Lewis County, WA Environmental Rules: Erosion Control (2026)
Key Facts
- Permit trigger
- 5,000+ sq ft new impervious surface
- Governing chapter
- LCC Chapter 15.45, Stormwater Management
- BMP technical standard
- DOE Stormwater Management Manual, § 15.45.120
- Small-lot exemption
- Single-family homes under threshold, lot < 0.77 acre
- Enforcement tool
- Public nuisance plus stop work order
- Penalty basis
- Civil/misdemeanor under LCC § 1.20.020/.040
Summary
In unincorporated Lewis County, construction adding 5,000 square feet or more of new impervious surface must obtain a Storm Drainage Approval under LCC Chapter 15.45 and include erosion and sedimentation control best management practices. LCC § 15.45.310 defines those BMPs as measures that trap sediment, curb off-site vehicle tracking, and stabilize exposed soil; LCC § 15.45.500 makes noncompliance a public nuisance subject to a stop work order.
(3) All construction, including remodeling, reconstruction, and new construction which add five thousand (5,000) square feet or more of impervious surfaces, including gravel parking areas. ... Erosion and sedimentation control ... BMPs are designed to prevent, minimize, or capture sediments and pollutants released during construction or under post project conditions. Some of these BMP's may be to trap sediments before it reaches the storm drainage detention system; to prevent or minimize vehicular tracking away from the project site; to address effects of seepage and slope failure; to construct energy dissipaters, bank reinforcement, and retaining walls; to landscape; or to stabilize exposed soils. ... It shall be unlawful for any person, firm, corporation, or association, or agent thereof, to violate any provision of these regulations, or any provisions of regulations adopted by reference in this chapter. ... all unlawful activity or development, except for erosion and sedimentation control activities, is to immediately cease until and unless notice is thereafter given by the administrator to proceed.
Full Breakdown
45 before certain construction proceeds in the unincorporated county. 100(5). 140. 310 defines Erosion and Sedimentation Control BMPs as measures "designed to prevent, minimize, or capture sediments and pollutants released during construction or under post project conditions," covering sediment traps ahead of the storm drainage detention system, controls on vehicles tracking mud off the site, treatment for seepage and slope failure, energy dissipaters, bank reinforcement, retaining walls, landscaping, and stabilization of exposed soil. 120, principally the Washington Department of Ecology's Stormwater Management Manual. 45 unlawful and a public nuisance; the county administrator or code compliance officer can issue a stop work order, but that order specifically exempts ongoing erosion and sedimentation control activities, which must continue regardless. 45 review.
Violations & Fines
Violating Chapter 15.45, including building without the required erosion and sediment control BMPs, is unlawful and declared a public nuisance under LCC § 15.45.500. The administrator or code compliance officer may issue a stop work order, the county may pursue civil penalties and misdemeanor enforcement under LCC § 1.20.020 and § 1.20.040, and the prosecuting attorney may sue to abate the nuisance or negotiate a civil penalty settlement. Erosion and sedimentation control work is exempt from any stop-work order and must proceed regardless.
Frequently Asked Questions
Does every construction project in Lewis County need an erosion control plan?
What erosion control measures does Lewis County require during construction?
Can the county stop my whole project if I violate the stormwater rules?
Sources & Official References
Other rules in Lewis County
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