Brown County, WI Environmental Rules: Stormwater Management (2026)
Key Facts
- TSS cut
- 80% new development
- Threshold
- 20,000 sq ft impervious
- Buffer
- 50-75 ft along waters
- Peak discharge
- capped at pre-development rate
Summary
New developments in unincorporated Brown County disturbing 20,000+ square feet of impervious surface must cut post-construction sediment runoff 80% and control peak discharge under Chapter 40's stormwater standards.
TOTAL SUSPENDED SOLIDS. BMPs shall be designed, installed and maintained to control total suspended solids carried in runoff from the post-construction site as follows. The total suspended solids reduction shall be based on the average annual rainfall, as compared to no runoff management controls.
1. For post-construction sites with 20,000 square feet or more of
impervious surface disturbance and post-construction sites with 1 acre or more of land
disturbance, the following is required:
a. Reduce the total suspended solids load by 80% for new
development.
b. Reduce the total suspended solids load by 40% for
redevelopment.
c. No total suspended solids load reduction is required for
routine maintenance areas, unless runoff from the routine maintenance area discharges into
a proposed water quality BMP.
2. For post-construction sites with less than 20,000 square feet of
impervious surface disturbance, reduce the total suspended solids load using Wisconsin
BMPs. These sites are not required to satisfy a numeric performance standard.
3. Sites with a cumulative addition of 20,000 square feet or
greater of impervious surfaces after the adoption date of this ordinance are required to
satisfy the performance standards within 40.12 (3)(a)1.a, b, and c.
Full Breakdown
Brown County Code § 40.12 sets post-construction stormwater performance standards for sites with 20,000 square feet or more of new impervious surface, or 1 acre or more of land disturbance: BMPs must cut total suspended solids 80% for new development (40% for redevelopment), hold peak discharge at or below pre-development rates for the 2-, 10- and 100-year storms, and infiltrate up to 90% of pre-development runoff volume for residential sites. A protective buffer of 50 to 75 feet applies along lakes, streams and wetlands. The County Highway Commissioner reviews the required plan under § 40.09.
Violations & Fines
Noncompliance draws a forfeiture of $500 to $5,000 per day of violation plus prosecution costs, and the Highway Commissioner may issue a stop-work order or pursue an injunction to force compliance.
Frequently Asked Questions
What size project triggers the stormwater standards?
Are streams and wetlands specifically protected?
Sources & Official References
Other rules in Brown County
Compare Brown County to another location·View the Wisconsin environmental rules overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.