T Cover
T Cover
T Cover
T Cover

Example of an environmentally sensitive area (ESA). A stream is buffered by undeveloped land to either side.

What is an ESA? 

An ESA, or Environmentally Sensitive Area, is a landscape feature identified in a Sewer Service Area Plan due to its role in maintaining and protecting water quality. ESAs, which may include waterways, wetlands, sloping land, Karst features, floodways, and setback areas, are prohibited from development to ensure local water quality is maintained. ESAs and ESA setbacks are not buildable areas. Development and earth moving activities should not occur within ESAs or ESA buffers. 

Can I change an ESA boundary on my property?

ESAs are identified, mapped, and published online to provide notice to communities, the public, and developers of areas prohibited from public sewer development.  Properties purchased after the delineation of an ESA (displayed on the property’s plat map) should be maintained. Questions involving acceptable activities within and near an ESA can be directed to the Brown County SSA Plan Contact Devin Yoder at devin.yoder@browncountywi.gov.

Unique circumstances may arise in which an applicant wishes to petition for an amendment to the Wisconsin DNR for an ESA modification.  The Brown County Urban Service Area Water Quality Plan provides directions on requesting such a change. Depending on the request, the amendment may be approved by Brown County Planning Commission staff, while more complicated requests may also include the Brown County Planning Commission Board of Directors, and Wisconsin DNR. 

Legal Background

The indentification and protection of ESA's begins with the Areawide Water Quality Management Plan.  The Areawide Water Quality Management Plan is a requirement under Wisconsin Administrative Code NR 121.  Through an agreement with the Department of Natural Resources, Brown County Planning Commission was designated as the Areawide Water Qualtiy Management Agency that would administer the Areawide Water Qualtiy Management Plan (Brown County Sewage Plan) and thereby protect the designated ESA's.
ESA's Defined

NR121.05(1)(g)2c defines environmentally sensitive areas as: "major areas unsuitable for the installation of waste treatment systems because of physical or environmental constraints are to be excluded from the service area. Areas considered for exclusion from sewer service areas due to potential adverse impacts on water quality from both point or nonpoint source pollution include (but are not limited to) wetlands, shorelands, floodways and floodplains, steep slopes, highly erodible soils and other limiting soil types, groundwater recharge areas, and other such physical constraints."

ESAs are defined in the SSA plan, along with the rules and procedures for identifying necessary protections such as setbacks and stormwater/groundwater or related water management actions. A sewer service area plan outlines sewer service for 20 year time horizons. Environmentally sensitive areas should be determined with the aid of the following sources:
ESAESA/Setback Requirement
Navigable Waterbody ESANavigable Waterbody ESA Setback Requirements
Navigable waterways based on DNR navigability determinationLand within 75 feet from the OHWM of navigable waterways (with no flood study)*
Floodway ESAFloodway ESA Setback Requirements 
Floodways identified on FEMA maps, and DNR-approved floodway maps and flood studies30 feet from the floodway line, or 75 feet from the OHWM, whichever is greater**
Non-navigable Waterway ESAsNon-navigable Waterway ESA Setback Requirements
Waterways determined to be non-navigable by the DNR25 feet from non-navigable waterways*
Wetland ESAsWetland ESA Setback Requirements


WDNR Wetland Inventory – Mapped Wetland Area


50-foot buffer area


Areas with wetland indicator soils (no certified wetland delineation has been completed)


50-foot buffer area


Areas with a wetland delineation completed (wetland susceptibility definitions based on NR 151.125 – (Runoff Management) Protective areas performance standard
  • For highly susceptible wetlands, 75 feet***
  • For less susceptible wetlands, 10 percent of the average wetland width, but no less than 10 feet or more than 30 feet***
  • Low-quality wetlands that have a certified delineation and do not contain any exemptions listed in Wisconsin State Statutes 281.36(4n), and have DNR Wetland Exemption or a General/Individual permit, do not have a wetland setback****
Steep Slope ESAsSteep Slope ESA Setback Requirements


Land within 20 feet from the top and bottom of steep slopes that are 20% or greater and that overlap with a buffer of another ESA (like wetland or navigable stream).


20 feet from the top and bottom of the slopes*****
Other Significant Natural Resources

Including (on a case-by-case basis) river and stream headwaters, groundwater recharge areas, unique woodlands, high- value wildlife habitat areas, geologic and natural area sites and wet, poorly drained, and organic soils, and areas identified in the Wisconsin Land Legacy Report and where rare plants, animals, and natural communities are known to be located as identified in Wisconsin’s Natural Heritage Inventory.


* The 75-foot ESA setback from navigable waterways and 25-foot ESA setback from non-navigable waterways should be defined using lines that are, at minimum, parallel to the waterway. Points and straight lines may be used to define the boundary; however, in no instance shall the resultant straightened line be closer than the designated ESA width.
** The 30-foot ESA setback to floodways should be defined using points that are 30-feet from the actual ESA. The points should be connected with a straight line that is surveyed and scaled, similar to a meander line. In no instance shall the resultant straightened line be closer than 20-feet from the actual ESA.
***The wetland boundary shall be made in accordance with NR 103.08 (1m)
****Additional information for low-quality wetlands is outlined in this chapter in this chapter in Definitions, 4. Wetlands d). Low-Quality Wetlands.
*****The 20-feet ESA setback to steep slopes should be defined using points that are 20-feet from the actual ESA. The points should be connected with a straight line that is surveyed and scaled, similar to a meander line. In no instance shall the resultant straightened line be closer than 15-feet from the actual ESA.

ESA's and the Brown County Land Division and Subdivision Ordinance

In an effort to be more proactive in protecting ESAs defined by NR 121 and adopted witihin the Brown County Sewage Plan, Brown County Planning incorporated the same ESA language and protective areas (setbacks) as elements of land division reviews.  This effort makes property owners and developers aware of areas that are not able to be disturbed near the begining of a project timeline so that building and site layouts can be planned accordingly.
ESA Amendments
Additional Information on Sewer Service Area Planning and Environmentally Sensitive Areas