The authorities scattered around Kilauea are doing everything they can to keep people safe. Despite the inherent unpredictability of the eruption, methods are in place to ensure that lava flows are avoided, acidic laze and vog aren’t inhaled, and people aren’t hurt.
Over at the Puna Geothermal Venture (PGV), however, there’s a different story unfolding. It must be stressed that no one’s in any immediate danger in the area, but lava entering a geothermal plant in this way is an unprecedented event.
Although officials have done – and are doing – everything they can to make sure nothing untoward happens, the situation is certainly unusual, and not without its dangers. Here’s what you need to know.
About a week ago, it became clear that lava flows advancing from the fissures in the lower East Rift Zone (LERZ) were approaching the PGV. Like other geothermal plants, it uses boreholes to tap the heat of the underlying magmatic plumbing, allowing water to turn into steam and power turbines. Lava could easily destroy this equipment, but there’s more to it than that.
On May 27, the Hawaii County Civil Defense Agency (HCCDA) explained that lava from the Leilani Estates had crossed into PGV property overnight. Telling the public that they must avoid inhalation of volcanic gases, and keep an eye on the lava flow, they also said that they must be ready to be evacuated at a moment’s notice.
So far, so normal, but the lava’s approach caused a bit of a mad dash beforehand. The plant was shut down in May, and a decent amount of pentane – a highly explosive fuel – had to be taken to a safe distance. Forget the blue fires created by buried, burning vegetation; a spark on this lot could have generated a sizeable crater in the ground.
If you’re wondering why pentane is hanging around a steam-powered plant, ArsTechnica has got you covered: it has a lower boiling point than water, which means that when it's near water already heated by the underlying magma, it quickly heats up itself, generates vapor, and spins those turbines.
Notably, the agency also mentioned this: “County, State and Federal agencies continue to monitor Hydrogen Sulfide levels and no Hydrogen Sulfide has been detected. Again, no Hydrogen Sulfide has been detected.”
Hydrogen sulfide (H2S), sometimes released by volcanic systems, is most well known for giving rotten eggs or grim bottom toots their characteristically awful smell. It’s a colorless, flammable gas, one that is normally emitted in very small quantities from these borehole wells during standard operating procedures.
As noted by the United States Geological Survey (USGS), however, in high concentrations, it’s highly toxic – and potentially difficult to detect. When the air contains as little as 0.000001 percent H2S, we smell rotting eggs, but when that’s raised to 0.01 percent H2S, it becomes odorless.
At these mixtures, it can cause “irritation of the upper respiratory tract and, during long exposure, pulmonary edema. Exposure to 500 parts per million can cause a human to fall unconscious in 5 minutes and die in an hour or less.”
Unsurprisingly, then, authorities working at the privately-owned PGV site – which isn’t affiliated with the USGS – have been working to both depressurize and plug these wells, so as to minimize the risk of the lava damaging them, perhaps triggering a blast and causing any H2S to escape. So far, it hasn’t, and there’s a minimal chance anything untoward will happen.
At present, the lava flow at PGV has capped two wells, stalled, and all appears fine. “Due to preventative measures, neither well is expected to release any hydrogen sulfide,” an HCCDA advisory explains.
As ever, the lava flows and the sulfur dioxide gas emissions remain the greatest threats, but if H2S emissions are detected, the authorities will be sure to let you know and act accordingly.