest Y.W. Lau said that water was being pumped from the dam on the Ewa-side of the Pali Highway to keep the water level below the dam’s spillway.

At about 10 a.m., BWS sent out a news release saying that the water was about 18 inches from spillway and that BWS crews and the Honolulu Fire Department were pumping water to keep the level below the spillway after overnight heavy rain in the aftermath of former Tropical Storm Olivia. The release also noted the the board was working with city officials on an operations plan “which includes public evacuation notification and sheltering if needed. Approximately 10,000 residents would be affected.” It did not specify what areas would be affected.

More than an hour later, BWS and city officials said there was no need for evacuations.

Lau said at an afternoon news conference that there was never a need for evacuations, but that the board had received inquires about the water coming downstream from the dam as it was being pumped. He said there was never any danger of dam failure.

He also said the board would use this as an opportunity to improve its communications with the public.

“I think there is an opportunity for greater communication with our communities downstream from these dams about the unlikely failure of a dam and what the evacuation requirements would be,” Lau said.

At the news conference, board officials distributed a map of the area that would have been affected if an evacuation was needed.

11:30 a.m.

Board of Water Supply officials say that water levels at Nuuanu Dam #1 have stabilized and there is no need for evacuation.

“There is no need to order an evacuation at this time,” city spokesman Andrew Pereira said late this morning. “The water level is not rising. As long as nature cooperates, we should see a situation that is getting better and not worse.”

Hawaii firefighters dispatched three engines, a battalion chief and the department’s Air One helicopter to help remove water from the dam, HFD Capt. Scot Seguirant said. The first unit arrived at 7:55 a.m.

The dam has a capacity of 21 million gallons of water.

In the 24 hours ending at 10 a.m. former Tropical Storm Olivia and its aftermath dumped more than 8 inches on upper Nuuanu, according to a National Weather Service guage.

Heavy rains over Oahu this morning have eased and moved west, but the island remains under a flash flood warning until noon.

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Heavy rain from former Tropical Storm Olivia sent the water level in Nuuanu Dam #1 up nearly 4.5 feet overnight to about 1.5 feet below the spillway, raising the possibility of an evacuation of up to 10,000 residents, officials said this morning.

For businesses and residents downstream of the dam, city spokesman Andrew Pereira said, “right now there’s no need to panic. … There’s no need to take action at this moment.”

Pereira urged residents and businesses to monitor local media and Mayor Kirk Caldwell’s social media sites for updates.

The earthen dam was built in 1905. It is 33.5-feet high and 588-feet long.

“BWS 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,” board officials said. “However, with the passing of Olivia, the rain exceeded the siphoning capacity. BWS and Honolulu Fire Department personnel are currently deployed at the dam with water pumps to bring the level of the reservoir down further.” About 10,000 residents would be affected, they said.

Kathleen Elliott-Pahinui, spokeswoman for BWS, said, “If something were to breach, there’s the possibility that it could end up all the way into the harbor. … Anything in the immediate area and everything downstream” is potentially at risk.

BWS said it is working with the mayor’s office and city Department of Emergency Management to coordinate the operations plan, which includes public evacuation notification and sheltering if needed.