Three weeks into the dramatic Kīlauea Volcano eruption event on Hawaii’s big island and locals are handling the crises with laudable calm.

Increasing numbers of fissures continue to open in the ground around Puna – a neighborhood located in the volcanic rift zone east of the Kīlauea crater – streaming out lava fountains, toxic gas plumes, and refrigerator-sized chunks of molten rock. Yet despite the very hot hotspot of geological activity, evacuations have gone smoothly, there have been no deaths, only one reported injury, and life has resumed, seemingly as usual, in communities like Hilo, less than 65 kilometers (40 miles) away.

Now, a new development in the eruption has sparked significant concerns.

^{The geothermal plant, represented as the letters PGV, can be seen on the recent map by the USGS}

Per the County of Hawaii Civil Defense alert system, lava flowing from fissure number 22 has reached the property edge of the Puna Geothermal Venture (PGV), an energy conversion plant that draws a soup of hot underground liquid to the surface through deep wells. The mixture is used to operate a steam turbine generator, creating electricity, then injected back into the bedrock.

Aside from potentially destroying costly infrastructure that provides part of the Big Island’s power, the lava’s encroachment on PGV could trigger an explosive release of dangerous chemicals from the active wells.

In a media briefing yesterday evening, Tom Travis of the Hawaii Emergency Management Agency explained the risks of the situation.

“There’s the steam release, there’s many chemicals, but primarily the critical factor would be hydrogen sulfide, a very deadly gas,” he said.

Travis explained that a response team has “quenched” four of five active wells (10 of 11 total wells), meaning that the subterranean tunnels whose lower depths contain the hot liquid-caustic gas combination have been filled with cold water.  

Though subterranean magna pockets are always present in the East Rift Zone (they drive the geothermal plant’s process, after all), the new surface and superficial underground lava flows fed by the eruption could overheat the tunnels to the point of extreme pressurization. Adding heavy, cold water on top neutralizes the pressure, thus preventing the expulsion of the hazardous materials below.

As of last night, the 5th well has still not been quenched because it has become too hot.

“We put cold fluid but couldn’t get pressure to zero, then [we] put salt water at the bottom, but this wasn’t dense enough, so now we are using mud material to plug the well while it’s under pressure,” said Travis.

He added that despite still scrambling to quench the final well, other safety precautions have already been taken, including removal of flammable materials stored at the site. Most importantly, the two large valves atop each well have been sealed shut since the eruption began earlier this month.

“[The valves] have trapped whatever is below, and there’s no way for that to get out unless there’s a breach in the mechanical integrity. So that was the first step.”

He further commented that once the quenching has been completed, the site should be in a relatively safe state for the lava to cross it. Travis conceded, however, that his team's emergency response protocol is based upon theories and best guesses.

“I have researched this, and again, I’m not going to overstate my knowledge, but I’ve found no case in which lava has overrun a [geothermal] well that has been shut down like these have been.”

The third step, which is to add plugs to all quenched wells, will be done next if the team is able. At the time of the conference, the lava was holding, temporarily, behind a natural barricade about 250 meters (820 feet) away from the nearest well.

Let’s hope they’re working quickly, because as of this morning, lava from another fissure began flowing toward the PGV property as well.