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Fall City on-site community septic system

Construction August 2024-spring 2026

Construction update

November 18, 2025

Work is progressing on the upgraded septic system for private properties in the Fall City Business District. Since our October update, workers have installed 14 new septic tanks and connected them to the underground on-site treatment plant. This means wastewater from homes and businesses is now flowing into the new tanks and being pumped to the treatment facility for processing.

This project is being done in phases, as shown on the updated map below. Work on the properties in Phase 1 is finished, and we’re working on the ones in Phase 2, which includes properties east of Preston-Fall City Road. We'll be moving into Phase 3 in the coming weeks.

Meanwhile, the underground treatment plant is operating. Here’s a recent photo showing sunrise over the completed area:

Sunrise over covered treatment plant

Effects on traffic

Installing septic systems across multiple properties is a complex and disruptive process. It involves heavy equipment, noise, and dust. There will be intermittent road closures or delays through June 2026. For the most up-to-date information about impacts on traffic, check MyCommute and sign up for Road Alerts.

King County truly appreciates the patience and support of everyone in the Fall City Business District as we work to improve local infrastructure. This project will repair all failing and non-conforming systems, and the new system will provide capacity for conservative growth in the business district and treat waste to the highest quality standards required by the Washington State Department of Health.

Learn more and see more recent work photos on the King County Local Blog.

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 supports the Fall City Business District and the community’s economic future.

The Fall City Business District has 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.

Currently, local businesses cannot 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 are moving forward with the Fall City on-site septic project, which will connect 46 businesses to an underground pre-treatment facility. The project will repair all failing and non-conforming systems and the new system will provide capacity for conservative growth in the business district. It will treat waste to the highest quality standards required by the Washington State Department of Health.

Cross-section of Septic System

Septic system diagram

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

What to expect during construction

  • Access to local business will be maintained throughout construction.
  • Crews will work during the day. Work will sometimes be noisy.

Temporary closures and parking impacts

  • Bernard Memorial Park, near the Roadhouse Inn, will be completely closed to the public for up to 12 months.
  • The alley behind businesses on Redmond-Fall City Road SE between 334th Place and Preston-Fall City Road SE will be closed intermittently in 2025 and early 2026.
  • Parking on the south side of Redmond-Fall City Road SE will be intermittently unavailable during active construction in 2025 and 2026.

How to stay informed

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

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