Lake Whatcom


The following provisions of the Lake Whatcom Watershed Overlay District (WCC 20.51) apply only within the geographical boundaries of the Lake Whatcom watershed.

Stormwater Facilities

Stormwater Facilities (WCC 20.51.420) on parcels within the Lake Whatcom watershed boundaries, a permanent stormwater quantity and quality facility is required for:

  • Land disturbing activities (per Chapter 20.97 WCC definition) of more than 5,000 square feet in total area, excluding any impervious surface area work within the land area disturbed.
  • Projects, work, or activities that create or replace more than 200 square feet of hard surface area (which includes gravel and permeable pavement areas).
  • Note: WCC 20.51.420(1) contains a complete list of activities that are exempt from the stormwater facility requirement. Generally, these are activities such as underground pipe installation and power pole installation and do not apply to residential development which requires a building permit. Please refer to the code or speak to a watershed staff member for further information.

If a Stormwater Facility is required, the proposed facility must be designed to meet one of the following criteria from the  2019 Department of Ecology (DOE) Stormwater Management Manual for Western Washington:

  • Downspout Full Infiltration per Best Management Practice (BMP) T5.10A of the 2019 DOE Manual (Volume V, Section 4)
    • Downspout Full Infiltration is a method in which stormwater is directed back into the ground via infiltration trench or dry well (or other methods as specified in the DOE Manual).
    • A soils assessment prepared by a professional soil scientist, a locally licensed on-site sewage designer, professional engineer, professional geologist, hydrogeologist or engineering geologist registered in the State of Washington must be submitted to use Full Infiltration.
  • Full Dispersion per BMP T5.30 of the 2019 DOE Manual (Volume V, Section 3):)
    • Full Dispersion is a method in which no more than 10% of site is covered with impervious surface and 65% of the site is kept in a forest or native condition. Stormwater from development must be dispersed using certain methods (splash blocks, dispersion trenches, etc.) to the native or forested area. Dispersion refers to BMPs which disperse stormwater over the ground surface so that surrounding plants and vegetation can utilize stormwater.
    • Because Dispersion relies on surrounding vegetation to treat stormwater, a Protected Native Growth Area document must be filed with the Whatcom County Auditor's Office to protect the forest or native area prior to building permit issuance.
  • A design by a licensed civil engineer which meets at least one of the following criteria:
    • The design limits the estimated phosphorous loading from stormwater generated by the project to be less than 0.1875 pounds of Phosphorous / acre / year.
    • The stormwater volume from the project does not exceed the monthly natural stormwater volume as determined by an approved DOE continuous runoff model.
    • Development stormwater runoff does not occur.

Seasonal Clearing Limitations

On parcels within the Lake Whatcom watershed, clearing activities which expose more than 500 square feet of soil are not permitted from October 1 through May 31 per WCC 20.51.410:

  • Development permits may be submitted at any time during the year. However, permits for work that exceeds 500 square feet of exposed soil cannot be issued prior to June 1.
  • Development permits which propose to exceed more than 500 square feet of exposed soil will not be issued during the 2 weeks prior to October 1 to allow for earthwork to be done and stabilized prior to October 1.

Temporary Erosion and Sedimentation Control (TESC)

A TESC plan must be submitted at the time of Natural Resource Assessment submittal or building permit submittal (whichever comes first). Appropriate TESC measures must be installed prior to any clearing activity. A TESC inspection must occur prior to the first building permit inspection.

Tree Retention 

On lots within the Lake Whatcom, Lake Padden and Lake Samish watersheds, a Tree Removal Permit is required for the removal of any tree, unless the tree(s) to be removed is associated with a development proposal. For specific tree removal requirements please refer to our Tree Removal Page. If the tree(s) is/are an immediate threat to person or property, the tree may be removed without review.
For more information on tree removal limits in the Lake Whatcom, Lake Padden and Lake Samish watersheds, please refer to our Tree Removal Page.

Lake Whatcom Watershed