Winnebago County, IL Environmental Rules: Stormwater Management (2026)

Chapter 50, Article IV, the Surface Water Management Ordinance readopted June 13, 2024 (Ord. No. 2024-CO-036), regulates stormwater in two ways under § 50-247(a): quantity and quality. On quantity, § 50-247(a)(2) sets the maximum controlled stormwater runoff release rate at 0.2 cubic feet per second per acre, the rate the county has found matches the natural safe drainage capacity of its downstream system, with the engineering details spelled out in the county's Technical Regulations. The rule exempts traditional agricultural uses, single-family homes on lots recorded before June 24, 1982, modifications to existing single-family homes that stay single-family, land that drains straight into the Rock, Pecatonica, Sugar or Kishwaukee Rivers, and roadway resurfacing that doesn't add traffic lanes. Section 50-247(a)(3) layers on post-construction runoff quantity controls as a federal NPDES Phase II best-management-practice requirement.

On water quality, § 50-247(b)(1) requires a construction site erosion and sediment control plan for any land-disturbing activity of an acre or more, built to the U.S. Department of Agriculture's Illinois Urban Manual, unless the applicant instead files a Phase II NPDES Notice of Intent and an approved Storm Water Pollution Prevention Plan at least 30 days before construction starts.

A surface water management permit is required before covered land-disturbing activity begins; § 50-255(d) sets the term at two years for minor developments and three years for major ones (or the building permit's term, whichever is less), extendable by the administrator in six-month (minor) or twelve-month (major) increments on written request, but not more than 90 days before expiration. Fees follow the county's Surface Water Management Fee Schedule under § 50-256, on file with the Highway Department at 424 North Springfield Avenue, Rockford. Violations are enforced by the county engineer as administrator, who can issue a stop-work order and, under § 50-250(n), fine violators $25 to $500 per day.