Study confirms evidence of human fecal bacteria in Seattle’s Thornton Creek

The Thornton Creek Watershed reaches into Shoreline as far as NE 193rd.

A two-year investigation by Seattle Public Utilities (SPU) has confirmed human fecal bacteria are likely entering North Seattle’s Thornton Creek at multiple locations.

Funded by the Washington Department of Ecology and led by SPU stormwater scientist Jonathan Frodge, the study was based on samples collected at 45 sites throughout the watershed, under a variety of conditions

It has been known for years that fecal coliform bacteria concentrations in Thornton Creek exceed the state water quality standard and pose a potential threat to public health. The new study confirms human bacteria are present and contribute to the water quality problem. The study is also the first to identify sub-basins (general areas) where bacteria appear to be entering the stream.

The study is seen as an important step toward identifying and correcting bacterial sources in the creek.

Among the most urbanized streams in King County, Thornton Creek consistently ranks among the highest for fecal coliform bacteria.

SPU stormwater investigators are continuing their work to locate sources of bacteria in the creek, and will be working in the Thornton Creek watershed this summer.

“Human waste shouldn’t be in this creek,” said SPU Director Ray Hoffman.