HONOLULU (AP) — More than 48,000 Hawaiian Electric Co. customers living in some of the state’s driest areas will soon face the prospect of advance power shutoffs — and outages that could last several days — in order to reduce the risk of sparking a wildfire when the weather turns especially windy.

The state’s largest utility company unveiled the details of its much-anticipated “public safety power shutoff” plan Wednesday, the latest move to try and reduce wildfire risk in Hawaii following last year’s deadly blazes on Maui.

Those shutoffs will be ready to take effect starting July 1 in some of the drier and more fire-prone parts of Oahu, Molokai, Maui and Hawaii island.

“This is our first shot at this,” Hawaiian Electric Co. Vice President of Communications Jim Kelly said during a press conference at the Ward Avenue operations office, which various police, fire and emergency responder personnel also attended.

“In certain extreme conditions, it is the last line of defense,” Kelly said of the new plan.

HECO faced widespread criticism after the Lahaina devastation for not having a shutoff plan in place prior to the fires. Many of the utility’s counterparts in California and other wildfire-prone states on the mainland already had those plans and had used them.

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Ever since the Maui fires, the island utility has repeatedly stated that shutting off the power in such a manner could have enormous impacts on the surrounding community.

On Wednesday, company officials asked the residents living within its new shutoff plan boundaries — particularly those who depend on ventilators, dialysis machines and other medical devices — to have their own plan ready should such an extended outage occur. That could involve using a backup generator or arranging to stay with friends and family outside of the affected area.

Some 1,180 “medically vulnerable” customers living in the new shutoff boundaries have already registered with HECO, allowing the company to work with them directly in an outage, according to Brendon Bailey, HECO’s vice president for customer service.

Still, “we know there’s a lot more out there,” Kelly said Wednesday.

The shutoff area maps that Hawaiian Electric Co. provided on Wednesday will be used for the wildfire season that just started, Kelly said. It could be refined in subsequent seasons once the company sees how the plan performs and as it hardens more parts of the grid against wildfire, he added.

Company officials said that they consulted with local wildfire experts when crafting those maps.

“I’m pleased with the collaborative process. They’re not just inventing random things. It’s been vetted, it’s been thoughtful,” said nonprofit Hawaii Wildfire Management Organization Co-Director Elizabeth Pickett, who met with HECO regarding the maps.

But whether the map areas will be effective? “I have no idea,” she added.

The shutoff program hasn’t been used in Hawaii yet and “good faith effort is pretty much all we can ask for,” she said.

Pickett added that she’s concerned the public might confuse the new HECO maps as the only areas in the state that face wildfire risk.

“Hawaiian Electric is doing its part, but it’s important to understand the fire risk areas are well outside of this” from other ignition sources beyond damaged and downed transmission lines, she said.

The company aims to give the public as much as two days advance notice that it might shut off the power in certain areas. However, it might have to shut off the power more quickly depending on the weather, said Colton Ching, Hawaiian Electric Co.’s Vice President for Planning and Technology.

The company will consider red flag warnings issued by the National Weather Service plus data from its own weather stations and humidity levels near its equipment when deciding whether to cut the power, Ching said Wednesday.

Typically, red flag warnings require wind gusts of 25 mph or greater. However, HECO likely would not issue its alert for a potential shutoff until those gusts reach 45 mph, he added.

Company officials did not have an estimate for how many times it expects to shut off the power in advance during this wildfire season, if at all — it all depends on the weather, they said.

If the shutoffs do occur, HECO estimates they could last anywhere from six hours to several days depending on the severity of the weather and the damage done to its transmission lines and equipment.

Some 94 circuits on the grid on the four islands are located within the shutoff plan boundaries, according to Ching. The company could isolate the shutoffs to circuits that fall within the areas affected by bad weather, he added.

Hawaiian Electric Co. is installing 54 weather stations across its coverage area to better monitor conditions around its equipment, Kelly said.

On Oahu, the areas included in the shutoff plan are restricted to the Leeward Coast and could potentially shut down all of the pumps, wells and other equipment used by the Honolulu Board of Water Supply to provide water to the 50,000 or so residents there, according to BWS Manager and Chief Engineer Ernie Lau.

If that happens, BWS would rely on two gravity-powered tunnels in Waianae that can provide some of that water without electricity, Lau said. The agency would also pump in water from the neighboring areas of Koolina and Barbers Point and mobilize generators at some of its Leeward Coast pumping stations to get water to the community there, he added.

Still, the communities would likely have to conserve water during those outages, Lau said.

The kits and supplies that residents gather for hurricanes could also work well for the wildfire power shutoffs, emergency officials said Wednesday. Plus, the wildfire and hurricane seasons largely coincide, they added, with the wildfire season having started in May and the new hurricane season about to start in June.

“We’re all getting better at what we do,” Pickett said Wednesday of the emergency preparedness efforts across Hawaii. “I feel hopeful that we’re moving the needle — but we’re not there yet.”

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This story was originally published by Honolulu Civil Beat and distributed through a partnership with The Associated Press.