Hawaii's Mount Kīlauea eruptions have caused damage in the southeast corner of the Island of Hawai'i, but a new concern has been slowly building: earlier this week Reuters reported that lava is creeping onto the property of a 38 MW geothermal plant called Puna Geothermal Ventures (PGV). Lava damage could cause problems for the plant's operations in the future, and some officials are concerned that damage to geothermal wells could result in releases of hydrogen sulfide gas, which is toxic to humans. Although lava had been held back by a natural berm for days, yesterday Reuters again reported that a new lava flow had entered the 815-acre PGV property.

Thus far, the only structure that has been destroyed at the geothermal plant has been an old warehouse that was used in the early days of the plant and had been used for storage since, according to a Hawai'i County spokeswoman

Geothermal power, which uses the natural heat of underground rocks to create electricity, is a low-carbon way to generate a relatively constant supply of electricity. However, no modern geothermal plant has suffered lava damage, Reuters notes, so there's no precedent for this situation.

The first fissure to enter PGV property earlier this week, Fissure 6, is 200 to 300 yards from one of PGV's 11 geothermal wells. The new fissure that entered PGV property on Saturday night is Fissure 21. In a tweet Sunday morning, the US Geological Survey tweeted that "Fissure 21 continues a slow advance eastward on PGV property." (For a detailed look at why the volcano has been erupting the way it has, check out our earlier story on Kīlauea's activity.)

In a 6 am update on Sunday morning, The County of Hawai'i issued a Civil Defense Message saying, "The Hawaiian Volcano Observatory reports the lava flow in Leilani Estates has crossed into PGV property overnight. County, State and Federal agencies continue to monitor Hydrogen Sulfide levels and no Hydrogen Sulfide has been detected."

PGV usually is able to provide about 25 percent of the big island's power, but the plant was taken offline after the first eruption of Mount Kilauea. Hawai'i Electric Light, the power provider for Hawai'i Island, said on Tuesday night that there was no danger of outages for the rest of the island due to PGV's downtime because Hawai'i's grid had sufficient backup generation.

After the plant was taken offline in early May, about 60,000 gallons of pentane, a highly-flammable chemical, were moved from the site. Pentane is often used as a "working fluid" for geothermal plants—it has a lower boiling point than water so it heats up quickly when it's near water from a geothermal well, and the resulting vapor can be used to power the plant's turbines and then be recirculated.

Despite the removal of the pentane, danger remains if the lava reaches the wells. Geothermal wells often release small amounts of toxic hydrogen sulfide during the course of normal operations, usually well below emissions limits set by local governments. But lava could destabilize a well and release more.

The best case scenario is that the lava continues to bypass the plant. Ormat, the company that owns PGV, told Reuters that it won't be able to asses any potential underground damage to the wells (from lava or the periodic earthquakes that come with it) until the situation stabilizes.

Since last week, workers have been attempting to de-pressurize the wells by pouring thousands of gallons of cold water into them. One well was not able to depressurize, so it was sealed with a mud-like substance, the AP wrote. The wells are each 6,000 to 8,000 ft deep.

Correction: This article has been changed to reflect that damage from eruptions has been focused on a small portion of Hawaii, the damage has not been throughout the island.

Listing image by US Geological Survey