Decennial Flow Monitoring Project – Installing and Maintaining 235 Flow Monitoring Locations in Support of King County Conveyance System Improvement Program

In September 2009, the King County Wastewater Treatment Division (WTD) initiated the Decennial Flow Monitoring (DFM) project with the objective of collecting accurate flow data over two wet seasons coincident with the 2010 census, for use in updating the prioritization, timing, and sizing of Conveyance System Improvement (CSI) capital projects.WTD replicated a portion of the flow monitoring effort that was conducted during the 2000 – 2002 Regional Infiltration/Inflow (I/I) control flow monitoring program, which involved over 800 meter locations. The DFM project monitored the same model basins defined in the 2000–2002 Regional I/I Control Program monitoring so that assumptions about new growth, sewer degradation, and I/I from existing sewers could be assessed and updated.A total of 223 area-velocity (AV) meters were installed in 2009 to collect flow data for the DFM project. Data from 12 pump station locations were also used to minimize the number of AV meters and collect more accurate flow data at certain locations.The flow monitoring tasks were performed using in-house staff. Flow meters were purchased for the DFM project using an Invitation to Bid (ITB) process through which a particular meter was selected for use in most of the metering sites. Coordinating with local agencies (cities and sewer and water districts) was critical during the site selection and installation process.The County achieved a 97 percent uptime system-wide on processed flow data which exceeded the primary Key Performance Indicator (KPI) of 95 percent. Flow monitoring was completed in May 2011, and data analysis completed by the end of December 2012.This paper represents the approaches used in siting monitoring locations; installing and maintaining flow meters; staffing; data collection and analysis processes; values of coordination with local jurisdictions; and lessons learned on equipment procurement and writing specifications for bids. The information presented is beneficial to agencies planning to embark on a large scale monitoring program to support conveyance system improvement programs.