Testing for PFAS and Keeping Tacoma's Drinking Water Safe

What are PFAS? 

PFAS (per- and polyfluoroalkyl substances) are a group of human-made chemicals that have been manufactured in the U.S. since the 1940s. Although manufacturers are slowly phasing out their production because of human health concerns, PFAS are used in a variety of non-stick, stain-resistant, and water-resistant consumer products. Certain types of firefighting foam also contain PFAS. 

PFAS are widespread and they do not break down easily in the environment. These “forever chemicals” have been found in people, wildlife, and water bodies all over the world. PFAS can contaminate drinking water supplies and can commonly enter groundwater supplies when PFAS-containing firefighting foams are used at nearby training facilities, military bases, or airports. 

Like many other water systems in Washington and across the country, Tacoma Water is working to address the presence of PFAS in drinking water supplies. 

How are PFAS regulated? 

In April 2024, the U.S. Environmental Protection Agency (EPA) finalized a National Primary Drinking Water Regulation for PFAS. This rule provides the first enforceable standard for PFAS levels in drinking water in Washington State, setting limits for six PFAS compounds. The rule regulates two of the oldest and most common compounds – PFOS and PFOA – along with four additional compounds (PFHxS, PFNA, HFPO-DA or GenX, and PFBS). 

The federal PFAS rule requires all water systems to comply with the limits by 2029. Compliance will be based on a running annual average. 

PFAS health concerns 

Some PFAS may be toxic to humans at low levels with sustained exposure. Because PFAS chemicals at low levels can slowly accumulate and do not break down in the body over time, health effects are primarily due to chronic exposure to PFAS. 

 Across the country, research is ongoing to better understand how PFAS may affect our health. 

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

Tacoma Water supply and PFAS 

Tacoma Water’s primary drinking water source is the Green River, which is supplied by a protected watershed in the foothills of the Cascade Mountains. In a typical year, the Green River provides over 95 percent of Tacoma Water’s annual supply, meaning that most Tacoma Water customers receive Green River water most of the time.  

Tacoma Water has tested all its sources for PFAS with results to the lowest detection limits available. To date, no regulated PFAS chemicals have been detected in the Green River supply. To the best of our knowledge, there are no sources of PFAS within the Green River Watershed. 

Tacoma well water and PFAS 

Tacoma Water owns more than 20 wells, with the majority located in the South Tacoma Wellfield. Groundwater is a critical back-up supply for Tacoma Water, providing approximately 5 percent of the annual supply in a typical year, with increased use in some years. Most of Tacoma Water’s wells flow to combined treatment locations, such as Hood Street Reservoir, so water from multiple wells can be blended and treated together prior to entering Tacoma Water’s system. When wells are not operating, Green River water feeds those locations. 

All wells were individually sampled in 2018 and 2023. Low levels of PFAS were detected in most of Tacoma Water’s wells. For many wells, levels were just barely higher than laboratory detection limits, but some wells do have individual PFAS levels greater than the new federal standards. 

To mitigate the PFAS levels in the well water, Tacoma Water prioritizes use of the Green River supply. When groundwater is needed, we selectively operate wells with lower PFAS concentrations and blend well water before it enters the system. These efforts ensure that PFAS levels in the drinking water provided to our customers will meet the new federal standards.  

We are also planning for a point in the future when greater volumes of well water will be required for longer periods each year. We are working with an engineering consultant to develop conceptual PFAS treatment recommendations for the wells and prepare an implementation plan so that treatment can be built when it is needed. Construction of PFAS treatment for our wells will be scheduled so that it is online by the time that Tacoma Water must rely on groundwater more often. 

Note that two wells with the highest PFAS levels were removed from service in 2018 with no current plans for future use. 

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