An odor advisory first issued more than a week ago due to elevated levels of hydrogen sulfide wafting up from the Salton Sea.
This gas is creating a smell similar to rotten eggs in the Coachella Valley and the odor advisory has been extended again. What the heck is going on…
The South Coast Air Quality Management District first issued the advisory on Aug. 18 after detecting hydrogen sulfide concentrations at 239 parts per billion, exceeding the state standard of 30 parts per billion, in a sparsely populated area immediately downwind from the Salton Sea. Since then, the odor advisory has been extended at least 4 times.
The odor advisory was originally to expire last Tuesday morning, but that day, the district extended it for two more days.
On Thursday, the district detected hydrogen sulfide concentrations were even higher than the original readings, at 253 parts per billion near the Salton Sea shore and 63 parts per billion in Mecca, and again extended the advisory through Saturday afternoon.
On Saturday morning, the district picked up hydrogen sulfide concentrations of 76 parts per billion near the shore and 35 parts per billion in Mecca – much lower than earlier readings, but still above the state standard – and the advisory was extended yet again through Monday afternoon. Then, officials extended the advisory for a fourth time.
Elevated levels of the gas near the lake are relatively common and are a product of natural processes in the water. There is increased potential for the foul-smelling odors as winds shift, especially during the summer in the early morning and late afternoon, or as thunderstorms occur over the southwestern U.S. deserts, according to the AQMD.
At 30 parts per billion, “most individuals can smell the odor and some may experience symptoms such as headaches and nausea,” according to an AQMD statement. “However, the symptoms associated with this level of exposure are temporary and do not cause any long-term health effects. Humans can detect hydrogen sulfide odors at extremely low concentrations, down to a few parts per billion.”
The Earthquake and Geologic Settings of Salton Sea
The Salton Sea and surrounding basin sits over the San Andreas Fault, San Jacinto Fault, Imperial Fault Zone, and a “stepover fault” shear zone system. Geologists have determined that previous flooding episodes from the Colorado River have been linked to earthquakes along the San Andreas Fault.
Sonar and other instruments were used to map the Salton Sea’s underwater faults during the study. During the period when the basin was filled by Lake Cahuilla, a much larger inland sea, earthquakes higher than magnitude 7 occurred roughly every 180 years, the last one occurring within decades of 1700. So the region is pretty much overdue for a large quake.
Currently, a risk still exists for an earthquake of magnitude 7 to 8. Simulations also showed, in the Los Angeles area, shaking and thus damage would be more severe for a San Andreas earthquake that propagated along the fault from the south, rather than from the north. Such an earthquake also raises the risk for soil liquefaction in the Imperial Valley region.
So why is it stinking so much? Is a large earthquake on its way to Salton Sea and region?
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The Dalton Sea is fed from the south by a constant stream known as New River. Following New River back to its source on Google earth will reveal that New River is the sewage outflow from the large nearby city of Mexicali, capital of the Mexican state of Baja California Norte.
The Salton Sea has a very high bacterial count and solid waste content. Guess why?