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Black Diamond sewer upgrade

The Black Diamond Sewer Upgrade Project will increase capacity for 6 miles of regional sewer pipe in Black Diamond. The project will help us treat more wastewater to meet the needs of the growing Black Diamond community.

Project description

Upgrading the sewer pipe to meet Black Diamond's growth

Black Diamond is one of the fastest-growing communities in the Puget Sound region. In 1992, King County built a regional sewer line to serve the area’s much smaller population at the time. Today, we need to upgrade the existing sewer line because it’s reaching capacity. Upgrading the sewer line may include a combination of repairing the existing pipe and installing new pipes

The project will look at options to upgrade 6 miles of sewer pipe in Black Diamond. The option we select will:

  • Serve the community’s wastewater capacity needs through 2070
  • Ensure reliable wastewater service to Black Diamond's homes and businesses
  • Foster a healthy and resilient community with reliable wastewater infrastructure

Project update

August 2024

Exploratory surveys starting as early as September 9th for the Black Diamond Sewer Upgrade Project

King County Wastewater Treatment Division is in the early stages of design for the Black Diamond Sewer Upgrade Project. Starting as early as September 9, the project team will collect soil samples along the existing pipeline. The samples we collect will help us understand underground conditions in the project area.

The existing Black Diamond sewer pipeline begins in Black Diamond, runs along 224th-228th Avenue Southeast, and Southeast Covington Sawyer Road, and ends in Covington near Timberlane Way.
Soil sampling will take place all along the existing sewer pipeline that runs north to south between the cities of Covington and Black Diamond.

What to expect:

  • Crews will work in the right-of-way along the existing pipe alignment.
  • We expect to close one lane to allow crews to work safely. Flaggers will direct traffic around the work area.
  • Sampling will take approximately 30 days to complete. This work may take longer depending on site conditions.
  • Crews expect to work from 7 a.m. to 5 p.m. Monday to Friday.
  • Near neighbors may notice noise, dust, and vibrations. These are typical construction impacts.
  • Service providers will maintain garbage, recycling, composting, and mail service.
    • Please contact your service provider or call Annie Plumley, at 206-263-3203, if you experience a service disruption.
  • Crews will maintain emergency vehicle access, if needed.

For more information, view the August bulletin.

Project location

Understanding site conditions and community needs

Our team is in the early stages of design for the project. During the design phase, the project team will:

  • Survey the project area to understand existing conditions in Black Diamond
  • Conduct geotechnical surveys to understand underground conditions
  • Inform community members about the project and upcoming survey work
  • Analyze design alternatives and identify a preferred option to upgrade the sewer
  • Complete 30% design for the project

View fact sheet to learn more.

Working with the community

We’ll share details about specific engagement opportunities as the project progresses

We’re committed to engaging with the community during each stage of the project, and we want to make sure everyone has access to information. We welcome you to take part in the project in the following ways:

  • Contact us to have a one-on-one conversation by phone, video chat, email, or in person. 
  • Invite us to a meeting hosted by your group or organization. 
  • Join our team remotely or in person at future meetings at project milestones. We will post these meetings on our website and email list once they are scheduled.  

Interpretation and translation services are available to you at no cost. If you need them, please contact Annie Plumley, aplumley@kingcounty.gov, 206-263-3203

Los servicios de interpretación y traducción están disponibles para usted sin costo alguno. Si los necesita, comuníquese con Annie Plumley, aplumley@kingcounty.gov, 206-263-3203

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