St. Louis County, MO Environmental Rules: Erosion Control (2026)
Key Facts
- Idle-soil trigger
- 14 days without activity
- Stabilization deadline
- 7 days once triggered
- Settling basin threshold
- 10+ disturbed acres
- Max cut/fill slope
- 3:1
- Enforcing agency
- Dept. of Transportation & Public Works
Summary
St. Louis County's Land Disturbance Code sets hard deadlines for stabilizing bare soil on active construction sites, plus sediment-trapping design standards.
Permit holder shall install temporary stabilization when soil disturbing activities will cease on any portion of the site and are not planned to resume for a period exceeding fourteen (14) calendar days. Temporary stabilization must be initiated immediately upon knowing the duration is more than fourteen (14) days. Temporary stabilization must be completed within seven (7) calendar days.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 85 | Traffic: Supplement 80).
Full Breakdown
Any construction or land disturbance site in unincorporated St. Louis County must control erosion under the county's Land Disturbance Code (Chapter 1114). Bare soil that will sit idle more than 14 days needs temporary stabilization started immediately and finished within 7 days; once grading permanently stops, final stabilization must start immediately and finish within 7 days too. Sites over 10 disturbed acres need settling basins sized for a two-year, 24-hour storm, and cut/fill slopes are capped at 3:1. The Department of Transportation and Public Works enforces this through the land disturbance permit and required weekly/after-rain inspections by a qualified special inspector.
Violations & Fines
Unpermitted land disturbance or failing to correct a cited violation within 7 days of written notice is unlawful; the County Counselor can pursue a court action to restrain, correct, or abate the violation.
Frequently Asked Questions
When does a construction site have to stabilize bare soil?
Does this apply inside incorporated cities in the county?
Sources & Official References
Other rules in St. Louis County
Compare St. Louis County to another location·View the Missouri environmental rules overview
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