Municipal Separate Storm Sewer Systems (MS4) is a conveyance or system of conveyances:

• Owned by a state, city, town, village, or other public entity discharging to U.S. waters;
• Designed or used to collect or convey stormwater (i.e. storm drains, pipes, ditches, etc.);
• Not a combined sewer; and
• Not part of a Publicly Owned Treatment Works (sewage treatment plant).

Since 2016, the County of Rock has been authorized by the Department of Natural Resources (DNR) to discharge stormwater from the County owned (MS4) in the Urbanized Area of Rock County under a Wisconsin Pollutant Discharge Elimination System (WPDES) general permit.

Rock County’s conveyance systems (ditches or curb and gutter) is associated with County Highways within Urbanized Area, as determined by population density based on 2000 census.

View County Highways that fall into this category.  

Each regulated MS4 operator is required to develop and implement a stormwater management program to reduce the contamination of stormwater runoff and prohibit illicit discharges.  The minimum program elements are:

• Public Education and Outreach
• Public Involvement and Participation
• Illicit Discharge Detection and Elimination
• Construction Site Pollution Control
• Post-Construction Storm Water Management
• Pollution Prevention/Good Housekeeping

Rock County’s stormwater management program is intended to be implemented in the areas of land under the jurisdiction of the County that drain into the Rock County MS4. Areas excluded from program coverage are agricultural facilities and practices, industrial or land disturbing construction activities that require separate WPDES permit coverage and storm water discharges that do not enter the County’s MS4.

View Rock County Municipal Storm Water Management Plan

Rock County is required to provide an annual report to the DNR summarizing yearly program element activities.  The yearly program activities and the annual report will be discussed during the Rock County Land Conservation Committee March meeting each year.  The public is invited to attend the meeting to provide input on the program activities and annual report.

View the Most Recent Annual Report