Water Quality Monitoring

The City of Sammamish monitors water quality in streams, rivers and other water bodies. Monitoring is used to determine whether water bodies are meeting state water quality standards.

Sammamish Water Quality and Riparn Habitat Monitoring Plan

The City conducts a variety of water quality and flow monitoring activities of its natural resources and receiving waters for the purposes of (1) establishing baseline conditions to measure improvements, (2) ensuring safe swimming beaches, and (3) monitoring ecological changes.

In 2019, 2020 and 2021 monitoring activities increased to include the original Ebright Creek monitoring as well as Zackuse Creek, George Davis Creek and the Allen Lake watershed. More information can be found in the Water Quality Monitoring Reports listed below.

Hydrology gages collect data such as streamflow, temperature, water level, and/or precipitation Hydrology monitoring will be done at the following locations:

  • Zackuse Creek
    • Continuous streamflow and temperature gaging (1 site)
  • George Davis Creek and Allen Lake watersheds
    • Continuous wetland water-level gaging (2 sites)
  • City Hall

In addition, stream monitoring for water quality, aquatic habitat field measuring, and laboratory analyses will be done at the following locations and will include the following sampling:

  • Zackuse Creek (1 site)
    • Monthly water quality monitoring for:
      • Bacteria
      • Nutrients (nitrogen and phosphorus)
      • Conventionals (e.g., conductivity, turbidity, dissolved oxygen, pH)
    • Annual B-IBI sampling
    • Metals sampling (e.g., mercury, lead, copper, zinc), plus dissolved organic carbon

(DOC) to access toxicity

  • 3-4 wet-weather samples (i.e., following ¼’’ or more of rainfall)
  • 1-2 baseflow samples
  • Assess entombment of kohanee spawning areas in Ebright, George Davis, Pine Lake, and Zackuse Creeks.
    • Annual field assessment
  • Measure stream health at 5 upstream sites: two on Laughing Jacobs Creek, and one each on George Davis, Kanim, and Pine Lake Creeks.
    • Annual B-IBI sampling

Riparian monitoring in areas along the City of Sammamish streams and lakes will help to map tree cover. Riparian areas are expected to be defined in 2019.

Ebright Creek monitoring is on-going for flow and turbidity. Former annual monitoring reports involved the following activities and are provided below:

  • Continuous flow and temperature gaging in stormwater outfalls (3 sites).
  • Monthly turbidity measurements in stormwater outfalls (3 sites).
  • Continuous wetland water-level gaging (2 sites).
  • Channel morphology and streambed substrate assessment
  • Annual B-IBI sampling

Ebright Creek - Annual Report, 12-20-2017
Ebright Creek - Annual Report, 12-14-2016
Ebright Creek - Annual Report, 12-15-2015

Stormwater facility monitoring will include two stormwater outfalls near the intersection of Inglewood Hill Rd (NE 8th St) and 228th Ave SE. Samples will be collected on 3-4 dates during wet-weather conditions and analyzed for turbidity and metals (e.g., mercury, lead, copper, zinc).

Pine and Beaver Lakes

King County, through its Lakes and Streams Monitoring Group, works with volunteers to collect water quality data at Beaver and Pine Lakes. Physical parameters such as water level, precipitation, temperature, and water clarity have been collected at frequencies ranging from daily to biweekly since about 1995. Water samples are also collected between May and October (the growing season) for analysis of phosphorus, nitrogen, chlorophyll, and other parameters to evaluate productivity and indicators of trophic state or potential for algal blooms. Sammamish provides monetary support to King County for this program.

Swimming Beaches

The City through an interlocal agreement with King County also monitors water quality at local swimming beaches during the summer months for fecal coliform bacteria. Beaver Lake, Pine Lake, and Sammamish Landing beaches are all monitored approximately every other week during the summer months. If results exceed certain criteria, beaches are posted for closure until water quality improves.

Stormwater Action Monitoring

The City also contributes to Ecology’s Stormwater Action Monitoring (SAM), previously known as Regional Stormwater Monitoring Program (RSMP), through its NPDES Phase II Permit and participates in a municipal caucus related to the program. The amount Sammamish contributes is based on population, so with the increase in population due to annexation, this contribution is expected to increase in the future. The water quality monitoring fund is used for status and trends monitoring to evaluate water quality in small streams and nearshore marine areas, stormwater program effectiveness monitoring, and implementation of the Source Identification Information Repository (SIDIR) program. The City does not have any streams or stormwater facilities included in the regional water quality monitoring program. 

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