Black Diamond Wastewater Infrastructure Upgrade
New wastewater facilities to serve Black Diamond's growing population

As part of its mission to protect public health and the environment, King County is responsible for conveying and treating wastewater collected by 34 local city and sewer agencies in the King County region. Wastewater from Black Diamond homes and businesses is collected by the City of Black Diamond's local sewer system and then transported to King County's South Treatment Plant in Renton through a network of conveyance pipelines and pump stations operated by the county and the Soos Creek Water & Sewer District (external link).

King County is working with the City of Black Diamond to build new wastewater facilities

Growth in Black Diamond is projected to reach approximately 20,000 residents by 2025. As the city's wastewater conveyance and treatment provider, King County must build additional wastewater capacity in Black Diamond to accommodate the projected growth.

The City of Black Diamond and King County are working together on plans to build new wastewater management facilities that will provide additional capacity in two phases. The capital and operating costs for these new facilities will come from revenues generated by sewer rates and hook up charges for new development.

Phase One: wastewater storage facility

The first phase centers on construction of an enclosed storage facility to equalize peak flows entering the existing pump station near Jones Lake. Peak flows will be stored and released slowly over time to avoid overwhelming the downstream conveyance system. See the map for information about the general location of storage facility alternatives.

The 750,000-gallon storage facility will extend the life of existing equipment and defer the need to build additional new pumping and pipeline facilities for several years. The phase one storage facility is currently projected to be built in the 2012-2013 timeframe.

Phase Two: additional wastewater capacity to accommodate Black Diamond as it grows

Phase two improvements could include larger conveyance facilities, a satellite treatment facility or a combination of both. A satellite treatment facility would be required to treat effluent to a standard high enough for it to be used to recharge wetlands, irrigate nurseries and parks, and for some industrial uses. Planning for phase two will be conducted simultaneously with the development of the phase one storage facility. The phase one storage facility will be compatible with any other improvements built in phase two. Phase two facilities are projected to be operating by 2020.

Project Schedule

Your comments and ideas are welcome

King County is committed to being a good neighbor and is interested in learning your view
about this project. Together with the City of Black Diamond, King County's project team is
working to ensure the new facilities fit with the community. The project team will work directly
with the City and community to address concerns and minimize the project's potential
community and environmental impacts. These efforts will continue during environmental
review, permitting, construction and the facilities' long-term operations and maintenance.

For more information

• Contact Doug Marsano about King County's project at 206-684-1235 or doug.marsano@kingcounty.gov

>> back to top

Department of Natural Resources and Parks
Wastewater Treatment Division
201 S. Jackson St.
Seattle, WA 98104-3855
Fax: 206-684-1278

Updated: May 8, 2008

WTD Construction Projects

Conveyance System Improvement Program

Regional Wastewater Services Plan