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Winnebago County, WI Environmental Rules: Erosion Control (2026)

Some Restrictions
Compiled from the official code textEditor Martyn O'NeillLast verified August 2026

Key Facts

Trigger
1 acre or 15,000 sq ft impervious
Standard
Match pre-settlement peak runoff
Fine
$500-$1,000 per offense
Scope
Unincorporated county only
Distinct from
Section A erosion permit

Summary

Winnebago County requires a stormwater management permit before grading or land development that disturbs one acre or adds more than 15,000 square feet of new impervious surface in the unincorporated county.

City-specific rules exist: Neenah has its own erosion control rules that differ from Winnebago County's county-level regulations. If you live in Neenah, check the city-specific page instead.

A permit shall be required for all construction sites with one acre or more of land disturbance, and to

sites of less than one acre if they are a part of a larger common plan of development or sale. A permit shall be required

for land development or redevelopment which increases impervious surfaces greater than 15,000 square feet. The total

area of imperious surfaces shall be considered within the area of the parcel(s). Land development activities generally fall

into the following categories: commercial, industrial, platted subdivisions, or single lot activities. Stormwater plans for

commercial, industrial, subdivisions, will require more detailed information generally provided by an engineer whereas,

single lot activities normally will require non-engineered plans. Minor land development activities such as the

construction of a fence, minor landscaping, or construction of minor structures (10 x 10 or smaller) may be considered

exempt from permit requirements if the administering authority determines that no, or very minimal, adverse impacts

will result. The determination of impact shall be based, without limitation, upon criteria such as ponding of water,

backing up of water, or a threat to neighboring properties.

(2) PERMIT APPLICATION AND FEE. Unless specifically excluded by this ordinance, any land owner or operator

desiring a permit shall submit to the administering authority a permit application made on a form provided by the

Full Breakdown

Section B of § 23.15 requires a permit from the Planning & Zoning Department before grading or draining land for commercial, industrial, subdivision, or single-lot development that disturbs one acre or more, or adds over 15,000 square feet of impervious surface. The stormwater management plan must hold post-development peak runoff at or below pre-settlement rates for the 1-, 2-, 10-, and 100-year storms, and the administering authority can require a maintenance agreement and financial guarantee. This permit is separate from the Section A construction-erosion permit and applies only in the unincorporated county, not the cities of Oshkosh, Neenah, or Menasha.

Violations & Fines

Noncompliance draws a forfeiture of $500 to $1,000 per offense plus prosecution costs, with each day of violation a separate offense; the county may post a stop-work order or seek a court injunction.

Frequently Asked Questions

How is this different from the erosion control permit?
Section A covers erosion during construction; this Section B permit governs long-term stormwater and drainage after grading, triggered by acreage or impervious surface added.
What size project needs a stormwater permit?
One acre or more of land disturbance, or any project adding over 15,000 square feet of new impervious surface such as pavement or roofs.

Sources & Official References

Other rules in Winnebago County

All Winnebago County rules

Compare Winnebago County to another location·View the Wisconsin environmental rules overview

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