Tacoma is a city of contradictions when it comes to water. Its drinking water source — the Green River watershed in the Cascade foothills — is among the most protected in the Pacific Northwest, so clean that it qualifies for filtration avoidance. Meanwhile, the ground beneath and around the city carries the contamination legacy of the ASARCO copper smelter, one of the most significant industrial pollution sources in Washington state history.
Green River Watershed: Exceptional Source Water
Tacoma Water draws from the Green River at the Howard Hanson Dam, roughly 35 miles southeast of the city in the Cascade foothills. The watershed above the dam is almost entirely forested — owned by the City of Tacoma, the federal government, and timber companies — with virtually no residential or agricultural development.
This protected watershed produces water of exceptional quality. Turbidity is consistently low, bacterial contamination is minimal, and industrial chemicals are essentially absent. Tacoma Water has a filtration avoidance determination from the EPA, meaning the source water is clean enough that conventional filtration is not required — a designation held by only about 50 systems nationwide.
Treatment is minimal: ozonation for primary disinfection, UV treatment for Cryptosporidium inactivation, and chloramine for residual disinfection in the distribution system. The absence of heavy treatment means fewer chemical additions and lower disinfection byproduct formation.
The vulnerability is supply, not quality. The Green River is a relatively small watershed, and during drought years, Tacoma Water supplements with wells drawing from the Tacoma-area aquifer system. Those wells produce good water but lack the exceptional quality of the Green River source.
ASARCO: A Century of Contamination
The American Smelting and Refining Company (ASARCO) operated a copper smelter on the Tacoma waterfront from 1890 to 1985. For nearly a century, the smelter released arsenic, lead, cadmium, and other heavy metals into the air and soil of the surrounding community.
The arsenic contamination is staggering in scope. The EPA’s Tacoma Smelter Plume covers approximately 1,000 square miles across portions of Pierce, King, and Kitsap counties. Soil contamination extends miles from the former smelter site, with arsenic and lead at levels requiring remediation in residential yards, parks, and schools.
The smelter didn’t directly contaminate the Green River watershed (that’s in a different direction), but it saturated the local environment — soil, shallow groundwater, and the Commencement Bay waterfront — with metals that persist indefinitely.
For residents on city water, the smelter contamination doesn’t affect drinking water quality. For anyone with a private well in the smelter plume area, arsenic and lead testing is absolutely essential. The Washington Department of Ecology maintains detailed maps of the plume and offers resources for property owners in affected areas.
Commencement Bay Superfund
Commencement Bay — Tacoma’s industrial harbor — was designated a Superfund site in 1983. Decades of industrial activity along the waterfront contaminated bay sediments with PCBs, heavy metals, petroleum, and other chemicals from pulp mills, chemical plants, shipyards, and the ASARCO smelter.
The cleanup has been extensive and ongoing for over 40 years. Multiple individual sites within the broader Commencement Bay designation have been remediated, with contaminated sediment dredged, capped, or treated. The cost has been in the hundreds of millions.
The bay cleanup is primarily an environmental and ecological issue rather than a drinking water concern — Tacoma drinks from the Green River, not the bay. But the contamination reflects the industrial burden this city has carried and the long timescales of environmental remediation.
PFAS at Joint Base Lewis-McChord
Joint Base Lewis-McChord (JBLM), one of the largest military installations in the western United States, sits just south of Tacoma. AFFF firefighting foam use at JBLM’s airfields has resulted in PFAS contamination in groundwater on and around the base.
The Department of Defense has confirmed PFAS in monitoring wells at JBLM at levels above EPA health advisory thresholds. The contamination is being investigated for potential migration toward community water supplies and private wells in the areas surrounding the base.
Tacoma Water’s primary Green River source is not affected by JBLM contamination (wrong watershed). However, the supplemental groundwater wells used during peak demand or drought may be vulnerable depending on their location relative to PFAS plumes. Tacoma Water monitors all sources for PFAS.
What Tacoma Residents Can Do
Tacoma’s municipal water quality is excellent — among the best of any major city on the West Coast. The concerns are environmental rather than tap-water related:
- If you have a private well: test for arsenic and lead if you’re within the ASARCO smelter plume footprint, and for PFAS if near JBLM.
- Soil testing: if you garden or have children playing in soil in central Pierce County, the Department of Ecology’s Tacoma Smelter Plume program offers free soil testing.
- Review the CCR — Tacoma Water publishes detailed annual reports showing the exceptional quality of the Green River source.
If you’re concerned about your water quality, a certified water treatment professional can help you test your water and recommend the right solution for your home.