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When is a wastewater system plan submittal required?

A "reviewable project" means any construction or installation project for which a DNR approval is required pursuant to s. 281.41, Wis. Stats. A reviewable project includes any new sewerage system, or any improvement, extension or alteration of an existing sewerage system that may affect the quality or quantity of effluent, or the location of any effluent outfall structure.

Collection system projects

For sewer rehabilitation or replacement projects, if a sewer is being repaired or replaced at the same location, and with the same pipe size and slope, then the project is considered a "maintenance project" and plans do not need to be submitted to the department unless the project will be financed through the Clean Water Fund. For lift stations, if there is no relocation and if the replacement pumps or equipment being installed are substantially the same in design and function as the existing, then it would be classified as a maintenance project. All other sewer and lift station projects must be submitted for review.

Plan review is required for collection system projects financed through the Clean Water Fund. An abbreviated facilities plan process may be used for sewer rehabilitation or replacement projects. See facilities plans for sanitary sewer replacement and rehabilitation.

Treatment facility projects

The department makes determinations on reviewable projects based on the potential effects on the quality or quantity of effluent. For example, a project may consist of replacing an aeration system with a different type of aeration system, but with the design goal of maintaining the same level of treatment and effluent quality. An aeration system is subject to NR 110 design requirements and is a critical element of any treatment process that potentially could affect effluent quality if not properly designed. Therefore, the project would be classified as a reviewable project regardless of whether a design capacity or performance change is proposed.

A reviewable project may also consist of modifications that do not directly have potential effects on the quality or quantity of effluent, but are subject to design requirements in ch. NR 110, Wis. Adm. Code. For example, NR 110 contains building ventilation requirements for chlorine rooms and sludge processing rooms. A proposed project that would modify the ventilating system in these types of rooms at a wastewater plant would be considered a reviewable project and must be submitted for department approval. Additional typical reviewable projects of this sort include:

  • Sludge handling and processing systems;
  • Proposed buildings to enclose chemical or sludge processing areas, or other areas subject to NR 110 ventilation or other building requirements;
  • Proposed new or modified instrumentation and controls performing functions subject to NR 110 requirements;
  • Proposed new or modified standby generators or other emergency operating provisions installed as an integral component in a lift station or treatment plant (not portable pumps or generators); and
  • Proposed new or modified monitoring devices used to determine compliance with WPDES permit requirements.

Maintenance projects that do not require plan approval

A proposed project not meeting the criteria for a "reviewable project" is considered to be a "maintenance project" and does not need to be submitted for department approval unless the project will be financed through the Clean Water Fund. Although a department approval is not necessary, it is normally expected that maintenance work will be accomplished with materials and methods consistent with applicable state requirements for sewerage systems, thus maintaining or improving the system's structural integrity and level of performance. Any "sub-standard" component of an existing sewerage system may be required by the DNR to be brought into compliance with applicable state standards when a future reviewable project is submitted for that component, or related components. A maintenance project would also still be subject to other standard permits necessary for stream crossings, wetland impacts, dewatering or other construction related activities.

Whether or not formal plan approval is required, it is a good practice to keep the department’s basin engineer informed of any modifications.

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In some instances, repair or replacement work may involve only minor changes or otherwise be uncertain as to whether it should be classified as a reviewable project. Engineers are encouraged to contact the applicable DNR plan reviewer to discuss these situations. In some cases, the department will not conduct an official plan review or issue an approval, but will provide a letter confirming that the department has no objection to the proposed work proceeding as a maintenance project.


After a plan approval is issued, it is not unusual for some refinements or design changes to occur. If the changes are significant, revised plans should be submitted for department approval. Additional information is available from the specific guidance on revisions pertaining to construction plans and specifications and to wastewater facility planning studies.

Clean Water Fund Loan projects

Any project that will be seeking a state Clean Water Fund (CWF) loan must be submitted for department plan review and approval, regardless of whether it would otherwise be classified as a maintenance project. All CWF projects must also have a facility plan approval under s. NR 110.09, Wis. Adm. Code, to demonstrate that the proposal is necessary and cost-effective.

Use of existing facilities

In some cases, no actual construction or installation is necessary because an existing structure is proposed for use. For example, an existing tank previously used for animal waste may be proposed for storage of municipal sludge or wastewater. A department plan approval is still necessary because the project is proposing a new use for the structure as a component in a sewerage system. In these cases, the department will normally require that a registered Wisconsin Professional Engineer inspect, and possibly test, the structure to verify that it is structurally sound and complies with applicable code requirements.