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CLEARLAKE – For the last day and a half local health and public safety officials have been working to put safety measures in place in response to a natural hydrogen sulfide leak discovered in a Clearlake neighborhood.
The leak was found in an empty lot off of Division Avenue between Pearl and Uhl avenues late Wednesday, according to Doug Gearhart, Lake County's air pollution control officer.
Work continued throughout the day on Thursday to put equipment in place that would help diminish the problem, Gearhart said.
On Thursday evening, Gearhart and crews were finishing up operations to mitigate the leak, which was giving off a very strong sulfur smell reminiscent of a truckload of rotten eggs.
In addition to Gearhart from Lake County Air Quality Management, officials working to install the equipment and manage the scene included Lake County Fire Protection Battalion Chief Willie Sapeta, Clearlake Police Chief Allan McClain and some of his officers, Environmental Health Director Ray Ruminski, Clearlake Public Works Director Doug Herren, as well as Office of Emergency Services and Lake County Public Health staff.
Ruminski estimated there were eight homes within 200 feet of the leak.
“Nobody's in acute danger at this point,” he said.
Hydrogen sulfide is a colorless but highly flammable gas that is emitted by volcanoes and hots springs. An Occupational Health and Safety Administration fact sheet on the gas explains that it is heavier than air and collects in low-lying, poorly ventilated areas, and is both an irritant and an asphyxiant.
Such leaks aren't uncommon in Lake County, which owes its geothermal resources to the volcanic forces underneath the ground that emit such gases. Ruminski said it's part of the landscape, and it's one of the reasons why Lake County and surrounding areas have mineral springs.
Ruminski said that in an industrial setting like the geothermal operations at The Geysers, there are occupational health and safety staff who manage gases like hydrogen sulfide on a routine basis.
In certain concentrations, hydrogen sulfide can be poisonous, and when strong enough “it's very, very dangerous,” said Ruminski.
Ruminski said there was a similar incident of a natural hydrogen sulfide leak in the Clearlake area several years ago.
In that instance, a family with small children found the gas entering their home, he said.
He added, “They never did go back in that particular case.”
Gearhart said there are many such vents around Clear Lake giving off hydrogen sulfide, carbon dioxide and methane.
“This is the first one strong enough to be considered a health hazard,” Gearhart said.
Ground saturation had sealed the natural fissures through which the gas normally escapes, Gearhart said. So the gas ended up moving laterally until it could find a spot to get out, doing so in a concentrated fashion.
He said they made a gravel cone – which they later covered with soil – to help direct the gas through the vent, which was a large white pipe with a charcoal filter on the top. Ruminski called it a “scrubber system.”
A small, battery-operated fan that can run for weeks at a time exerts a slight negative pressure that is helping draw out the gas, Gearhart explained. A venting hose was placed so that it ran up a nearby power pole.
“We're creating an easy spot for the gas to come out,” he said.
By late Thursday the rotten egg smell was still extremely strong, but Gearhart said, “This is really good for what it was.”
The equipment setup at the Division Avenue site is considered a short-term measure, Gearhart said.
“The is a temporary thing but we don't know how long it will be needed,” he added.
By summer he said the ground will be dry and the gas will start moving out of natural fissures again.
The readings were zero after the equipment was in place, Gearhart said.
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