Project approach, 1999-2003

CSI subregional planning areas within the WTD wastewater service area. Click map for larger view and links to planning area documents.

In 1999, the Conveyance System Improvement (CSI) program was charged with developing a system to identify and prioritize ten planning areas in the wastewater service area. This would enable the CSI team to target system improvements in the basins with the most critical need.

Inventory

At the start of the project, documentation on subregional planning areas including specific facilities, sewer agencies and wastewater service basins was completed. Information gathered included regional and local wastewater planning records, descriptions of the current regional and local facilities, demographics, infrastructure, environment and governance within each basin. A core team at the County, in conjunction with a consultant team, developed measured criteria for each area and a process for determining the overall system planning priorities. The criteria included conditions such as growth, flow/overflow, consequences and management and improvements. This information formed the basis for determining the overall system planning priorities.

Determining needs

The preparation to identify the range of necessary improvement projects within each planning area (one or more individual King County sewer basins) was no small task. The initial results were broad conceptual alternatives of various ways to manage wastewater flows in the regional system. Everything from conceptual wastewater flow management alternatives with storage improvements to pumping and conveyance, or diversion of flows to another basin was considered. Local sewer agency involvement was critical during this development and analysis of alternatives.

Determining specific improvements

The next step was to refine the specific improvement contemplated in the particular planning areas in the wastewater service area. This entailed facility condition, operational issues and specific facility identified improvements. The reports on this site describe the type, size and general location of the proposed improvements. The teams refined specific working alternatives to address the needs in the various wastewater planning areas with respect to general alignment, sizing, phasing and costing. Importantly, possible impacts of the County's Infiltration and Inflow Control Program were investigated by a sensitivity analysis applied to the design side and phasing of the working alternative. Planning is now complete in all the service planning areas.

Implementation

The reports serve as the basis for the transfer to the Major Capital Improvement program and the Asset Management Program for scheduling and budgeting as part of the regular WTD priority setting process.

Some of the projects that have progressed to planning or construction include:

• Bellevue Pump Station Upgrade Project 
• Carnation Wastewater Treatment Facilities 
• Hidden Lake Pump Station and Sewer Improvement Project 
• Juanita Bay Pump Station Replacement Project 
• Matthews Park Pump Station and Sewer Improvement Project 
• North Creek Storage Facility