PHOTOS: What Is The ‘Brown Gunk’ Found Seeping Into Seahurst Stream?

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BTB Reader Bob Smith sent us some photos recently, of what he calls “brown gunk” that he recently discovered seeping into a stream in Seahurst Park, just south of the main entrance driveway near the upper parking lot.

We don’t like seeing ‘gunk’ in streams ourselves, so we sent the photos on to Doug Osterman, who serves as Green/Duwamish Watershed Coordinator for King County. Doug wasn’t exactly sure himself, so he forwarded the following pics on to Doug Navetski of the King County Water Quality Compliance Unit:

“The ‘brown gunk’ could be iron bacteria,” said Osterman. “Doug (Navestski) told me that they do not view, at this point in time, the appearance of this bacteria as an indicator of pollution.”

Here’s what Navetski said in an email reply after viewing the pics:

This looks like iron bacteria that we often encounter in well sampling. We see it pop up to the surface every once in a while.

Clues which indicate that iron bacteria may be present in well water are:

  • TASTES AND ODORS – Iron bacteria often produce unpleasant tastes and odors commonly reported as: “swampy,” “oily or petroleum,” “cucumber,” “sewage,” “rotten vegetation,” or “musty.” The taste or odor may be more noticeable after the water has not been used for some time. Iron bacteria do not produce hydrogen sulfide, the “rotten egg” smell, but do create an environment where sulfur bacteria can grow and produce hydrogen sulfide.
  • COLOR – Iron bacteria will usually cause yellow, orange, red, or brown stains and colored water. It is also sometimes possible to see a rainbow colored, oil-like sheen on the water.
  • RED SLIMY DEPOSITS – Iron bacteria produce a sticky slime which is typically rusty in color, but may be yellow, brown, or grey. A “feathery,” or filamentous growth may also be seen, particularly in standing water such as a toilet tank.

The characteristics listed above are typical of iron bacteria. However, objectionable stains, tastes, or odors may be due to other causes including iron, sulfate, hydrogen sulfide, manganese, or other nuisance organisms such as sulfur bacteria. Identification of substances in water is best done by having a laboratory test a water sample. Many laboratories provide iron bacteria tests for costs under $35. It is also a good idea to evaluate the sanitary quality of the well by doing two things: (1) testing the water for nitrate-nitrogen and coliform bacteria; and (2) assuring that the well is properly constructed, located, and maintained.

So…have YOU seen this ‘brown gunk’ before? Do you think it’s some kind of pollution, or do you accept the county’s explanation?

Please let us know in Comments below…

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2 Responses to “PHOTOS: What Is The ‘Brown Gunk’ Found Seeping Into Seahurst Stream?”
  1. Lee Moyer says:

    I monitor the water off my metal roof because I use it in ponds in my yard. The first runoff of Monday’s rain on my roof was muddy and about the same color as the above. It seems to be pollen. Maybe the plants and trees really did their spring thing on Saturday, knowing it was all the spring they were going to get. It the above water is coming from a large surface, like a parking lot, it might be the same thing.

  2. Abby says:

    This looks just like the water over at Iron Springs Resort near Ocean City, WA. The fresh water that runs to the ocean is colored similarly and smells like rust. It was quite interesting to see it in person and I’ve never seen it again – until now, it appears.

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