Wisconsin Department of Natural Resources


Wastewater facility planning studies

Wastewater facility planning studies are required by Chapter NR 110 Wisconsin Administrative Code for all "reviewable projects" involving new or modified sewerage systems owned by municipal or other non-industrial entities. The basic purpose of facility planning is to assess the condition of a sewerage system, establish a need for improvement, evaluate options to address system needs, and to identify the cost-effective alternative. The cost-effective alternative is that which results in the expenditure of the minimum total resources costs over the planning period. The total resources costs include monetary costs, environmental and social considerations, and other non-monetary factors. A proposed municipal project demonstrated to be necessary and cost-effective may then be eligible to receive financial assistance from the state Clean Water Fund loan program.

The scope of a wastewater facility planning study can vary considerably based on the nature of the problem and type of project. A complete analysis as outlined in s. NR 110.09 Wis. Adm. Code, would be expected for a proposed new facility, whereas the scope of analysis could be reduced for a smaller project such as one involving only one unit process at an existing facility. The Department encourages contact with DNR plan reviewers early on in the planning process to discuss and define an acceptable scope of study.

In some instances, a DNR discharge permit may require a permittee to evaluate a problem and submit a report. This may be in the form of an "Operation and Needs Report" that addresses operational improvements and maintenance needs over a short-term planning period. These reports are typically not the same as a facility plan study conducted for satisfying NR 110 requirements. Any study expected to justify proceeding with construction of a "reviewable project" must be submitted and approved in accordance NR 110 facility planning requirements.

Ownership and new wastewater facility requirements

To comply with s. NR 110.08, Wis. Adm. Code, any proposal for a new wastewater treatment facility intended to serve residential development must include a demonstration that the proposed facility is necessary, cost-effective and will be owned by a municipal entity. An exception to municipal ownership may be made for new facilities intended to serve existing mobile home parks or condominium developments if the criteria contained in s. NR 110.08(5)(dm) are satisfied. A proposed new wastewater facility may be denied approval if the WDNR determines the facility would not be consistent with its responsibility to protect, maintain and improve the quality and management of the waters of the state.

A proposal for a new wastewater treatment facility to serve isolated non-residential development (such as parks, airports, hospitals, prisons, schools and highway oriented commercial development) must include a demonstration that it is not feasible to connect into an existing sewerage system. The DNR may then approve such a treatment facility provided service is limited to the non-residential development. Municipal ownership is not required for facilities serving isolated non-residential development.

Privately owned or other non-municipal wastewater treatment facilities subject to ch. NR 110 must provide a demonstration of project need and cost-effectiveness in facility plan studies, the same as for municipally owned systems. There are, however, certain facility planning requirements that do not apply to non-municipal systems. Specifically, the requirements of s. NR 110.09(1)(b) 3, 5 and 8, and (2)(b) through (e) and (j) through (m), do not apply to non-municipally owned facilities.

A "municipality" means any city, town, village, county, sanitary district, utility district, public inland lake protection and rehabilitation district, metropolitan sewerage district, or other public entity created pursuant to law and having authority to collect, treat or dispose of sewage.

Onsite wastewater treatment systems that discharge to groundwater via a subsurface infiltration system are defined as "Private Onsite Wastewater Treatment Systems" (POWTS). These systems are regulated by the Department of Safety and Professional Services (DSPS) with the exception that if the POWTS is defined as "Large" or if the POWTS is owned by a municipality, then certain DNR regulations would also apply. See the guidance for large POWTS for more information.

Facility planning for collection system projects

Any proposed reviewable project for a wastewater treatment facility is subject to the facility planning requirements of NR 110.09 including a demonstration of project need and cost-effectiveness. But the facility planning requirements for collection system projects will differ depending on the project type and funding. Any proposal for storage of wastewater, either within sewer lines or in remote storage facilities, is subject to s. NR 110.09 and a facility plan report must be submitted for Department review. For conventional sewer or pump station projects, the facility planning requirement is dependent on whether a state Clean Water Fund (CWF) loan will be sought.

If no CWF loan is involved, the applicant must comply with the requirements of ss. NR110.10 (for sewers) and NR 110.11 (for lift stations). These requirements can be satisfied by completing the standard DNR forms for sewer and lift station construction plan and specification submittals. There is no need to submit a separate facility plan report. If the Clean Water Fund will be used to finance a collection system project a facilities plan is required. For projects that include sewer replacement and/or rehabilitation only see facilities plans for sanitary sewer replacement and rehabilitation.

