O'Fallon, MO Environmental Rules: Stormwater Management (2026)
Key Facts
- Default responsibility
- Property owner/HOA unless City accepts dedication
- Underground detention
- Annual maintenance report required
- Correction window
- 30 days after deficiency notice
- Illicit discharge fine
- Up to $500 plus 90 days jail
- Native vegetation basins
- Must be mowed by November 1
Summary
O'Fallon Code Section 407.030 puts most stormwater detention basins in the hands of the property owner or homeowners' association rather than the City. The City only takes over maintenance once the infrastructure has been formally dedicated and accepted by ordinance, and the City Engineer periodically inspects privately owned systems to confirm they still work as approved.
The City Engineer and/or his/her designee shall inspect or cause to be inspected all stormwater detention facilities constructed within the City of O'Fallon, Missouri. ... Each owner of the property being developed or has been developed, whose property has caused the increase in runoff that has necessitated the need for detention, has the responsibility and duty to properly operate and maintain any stormwater management system and/or detention facility, which has not been accepted for maintenance by the City.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4860992; v58 updated 2026-05-14; through 05-14-2026).
Full Breakdown
The City Engineer inspects stormwater detention facilities during construction to verify they match approved plans, then continues periodic inspections afterward. Maintenance responsibility stays with the developer until the stormwater escrow is released to a homeowners' association or, if none exists, to all property owners in the subdivision. Owners of underground detention facilities must submit an annual maintenance report from a competent professional verifying the system still functions as approved. If an inspection finds a privately owned system deficient, the City notifies the owner, who gets thirty days, or another mutually agreed timeframe, to fix it before the City reinspects; enforcement follows if repairs are not made or are done improperly.
If a deficiency becomes an immediate danger to public health or safety, the City can act directly and bill the owner for the cost. No modification to a privately owned detention facility is allowed without a City permit, though owners may convert basins to native vegetation with a City-approved maintenance schedule, provided the basin is mowed by November 1 each year. Selling or abandoning an interest in a basin does not eliminate the owner's maintenance duty unless perpetual future maintenance has been separately arranged and approved.
Violations & Fines
Unpermitted modification of a privately owned detention facility violates Section 407.030(A)(7)(a). Separately, Section 407.040's illicit discharge provisions make it a prosecutable offense to discharge pollutants into the storm drain system, punishable by a fine of up to $500.00 and up to ninety days' imprisonment per charge, with each day of a continuing violation and each condition treated as a public nuisance the City may abate at the violator's expense.
Frequently Asked Questions
Who maintains my subdivision's detention basin, me or the City?
Do I need a permit to change my detention basin to a natural landscape?
What happens if the City finds my private stormwater system is deficient?
Sources & Official References
Other rules in O'Fallon
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