Conveyance System Improvement Program

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CSI Program Update
June 2007

A portion of the Executive Summary is presented below. The entire document can be viewed here.

Chapter 1. Executive Summary

This Regional Conveyance System Improvement Program Update implements conveyance policies contained in the Regional Wastewater Services Plan (RWSP), adopted by the King County Council in 1999. The update identifies projects needed for increasing capacity in the conveyance system to accommodate population growth; and, also provides a status on the County’s asset management program for replacing or substantially rehabilitating deteriorated portions of the system. It then lays out a schedule and budget for these projects. Component (local) sewer agencies were instrumental in helping to identify conveyance needs, and prioritize projects through their participation on MWPAAC’s Engineering and Planning (E&P) Subcommittee and through one-on-one meetings with Wastewater Treatment Division staff.

This chapter summarizes the detailed information documented in subsequent chapters of this update. It describes conveyance planning efforts on which this update is based, presents the processes used to identify capacity-related needs and the projects to address these needs, and concludes with next steps for implementing the program and for future conveyance system planning.

1.1 Background on Conveyance Planning

The RWSP contains policies that are intended, in part, to guide the planning, design, and construction of conveyance system improvement (CSI) projects to accommodate increased flows over a 30-year period (through 2030).

King County’s regional wastewater system is a large, integrated wastewater conveyance and treatment system. The 34 cities and sewer districts that are component agencies of the system are responsible for collecting wastewater from residences and businesses. King County’s over 335 miles of pipes and 62 pump and regulator stations convey this wastewater to 3 secondary treatment plants.

Planning for the regional conveyance system is an ongoing function for King County’s Wastewater Treatment Division (WTD). The conveyance program was last updated in 2004 to organize conveyance planning by 10 sub-regional planning basins and to integrate conveyance planning with component agency plans and with other RWSP programs such as infiltration and inflow control and combined sewer overflow (CSO) control.

The program is being updated now because flow monitoring and modeling information developed for the Regional Infiltration and Inflow (I/I) Control Program allowed for a more accurate analysis of capacity needs within the regional conveyance system.

This Conveyance System Improvement Program Update refines the previously identified needs; categorizes these needs based on system age, condition, or capacity; and presents a list of recommended projects and a schedule to address identified needs.

1.2 Scope of This Update

The Conveyance System Improvement (CSI) Program is being updated now because significant flow modeling and analysis has been completed since the last update in 2004. Additionally, information provided by the individual component agencies about population and employment growth rates and land use trends that can affect the timing or size of recommended RWSP regional conveyance improvements were used to update the list of needed conveyance projects, implementation schedule, and project cost estimates included in this CSI Program Update.

Unlike previous conveyance plans, this program update extends through 2050. This is the date when the regional wastewater service area is projected to be fully built out and all sewerable portions of the service area are expected to be connected to the wastewater system. Completion of an asset management plan in 2010 for the conveyance system will provide further refinement to capacity related needs in the future.

The CSI project recommendations in this program update focus on facilities in the separated portion of the county-owned regional conveyance system. It does not cover planned new facilities, such as Brightwater, nor does it cover component agency systems.3 However, the development of CSI project scopes, costs, and schedules assumes that Brightwater will begin operating in 2010.

No assumptions were made regarding I/I reduction across the region. As recommended in the Regional I/I Control Program, two or three initial I/I reduction projects will be completed by 2011. Each initial project, if successful, will eliminate the need for an identified CSI project. After completion of these initial projects, recommendations will be made to the King County Council regarding when and where to implement additional cost-effective I/I reduction projects.

View the rest of the Executive Summary and the program update files below.

For more information, contact Mark Buscher, CSI Project Manager, at mark.buscher@kingcounty.gov or 206-684-1242.

Table of Contents

If you need a free copy of the Adobe Acrobat Reader to view these documents (.pdf), visit the King County Acrobat help page. For some documents, the file size (in KB or MB) is shown.

CSI Program Update, June 2007, report only (2.2 MB),
view appendix files below

• Cover and title page
• Contents
• Appendices (in one file, 22 MB)
  • Title page
  • Appendix A. Conveyance System Technical Analyses – Processes and Assumptions (1.4 MB)
  • Appendix B. Project Descriptions Summaries (15.5 MB)
  • Appendix C. Regional Conveyance System Needs (Technical Memorandum) (5 MB)

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Updated: Sept. 27, 2007

Related Information:

Infiltration and Inflow (I/I) Control Program
Regional Wastewater Services Plan
Combined Sewer Overflow Control Program
Brightwater Project
Construction Projects
Planning for the Future