St. Peters, MO Environmental Rules: Stormwater Management (2026)

Chapter 550, adopted by Ordinance No. 5852 in 2012, requires on-site stormwater management for any development or area that is paved, expanded, redeveloped, or otherwise improved unless the City Engineer grants a waiver under one of the listed exceptions: participating in a shared off-site system with other developments, contributing to a City-programmed regional facility, paying into the Stormwater Management Improvements Fund in lieu of on-site detention, or using an alternative management technique that performs as well as a detention basin. Section 550.090 sets the numeric trigger: stormwater quantity and quality controls apply to any new development or redevelopment disturbing one acre or more, including smaller parcels that are part of a larger common project over one acre, and to any project generating a differential runoff of one cubic foot per second or more using the Rational Method.

Sites without existing detention must add it once that one cfs threshold is reached; sites with existing detention must add capacity for all increased runoff, and existing facilities being asked to handle more runoff must be retrofitted to current standards. The City Engineer inspects construction for compliance, can issue a stop work order when work departs from approved plans, and requires an escrow before permits issue to guarantee the approved stormwater work gets built and maintained. Under Section 550.180(C), violating any Chapter 550 requirement is an ordinance violation, and each day the violation continues counts as a separate offense, with the City also free to take any other lawful corrective action at the cost of the violator.