Standards are specific to each of the three watershed overlay zones and vary by watershed. In general the regulations are low impact development standards that are intended to protect a valuable resource, whether it be drinking water or aquatic habitat. For full list of requirements and standards related to watersheds please see Whatcom County Code Title 20.
If you intend to build or develop property within the Lake Whatcom watershed, it is important to realize that the Whatcom County Council has adopted regulations which are "...intended to manage and treat stormwater runoff and establish more stringent standards on clearing activities and reduce the phosphorus loading into Lake Whatcom, in order to preserve and protect a unique and important water resource, Lake Whatcom." (WCC 20.51.010).
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 (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 less 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 more than 500 sq. ft. of impervious surface area and/or permeable pavement;
- Projects, work, or activities that create more than 1,500 sq.ft. of replaced impervious surface area and/or replaced permeable pavement;
WCC20.51.420(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 2012 Department of Ecology Stormwater Management Manual for Western Washington (2012) DOE Manual).
- Downspout Full Infilitration per Best Management Practice (BMP) T5.10A of the 2012 DOE Manual (Volume III, Section 3.1.1 and Volume III, Chapter III, Section 3.3.9(A)
- Downspout Full Infiltration is a method in which stormwater is directed back into the ground via infiltration trench or drywell (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 2012 DOE Manual (Volume V, Chapter 5, pages 5-30 through 5-38)
- 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 (splashblocks, dispersion trenches, etc.) to the native or forested area. Dispersion refers to BMP's 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 creteria:
- The design limits the estimated phosphorous loading from stormwater generated by the project to be less than 0.1875 lbs. of Phosphorous/acre/year.
- The stormwater volume from the project does not exceed the monthly natural stormwater volume as determined by an approved DOE continous 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 sq. ft. of soil are not permitted from October 1st through May 31st per WCC 20.51.410.
- Development permits may be submitted at any time during the year. However, permits for work that exceeds 500 sq. ft. of exposed soil cannot be issued prior to June 1.
- Development permits which propose to exceed more than 500 sq.ft. of exposed soil will not be issued during the two 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.