Little Bear Creek Basin Plan (Water Quality Study)

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Snohomish County Public Works Surface Water Management (SWM) Division is preparing a watershed plan for Little Bear Creek to meet the County’s watershed planning requirement under Special Condition S5.C.5.c of the National Pollutant Discharge Elimination System (NPDES) Phase I Permit.

The Plan is due to the Department of Ecology on September 6, 2017. It will be based on the findings of a water quality study of the subject area - the portion of Little Bear Creek in unincorporated Snohomish County.

The objective of the watershed planning requirement is to:
Identify a stormwater management strategy or strategies that would result in hydrologic and water quality conditions that fully support “existing uses,” and “designated uses,” as those terms are defined in WAC 173-201A-020, throughout the stream system. (NPDES Phase I permit, Section S5.C.5.c)

Our Study Area: Little Bear Creek


The Little Bear Creek basin in south Snohomish County was selected as the focus of this plan, with Department of Ecology approval. Key reasons for this selection were:
  • Location: The basin is located predominately in Snohomish County, with a relatively small southern extension into King County. 
  • Current Land Use: The Snohomish County portion is predominately rural, covering 13 square miles and home to nearly 4,000 households. 
  • Environmental Amenities: The basin is an important watershed for several species of salmon and trout, with good water quality and stream habitat. 
  • Development Potential: Portions of this watershed are in areas adjacent to the cities of Bothell and Woodinville. 
In the course of this study, the County will identify a baseline for water quality conditions and options to manage future stormwater in a manner that will protect the basin’s water quality and habitat resources for the future.

Focus of the Study: Existing and Potential Future Stream Conditions


SWM staff studied existing stream conditions within the basin, and retained a consultant to support hydrologic modeling and strategy development to evaluate the impacts of stormwater on water quality, stream flows, and aquatic health.

The following steps have been completed:
  • In 2014 and 2015, the project team gathered data on: 
    • Habitat conditions along Little Bear Creek and its tributaries including stream bank stability, sediment sources, vegetation, and channel dimensions
    • Stream temperatures and pollutants such as dissolved copper, dissolved zinc, and fecal coliform bacteria
    • Biological health of the stream including the aquatic insects that fish depend upon
    • Stream flows during small and large storms 
    • Existing stormwater infrastructure such as detention ponds
  • In 2016, the project team:
    • Completed water quality and stream flow data collection
    • Conducted flow modeling, water quality modeling, hydrologic metric assessment, B-IBI analysis
    • Developed current future and fully-forested modeling forecasts for multiple parameters required by the NPDES permit
    • Completed the Current Conditions Report

How the Data is Being Used


The water quality data gathered in 2014, 2015 and the early part of 2016 has been entered into a computer model of the Little Bear Creek basin to help determine whether water quality standards will continue to be met in the future as the area continues to develop and grow.

The findings from this model will be used to create a Little Bear Creek Basin Plan, a watershed-scale stormwater plan, to protect future water quality and aquatic health. The plan will be available for public review and comment in June 2017. The finalized plan will be submitted to the Washington Department of Ecology by September 2017.

Where We Are in the Process


The timeline below shows what we’ve done, where we are, and what’s coming up. Click on timeline bullet items for more details
Little Bear Creek Timeline
Public and Stakeholder Outreach
Upcoming Events
  • June 21, 2017: Public Meeting to review and provide input on Draft Plan
  • September 6, 2017: Final Plan Submitted to the Washington State Department of Ecology