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Why we regulate
Learn what types of wastewater discharges are regulated and how.
Plan review
The DNR reviews plans for municipal and industrial wastewater treatment plant construction.
Discharge permits
Wastewater discharges to surface or groundwater.

Programs for Sanitary Sewer Collection Systems Capacity, Management, Operation, and Maintenance (CMOM)

CMOM logo

Two mediasite presentations can be viewed that provide useful information on CMOM programs:

Also available are the following publications:

Preventing sanitary sewer overflows and basement back-ups

Wisconsin has approximately 950 permitted sanitary sewage collection systems. Discharges of untreated or inadequately treated sewage from any place in sewage collection systems are commonly referred to as sanitary sewer overflows (SSOs). Discharges of untreated sewage are a potential hazard to human health and can have significant impacts on water quality. All SSOs must be reported to the DNR within 24 hours followed by a written report [PDF] within 5 days. Typically, SSOs occur as a result of either the entry of an excessive amount of precipitation and groundwater, known as infiltration/inflow (I/I), into the sewers or there is a mechanical, electrical or structural failure in a component of the collection system. When a sewage collection system has insufficient capacity to transport the sewage from the I/I entering it, the system will relieve itself by overflowing from the sewer system at some point or backing up through a building sewer into a basement.

Sewers deteriorate over time and develop cracks, breaks, and blockages if not properly maintained. Aging, out-of-sight, out-of-mind sewer systems can be neglected and thus not be inspected or maintained on a regular basis. A CMOM Program is an effective, holistic management tool that owners of collection systems (primarily municipalities) create to operate and manage a collection system to significantly reduce, if not eliminate, sanitary sewer overflows and basement back-ups. It assures sewage collection system owners proactively operate and maintain this significant and valuable community infrastructure through planned ongoing maintenance and prioritizing rehabilitation and replacement projects.

CMOM program requirements

Wisconsin Administrative Code NR 210.23 [PDF, exit DNR] requires that all owners of collection systems, including satellite sewage systems, develop and implement a Capacity, Management, Operation and Maintenance Program by August 1, 2016. A CMOM Program is to assure that a sewage system is properly managed, operated and maintained at all times; has adequate capacity to convey peak flows; and all feasible steps are taken to eliminate excessive infiltration and inflow from the system. A CMOM Program must mitigate the impact of overflows on waters of the state, the environment and public health. Public notification is required of each SSO.

A CMOM Program has eight components:

Additional information

For guidance on developing a Wisconsin CMOM program, see the Wisconsin CMOM Booklet [PDF]. This booklet provides a baseline template for smaller and medium sized communities in developing a CMOM Program.

All communities, especially larger communities, may additionally benefit by reading USEPA’s CMOM Program Self Assessment Checklist [PDF, exit DNR] and Guide for Evaluating CMOM Programs [PDF, exit DNR].

Operation and maintenance activities performed on sanitary sewer collection systems is one of the most important parts of an overall CMOM program. See References for other recommended resources for developing effective collection system operation and maintenance programs.

Contact information
For information on CMOM programs, contact:
Amy Garbe
Wastewater engineer, Central office
Nathan Wells
Wastewater engineer, Fitchburg office
Last revised: Monday May 06 2019