PUNA, BIG ISLAND (HawaiiNewsNow) - Highway 130 is now the only way into and out of Big Island residential areas like Kalapana, Kaimu, Kehena, and Opihikao.
That's because Highway 137 is now impassable. A wall of lava crossed the thoroughfare last week and continues to cascade into the ocean.
But authorities are increasingly concerned about how long Highway 130 will remain safe.
Large cracks in the roadway are being covered by heat-resistant plates. And those who travel through the area are told to keep their windows shut because of high sulfur dioxide levels.
HIDOT officials also announced on Sunday that they are lowering the speed limit on the highway between Leilani Estates and Kamaili Road, to 25 miles per hour as a safety measure for those driving over the steel plates.
"Even though the steel plates have slightly heated in the areas of Highway 130, the steel plates are heat resistant and are still safe," said Tim Sakahara, spokesman for the state Transportation Department. "No problems have been reported or associated with the plates."
No problems — so far.
They're also watching the potential impact to Highway 132.
Topography maps on Saturday showed the flow could start turning north, and may eventually threaten Highway 132. But the flow front remains a mile away, so it could take some time.
While officials have been able to maintain two lanes of traffic on Highway 130 for now, experts acknowledge the situation could change at a moment's notice as steam continues rising and cracks keep widening.
If 130 is somehow cut off, authorities are preparing for the possibility of air evacuations with help from Marine Sea Stallion helicopters.
"Our tasking is essentially to take 400 people within four hours from the furthest most LZ (landing zone) south up to Hilo to be evacuated," said Marine Maj. David Bachta.
Not everyone will need to go to Hilo, nearly two dozen landing zones have been identified across Keaau and Pahoa.
Pilots can move 43 passengers per aircraft at a time. And flight crews are on standby 24 hours a day and are prepared to be wheels up within an hour.
State transportation officials say they will try to keep Highway 130 open for as long as safely possible, but they understand that conditions can change quickly and they want all residents who live in the area to be prepared.