Dry Weather Screening

SPU has a Dry Weather Screening program to find pollutants in the drainage system and trace them to their source. From May to September, crews sample the drainage system at various key locations for a number of parameters, such as pH, fecal coliform, etc. Each parameter has a “trigger level” that may indicate there is pollution in the system. When “trigger levels” are exceeded, follow up sampling and tracing is done to find and eliminate the source of the pollution. This program has been successful in finding a number of pollution sources including:

  • Sewage from a single family residence entering the drainage system
  • Sewage from a fast food restaurant entering the drainage system
  • A leaking sewage pipe
  • Improper wash practices at a golf facility

The program is conducted in the summer, when flows in the drainage system are at a minimum (because there is no rain). Whenever problems are found, SPU uses its enforcement program to eliminate the source.

Property owners can proactively look for improper connections in their facilities by examining site plans and/or hiring a plumber to conduct a dye test of the plumbing connections. Learn more about the City Stormwater Code.

The Dry Weather Screening Program is part of the City’s overall Stormwater Management Plan, developed to comply with the requirements of the City’s National Pollutant Discharge Elimination System (NPDES) permit issued by the Washington State Department of Ecology. Requirements regarding spill prevention and control are provided and enforced under the City’s Stormwater Code, Chapter 22.800 – 22.808 and associated Director’s Rules.