Stormwater Credits

What is a credit?

A stormwater credit is a conditional reduction in the amount of the stormwater service charge to developed land based on the provision and continuing presence of an effectively maintained and approved on-site stormwater facility (structural control) that reduces the impact of the property’s impervious area and thus the cost of providing service. The credit is applied only to the portion of a site’s impervious area treated.

The structural control limits the impacts to the stormwater drainage system by reducing peak rates of runoff, total runoff volume, temperature, and/or removing pollutants. These measures can include on-site practices such as detention areas for flood control and other structural controls such as wet ponds, raingardens, and other approved designs that manage stormwater quality.

How do I earn a credit?

The credit program is focused on structural controls that reduce the impact of development on the stormwater drainage system. Two broad categories of controls are recognized: water quality controls and flood controls. Credits are available for residential properties and non-residential properties. To get a credit, a structural control needs to be built and a credit needs to be applied for with the City of Portland Department of Public Works.

Stormwater Credit Manual

For more information about credits available to residents and businesses see the Stormwater Credit Manual

How Do I Apply for a Credit?

Residential Applications

Existing Stormwater Structural Controls:
Residential applicants that have existing stormwater structural controls may apply for credits using residential credit application form 1A. Be sure to include all submission requirements as indicated on the form.

Proposed Stormwater Structural controls:

Residential applicants that are proposing to construct a new stormwater structural control can submit form 1A prior to installing the system.* If the Department of Public Works approves of the plan, the applicant will be notified that construction of the system can commence. After construction of the structural control, the applicant will need to submit simple follow up form 1B, and all applicable materials, in order to get final Department of Public Works credit approval.

*Note: After the Department of Public Works opens the credit application process, residents still may elect to construct stormwater structural controls and apply for credits via the existing stormwater structural controls procedure. However, it is recommended that residential applicants seek pre-approval from the Department of Public Works for a proposed plan prior to construction.

Residential Application forms:

Form 1A - Residential Stormwater Credit Application

Form 1B - Residential Stormwater Credit Follow-Up Application

Non-Residential Applications

New Developments/Re-Development Projects:

Commercial properties that will be undergoing site plan review for new/redevelopment projects shall submit a stormwater management plan and all supporting materials as required by the City of Portland’s site plan ordinance to the City of Portland’s Planning and Urban Development Department. Applicants shall also submit stormwater credit application form 2 to the Department of Public Works in order to determine what level of credit the proposed development/re-development project shall receive.

Existing Stormwater Management Facility:

Applicants applying to receive credits (basic, minimum standards) for existing stormwater management systems must submit application form 3. Applicants with existing systems must provide original system design information stamped by a licensed professional engineer in the state of Maine and a current inspection report form 4 by a qualified 3rd party post-construction stormwater inspector to be considered for stormwater credits. If any alterations have been made to the approved stormwater management system these changes must be reflected in an updated plan developed by a licensed PE in the State of Maine.

Retrofits of Existing Development Sites or Stormwater System Upgrades:

Applicants seeking to install stormwater retrofits on an existing developed site without structural stormwater controls or applicants seeking to upgrade existing stormwater systems to meet current stormwater standards should consult a professional engineer to determine if the retrofit or upgrade will trigger the City of Portland’s Site Plan Review. Applicants can set up meetings with Department of Public Works staff, through appointment, to help determine if a site plan application will be necessary. If site plan review is necessary, applicants will need to submit an appropriate level site plan application with the Planning Department, as well as, submit stormwater credit application form 3 to the Department of Public Works with all required supporting documents. If site plan review is not required, applicants will be required to submit form 3 and all supporting documents to the Department of Public Works for review. Any Applicants seeking retrofit credits must provide post construction certification by a PE or by qualified 3rd party inspector that the system is functioning as the design plans intended.

Annual Inspection of Commercial Systems:

In order to continue receiving these credits applicants must submit an annual inspection report by June 15th of each year, in accordance with Chapter 32, Article III and Chapter 24, Article V of the City of Portland’s Code of Ordinances. A qualified 3rd party post-construction stormwater inspector must conduct the inspection, and the Applicant must submit form 4.

Non-Residential Applications forms:

Form 2 – Non-Residential Stormwater Credit Application for New and Re-Development

Form 3 – Non-Residential Stormwater Credit Application for Existing Systems or Retro-fit of Existing Developments

Form 4 - Non-Residential Stormwater Credit Annual Inspection Form

Note: All Applicants are encouraged to set up a pre-application appointment with the Department of Public Works prior to the actual submission of the applications.

Appeal of Assessed Impervious Area

Property owners who suspect that they are being billed for an amount of impervious area that does not accurately reflect the conditions on their property may submit form 5 to the Department of Public Works. Applicants should note whether they are currently receiving credits, as the amount of credit they receive or for which they are eligible may change depending on the amount of impervious area on their property. After receiving your application, the Department of Public Works will verify the impervious area values proposed by the applicant. This may require a site visit.

Removal of Impervious Area

Property owners who wish to remove impervious area must submit form 5 to the Department of Public Works. Staff from the Department of Public Works will review the proposed removal project to determine whether it complies with Portland’s Code of Ordinances and Design and Technical Standards Manuals. Note that some impervious area removal projects, depending on the scope of work, might necessitate a site plan review. Applicants are encouraged to participate in a pre-application appointment with the Department of Public Works to help determine what requirements will pertain to their project.

Once the plan for the proposed project has been approved, the applicant may proceed. The applicant will have to demonstrate that the removal of impervious area was conducted in accordance with the guidelines below. This will likely require an inspection report from a qualified third party inspector.

Impervious Cover Removal Guide
Application for Appeal / Removal of Impervious Surfaces

Form 5 - Application for Recalculations of Impervious Area (Appeal or Removal)

Application for Reassignment of Fees from Condo Owners to the Association

Form 6A - Application for Reassignment of Condo Owner Fees to Condo Association

Submission of Applications

Applicants must send all completed applications to the Department of Public Works


Mail or hand deliver to:
Department of Public Works
Attn: Stormwater Utility Office
212 Canco Rd, Suite B
Portland, Maine 04103

Phone: 207-874-8462