The Clean Water Fund Program is intended to provide financial assistance for projects providing environmental benefits. A collection system project may be eligible if it is necessary to increase conveyance capacity to prevent bypassing, sanitary sewer overflows, or sewage treatment facility overflows, to eliminate excessive clearwater infiltration or inflow, or to maintain the structural integrity of the system. The loan program is not intended to fund routine maintenance or sewer extensions to new development. Sewer extensions to existing development may be eligible for funding if the project will eliminate adverse environmental or public health impacts associated with the use of private onsite wastewater treatment systems and certain additional criteria are met. Information on these requirements is available on the Environmental Loans unsewered projects web page.

Infiltration and inflow

The design of any wastewater treatment plant must include consideration of "clear water" that may enter a sewage collection system under wet weather or wet soil conditions, and be transported to the treatment facility. Depending on the scope of a facility planning effort and the extent of clear water flows, separate studies for an "Infiltration /Inflow Analysis" and a "Sewer System Evaluation Survey" (SSES) may be required. The content of these studies is addressed in ss. NR 110.09 (5) and (6), Wis. Adm. Code. A WPDES permit may require that a "System Evaluation and Capacity Assurance Plan" (NR 210.23 and NR 110) be conducted. A history of frequent sewage bypasses or overflows occurring in the sewerage system may result in a requirement to prepare one or more of these studies.

If infiltration/inflow can be demonstrated to be below certain threshold levels, the Department will consider the I/I to be "non-excessive" and separate I/I or SSES studies will not be required. The infiltration threshold criterion is whether the dry weather flow (the highest base flow plus infiltration occurring for a 7 to 14 day dry weather period during a year) is less than or equal to 120 gallons per capita per day (gpcd). The inflow threshold criterion is whether the maximum daily flow during a storm is less than or equal to 275 gpcd. These criteria are guidelines, not code requirements, and different guidelines or supplemental information may be considered when warranted by specific circumstances.

Existing conditions and design criteria

A facility plan study for a new facility, or a major upgrade or replacement, should identify a project planning area. A fundamental purpose of the planning area is to enable consideration of alternate sewer service area configurations. The planning area should be large enough to allow examination of possible efficiencies in regional systems, including providing service to areas with existing development served by onsite systems. Information should be provided to describe environmental resources, demographics, and land use within the planning and sewer service areas.

Planning and design parameters must be identified for the various alternatives to be considered. This includes service population projections, design flows and waste loadings, and discharge requirements. Additional information is available:

Identification of alternatives

The primary objective of facility planning is to identify and evaluate various potential solutions to address wastewater management needs. For new facilities or major upgrades, the alternatives analysis should consider the establishment of the sewer service area and possible connections to existing sewerage systems (regionalization). Facility plans must conform with approved sewer service areas contained in areawide water quality management plans. If a revision to a sewer service area is being proposed, the first step of the planning process will be to seek an amendment to the sewer service area.

Any proposal for a new or upgraded treatment plant may include consideration of different treatment technologies, facility sites, and discharge locations. Discharge may be to surface waters or to groundwater via land application systems such as spray irrigation or rapid infiltration basins. The Department encourages consideration of innovative as well as conventional technologies. If new or innovative methods of treatment are proposed, supplemental performance data may be required to support performance claims for the technology.

If a municipality is planning for a treatment facility upgrade that will result in a capacity increase of 20% or more, they are required to evaluate the need to include septage receiving facilities and additional treatment capacity specifically for septage. Please see the DNR program guidance [PDF] for septage considerations in municipal wastewater facility planning and for application of zero percent Clean Water Fund loans.

The alternatives analysis should include consideration of improving plant performance by improved operation and maintenance measures. In some cases, this may be addressed separately by an "Operation and Needs" study. Phased construction of upgrades may be considered, but all alternatives must still be compared on the basis of a 20-year planning period. When it is proposed to significantly upgrade any portion of an existing facility and to increase plant capacity, the facility planning analysis should also examine the condition of the other processes at the facility. If the other existing processes are not code compliant, or do not perform adequately, the facility plan should examine whether it is necessary and cost-effective to improve them.

All alternatives must be feasible in terms of being implementable from legal, institutional, financial and management standpoints. In some circumstances, local annexation requirements may be associated with a regionalization alternative. Annexation requirements would be evaluated along with project costs and non-monetary factors. In general, the Department does not accept annexation, by itself, as a factor that would necessarily prevent implementation of a project.

