This guidance was written to provide information on Environmental Activity and Sector Registry (EASR) requirements. It should not be construed as legal advice. While all efforts are made to ensure the accuracy of the requirements summarized below, if there is any discrepancy between this summary and the acts or regulations, the provisions of the Acts and regulations take precedence.

Overview of the report

Ontario Regulation 137/25: Registrations under part II.2 of the Act - Storm water management works (SWM EASR regulation) requires certain storm water management (SWM) works to be registered in the Environmental Activity and Sector Registry (EASR). For SWM works to be registered, a storm water management works report (SWM report) that satisfies the requirements of the regulation must be prepared and filed in the registry. The SWM report informs the EASR registration and must set out the practices and procedures for constructing and operating the works. A site assessment, along with other relevant information such as the receiving environment, municipal requirements and consultation with others, will inform the design of the works, all of which will provide the basis for the information contained in the SWM report. During the site assessment, licensed engineering practitioners (LEP) are encouraged to incorporate Indigenous knowledge, alongside engineering and scientific principles, into their site-specific assessments, particularly for projects near sensitive ecosystems or traditional harvesting areas.

The assessment must be reflective of the conditions within the catchment area and the site where the storm water management works will be or is located. The SWM report must set out procedures and practices to be followed for the use, operation, establishment, alteration, extension or replacement of any new or existing storm water management works. The owners and operators of the works must follow the procedures and practices set out in the SWM report. A SWM report must be prepared, signed and sealed by a licensed engineering practitioner (LEP) and contain the following sections:

  • introduction section of SWM report
  • general information section
  • design section
  • assessment of monitoring section
  • operations and maintenance manual section
  • erosion and sediment control plan section

The SWM report must be uploaded in the registry upon registration.

Introduction section of the SWM report

Information required in this section of a SWM report is specified in Ontario Regulation 137/25 and summarized as follows:

  • Date the report was prepared. This is the date that the entire report is completed, signed and sealed by a LEP.
  • The name, licence number, signature and seal of the LEP that prepared the report, and a summary of their qualifications. If more than one LEP is involved in preparing the report, the report must contain this information for each LEP in the introduction section. For example, a LEP could prepare the design of the works but a different LEP could prepare the erosion and sediment control plan and each LEP would provide this information in the introduction section. Each LEP could also repeat this information at the end of the section they prepared.
  • A statement from a LEP confirming the following:
    • based on the information provided the report is accurate as of the date it is signed and sealed
    • the information in the report considers the results of the site assessment of the catchment of the works
    • the works is designed in a manner that mitigates any adverse effects to the natural environment

In addition, the SWM report must contain a statement from the person engaging in the activity confirming that all the information given to the LEP to prepare the report was complete and accurate. The person engaging in the activity includes the same people as listed in section 2(3) of Ontario Regulation 245/11.

General information section

Below is a summary of the requirements for the general information section of a SWM report along with examples for completing each requirement:

  • description of the catchment area
  • site plan of the catchment area
  • description of the site assessment of the catchment area
  • considerations for significant drinking water threat activities

Description of the catchment area

The description of the catchment area should:

  • describe the size, contours and drainage patterns of the area that the storm water management works will be collecting storm water from
  • identify all activities performed within the catchment area
  • identify all contaminants associated with the activities performed within the catchment area

Site plan of catchment area

The site plan should provide details of the catchment area and the storm water management works.

The site plan should have:

  • a north arrow
  • a scale of 1:5,000 or larger
  • all dimensions and sizes in metric units

The site plan should include the following:

  • The entire property where the facility is to be (or is) located, including the property lines and the use of the adjoining lands.
  • The boundaries of the catchment area that drain into the storm water management works that are being registered.
  • Areas outside of the catchment area that drain into neighbouring properties without treatment or quality control.
  • The 100-year flood line.
  • Existing and proposed building facilities and water well locations
  • All major topographic features including drainage areas; existing and proposed streets, watercourses, land surveying data used or assumed benchmark.
  • Location and use of all proposed sewage works and existing sewage works associated with the proposed works, together with their individual geo-reference coordinates (UTM Easting and Northing).
  • Waste disposal areas and temporary holding areas for waste.
  • Layout, size and use of the existing, proposed and future structures and buildings on the property showing distances from property lines, private residences and other structures on adjoining properties.
  • All storage areas and loading and unloading areas.
  • Any sanitary sewage treatment facilities.
  • Storm water management works including effluent streams, ditches, conduits, sewers, overflows, discharge points with the direction of flow to the local watercourse (as applicable), infiltration and treatment equipment. Low impact development areas and the ultimate receiver should be shown or indicated, including its size, area and depth.
  • Overlay of any provincial plan areas and source protection areas, including wellhead protection areas and intake protection zones.

