Seattle.gov Home Page
Seattle.gov This Department

Water Quality Analyses

Analyses of Cedar and Tolt River drinking water supplies

Seattle Public Utilities' Water Quality Annual Reports (Consumer Confidence Reports) provide information about regulated compounds that have been detected in our drinking water, and additional information about drinking water sources, protection, treatment, testing, and compliance. The Annual Analyses provides additional information about regulated compounds, plus information about compounds that were not detected, and compounds that are not regulated or that relate to the aesthetics of the drinking water.

The compounds listed in the Annual Analyses are divided into one of three groups:

  • Primary Standards, which relate to public health. The public is notified if any of these levels are exceeded.
  • Secondary Standards, which relate to aesthetic qualities such as taste, odor and appearance.
  • Unregulated compounds, which are monitored in the interest of our customers, or to assist regulators in developing future regulations.

Before you proceed, you'll want to know which source provides your drinking water. More than 80 percent of the residences of Seattle receive their drinking water from the Cedar supply. Neighborhoods that regularly receive Tolt water include Broadview, Bitter Lake, Crown Hill, Northgate, Haller Lake, and Pinehurst, and parts of Maple Leaf, Wedgewood, Greenwood, View Ridge, and Roosevelt. All other areas of Seattle receive Cedar water.

2014 Quarterly Analyses

2013 Quarterly Analyses

Archived Analyses

Interpreting the tables

Here is more information regarding columns in the water quality analyses table:

  • Column 1: Lists the names for each of the compounds and their group name.
  • Column 2: Lists the maximum contaminant levels (MCLs) for each compound if there is one, or the action level in the case of lead and copper. To comply with state and federal standards, drinking water may not contain more than the MCL.
  • Columns 3 and 4: List the levels observed in Seattle's sampling program for treated Cedar and Tolt water.
  • Column 5: Lists the minimum reporting level for each compound. If a result is listed as ND (not detected), the result was below the minimum reporting level for that parameter.