After identifying feasible alternatives, they may be systematically compared and screened to identify the principal alternatives to be subjected to the detailed cost analysis. The level of detail in the analysis will depend upon the size and complexity of the project, and the range of cost differences among alternatives.

Cost-effective analysis methodology

To provide valid monetary cost comparisons, all opportunity costs associated with an alternative over the 20-year planning period should be identified and presented on a total present worth or equivalent uniform annual cost basis. Sunk costs should not be included in the cost-effectiveness analysis because these costs have already been committed regardless of the alternative selected. Sunk costs include investments in existing wastewater facilities and associated lands, outstanding indebtedness and costs for preparing the facilities plan.

Costs should be based on market prices prevailing at the time of the study. Except for energy and land costs, the inflation of costs over the planning period is not allowed. The analysis should account for initial capital costs, future capital costs, annual operation and maintenance costs, and salvage values. Salvage values are determined by assigning a design service life to various components and then calculating the remaining service life and associated value of the component at the end of the planning period.

Current discount rate

Present worth factors must be based on the current discount rate as established by the DNR in accordance with NR 110.09(1)(a), Wis. Adm. Code. [The discount rate for the Federal Fiscal year 2020, which applies to facility plans beginning on or after October 1, 2019, is 3 3/8 percent (3.375%).]

Connection fees or other charges should not be included in a cost-effective analysis if they are a method of cost recovery for a sunk cost, or if they only reflect a transfer of payments from one entity to another.

Costs for treatment capacity acquisition from an existing treatment plant may, or may not, be included in the cost-effectiveness analysis depending on specific circumstances. If an existing facility has planned (or excess) capacity to service an area, then no capacity acquisition cost should be included in a cost-effectiveness analysis conducted for connecting that area (the capacity is already available and cost is sunk). But if an existing treatment facility does not have planned (or excess) capacity to service a certain area, then serving that new area would reduce the plant's reserve capacity intended for its remaining service area, and thus shorten its design service life. As a result, the plant would need to be upgraded sooner than what would otherwise be necessary. This represents an actual future cost that should be accounted for in the cost-effective analysis if the plant upgrading would be expected to occur within the 20-year planning period.

Compare alternatives based on total present worth or equivalent uniform annual costs. The Department typically considers alternative costs within 10% of each other to be essentially equal in monetary value due to normal cost estimating variability. In some situations, the Department may require the provision of a sensitivity analysis to assess how project costs would vary based on a range of planning assumptions or circumstances.

The facility plan report should contain both a cost-effectiveness analysis and a fiscal impact cost analysis. The fiscal cost analysis will consider grant or loan assistance, financing arrangements, and provide estimates of expected user charges or fees (which should include any existing indebtedness).

The final determination on cost-effectiveness is made with consideration of monetary costs, fiscal impacts, environmental impacts, and possibly other non-monetary considerations.

Environmental impacts

To enable a valid comparison of alternatives, the facility plan report should include environmental impact information on all the alternatives. More specific environmental impact information should be provided for the recommended alternative. See the Resources Impacts Summary outline for more information.

Public involvement

Public involvement is an important aspect of any planning effort for a new or significantly modified sewerage system. Municipalities must conduct at least one public hearing as required by s. NR 110.09(4), Wis. Adm. Code. A copy of the facility plan report should be available for public review before the hearing and at the hearing. Exceptions to the public hearing requirement may be provided if the proposal is for a minor upgrade or if it is a revision to a previously approved project subject to a previous public hearing. Prior to issuing a facility plan approval letter, the Department will issue a news release and typically allow a two-week time period for public comments.

For major projects, such as constructing both a new collection system and treatment facility, the Department encourages public informational meetings in addition to the required public hearing. A newsletter may also be useful to keep residents informed of ongoing planning developments. It is critical that comprehensive and accurate user cost estimates, planning options, and associated environmental impact information are made available to the public. The Department will consider all comments received as part of the decision-making process on a community's proposed cost-effective alternative.

Facility plan revisions

After a facility plan report receives Department approval, there are typically minor design refinements or project changes that occur as the final construction plans and specifications are developed. Minor changes from approved facility plan recommendations should be identified and justified as part of the construction plan and specification review. But if the changes are significant, it may be necessary for the sewerage system owner to prepare and submit a facility plan amendment report to the Department for review under the s. NR 110.09 facility planning rules. The review of an amendment may include a requirement for an additional public hearing. Changes that are normally considered "significant" would involve proposed use of a new site, significant changes to project cost estimates, significant changes to effluent limits or other design parameters, or the discovery of potential environmental impacts not previously identified.

