There have been questions as to why Puna Geothermal Venture’s 38-mega- watt power generating station remained online when Tropical Storm Iselle was imminent.

While "powering off" may seem logical, PGV continued operating for good reason. PGV is a committed energy provider. Three-quarters of energy generated serves residents and businesses outside Puna. In collaboration with HELCO, we reduced output to 80 percent. PGV wanted folks to have the energy needed to prepare and receive critical updates.

PGV anticipated bad weather and took precautions. We reviewed emergency procedures, increased personnel, secured the facility and removed loose items that could become projectiles. While our system is computer-controlled, personnel ensured valves were closed; this is standard procedure no matter the weather.

We are confident in our plant’s ability to provide power during extreme weather. PGV’s parent company, Ormat, operates geothermal facilities globally. The 2010 volcanic eruption in Guatemala and the 2013 typhoon that hit the Philippines devastated both areas, severely handicapping electricity production. Ormat facilities withstood the harshest weather conditions. Post-disaster, geothermal was the first power provider, supplying reliable energy during recovery.

Here’s what happened at PGV during Iselle:

As the storm hit Hawaii island, HELCO started losing transmission lines. About 7:30 p.m., lines serving PGV were lost. The facility did not fail because of the storm. The plant shut down as a result of the storm knocking out HELCO’s transmission system. Immediately after losing connection, the plant shut down as designed and personnel followed PGV’s approved emergency response plan.

The shutdown triggered the plant’s Emergency Steam Release System. The steam was abated, that is, caustic soda and water were added to scrub the steam of hydrogen sulfide (H2S). This approved procedure is part of PGV’s Department of Health air permit requirements.

The bulk of the steam was released within the first 10 minutes. Residual energy of the steam system was safely released; the wells completely shut in approximately 45 minutes. A relief valve malfunction resulted in a low flow of steam released for slightly longer until isolated approximately 60 minutes later.

The release produced a sulfur smell. A PGV employee monitored H2S levels at the facility’s perimeter (Leilani/Pohoiki Road) and outside its southern boundary at Lani Puna Gardens, the closest subdivision; there was a peak reading of 25 parts per billion (ppb), which was not sustained. DOH requires that we do not exceed 25 ppb on an hourly average.

Air monitoring during the shutdown showed emissions remained below permitted levels; there was never any violation of environmental limits or need to evacuate. Hawaii County Civil Defense alerted residents and said they could evacuate voluntarily.

In March 2013, PGV tripped offline and the same emergency response procedure kicked in. The release lasted less than 15 minutes, with a peak reading of 29 ppb. Civil Defense alerted residents, informing them that while the release presented no public danger, Pahoa Community Center was open. One couple arrived after the center had been notified to "stand down."

OSHA standards allow workers without protective equipment to work in H2S areas with 10,000 ppb.

PGV remained offline since the storm. Scheduled maintenance, planned with HELCO one year ago, began on Aug 11. Start-up commenced Aug. 18, and energy generation has increased steadily since.

The storm caused PGV no major damage. We anticipate returning to full output and routine operations by early September.

PGV has been transparent about the night of the storm. I met with community groups and explained what I have outlined here. I have reached out to Lani Puna residents and will participate in forums with other agencies.

PGV continues to support recovery efforts and has committed $25,000 to the local Red Cross.

PGV takes its responsibility to provide power very seriously. Our team mobilized quickly to ensure that it was ready for whatever Mother Nature brought.

We look forward to continuing to produce and provide locally sourced energy.