Island County, WA Environmental Rules: Erosion Control (2026)
Key Facts
- Enforcing agency
- Planning and Community Development Director
- Small-project threshold
- 5,000 sq ft new impervious surface
- Trench limit
- 500 feet open at one time
- Criminal penalty
- Up to $1,000 fine, 90 days jail
- Civil penalty
- Up to $500/day, $5,000 cap critical areas
- Appeal
- Hearing Examiner within 14 days
Summary
Anyone grading or cutting a lot in unincorporated Island County under a Title XI clearing and grading permit must stabilize every cut and fill slope against erosion, using planting, hydroseeding, mulching, check dams, riprap, or silt fences before the county signs off on final project approval.
A.The faces of cut and fill slopes shall be prepared and maintained to control against erosion. This control may consist of effective planting, hydroseeding, or mulching. The protection for the slopes shall be installed as soon as practicable and prior to calling for/or requesting final project approval. Where cut slopes are not subject to erosion due to the erosion-resistant character of the materials, such protection may be omitted.B.Where necessary, check dams, cribbing, riprap, silt fences, or other devices/methods shall be employed to provide safety to adjoining properties or to minimize impacts.C.Small residential development and other small development activity, as defined in chapter 11.03, that creates less than 5,000 square feet of new impervious surface must comply with erosion control and best management practices requirements of chapter 11.03.D.Major development and redevelopment, as defined in chapter 11.03, must comply with erosion control and best management practices requirements of chapter 11.03.
Full Breakdown
330 requires the faces of every cut and fill slope created under a clearing and grading permit to be prepared and maintained against erosion, using effective planting, hydroseeding, or mulching, installed as soon as practicable and before the applicant can request final project approval; slopes cut into erosion-resistant material can skip this step. Where a slope still needs help, subsection B calls for check dams, cribbing, riprap, silt fences, or other devices to protect neighboring properties or cut down on impacts. 03's erosion control and best-management-practices requirements, and so must major development and redevelopment above that threshold, along with any other regulated grading.
230 fills in what those BMPs look like in practice: minimizing erosion and sedimentation on- and off-site during and after construction, cleaning any sediment tracked onto paved surfaces by the end of each day, stabilizing denuded areas and stockpiles, protecting storm sewer inlets so runoff is filtered before it enters them, and keeping temporary erosion and sediment controls in place until the site is fully stabilized. Underground utility trenches get an added limit: no more than 500 feet may stay open at one time. 03, with the County Engineer providing technical support on every erosion and grading complaint.
Violations & Fines
Island County Code § 17.03.260, which governs enforcement of chapter 11.02, makes a willful, knowing erosion-control violation a misdemeanor punishable by up to a $1,000 fine and 90 days in the county jail, with each day of continued violation counted as a separate offense. The Planning Director can also issue a cease-and-desist order and an administrative enforcement order carrying a civil penalty of up to $500 per day, capped at $5,000 for critical-area or shoreline violations and $1,000 for other violations, appealable to the Hearing Examiner within 14 days.
Frequently Asked Questions
What erosion control does Island County require during grading?
Does a small residential lot have to follow the same erosion rules as a big development?
What happens if I don't control erosion on my Island County construction site?
Sources & Official References
Other rules in Island County
Compare Island County to another location·View the Washington environmental rules overview
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