The subdivisions depend on community septic drain fields (LOSS) placed near town wells. The scale, number and placement of the drain fields is unprecedented and the modeled impacts are significant to groundwater and drinking water quality.
In short:
Fall City’s drinking water is at risk. Seven new housing developments are being approved that use a wastewater treatment approach never before concentrated this densely in King County. The systems themselves are not new - but placing so many side-by-side in an area with our unique soils and groundwater conditions is. No agency has studied how these clustered systems will interact, or what the combined impact could be on our shared aquifers.
What we want:
We are asking King County, the Department of Ecology, and the Department of Health to work together to assess the cumulative impacts of this clustered wastewater approach before any further permits are issued. We need a full, transparent evaluation to ensure our drinking water remains safe - for us and for future generations.
Why this matters to every Fall City resident
Our aquifers are directly connected. Fall City sits atop a shallow unconfined aquifer that is hydraulically linked to the deeper aquifer feeding our community wells. This means contamination from surface wastewater can migrate into the drinking-water supply.
Our soils are highly permeable. The sandy, silty soils of the Snoqualmie Valley allow water (and contaminants) to move freely underground. This region is officially designated a Critical Aquifer Recharge Area because pollutants can travel quickly through soil into wells.
Nitrates are the key concern. Nitrates are a wastewater by-product that can enter groundwater through drainfields and treatment failures. Elevated nitrate levels can cause serious health risks, especially for infants and pregnant women. Fall City’s background nitrate data already suggest we may be at or beyond the safe limit for what our soils can naturally filter. Once an aquifer exceeds the nitrate standard, it cannot be fixed—the contamination is permanent.
Seven new developments, seven community-scale systems. These projects all propose to use Large Onsite Sewage Systems (LOSS)—small wastewater treatment plants serving 20–30 homes each—discharging to shared drainfields above the aquifer. Only six residential LOSS systems exist in all of King County. Adding seven in one small area is unprecedented.
No cumulative groundwater review. Each development is being reviewed in isolation, even though all draw on the same groundwater basin. There has been no modeling of how wastewater plumes will overlap or migrate over time.
Past performance raises red flags. The developer’s first LOSS system, at Arrington Court, has already failed to meet state nitrate limits and required retrofitting with a community denitrification system. The state Department of Health confirmed that nitrate levels likely exceeded moderate-impact thresholds for the unconfined aquifer.
Fall City residents need the county and state to intervene and conduct studies to understand the impacts and risks to groundwater quality.
Before permits can be issued the following must be completed:
An updated well-head protection plan from the Fall City Water District, with guidance from the Department of Health, Office of Drinking Water and King County’s Source Water Protection Program.
A hydrology study to document and understand the soils, watershed, water availability, and recharge dynamics in the Fall City area. This does not exist.
The maps below show community wellheads and the underground water systems at risk.
The LOSS systems are within many town wells and our shared water system.
Soils in Fall City are at high risk of contamination.
4 of the developments have large septics placed within the 1 year wellhead protection area.
4 of the developments are within the 5 year wellhead protection area.
All of the developments are on either category 1 or category 2 critical aquifer recharge areas. -
4 of the developments are within a tributary basin.
Fall City has long running issues with draining, including previous development applications turned down based on their inability to perc. Those records have disappeared and not been included in the county permitting process.