Tropical Storm-related Information from Puna Geothermal Venture
Photo copyright: Hawaiian Electric Company
PUNA, BIG ISLAND (HawaiiNewsNow) -
(The following is a news release from Puna Geothermal Venture)
The night of Tropical Storm Iselle, Puna Geothermal Venture’s 38-megawatt power generating station on Hawaii Island was shutdown as designed. There was no “uncontrolled release” or “spill” at the facility contrary to some initial reports by commentators.
To prepare for the storm, PGV staff reviewed emergency procedures in anticipation of bad weather. PGV increased night shift crews through the storm and actively reduced the plant’s output in preparation of extreme weather conditions.
At about 7:30 p.m. Hawaii Electric Light Company (HELCO) lost both transmission lines that PGV connects to in order to transmit power to the electrical grid. With the loss of the transmission lines, the plant shutdown as designed.
By design and following approved procedures, steam was released through the emergency steam release facility. That steam was ABATED, that is, caustic soda and water were added to scrub the steam of hydrogen sulfide (H2S). This was done according to regulatory procedures, per the approved emergency response plan. This process is part of PGV’s Hawaii Department of Health (DOH) air permit requirements.
The bulk of the steam was released within the first ten minutes. The residual energy of the steam system was safely released and the wells completely shut in in approximately 45 minutes. A relief valve malfunction resulted in a low flow of steam released for slightly longer until isolated approximately 15 minutes later.
During the early part of the steam release, there was a sulfur smell. A PGV employee monitored levels at the fence line and had a peak reading of 25 parts per billion. The DOH regulation requires that we not exceed 25 parts per billion (ppb) on an hourly average. The 25 ppb reading was a “peak,” and not sustained. This emission event was well below DOH regulatory limits.
Based on the air monitoring during the shutdown, emissions remained below permitted levels and there was never any danger or violation of environmental limits. There was no need to evacuate, but Hawaii County Civil Defense alerted residents that they could evacuate voluntarily.
To put this into perspective, it is important to note that OSHA standards allow workers without protective equipment to work in an area with 10 parts per million, or 10,000 parts per billion.
The plant has remained offline since the storm and PGV began scheduled maintenance work on Monday, August 11; this scheduled maintenance had been planned with HELCO a year ago. We anticipate restarting the plant as early as Friday, August 15 depending on transmission line availability from HELCO.
The scheduled maintenance includes routine inspections, equipment overhauls, mechanical and electrical repairs and testing.
There are about 70 employees and contractors at the PGV site on Pohoiki Road in Pahoa supporting the maintenance activity, and we have no reports of illness or nausea.
PGV continues to support the local community in recovery efforts through the local Red Cross.
What it means to “shut in wells”
The pressure and flow control valves automatically shut, through computer programming overseen with human interface. This stops the flow from the geothermal resource to the generators that produce power.