Scientists with the city of Seattle are narrowing in on the source of polluted water that flows through the city’s largest watershed. With a new study, they’ve confirmed human fecal bacteria are likely entering Thornton Creek at multiple locations near Northgate and Lake City Way.
Seattle Public Utilities has known for at least a decade that fecal coliform bacteria concentrations in Thorton Creek exceed the state water quality standard and pose a potential health risk. But they were looking for the source in 22 square miles of the watershed.
Now, after a two year investigation with new testing methods, they’ve narrowed it down to about ten segments of the stream that cover six or eight city blocks. Jonathan Froge, the storm water scientist who led the study, says they have also confirmed that human waste is a significant part of the problem.
“We have small segments of stream that are the prime areas that we’re going to look at where we think the major sources of the bacteria originate. So that we think that will improve our probability of being able to find the actual sources and correct them,” Froge said.
He says the problem could be old sewer pipes leaking into the creek. Or it could be people, dumping sewage from RV containers or relieving themselves near the water.
Inspectors from SPU will perform visual and smell tests above ground. And they’ll use smoke tests, dyes and cameras to examine inside the pipes in the areas in question.
The utility will be posting signs, advising people to stay out of Thornton Creek. Public Health recommends staying out of all urban streams and washing with soap and warm water if creek water gets on your skin.