Requirements Jan 22, 2016 – June 30, 2021

Stormwater, Drainage and Land Disturbing Activity

This page is for information for projects vested January 22, 2016 through June 30, 2021.  To find current regulations, please visit our Land Disturbing Activity page


Every five years the County is required to update the stormwater, drainage and land disturbing activity (LDA) requirements in accordance with reissuance by Washington State Department of Ecology of the Phase I Permit.  Ecology is the agency responsible for statewide compliance with the state and federal clean water and pollution control laws.  The Phase I Permit allows the County to discharge stormwater into ‘Waters of the State’.  Stormwater that is discharged from public or private property into the County’s stormwater system must meet the standards described in the Phase I Permit.  These standards can be found in the County code and administrative rules.

For the time period of January 22, 2016 through June 30, 2021, the following code and administrative rules were in effect:

SCC 30.63A  Drainage

SCC 30.63B  Land Disturbing Activities

Snohomish County Stormwater Drainage Manual (Volume I – V) 

Snohomish County Engineering Design and Development Standards (EDDS)