Announcements, Sewers/Drainage

Crown Hill – North Beach CSO

OK, what is all this talk about CSO’s? And what is a CSO? And why should I care? Beware that various areas in Crown Hill drain to different treatment plants. Areas south of 85th drain southward rather than to the North Beach and Carkeek treatment plants. If you are reside in the area outlined on the map below, this information affects you. If you reside outside, you may be affected by a different drainage area, and the information may also be of interest. At the end of the article are some more resources you may want to consult. Read on for some easy to understand information extracted from a recent letter from King County, and there is a meeting on March 30 at Loyal Heights Community Center, 6:30-8 PM:

What is a CSO?

Combined sewer overflow

Why are CSOs a problem at North Beach?

Like many cities around the country , the older parts of King County’s wastewater system carry both wastewater and stormwater to the treatment plant. When heavy rains fill the pipes, excess stormwater and sewage flow directly into Puget Sound near North Beach. These events, called combined sewer overflows, or CSOs, help to avoid sewer backups into homes and businesses and onto streets during storms, but they are a public health and environmental concern. When a CSO happens, about 90 percent of the overflow is stormwater and the rest is dilute sewage.

In 2008, King County reported that the North Beach CSO facility has 10 overflows per year on average that discharge a total of 2.2 million gallons into Puget Sound off North Beach. King County’s goal is to reduce the number of CSOs each year, with a long-term goal of no more than one untreated discharge per location per year on a long-term average to meet state regulations.

North Beach Crown Hill CSO Project Area
North Beach Crown Hill CSO Project Area

What are the approaches being considered to control CSOs?

Conveyance/treatment – Sending flows from the basin to an existing treatment plant.

  1. Storage – Retaining flows during large storms to prevent CSOs. Following the storm event, flows are sent for treatment.
  2. On-site treatment – Providing primary treatment for flows exceeding system capacity during large storms.
  3. Peak flow reduction (demand management) – Implementing one or more methods of limiting stormwater flow into the sewer system.
  4. Combination of approaches – These options can be used alone or in combination, depending on local conditions at each project location.

Questions? Feedback?

Contact:

Public Information Meeting

March 30, 6 – 8:30 p.m.
Loyal Heights Community Center

Additional Resources