A geothermal well field next to a volcanic rift that is fountaining lava was declared “essentially safe” Tuesday after measures were taken to prevent uncontrolled releases of underground fluids and gases.

Crews used water to quench two Puna Geothermal Venture wells and inserted a chemical plug into a third well on the property.

Tom Travis, administrator of the Hawaii Emergency Management Agency, said the wells are isolated and are each sealed off with two large valves on top “so the status is stable, predictable and understandable, and there’s no reason as a result of any of the status of wells to feel any undue concern.”

State and county officials working with PGV still hope to install mechanical plugs into the shafts of 10 wells to further secure them, but Travis said he is unsure when that can be done. He said crews will make a “day-to-day decision” about when and whether that work can be completed.

Lava from the Lower East Rift Zone destroyed a state-owned warehouse on a property adjoining the PGV land Monday evening, bringing the number of structures that burned since the eruption began May 3 to at least 47. The actual number of buildings destroyed is believed to be higher, however.

The top executive in Hawaii for PGV said Monday the concerns about lava inundation at the geothermal plant have been overblown.

Michael Kaleikini, senior director of Hawaii affairs for PGV, said noise and gas emissions from more than 20 fissures and the enormous lava flow that now extends to the ocean dwarfs any emissions or damage that could result from an uncontrolled breach of the geothermal wells on the PGV site.

“From our perspective, there’s nothing that could occur at the PGV facility at the wells that would be any worse than what’s already occurring with the eruption,” Kaleikini said. “This is all about the eruption, and PGV is just a small component that happens to be in the area.”

Scientists with the U.S. Geological Survey announced Tuesday that the East Rift eruption is producing 15,000 tons of sulfur dioxide gas per day, an amount that is far beyond the amounts normally produced at the Kilauea Volcano summit or at the Puu Oo crater.

Sulfur dioxide is released by magma as it rises toward the earth’s surface during an eruption, and the dramatic increase in the volume of gas at the rift zone since last weekend is a symptom of the escalating pace of the East Rift eruption during the past week.

By comparison, the summit produced an average of 3,000 to 6,000 tons of sulfur dioxide per day when there was a lava lake in the caldera, while Puu Oo normally produced 200 to 300 tons. Sulfur dioxide contributes to the volcanic haze known locally as vog, but the tradewinds have been blowing most of that haze out to sea, scientists said.

Jim Kauahikaua, geophysicist with the U.S. Geological Survey, said a series of fissures extending from the intersection of Leilani Avenue and Kahukai Street to an area just south of the shuttered PGV plant were actively fountaining lava Tuesday, and one of those fissures is feeding into the river of lava that is dumping into the ocean.

Although most of the lava from those fissures is headed downhill toward the sea, some of the spatter from the fountains is filling elevated lava ponds that are leaking lava that has been slowly advancing on the PGV property.

Kaleikini said the nearest lava pad is within 100 feet of an area known as the Boneyard, where the company stores old parts and equipment. The lava has reached to within about 300 yards of the nearest well, he said.

“There’s not a lot of lava going into it, and probably the reason the flow is not really advancing very quickly is the terrain actually rises a bit on that side,” Kauahikaua said. The USGS has crews at PGV to monitor the movement of the flow near the 815-acre property.

PGV crews and contractors have successfully quenched two geothermal production wells by pumping cold water into them in a process that uses the weight of the water to suppress the gases and hot brine far below the surface. Those wells were originally drilled 6,000 to 8,000 feet down to tap the steam and hot water stored below the surface to run turbines that produce electricity.

A third production well, known as KS14, presented special problems because the advancing magma in the area apparently caused the contents of the well to heat up.

Crews used denser “mud materials” — also known as a “hot plug” — to try to seal that well, and Travis said all indications are that the well has in fact been sealed. He said crews will likely confirm the status of the well by the end of today.

However, “even if the plug leaks a little bit, it’s going to be very little and is not going to be of much public-safety impact,” Travis said.

Eight other wells on the site did not need to be quenched with cold water because they were not pressurized, he said. In other words, those wells were not generating upward pressure that could cause gases or fluids to escape. Current plans call for those wells to be closed with metal plugs or the chemical “mud” that hardens when it is heated.

Gov. David Ige visited Hilo for a briefing and a public meeting in Pahoa on Tuesday and told reporters that “the biggest risks have been mitigated” at PGV.

If there is a need for a large-scale evacuation, Ige said, extensive plans are in place to carry that out “regardless of whether it’s 1 a.m., 3 a.m., 5 a.m., so that we can notify the community and remove the residents if necessary.”

“If we really felt that the plant was at risk of being overrun and could trigger a well being exposed, then that’s when we would order the evacuation,” he said. The evacuation area in that case would be 1.3 miles in diameter in the daytime and more than 3 miles at night, Ige said.

Much of the area around the geothermal plant is already under mandatory evacuation orders, including the subdivisions of Leilani Estates and Lanipuna Gardens, but some residents have returned to their homes.

Star-Advertiser staff writer Kristen Consillio contributed to this report.