Seattle Public Utilities

Water Quality

Testing for PFAS and keeping Seattle’s drinking water safe

November 2, 2018 Update:

Seattle’s drinking water remains safe and protected from contaminants, including the group of man-made chemicals labeled PFAS (per- and polyfluoroalkyl substances).

PFAS are manufactured for a variety of industrial purposes. If detected in drinking water, PFAS have the potential to raise health concerns.

For more information about PFAS, including the health and safety risks associated with these compounds, visit the Environmental Protection Agency and Washington State Department of Health websites.

Although PFAS are not regulated contaminants and routine testing is not required, Seattle Public Utilities (SPU) tested its Tolt and Cedar River surface water sources for six types of PFAS in 2015.

Test results in 2015 showed no detection of PFAS was found.

In October 2018, SPU conducted additional tests on the Tolt and Cedar water supplies, this time using a more sensitive sampling method and testing for 14 types of PFAS. Test results again showed no detection of PFAS and Seattle’s drinking water continues to be safe and protected from contaminants.

A summary of the 2018 tests are shown below and the 2015 test results can be found in SPU’s 2015 Annual Water Quality Report .

In addition to the City’s primary surface water sources, Seattle also has seasonal wells. The wells are not used very often and are not in service right now. They have not been used since 2015, but as a precaution SPU tested the wells for PFAS in October 2018. Two of the three wells had no detection of PFAS. Trace detections of several PFAS compounds were measured in the third well with a maximum concentration of 5 parts per trillion. This amount is far below the health advisory level of 70 parts per trillion established by the U.S. Environmental Protection Agency (EPA).

Results Summary for PFC Sampling – October 2018
(ug/L)

PFC Compound Name

Acronym

Cedar

Tolt

Riverton1

Riverton2

Blvd Park

N-ethyl Perfluorooctanesulfonamidoacetic acid

NEtFOSAA

ND

ND

ND

ND

ND

N-methyl Perfluorooctanesulfonamidoacetic acid

NMeFOSAA

ND

ND

ND

ND

ND

Perfluorobutanesulfonic*

PFBS

ND

ND

ND

ND

0.0018

Perfluorodecanoic acid

PFDA

ND

ND

ND

ND

ND

Perfluorododecanoic acid

PFDoA

ND

ND

ND

ND

ND

Perfluoroheptanoic acid

PFHpA

ND

ND

ND

ND

0.0029

Perfluorohexanesulfonic acid*

PFHxS

ND

ND

ND

ND

0.0022

Perfluorohexanoic acid*

PFHxA

ND

ND

ND

ND

0.0047

Perfluorononanoic*

PFNA

ND

ND

ND

ND

ND

Perfluorooctanesulfonic acid*

PFOS

ND

ND

ND

ND

ND

Perfluorooctanoic acid*

PFOA

ND

ND

ND

ND

0.0050

Perfluorotetradecanoic

PFTeDA

ND

ND

ND

ND

ND

Perfluorotridecanoic

PFTrDA

ND

ND

ND

ND

ND

Perfluoroundecanoic acid

PFUnA

ND

ND

ND

ND

ND

Sample Location

-

CLT-5

TPT-3

RHW1-R

RHW2-R

BPW-R

*Compound was also part of UCMR3. EPA Method 537 was used for all analyses. Method Reporting Limit was 0.002 ug/L for all analytes. Sample date for Cedar and Tolt was 10/08/2018. Sample date for the wells was 10/03/2018. Field blanks did not have any detections.

Seattle Public Utilities (SPU) provides some of the highest quality drinking water in the nation because it comes from pristine, protected mountain sources: the Cedar River Watershed andSouth Fork Tolt River Watershed.

To ensure the safety of our drinking water, SPU’s water quality laboratory analyzes over 20,000 microbiological samples each year -- more than 50 a day -- and conducts chemical and physical monitoring daily, 365 days per year.

Each year, SPU publishes the Drinking Water Quality Report that summarizes water quality information for the year as required under the federal Safe Drinking Water Act. More detailed information can be found on the Water Quality Analyses page, which includes quarterly reports and annual summaries for dozens of drinking water quality parameters.

Water Quality Topics

  • Cross-Connection Control – Protecting the quality of our drinking water includes protecting the water as it passes through the pipes to all the buildings in the City.
  • Lead – Learn about lead and what you can do at home to lower your exposure to it from your drinking water.
  • Fluoride – SPU has supplied fluoridated drinking water to our customers since 1970.
  • Health and Water Quality Standards – Water quality standards are set to ensure your health is protected.
  • Cryptosporidium and Giardia – Find out about these microscopic organisms.
  • Water Taste, Odor and Color – Seattle has some of the finest tasting, purest source water in the world. But if your water doesn't come out of the tap tasting good and clean, there is usually something you can do about it at home.
  • Algae and Filter Clogging – If you filter your water, during an algal bloom you may notice your filter clogs faster than usual. Typically, the blooms occur in the late spring, but they can occur at unexpected times of year. To help alleviate the filter clogging problem, you can install an inexpensive pre-filter.
  • Home Water Filters – Some customers filter their water to improve the things such as taste and odor while others filter their water because they are concerned about water safety. If you decide to filter your water at home, it is important to do it correctly and maintain your system regularly. NSF International evaluates and certifies filters.