SANTA ANA, Calif. — After a day of “odor surveillance" and other scent-based sleuthing, Southern California air quality investigators confirmed Tuesday what they had already expected — that a pungent, rotten-egg aroma that stretched across the region came from the Salton Sea.
Investigators from the South Coast Air Quality Management District collected air samples, modeled weather patterns and measured hydrogen sulfide levels to determine that Monday’s stench came from the saltwater lake 150 miles southeast of Los Angeles, as strong winds from a storm churned the water and stirred up foul-smelling gasses from the lake bottom, where they normally are trapped.
A recent fish die-off was likely a contributing factor, said Andrew Schlange, general manager at the Salton Sea Authority.
“We now have solid evidence that points to the Salton Sea as the source of a very large and unusual odor event," AQMD Executive Officer Barry Wallerstein said in a statement.
Wallerstein said the agency sent technicians trained to gauge the severity of smells across the agency’s four-county jurisdiction, where they conducted “odor surveillance."
The air samples showed that levels of hydrogen sulfide, which has an unmistakable rotten-egg odor, were highest around the lake and grew weaker at bigger distances.
Modeling showed that a massive thunderstorm could have churned up bacteria and released the stench into the air, where it became trapped by low-hanging clouds.
The smell was strongest in the Riverside County town of Mecca, which had far worse problems Tuesday as torrential rains caused flooding in some areas.
Investigators also ruled out other possible causes like landfills or oil refineries.
The AQMD never had any other significant candidates for the odor’s cause, but they and others familiar with the sea still had doubts the wind could carry the stench more than 100 miles, through Riverside and San Bernardino counties through Los Angeles’ San Fernando Valley and all the way to Ventura County on California’s Central Coast.
“The problem I’m having is the magnitude of the area that was covered by the odor itself," Schlange said earlier Tuesday. “But I guess it can happen under the right conditions, and we had those conditions, apparently, the other night.
“What happened gives us an opportunity to let people know that the Salton Sea is dying and that we need to fix it," he said.