Greater St. Louis drainage permits & rules: what homeowners should know

Drainage work is not governed by one metro-wide rule. Requirements depend on the state, county, municipality, sewer or drainage district, property conditions, and exactly what the project changes.

The four questions to ask before drainage work

1. Who has jurisdiction over the property? A mailing address that says “St. Louis” does not necessarily mean St. Louis City. A property may be inside a municipality with its own permitting authority.
2. Does the project change grading or runoff patterns? Regrading, berms, swales, large excavations, and land disturbance can trigger requirements that a simple downspout extension may not.
3. Where will the water discharge? Moving water away from one problem area is not enough; the destination matters.
4. Does the work touch an easement, storm sewer, floodplain, stream buffer, or public right-of-way? Those conditions can add separate approvals.

St. Louis City

The City of St. Louis currently lists the 2018 International Residential Code among its adopted codes and separately administers building and trade permits. The City notes that construction projects may require review by multiple agencies depending on scope.

Work proposed within public right-of-way or on City property requires a public improvement permit. That can become relevant when a proposed drainage solution crosses or affects sidewalks, streets, alleys, or other public areas.

St. Louis County and its municipalities

St. Louis County contains many separate municipalities, so the correct permitting authority may be the County, the municipality, or both depending on location and project type. Homeowners should not assume that a rule applying in unincorporated County applies identically inside every city.

For larger grading or land-development work, local grading, erosion-control, watershed, and stormwater requirements may apply. The practical question is whether the project merely corrects a small residential drainage issue or materially changes site grading, runoff, or drainage infrastructure.

St. Charles County

St. Charles County states that it has adopted the 2021 I-Codes with local amendments. The County recommends that homeowners contact Building and Code Enforcement before beginning a project when they are unsure which permits or inspections are required.

St. Charles County also states that development disturbing 5,000 square feet or more requires a County land-disturbance permit and an approved site-protection plan. Development or redevelopment disturbing 1 acre or more is subject to additional stormwater-management requirements.

Jefferson County

Jefferson County regulates land disturbance and stormwater management, including special protections around streams, wetlands, sinkholes, and floodways. County rules restrict certain clearing, grading, filling, and other disturbance within designated stream-buffer areas, and floodway development may require floodplain approval.

Metro East Illinois

For properties in Madison, St. Clair, or Monroe County, begin with the municipality or county that has jurisdiction over the address. Illinois-side projects may also involve a township, drainage district, sanitary district, floodplain authority, or other local body depending on the property and proposed outlet.

Do not assume a Missouri permit threshold or sewer rule applies in Illinois. Ask the provider to identify the exact authority, confirm whether grading or land-disturbance approval is needed, and document where collected water will discharge.

What about draining water onto a neighbor's property?

A contractor should not treat “get the water off this yard” as permission to simply send it across a property line. Drainage design should consider adjoining property, existing drainage patterns, easements, discharge points, and applicable local rules. A solution that fixes one homeowner’s pooling problem by creating a new problem next door can create substantial practical and legal risk.

What about storm sewers?

A homeowner should not assume that a private drain, sump discharge, French drain, or downspout may simply be connected to a public storm or sanitary sewer. Connections can be regulated by the applicable sewer and permitting authority. The provider should identify the proposed outlet and verify that any connection is allowed before work starts.

Questions to ask a drainage contractor

• What jurisdiction controls permits for this address?
• Does this scope require a grading, building, plumbing, land-disturbance, floodplain, or right-of-way permit?
• Are there drainage or utility easements where you plan to excavate?
• Where exactly will the collected water discharge?
• Does the work change runoff onto neighboring property?
• Who is responsible for obtaining required permits and inspections?
• Will utilities be located before excavation?

Local rules are part of project cost

Permitting, engineering, restoration, erosion-control measures, special access, or a more complicated approved discharge point can all increase cost. That is one reason an online calculator should be treated as a planning range rather than a contractor quote.