Washington’s capital city sits at the southern tip of Puget Sound, where dioxin-contaminated sediments in Capitol Lake and PFAS from military installations have put water quality in the spotlight. Olympia may not make national water quality headlines the way Flint or Newark do, but the issues here are real.
Where Olympia Gets Its Water
The City of Olympia’s drinking water comes primarily from groundwater — specifically, wells drawing from the McAllister Springs wellfield and other aquifer sources in Thurston County. The city serves about 55,000 residents directly, with surrounding areas served by other utilities and private wells.
Groundwater in the Puget Sound lowlands is generally high-quality, filtered naturally through glacial deposits. Olympia’s water requires minimal treatment compared to surface water systems — typically just chlorination for disinfection and fluoride addition.
But “groundwater” doesn’t mean “invulnerable.” The aquifers feeding Olympia’s wells are recharged by surface water infiltration, and what happens on the surface — development, industrial activity, military operations — eventually makes its way down.
Capitol Lake: Dioxin in the Sediment
Capitol Lake is the centerpiece of Olympia’s downtown landscape, sitting at the base of the state capitol campus. Created in 1951 by damming the Deschutes River estuary, the lake has become one of the most contentious environmental sites in Washington state.
The lake’s sediments are contaminated with dioxins — among the most toxic synthetic chemicals known. Dioxin contamination in Capitol Lake has been linked to historical industrial activity in the Deschutes River watershed, including a former wood treatment facility that used pentachlorophenol. [NEEDS VERIFICATION: specific dioxin concentrations in Capitol Lake sediments and current remediation status]
The Washington Department of Ecology has been studying Capitol Lake for years, and a long-running debate continues about the lake’s future: should it remain a managed lake, or should the dam be removed to restore the Deschutes River estuary? Both options have environmental trade-offs, and dioxin-contaminated sediments complicate any approach.
Capitol Lake doesn’t serve as a drinking water source, but it flows into Budd Inlet and southern Puget Sound, affecting the broader aquatic ecosystem. The dioxin contamination has triggered fish consumption advisories for species caught in the lake and nearby waters.
PFAS at Military Installations
Thurston County is home to Joint Base Lewis-McChord (JBLM), one of the largest military installations on the West Coast. AFFF-based firefighting foam used at JBLM has contaminated groundwater with PFAS, and the plume extends beyond the base boundaries.
The Department of Defense has been conducting PFAS investigation and remediation at JBLM, but the scale of the contamination is significant. Testing of private wells near the base has revealed PFAS levels exceeding EPA health advisories, and some residents have been provided alternative water supplies. [NEEDS VERIFICATION: current PFAS levels at JBLM boundary wells and number of affected private wells]
The Olympia Regional Airport (OLM) is another potential PFAS source, as is the former Olympia Brewery site and other industrial locations where PFAS-containing materials may have been used.
For Olympia’s municipal wells, the question is whether PFAS from these sources has reached the aquifers that supply drinking water. Monitoring is ongoing, and results will be critical as the EPA’s 2024 PFAS MCLs take effect.
Stormwater: The Pacific Northwest Challenge
Olympia gets about 50 inches of rain per year, and all that water has to go somewhere. Stormwater runoff is one of the Puget Sound region’s most significant water quality challenges.
As rain flows across roads, parking lots, rooftops, and developed land, it picks up:
- Petroleum products from vehicles — oil, brake dust, tire wear particles (which contain 6PPD-quinone, recently identified as toxic to coho salmon)
- Heavy metals — copper from brake pads, zinc from galvanized surfaces
- Pesticides and herbicides from residential and commercial landscaping
- Nutrients from fertilizers and pet waste
- Bacteria from animal waste and failing septic systems
Olympia has invested in stormwater management, including low-impact development standards, rain gardens, and permeable surfaces. But the sheer volume of impervious surface in any urban area means runoff remains a persistent source of pollution to Budd Inlet and surrounding waterways.
For groundwater, stormwater infiltration is a double-edged sword — it recharges aquifers, but it can carry surface contaminants along with it.
Nitrate and Septic System Impacts
Parts of Thurston County outside Olympia’s sewer service area rely on septic systems. High-density development on septic can lead to nitrate contamination of groundwater — and Thurston County has documented this in several areas.
Nitrate levels above the EPA’s MCL of 10 mg/L have been found in some private wells in the county, particularly in areas with older septic systems and sandy, well-drained soils that allow rapid infiltration. [NEEDS VERIFICATION: specific areas in Thurston County with documented nitrate contamination in wells]
For residents on private wells, nitrate is one of the most important contaminants to test for — it’s especially dangerous for infants, causing methemoglobinemia (blue baby syndrome).
What the Data Shows
Olympia’s annual water quality reports show the municipal system meeting all Safe Drinking Water Act standards. Groundwater sources generally produce clean water with low levels of treatment-related contaminants. Key data points:
- Lead and copper — below action levels; Olympia’s groundwater is naturally less corrosive than many surface water systems
- Disinfection byproducts — minimal, given the low organic content of groundwater sources
- Nitrates — monitored and below MCLs in municipal wells
- PFAS — testing underway; results pending for compliance with new federal MCLs
The bigger concern in the Olympia area is for private well users, who don’t benefit from municipal treatment and monitoring. Thurston County Environmental Health provides well water testing guidance, but testing is voluntary and many well owners don’t test regularly.
What Olympia Area Residents Should Do
Know your water source. Are you on city water or a private well? This determines your risk profile and what you should test for.
Test your private well. If you’re on a well — especially near JBLM, the airport, or in areas with septic systems — test for PFAS, nitrates, bacteria, and any contaminants relevant to nearby land uses. Test annually at minimum.
Review the city’s water quality report. Available from the City of Olympia’s Public Works department. Pay attention to PFAS results as they become available.
Manage your own stormwater. Rain gardens, permeable driveways, and reduced pesticide use on your property all help protect the groundwater everyone shares.
Consider filtration. For well users concerned about PFAS or nitrates, reverse osmosis is the most effective point-of-use option. For city water users, a carbon filter can improve taste and remove residual chlorine.
Check fish advisories. If you fish in Capitol Lake, Budd Inlet, or nearby waters, check the Washington Department of Health’s fish consumption advisories for dioxin and other contaminants.
If you’re concerned about your water quality, a certified water treatment professional can test your water and advise on solutions.