Multnomah County, OR Environmental Rules: Erosion Control (2026)

Oregon DEQ administers the 1200-C Construction Stormwater General NPDES permit for sites disturbing 1 acre or more - applicants file a Notice of Intent and Erosion & Sediment Control Plan (ESCP) before groundbreaking. Portland City Code Title 10 (Erosion and Sediment Control) applies to all sites, even smaller residential projects, with Portland BDS reviewing plans. Standard BMPs required: silt fence along downslope perimeters, straw wattles on contour, inlet protection at all storm drains, stabilized construction entrance (typically 2-3 inch clean rock over geotextile for 50-foot length), covered stockpiles, and stabilization of disturbed areas within 7 days during the wet season (October 1 - April 30) or 14 days otherwise. Portland's 'stop-work at first rain' rule requires contractors to install controls before any measurable rainfall. Gresham GRC 6.18, Troutdale TMC 17, and Fairview FMC 17 have parallel programs. Unincorporated Multnomah County relies on DEQ plus MCC 39.5500 SEC overlays for sensitive areas. Sandy River, Willamette River, Columbia Slough, and Johnson Creek are priority waterways where discharge enforcement is strict. Post-construction stabilization through vegetation, hydroseed, or hard surface required before project close-out.