St. Louis County, MO Environmental Rules: Stormwater Management (2026)
Key Facts
- Permit required
- County land disturbance permit before grading
- Max cut/fill slope
- 3:1 unless county approves steeper
- Stabilization deadline
- 14-day trigger, 7-day completion
- State permit threshold
- 1 acre or more disturbed needs MDNR permit
- Watershed rule
- Grading may not redirect a watershed
- Enforcing agency
- Dept. of Transportation and Public Works
Summary
Before grading or disturbing land anywhere in unincorporated St. Louis County, from a single subdivision lot to a commercial site, the owner needs a land disturbance permit from the Department of Transportation and Public Works. Section 1005.230 bars any grading that would redirect a watershed, and Section 1114.200 caps cut and fill slopes at a 3:1 ratio unless the county specifically approves a steeper design.
1005.230 - Grading. —1. Where the preliminary plat indicates that extensive grading and compaction are probable, the Department of Transportation and Public Works may require the submission of additional information and modifications in the proposed plat before the developer may grade any land to be subdivided. 2. A land disturbance permit is required from the Department of Transportation and Public Works prior to any grading or other land disturbance activity on the site. Erosion and siltation control devices shall be provided as required by the Land Disturbance Code. Proposed grading which creates a change in watersheds shall not be permitted. ... 201.1 Design: The design of erosion and sediment controls required for land disturbance activities shall comply with the following minimum requirements: ... 3. Cut and fill slopes shall be no greater than 3:1 except as approved by the Department of Transportation and Public Works to meet other community or environmental objectives.
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
St. Louis County treats grading as land disturbance regardless of whether it happens inside a platted subdivision or on an individual building lot. 230 of the Subdivision Ordinance requires a land disturbance permit from the Department of Transportation and Public Works before any grading begins, and if a preliminary plat shows that extensive grading and compaction are likely, the Department can demand additional engineering information and plat changes before the developer is allowed to touch the site. The same section flatly bars any grading that would change the watershed a property drains into, and it requires erosion and siltation control devices as set out in the separate Land Disturbance Code, Chapter 1114.
Chapter 1114's design chapter fills in the engineering detail the Subdivision Ordinance only references. 1 caps cut and fill slopes at 3:1 unless the Department specifically approves a steeper slope to meet another community or environmental objective, and it bars clearing or grading of forests and wetlands except where another county ordinance allows it. 2 sets the clock for erosion control: once soil-disturbing work stops on any part of a site for more than fourteen days, temporary stabilization has to start immediately and be finished within seven calendar days, and final stabilization after work permanently ends follows the same seven-day rule.
4 layers a state permit on top of the county's: any site disturbing one acre or more, or part of a larger development that will eventually disturb an acre or more, needs a land disturbance permit from the Missouri Department of Natural Resources before county-authorized site work can begin. 2.
Violations & Fines
Grading without the required land disturbance permit, or grading that redirects a watershed, violates Section 1005.230 and can trigger a stop work order under the Land Disturbance Code's enforcement provisions. Cut or fill slopes steeper than 3:1 without Department approval, or a site left unstabilized beyond the fourteen-day trigger and seven-day completion windows in Section 201.2, are cited the same way, and the county can withhold future permits under Section 104.7 until unresolved violations are corrected.
Frequently Asked Questions
Do I need a permit just to grade my own lot in St. Louis County?
How steep can a cut or fill slope be on a St. Louis County site?
When does a project need a state stormwater permit in addition to the county's?
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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