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In King County’s wastewater service area, owners of buildings with new sewer connections, additions or changes of use pay their share of the cost of sewer infrastructure through a capacity charge. Two studies are underway that may lead to changes to the capacity charge.

May 2019 update

Affordability study report is now online: King County has been studying how to better serve low-income customers and improve the affordability of wastewater services and housing. This affordability study report is now available . The County will use the report to create recommendations for assisting customers who are low-income or experiencing temporary financial hardship. The King County Council and Executive will consider these recommendations in spring and summer 2019.

Capacity charge rate design review

The Rate Design Review looks at how the capacity charge is allocated to different groups of customers. Since the capacity charge program began in 1990, King County has experienced significant growth and change. Emerging trends include micro-housing, small efficiency dwelling units, accessory dwelling units, detached accessory dwelling units, group housing, adult care homes and the installation of low-flow plumbing fixtures. It is time to evaluate the best approach for allocating the capacity charge in light of the wastewater demand for today’s building types.

This study focuses on a technical question – how best to define the basis of the capacity charge. Our goal is for the charge to reflect the amount of wastewater that each type of building is likely to send to the King County wastewater system. The charge must also be administratively workable for both developers and development review staff. And it must be based on information that can be known at the time of development—before a particular building has a track record of water consumption.

See fact sheet for more information.

Low income customer assistance

A separate study is looking at low-income customer assistance for the capacity charge. King County Wastewater Treatment Division is interested in better serving low-income customers and improving housing affordability.

Now posted:

Next steps

Research findings from these studies will be available in 2019. Results will be used to develop recommendations about capacity charge policy for consideration by the King County Executive and Council. The results of these studies will not impact capacity charge rates for our existing customers.

For more information, please contact:

Erika Peterson, Community Services


Contact Us

Phone: 206-296-1450

Fax: 206-263-6073