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Below are a number of reports, studies, maps, and other technical resources related to the Conveyance System Improvement program.

Files are in Portable Document Format (PDF) .

For more information, please contact:

Steve Tolzman

CSI program updates

The 2017 Conveyance System Improvement program update will verify, make adjustments to, or identify new conveyance system needs.

WTD updated the planning assumptions in 2013 so that they reflect the most recent data available including flow monitoring measurements and population and employment forecasts.

Conveyance System Improvement Program Update (2013-2017)

The 2007 extended the planning horizon to 2050 and identified 33 projects needed for increasing capacity in the conveyance system to accommodate population growth. It also provided a status on the County's asset management program for replacing or substantially rehabilitating deteriorated portions of the system.

Conveyance System Improvement Program Update (2007)

The 2004 CSI update was a substantial reorganization, primarily to break down the service area into twelve sub-regional planning basins and to integrate conveyance planning with local agency plans and with other Regional Wastewater Services Plan (RWSP) programs such as infiltration and inflow control. The results of the update are presented in a series of reports. Another 20 projects were identified to meet capacity needs through 2030, the RWSP planning horizon.

CSI basin planning reports (1999-2003)

CSI project newsletters (1999-2002)

Other reports and documents

King County's Wastewater Treatment Division maintains 77 major facilities, 40 of which are situated adjacent to tidally influenced water bodies. As effects of climate change continue to grow, the potential for flooding at these facilities as the result of sea-level rise must be assessed and mitigated. The first step in planning for the effects of sea-level rise is to identify which facilities are at risk. This report identifies these facilities and their potential for flooding, considering the effects of both sea-level rise and storm surges, and then recommends the next steps in planning for this change.

Vulnerability of Major Wastewater Facilities to Flooding from Sea-Level Rise Technical Memorandum  (385KB)

In April 2007, the King County Council passed Motion No. 12498, which directed the Wastewater Treatment Division to work cooperatively with the Port of Seattle and other affected agencies to undertake a study of the potential for processing marine cruise industry-generated wastewater through the county's wastewater treatment system.

Cruise Ship Wastewater Management Report (648KB)

In 1999, the King County Council directed and authorized a seismic vulnerability study to evaluate all the county's major underwater conveyance pipelines. A comprehensive approach was developed to assess the vulnerability of these pipelines to earthquake damage and to recommend short- and long-term protective action if warranted. The study, which began in May 2000, assessed pipes under Lake Washington, Lake Sammamish, the Ship Canal, sloughs, rivers, and creeks.

For security reasons, these reports are not available online. Please contact Steve Tolzman at if you wish to obtain a copy.

Maps and technical resources

Tabula is a computer program developed for use by King County staff and consultants to provide conveyance cost estimates at the planning level. The software, user documentation, and technical memos can be downloaded and used to perform cost estimating with technical reports.

Tabula software documents

GeoMapNW (formerly the Seattle-Area Geologic Mapping Project) is a University of Washington-centered project to develop a detailed understanding and representation of the distribution of geologic materials on and beneath the surface of areas around the central Puget Sound area.

The King County Wastewater Treatment Division is a partner on the project, and has provided updated geologic databases and a new series of geologic maps throughout the Regional Wastewater Service Planning area.


Maps are available of the King County Wastewater Service System and the Conveyance System Improvement sub-regional planning areas.

King County Wastewater Treatment Division service area maps (maintained by KC GIS Center)

CSI sub-regional planning areas maps and documents (1999-2003)

Facility one-line system maps identify the King County regional wastewater conveyance system. They are available on CD by request.

Contact Shaun O'Neil at or 206-477-4432 for more information.

Steve Tolzman
Capital Project Manager