Puget Sound Beach CSO Control Projects

CSOs are discharges of untreated sewage combined with stormwater that is released directly into marine waters, lakes and rivers during heavy rainfall, when the sewers have reached their capacity.

Although the sewage in CSOs is greatly diluted by stormwater, both CSOs and stormwater may be harmful to public health and aquatic life because they carry chemicals and disease-causing pathogens.

As part of King County’s National Pollutant Discharge Elimination System (NPDES) permit, State of Washington standards require controls to reduce CSOs to an average of no more than one per year per location based on a long term average. Both the County and the City of Seattle are working to reduce CSOs to that standard.

More about King County's CSO Control Program.

King County expects to build about 20 CSO control projects during the next 20 years. King County has made CSO projects near beaches on Puget Sound a priority because these locations are where people are most likely to come in contact with water when engaged in recreational activities such as swimming, beach combing and water sports.

Refer to the CSO Control Annual Report for an overview of King County's completed, current and planned CSO control projects. Many early projects involved sewer separation, flow diversion, and new tunnels.

Public outreach for upcoming projects is a priority for King County Wastewater Treatment Division. In 2007, the CSO Beach Projects team began community outreach efforts to make people aware of the need for upcoming projects to meet regulatory requirements for CSO control. The team launched project Web pages and met with community members, neighborhood associations and other interest groups to present information about the CSO problem in each project area and approaches for CSO control. Community feedback collected to date was incorporated into the development of alternative means for CSO control in 2009.

In fall of 2009, King County hosted a series of open houses in all project basins (view a summary), and met with interested community groups in West Seattle and North Seattle to provide updated information, describe the upcoming process to evaluate and identify a short list of alternatives, and provide opportunities for public participation. In order to engage communities, we mailed newsletters, issued press releases, and sent e-mails for distribution through lists maintained by regulatory agencies, community groups, local blogs and the Seattle Department of Neighborhoods. We also worked with community blogs and newspapers to include notice of our meetings on websites and public meeting calendars.

In March 2010, the project team updated Web information about these alternatives and held public meetings. Communities were notified of meetings through communications venues described above and a broad postcard mailing. The project team continues to attend community group meetings and work one-on-one with citizens to answer questions and receive input from community members. We encourage people unable to attend the meetings to provide comments through the Web, by e-mail or by telephone (refer to public outreach staff listed on each basin page).

To address the high volume of feedback and questions received for the Murray and North Beach project basins, King County will host technical information sessions in June and provide opportunities for in-depth discussion of the proposals. We will provide broad notification of these events, and interested people may check the project Web page for updates.

Projects are designed to meet compliance requirements for CSO facilities, with a target of no more than one untreated discharge per year on a long-term average. King County will meet deadlines for project milestones set by the Department of Ecology in the West Point NPDES permit. In the event that unforeseen delays occur, King County must work closely with Ecology to address the issue. Ecology would use various means of enforcement, including fines and court-issued compliance orders, to address schedule noncompliance.

The US EPA is also enforcing the federal Clean Water Act through the Department of Ecology and the West point NPDES permit. The US EPA is closely monitoring CSO control programs nationwide to ensure compliance with the Clean Water Act.

King County will begin the State Environmental Policy Act (SEPA) environmental review process after a proposal for controlling CSOs in each basin has been defined. King County will prepare a SEPA environmental checklist that describes the environmental impacts of the proposal and identifies measures that would be taken to avoid or mitigate those impacts. King County, as the lead SEPA agency, will then make a threshold determination based on the analysis documented in the environmental checklist. If a determination of significance is issued, King County will proceed with preparation of an environmental impact statement (EIS) for the project. If a determination of non-significance (DNS) is issued, a formal public comment period would then begin.

Because these CSO control projects involve building new facilities in densely populated urban areas, site options include public parks, streets, and private property. When property acquisition such as easements or property purchase is necessary, King County works closely with property owners during the acquisition process.

Learn more about King County's regulatory compliance and land acquisition services.

While the construction of infrastructure may create temporary inconveniences, the infrastructure provides long-term benefits to property owners, communities and the region. King County’s capital construction projects benefit people throughout the Puget Sound area by providing safe, reliable wastewater service to residents and businesses throughout the region. The county’s regional wastewater conveyance and treatment system protects public health and the environment and helps to protect Puget Sound water quality.

