Caltrans: Slimy substance in the Sierra no big deal
By Barbara Barte Osborn, Sacramento Bee
On his way to Lake Tahoe earlier this month, Greg Service pulled into an eastbound rest stop along Interstate 80 about 40 miles west of Truckee.
The Santa Rosa resident tossed a ball to his dog at the Gold Run Safety Area, but was soon in for a nasty surprise.
“He came out of the bushes covered with slime,” Service said. “It smelled like sewage.”
Behind the bushes, Service said he saw a stream covered with a foamy, orange, foul-smelling substance.
“It was about 5-feet across in some places and almost 3 feet deep in some places,” he said. “It was full of what appeared to be sewage.”
He cleaned up his dog – “fortunately, I had the truck, so he could ride in back,” he said – and continued on.
But he was so concerned about the incident, he took photos of the stream and called the state Department of Transportation. Dissatisfied with the agency’s response, he checked the westbound Gold Run rest stop on his way home, where he found more of the substance, and later called the Bee.
“It was right after the Fourth of July holiday,” Service said, adding that he suspected that the rest stop’s sewage system had backed up or they flushed it “right into an open trench about 100 feet away.”
The red or orange slime in sluggish surface water is a well-known natural occurrence in the Sierra and is the result of iron fixing bacteria. The bacteria derive energy to live by adding an oxygen molecule to the iron. The oxidized iron yields the red color, much like rust on ferrous metals. When I worked at the Lahontan RWQCB, we would frequently get complaints about red slime in Truckee and Tahoe area streams and springs. Inevitably, they all turned out to be natural phenomena.
Another common misconception is the white foam seen on local streams in the spring and fall is the result of human-caused pollution. People often mistake this for soap suds. In fact, it is another naturally-occurring process – the biodegradation of lignin in woody plant materials falling into streams. The biodegradation process generates intermediate organic compounds that are surfactants. Surfactants are a class of compounds that allow water to entrain air as foam and includes soaps and detergents. Eventually, these natural surfactants decompose into harmless compounds that are recycled by nature.
Finally, most people think anything foul smelling in the environment must somehow be caused by sewage. For those of us who have worked in the water and wastewater field, we know that sewage in various states of decomposition has unique odors. Even different sources of waste from different animals have distinctive odors. It’s hard to describe in print, but to paraphrase Justice Potter Stewart; We know it when we smell it.