IC/ID Field Screening and Source Tracing Guidance Manual

Project Background

Using funding from a Washington State Department of Ecology Grant of Regional or Statewide Significance (GROSS grant), King County  partnered with the Washington Stormwater Center and Herrera Environmental Consultants to develop an Illicit Discharge Detection and Elimination (IDDE/ICID) Field Screening Manual (Manual) for the State of Washington. This Manual was developed to help municipalities in Washington perform IDDE (IC/ID) field screenings pursuant to requirements identified in the National Pollutant Discharge Elimination System (NPDES) Phase I and Phase II Municipal Stormwater Permit.

These municipalities currently use a wide variety of field screening methodologies to identify illicit discharge and illicit connections, with varying levels of success. Some flexibility is required for determining which field screening methodology is the most appropriate given each municipality’s unique program requirements and storm drainage infrastructure. Most municipalities face financial challenges trying to achieve regulatory permit compliance and do not have sufficient resources to analyze other jurisdictions’ methodologies or successes, or to research alternative IDDE (IC/ID) screening methodologies for their specific needs. The purpose of this project was to develop a single, detailed Manual that municipal staff across Washington State can use for field screening their storm drainage systems for illicit discharges and illicit connections based on their specific circumstances.

 As an initial step towards the development of the Manual, a survey of Phase I and II jurisdictions in Washington State and literature review was conducted with the goal of determining which IDDE (IC/ID) field screening methodologies are the most effective, what innovative techniques are currently being used in the United States, and which methodologies should be included in the Manual for use in Washington State. The results from this effort have been compiled in a summary report.


IC/ID Manual (pdf)

IC/ID Manual (Word file) - NOTE file is 50 MB

Appendix B - Example Field Forms
  Appendix B - King County WQ Sampling Data Sheet
  IC/ID Field Screening Survey Results and Literature Review

 Illicit Discharge Indicator Thresholds Memorandum


Training Presentations

Guidance Manual Training - PDF of Powerpoint Presentation (May 2013)