King County would not be able to address specific mitigation at this stage in the CSO Beach projects. Mitigation would need to be based on an assessment of project impacts. After a proposal for controlling CSOs has been identified in each basin, King County will assess the impacts of the proposed project and identify appropriate mitigation measures.

King County recognizes that constructing essential infrastructure can impact communities, and being a good neighbor is a priority. King County will work closely with communities through environmental review, design, permitting, and construction on mitigation to limit construction impacts such as noise, dust, and traffic and parking.  King County policies and ordinances, as well as agencies and jurisdictions that grant permits, can require mitigation to protect the environment and interests of the community.

If CSO control projects are sited in public park areas, park restoration would be a key element of design and construction. King County would work closely with the community to design and construct the CSO facility below-ground and reconstruct a park above ground that would be enjoyed by the community in the years ahead.

All WTD capital projects incorporate odor control into the upgrade of existing facilities and new facilities. Odor will be controlled through odor control facilities included in storage alternatives proposed in all CSO project basins.

Historically, wastewater conveyance systems were designed to use gravity where possible to carry flows toward the nearest water body and eventually treatment plants. Using gravity limits the number of pumping facilities and forcemains that have to be built and maintained, reducing community impacts, land use needs, and costs for construction, operations, maintenance, and future upgrades or replacements. In these project areas, flows travel from ridge areas and collect at the bottom of the basins. Facilities are located where most flows can be collected by gravity.

No. King County would not receive permitting approval from federal, state, and local jurisdictions to place such a structure on beach areas within Puget Sound.

New facilities are subject to stringent review criteria within Puget Sound shoreline areas. For example, the Corps of Engineers (COE) and the Washington State Department of Fish and Wildlife (WDFW) would require King County to demonstrate whether there are other alternatives that are less harmful to fish and wildlife habitat than a proposed storage tank buried on a beach. Since King County has identified alternatives that are feasible and require no in-water work, neither the COE or WDFW would approve a project that proposes to dredge nearshore areas in Puget Sound.

The project team has evaluated Lincoln Park as a potential site for storage facilities. Project engineers considered construction of a large bore tunnel in Lincoln Park for storage of combined flows between the Barton and Murray Pump Stations. This alternative was not developed due to the following challenges:

• Preliminary geotechnical evaluation identified major soil stability issues along the slopes leading up to Lincoln Park. These soil stability issues would pose substantial risks during a tunneling operation.
• Tunneling portals would be required at each end of the storage tunnel, impacting both Lowman Beach Park and Lincoln Park.
• Costs for this option would be much higher than alternatives for CSO control sited in other locations.
• This tunnel would up to 200 feet deep, increasing construction risk.
• A new peak flow pump station would be required at the bottom of the Barton basin and a new force main pipeline would be required along Fauntleroy Avenue SW to convey flows to a new storage pipeline in Lincoln Park.
• Permanent facilities would be required at the tunnel portals for access, ventilation, odor control, and electrical.

Locations higher in the basin were examined, but they could not capture enough peak flow to meet CSO control requirements. The existing system brings flows together within two blocks of Lowman Beach Park, making the bottom of the basin the only location to capture an adequate quantity of the peak flow to meet compliance requirements.

In addition, we evaluated ways to reduce peak flow by separating stormwater from the combined system and rerouting it to a new or existing storm drainage system. We also considered flow reduction through green stormwater infrastructure measures (rain gardens and bioswales). Unfortunately, these methods would not be able to control the one million gallons needed in the Murray basin, and storage would still be required at the bottom of the basin to meet the overall control requirement.

There are no plans to replace Lowman Beach Park with a wastewater facility. If CSO control projects are sited in public park areas, park restoration would be a key consideration. If the Lowman Beach alternative moves forward, King County would construct facilities in the park below-ground and reconstruct a park above ground that would be enjoyed by the community in the years ahead.

Because King County currently has an operating pump station in Lowman Beach Park (which requires upgrades regardless of the CSO project location), any CSO control alternative in this basin will require some work in the park, at least involving connection to the existing wastewater system and construction staging.

Because the CSO Control projects involve building new facilities in densely populated urban areas, site options include public parks, streets, and private property. Alternatives for CSO control in the Murray basin include all of these options, including one located in Lowman Beach Park.