Under the NPDES permit, Swamp Creek is identified as an impaired waterbody due to excessive fecal coliform bacteria. The permit requires a Total Maximum Daily Load (TMDL) program to test and monitor bacteria levels in the watershed. Swamp Creek runs through several municipalities including Kenmore, Bothell, Brier, Everett, Lynnwood, and Mountlake Terrace.

All TMDL data and other ecological studies are submitted into a larger database for general use and reference supported by Department of Ecology.

Once a water sample is collected from each of the sites shown on the map a bacterial test is run on the samples and the raw data is reported in cfu/100 ml (number of bacterial colonies in each 100 milliliters of water). Water quality criteria for bacteria in Washington State for waters that have “extraordinary primary contact” (including Swamp Creek) state that the geometric mean value of samples should be less than 50 cfu/100mL and the 90TH percentile value should be less than 100 cfu/100mL.  

It is very common for the results to spike in the summer because there is significantly less rain water moving through the system and flushing out the bacteria. When the water remains stagnant and warm the bacteria can flourish. Additionally, people and animals are outdoors more often in the summer and the pet waste is a major pollution problem.

The City identified Muck Creek (a small tributary to Swamp Creek) as a high priority area, which requires additional analysis per the Permit. In 2017, four additional sampling sites were added to better understand bacteria concentrations in this area. In 2021, the Muck Creek sites were redistributed further downstream in order to narrow down tracing and elimination efforts.

The map below indicates sample site locations in 2021 with retired 2017-2020 Muck Creek sites for reference. Data from all sites can be downloaded below.