CSO Control Annual Reports

These reports are developed every year and include overviews and the status of the CSO Control Program, and information on annual CSO volumes and number of discharges from each King County CSO. They are submitted to the state Department of Ecology in accordance with WAC 173-245-090 (external link) and with the requirements for annual CSO reports as established in the NPDES Permit, Number WA-002918-1 for the West Point Treatment Plant.

Changes to Annual Report

The West Point Treatment Plant NPDES Permit was renewed effective July 1, 2009. Changes in reporting requirements, listed below, have resulted in a different report structure and content from previous years:

• Submittal deadline of July 31 each year
• Reporting of information by calendar year
• "Event-based" data reporting by CSO site
• Include duration of each CSO event. The duration represents the period from the start until the end of the overflow, as defined by a subsequent 24-hour non-overflow period. The overflow itself may be intermittent within this duration period.
• Include rainfall data for each CSO event as measured by the nearest King County rain gauge. This event-based rainfall reporting will begin with the August 2009 monthly report and will be compiled in next year's 2009 annual report.
• Provide event-based data in electronic form along with the report
• Reporting of the average of the overflow frequency at each CSO site over the last 20 years. Because 20 years of data are not available for all sites, Ecology has specified that missing data from the early years or pre-control project years will be reported from the hydraulic model for those sites identified as having achieved control to the state standard. These modeled data will be provided in the 2009 report.
• Identification of CSOs considered controlled in both the annual reports and the control plan amendments.

2008 Annual Report (662KB), issued July 2009

Reports for earlier years are listed below:

• 2007-2008 (772KB)
• 2006-2007 (1.1MB)
• 2005-2006 (513KB)
• 2004-2005 (381KB)
• 2003-2004 (313KB)
• 2002-2003 (264KB)
• 2001-2002 (300KB)
• 2000-2001 (255KB)
• 1999-2000 (2.9MB)
• 1998-1999 (3.7MB)
• 1997-1998 (4.0MB)
• 1996-1997 (3.3MB)
• 1995-1996 (3.3MB)
• 1994-1995 (4.2MB)
• 1993-1994 (2.0MB)
• 1992-1993 (1.3MB)
• 1991-1992 (1.2MB)
• 1990-1991 (1.2MB)
• 1989-1990 (862KB)
• 1988-1989 (739KB)
• 1987-1988 (400KB)