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King County Washington home

Fall City on-site community septic system

Status: Construction is complete

Construction update

Project Complete: Fall City’s On‑Site Septic System is Officially Up and Running 

We’re thrilled to share some big news: the Fall City business district’s on‑site septic system project is officially complete. Our team installed the final septic tank—No. 46—and completed the finishing touches. Now, the long‑awaited infrastructure upgrade is in place and supporting businesses and houses in the business district. King County’s final step is some landscaping on the drainfield this fall.  

With construction complete, the Fall City Septic Association is officially the system manager. Portions of the system have already been operating under their care, and full management has now been transferred. 

This achievement has been years in the making, and it marks an important step forward for the community. The new system will enable businesses to fully use their buildings and better serve Fall City residents and visitors. To everyone involved—from partners and contractors to community members—congratulations and thank you for your patience, support, and teamwork. This is a major win for Fall City, and there’s plenty to celebrate. 

To contact the Fall City Septic Association, email pete@nelsontreehouse.com or call 206-999-5981

Overview

Fall City is an unincorporated rural town with a population of less than 5,000 people and more than 40 businesses in the business district. The town sits where the Snoqualmie River and Raging River come together. The area is important to local Native American tribes. 

This project supported the Fall City Business District and the community’s economic future. 

The Fall City Business District had many businesses and residences with broken wastewater systems. A 2016 survey showed that only 14 of 62 properties in the business district had updated septic systems. The failing older systems posed a public health risk to the surrounding community and an environmental threat to nearby rivers.  

Local businesses could not expand or keep up with changing demands from customers. For more than 10 years, the Fall City community asked for help to solve this problem. 

With the support of state and local elected leaders and King County, we moved forward with the Fall City on-site septic project, which connected 46 businesses to an underground pre-treatment facility. The project repaired all failing and non-conforming systems and the new system will provide capacity for conservative growth in the business district. It treats waste to the highest quality standards required by the Washington State Department of Health. 

Cross-section of Septic System

A cross‑section diagram showing how wastewater moves through an individual property’s septic system. The image illustrates a house connected by a main sewer line to a septic tank and an underground septic treatment plant. Arrows show the flow of wastewater through each treatment stage before it travels to the drainfield at Bernard Memorial Park. The drainfield is shown with treated water dispersing downward through layers of topsoil, sandy loam fill, a sandbed, and soil, eventually reaching groundwater. Landscape features such as trees, grass, mountains, and a labeled property line appear aboveground for context.

Location

The project site is in the Fall City Business District, next to the Snoqualmie River and near the intersection of state routes 202 and 203.

Area map showing construction zones

Project schedule

  • August – October 2024

    Build drain field

  • October – December 2024

    Install main sewer line

  • January – July 2025

    Install and commission treatment facility

  • October 2025 – June 2026

    Install and connect septic tanks

  • June 2026

    Project complete