PUNA, Hawaii >> Workers at the Puna Geothermal Venture power plant found themselves in a race against nature Monday as they attempted to seal off a particularly troublesome, deep geothermal well while lava from Kilauea Volcano advanced from the south to a point uncomfortably close to the well pad area.

The plant has been closed since shortly after the May 3 eruption began, and the company sealed the production wells with metal valves. Still, area residents and state and county officials have worried that a lava flow or earthquake could damage the wells, causing an uncontrolled release of hydrogen sulfide or other potentially dangerous volcanic gases.

Most of the lava on the surface of the Lower East Rift Zone is pouring toward the Puna coastline, but on Tuesday morning county officials said a relatively small lava flow had begun to move in the opposite direction and was advancing into the PGV property.

A Hawaii County Civil Defense spokeswoman said fissure 22 just south of PGV site displayed “very active fountaining” that scientists said reached as high as 140 feet at times, and it was a finger of lava from that fissure that advanced to the northeast toward the well pad at PGV.

TOM TRAVIS, administrator of the Hawaii Emergency Management Agency, said that by Monday afternoon the lava advanced to within about 200 or 300 yards of the PGV facilities but stalled at a berm on the 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 contain 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.

However, a third production well, known as KS14, presented special problems because the advancing magma in the Lower East Rift Zone apparently caused the contents of the well to heat up, said Travis.

Even after pumping cold salt water into KS14, the fluid and steam below continued to generate pressure at the well head, Travis said. The latest plan is to use denser “mud materials” that are used in drilling operations to seal off the well, he said.

“We should have an idea of whether that’s successful or not tonight,” Travis said Monday. “Once that step is taken, we will be in a much more solid state for having lava overflow the site.”

VOLCANIC FUMES have further complicated the effort to quench the wells as crews had to suspend operations for more than a day last week because of high sulfur dioxide concentrations, Travis said.

In a third and final step to close out the wells, metal plugs are to be used to finally seal the shafts. Travis said those plugs should be at the PGV site by this morning, and “if time permits we’ll start the third step.”

Travis said he is unaware of any other case where lava has overrun a well that was sealed off in the way that crews are closing down the PGV wells, which suggests experts may not be absolutely certain what the final outcome will be.

Gov. David Ige earlier this month issued a supplemental emergency proclamation instructing Travis, Hawaii County Mayor Harry Kim, and Hawaii Civil Defense Agency Administrator Talmadge Magno to “lead a team to develop and implement mitigation steps as necessary to protect public health and safety.”

That team includes federal and state agencies as well as PGV, and the group was tasked with reviewing and assessing the existing PGV Emergency Response Plan as well as to “develop a specific mission strategy deemed appropriate to mitigate potential impacts from lava,” according to the Ige administration.

Earlier this month PGV relocated 60,000 gallons of flammable pentane away from the site as a safety precaution.

Jim Kauahikaua, geophysicist for the U.S. Geological Survey, said the lava flowing into the sea from fissure 22 has formed a “small delta” of new land about 80 yards deep on the coast where the lava reached the ocean.

That same fissure was erupting in a short line of low lava fountains that fed a channelized flow that reached the sea just north of MacKenzie State Park, scientists said. Fissures 6, 17 and 19 also continued spattering, according to USGS.

At the summit of the volcano about 25 miles away, scientists reported a small explosive eruption at Halemaumau Crater at 12:55 a.m. Monday that lofted ash as high as 7,000 feet above sea level, and another explosive ash eruption at 5:51 p.m. Monday.

The plume from the early morning summit ash eruption was blown to the southwest, and authorities warned the communities of Wood Valley, Pahala, Naalehu and Waiohinu that ash could be blown their way.

“Additional explosive events that could produce minor amounts of ashfall downwind are possible at any time,” according to the Hawaiian Volcano Observatory.

Seismic activity at the summit abruptly decreased after the recent explosive eruptions, and scientists said it is again slowly increasing, suggesting more explosive ash eruptions are likely.