Water Quality Lab Testing

The mission of the Seattle Public Utility (SPU) Water Quality Laboratory is to provide water laboratory services including sample collection, analysis, data management, reporting, and consultations that sustain regulatory compliance, facilitate operational decisions, and help protect customer health. Analysts conduct microbial, chemical and physical monitoring daily, 365 days per year, testing over 20,000 samples each year.

This facility is the largest state-accredited water utility laboratory. Tests are conducted on water from all parts of the Seattle system as well as for other water utilities in the region.

 

Chemistry, Limnology, & Microbiology

Chemistry staff members provide sample processing for fluoride, turbidity, pH, alkalinity, conductivity, UV absorbance, chlorine demand, and screening for synthetic and volatile organics. Some of these analyses are also conducted at the water treatment facilities.

The SPU laboratory conducts tests for inorganic chemicals (including lead, copper, cadmium, arsenic, barium, chromium, selenium, silver, nitrate and nitrite) and organic chemicals (such as haloacetic acids and trihalomethanes).

Limnology staff members monitor and sample Seattle’s two drinking water sources: the South Fork Tolt River and Cedar River source waters, the Lake Youngs reservoir, and the storage reservoirs within the City of Seattle. Analyses of biological samples, algae identification, algal toxins, and taste and odor flavor profile analyses are also conducted.

Microbiology staff members provide testing of water samples collected from both the Cedar and Tolt River watersheds, and from sites throughout the retail and wholesale distribution systems. Samples are tested for coliform bacteria, E. coli, and heterotrophic bacteria. Additionally, water temperature and chlorine residual tests are done in the field at each sample collection site.

 

Testing for PFAS

January 22, 2020 update: Seattle's drinking water remains safe and protected from contaminants. Our customers receive high quality drinking water that meets state and federal health-based standards, 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 (pdf).

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).

In January, 2020, the Environmental Working Group (EWG) published a national report about PFAS in drinking water titled "PFAS Contamination of Drinking Water Far More Prevalent than Previously Reported." The report includes information about Seattle's drinking water and appears to be based on one sample that was collected from an unknown location and analyzed with a modified EPA method. We are following up with EWG to get additional information, which will be shared with customers on this web page.

 

Results Summary for PFC Sampling (October 2018)

All results in ug/L.

PFC Compound NameAcronymCedarToltRiverton1Riverton2Blvd Park

N-ethyl Perfluorooctane sulfo namido acetic acid

NEtFOSAA

ND

ND

ND

ND

ND

N-methyl Perfluorooctane sulfo namido acetic acid

NMeFOSAA

ND

ND

ND

ND

ND

Perfluorobutane sulfonic*

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

Perfluorooctane sulfonic 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 and South 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 a 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.