Abbreviated form of a facilities plan

An abbreviated facilities plan (sometimes called an "Engineering Report") can be used to satisfy the facilities planning requirements for minor modifications to municipal treatment plants.

The abbreviated form may be appropriate for modifications to existing treatment facilities where: the construction is at the existing plant site, does change the overall treatment capacity, does not involve new treatment technology or a change of outfall location and will have no significant environmental effects.

The abbreviated facilities plan will include the following components:

  • A brief description of the treatment facilities
  • A concise problem statement
  • Relevant background information
  • Description of any significant environmental issues. It is assumed that the work will largely occur on the existing plant site limiting the need to evaluate the effects on archaeological, historical or endangered resources. Any air permit requirements or encroachments on wetlands or floodplains should be addressed.
  • Alternatives Considered. For some types of projects the department recognizes that the number of feasible alternatives may be limited.
  • Cost-effectiveness Analysis. This must be done on a 20-year Total Present Worth or Equivalent Uniform Annual Cost basis. The plan must include an estimate of the effect of the project on user charges for a typical residential customer.
  • Public Participation. The municipality is encouraged to keep the public informed. However, a formal public hearing will not be required if user charges are not anticipated to increase by more than 20%.

Department approval of a common construction or minor addition project is a minor action under NR 150.

Facilities plans for sanitary sewer replacement and rehabilitation

A facilities plan is required if the Clean Water Fund is used to finance a sanitary sewer replacement or rehabilitation project. The abbreviated form of a facilities plan for sewer replacement and rehabilitation, as outlined below, may be used.

The report may be submitted concurrent with the construction plans and specifications. However, you must submit them sufficiently early to allow DNR to review and approve the facilities plan prior to the Clean Water Fund Program application deadline; please contact municipal wastewater plan review staff to determine an appropriate submittal timeline. This does not apply to new interceptor sewers or replacement sewers that provide capacity for growth in areas outside of the existing sewer service area. Construction plans and specifications for sewer replacement and/or rehabilitation should be submitted using the normal sewer plan submittal procedures.

Contents of a sanitary sewer replacement and rehabilitation facilities plan

Use the following outline for an abbreviated "Engineering Report" format for the sewer replacement and rehabilitation plans when Clean Water Fund financing is anticipated. Allow at least 6 months for facilities plan approval prior to the CWFP application deadline. If not seeking Principal Forgiveness from the CWFP, allow time for plan approval prior to your expected CWF application submittal date; please contact municipal wastewater plan review staff to determine an appropriate submittal timeline. A public hearing will generally not be required.

The elements to be included in the Engineering Report are as follows:

  1. Description of the proposed project and demonstration of need for the project.
    The age and condition of the sewer should be given. Documentation of the problem to be corrected may include inspection reports, flow monitoring or other information as appropriate. It is usually not necessary to submit copies of inspection reports or television logs but the source of the information should be provided.
    Justification for funding may include structural deficiency, inadequate capacity or removal of infiltration and inflow. Storm sewer replacement or rehabilitation is eligible for funding only if the work will prevent clear water flows from entering a sanitary sewer from a storm sewer. In those cases evidence of the connection between the storm and sanitary sewer (such as results of a dye-water flooding test) must be provided.
  2. A brief evaluation of alternatives to correct the problem.
    Generally it would be expected that rehabilitation would be considered as an alternative to replacement. Provide a brief discussion of alternatives considered and the reason for selecting the recommended alternative.
  3. Project cost and user charge estimate
    An estimate of the cost of the project and expected effect, if any, on user charges to the typical residential customer should be provided. If no change is expected that should be stated. If user charges will increase by more than 20% a public hearing should be held.
  4. Environmental effects
    The environmental effects of sewer replacement and rehabilitation projects would be expected to include consumption of fuel and materials of construction, noise, dust, and odor and traffic disruption. It is not necessary to document such effects. Any impacts on floodplains, wetlands or other environmentally sensitive areas, however, should be discussed.
  5. Parallel cost estimate
    A parallel cost estimate must be included. In most cases the estimate would be 100%. However if a replacement sewer provides capacity for growth outside the existing sewer service area a parallel cost estimate must be prepared as described in NR 161.