2024 Testing Overview

• Compliance Status: Tacoma’s 2024 Water Quality Report confirms the system met all federal and state drinking water standards. Tacoma Water routinely takes more than 200 bacteria/chlorine samples per month, exceeding Washington State Department of Health’s requirement of 150 samples. The utility also tests for over 80 regulated and more than 50 unregulated contaminants annually. Use our water quality checker to explore data relevant to your address.
• Contaminants Above Health Guidelines (EWG): While the water is legally compliant, independent EWG analysis based on 2021–2023 data identifies 11 contaminants exceeding health guidelines — key concerns include arsenic at 0.365 ppb (91x above health guideline), total trihalomethanes at 9.81 ppb (65x above health guideline), and hexavalent chromium at 0.164 ppb (8.2x). These health guidelines are set by independent scientists and are stricter than EPA legal limits. For effective reduction, see our filter recommendations.
• PFAS Monitoring: No regulated PFAS chemicals have been detected in Tacoma’s Green River supply. Some backup groundwater wells in the wider region show PFAS contamination linked to historical firefighting foam use at Joint Base Lewis-McChord (JBLM), approximately 9 miles south of Tacoma. Tacoma manages this by prioritising Green River water and operating affected wells selectively. The EPA’s new PFOA/PFOS MCLs of 4 ppt (finalised April 2024) require full compliance by 2031.

Water Sources

• Green River Watershed: Primary source (over 95% of supply), located in the protected Cascade Mountains foothills. The 65,000-acre watershed is managed under strict access controls with federal, state, tribal, and private ownership. The Howard Hanson Dam — operated by the U.S. Army Corps of Engineers — regulates flow from the reservoir, providing resilience against drought and flood conditions.
• South Tacoma Wellfield: Backup groundwater supply from over 20 wells providing approximately 5% of annual supply, with increased use during peak demand periods. Some wells in the wider region have been affected by PFAS contamination from JBLM; Tacoma monitors and manages these wells carefully. Treatment systems to remove PFOS and PFOA have been installed at affected JBLM-area wells, with finished water results below advisory levels.
• Watershed Protection: Tacoma Water owns key portions of the watershed and implements a comprehensive Habitat Conservation Plan protecting fish and wildlife while maintaining source water quality. The remote, rugged terrain provides natural filtration through pristine forest before water reaches the river intake.

Advanced Treatment Technology

• Green River Filtration Facility: State-of-the-art treatment plant completed in 2015, capacity 150 million gallons per day, using multi-barrier treatment including coagulation, flocculation, sedimentation, and granular activated carbon (GAC) filtration to remove cryptosporidium and organic contaminants.
• Disinfection Process: Chlorine disinfection provides pathogen protection throughout the distribution system. This process creates disinfection byproducts (trihalomethanes and haloacetic acids) that exceed health guidelines but remain well below EPA legal limits. Reducing hot water exposure during showering (which volatilises THMs) is one practical household measure.
• Real-Time Monitoring: Continuous monitoring throughout treatment and distribution, with automated controls and alarm systems. Over 20,000 annual water quality tests ensure rapid response to any variation in water quality.

Infrastructure & Rate Context

The Portland Avenue Reservoir was taken out of service following the closure of the WestRock paper mill in 2024 — formerly Tacoma’s largest commercial water customer, drawing up to 35 million gallons per day at peak. With reduced demand from the mill gone, water retention times in certain parts of the distribution system increased, prompting Tacoma Water to make operational adjustments to maintain chlorine residual and biological safety throughout the network. Rate increases of approximately 6% annually for 2025–2026 reflect infrastructure investment needs following the loss of this major industrial customer. Tacoma offers the Bill Credit Assistance Plan for qualifying low-income households. For statewide context, see our Washington state page; nearby cities including Seattle and Spokane face distinct but related water quality challenges across the Pacific Northwest.