Drainage & Land Disturbing Activity

This page is for information for projects vested September 30, 2010 through January 21, 2016. To find current regulations, please visit this page.


Snohomish County maintains regulations that govern drainage, land disturbing activities and low impact development in accordance with State laws and policies. The regulations that became effective on September 30, 2010 and remained in effect through January 21, 2016 can be found here SCC 30.63A, 30.63B, and 30.63C.

The term "land disturbing activity” is broadly defined (PDF) by Snohomish County as any activity that will result in movement of earth or a change in the existing soil cover or the existing soil topography. This includes to soils that are vegetative and non-vegetative by nature. Land disturbing activities often result in the creation and replacement of impervious surfaces (broadly interpreted to be any hard surface that prevents or retards water penetration of the soil) as well as the grading and clearing of land.

Due to NPDES Permit requirements adopted in the new stormwater regulations, applicants for projects that meet or exceed new development and redevelopment thresholds will likely need to obtain professional assistance in preparing land disturbing activity permits, stormwater site plans, and stormwater pollution prevention plans. Please plan accordingly to ensure a quality application submittal and a timely permitting process.

Key Codes and Manuals