Cowlitz County, WA Environmental Rules: Erosion Control (2026)

020. 080(A): appropriate erosion control structures must be installed prior to any grading activity, must be maintained in place until vegetation is established for suitable erosion and sedimentation control, and no sediment from grading operations may be permitted to leave the site or enter any surface waters or wetlands. 080(C) adds a closeout requirement: sites must be cleaned upon project completion, including installation of permanent organic erosion control such as grass seeding or landscaping. 080(B) requires finished grades to drain away from structural foundations for a minimum of 10 feet, reducing the volume of runoff that can carry sediment offsite.

070(J) and (K) require the plan to show the location of proposed erosion and sedimentation control measures and detailed plans of drainage devices, walls, cribbing, dams, berms, and settling ponds. Erosion control measures may follow the specifications in Appendix A to the grading ordinance unless a project engineer recommends otherwise. 040.