Drainage Manual

Drainage Manual Volume I Revised November 2017


Pursuant to Snohomish County Code (SCC) 30.82.040 (Rulemaking), Snohomish County Public Works revised Volume I to add explanatory information about the function, use, and selection of stormwater low impact development best management practices. Pursuant to SCC 30.82.065, persons who submitted comments during the 21 day comment period may request a review of the adopted rules by the County Council within 120 days of rule adoption (by March 30, 2018). A request for Council review should be sent to the County Council at contact.council@snoco.org or mailed to Snohomish County Council, 3000 Rockefeller MS 609, Everett WA 98201. Council review will determine whether the adopted rules are consistent with the scope of DPW’s rulemaking authority.

Current Manual (January 2016, November 2017 for Volume I)


The documents listed below compose the entire Snohomish County Drainage Manual. The drainage manual is used in concert with Snohomish County code and Snohomish County engineering design and development standards (EDDS).
  • Volume I - Minimum Technical Requirements
  • Volume II - Construction Stormwater Pollution prevention best management practices (BMPs)
  • Volume III - Hydrologic Analysis and Flow Control BMPs
  • Volume IV - Source Control BMPs
  • Volume V - Runoff Control BMPs