Description of site assessment of the catchment area

The LEP must include a description of the site assessment that was undertaken. The LEP should explain how they conducted the site assessment, including describing the methodology used and other relevant information.

Results of site assessment of the catchment area

The LEP must include a statement that, in their opinion, the SWM works meet the criteria to be registered in the EASR.

For example, the statement should confirm:

  • that the works are not owned by a municipality or local board that manages public utilities on behalf of a municipality
  • that there is no processing, repair or maintenance of goods and materials conducted outdoors at the property
  • that there is no contact or mixing of storm water with process water, cooling water, wash water or sanitary sewage before entering the works

In addition, the results of the site assessment section must include:

  • A description of the quantity and quality of storm water that is expected to be collected, transmitted, treated, or disposed of at or by the works, informed by the list of activities in the catchment area and contaminants of concern identified in the description of the catchment area section.
  • An assessment of the precipitation patterns, drainage patterns, site contours and hydrological conditions of the catchment area. For example, rainfall records for previous years, the topography of the site and how storm water moves across the site.
  • An assessment of whether the works is or would be a significant drinking water threat activity, including identifying the applicable source protection area, wellhead protection areas, surface water intake protection zones and vulnerability scores for the location of the works.
  • An identification of whether the SWM works is or will be located in the Lake Simcoe watershed, Niagara Escarpment Planning Area, the Oak Ridges Moraine Area where the Oak Ridges Moraine Conservation Plan applies, or an area designated as Protected Countryside in the Greenbelt Plan.

Significant drinking water threat activities

If the storm water management works are assessed to be a significant drinking water threat, which would be indicated as part of the results of the site assessment, this section of the SWM report must also include a description of how the considerations included in the report are intended to achieve the objective of ensuring that the activity ceases to be or never becomes a significant drinking water threat. In other words, the report must describe how the activity is managed to sufficiently reduce the likelihood that the activity will contaminate the drinking water source. This could include referring to any requirements or considerations included in any of the sections of the SWM report for example, design considerations, operations and maintenance procedures, erosion and sediment control measures that are expected to achieve this objective.

For SWM works that have been assessed to be a significant drinking water threat activity the LEP should consult the ministry’s drinking water source protection risk management measures catalog and other available ministry guidance documents and manuals to inform the selection of  the risk management measures or best management practices that will be implemented to manage the risks posed to sources of drinking water by the storm water management works.

Learn more about how to do a significant drinking water threat assessment.

Design section

The SWM report must contain a section that details the design of the works, this means the various components and equipment that together form the SWM works.

The design section of the SWM report must include:

  • design calculations
  • storage and treatment capacity
  • description of the works
  • engineering drawings of the works, including design details
  • pre-development and post-development catchment areas, including size and associated run-off coefficient or imperviousness
  • manufacturers specifications, if any
  • calculation of hydraulic routing of major storms
  • storm water run-off analysis

Note: a storm water run-off analysis is an analysis of storm water run-off during storm events, minor and major systems, and hydrologic parameters for pre-development and post-development conditions.

When designing the works, the LEP should review the Stormwater Management Planning and Design Manual, 2003. This manual provides technical and procedural guidance for the planning, design, and review of storm water management practices.

When preparing the design section of the SWM report, the LEP should discuss and consider certain factors such as:

  • results of the site assessment
  • municipal consultation
  • the catchment area
  • activities undertaken at the site including any outdoor storage
  • the receiving environment
  • protection of drinking water sources

Based on the factors listed above, the LEP should discuss the established water quantity, water quality and water balance criteria. The explanation of how the design criteria were established should include the sources from where this information was obtained; for example, master drainage plan and any authorities such as the municipality or conservation authority that established or approved the design criteria. The explanation for how the design criteria is expected to be met should include details of design strategies that are being proposed and their expected outcomes.

If a new SWM works will be discharging directly into the natural environment or if the establishment, operation or maintenance of a new SWM works is assessed as a significant drinking water threat, the water quality criteria must include achieving at least enhanced protection.

Note: enhanced protection means the long-term average removal of 80% of suspended solids.

If water from the site is discharging to another sewage works and not into the SWM works on site, the SWM report should provide information demonstrating that the storm water receives the necessary treatment prior to discharge, for example both:

  • provide a description of the sewage works that is receiving the storm water
  • level of treatment or rationale for not treating

If the works are determined to be a significant drinking water threat, the design section of the SWM report must include specific reference to design considerations.

Learn more about technical and procedural guidance for planning and designing storm water management works by reviewing Understanding storm water management: an introduction to storm water management planning and design.

Low impact development works

Low impact development (LID) works means a storm water management facility for managing rain and other precipitation as close as possible to where the precipitation falls to mitigate the impacts of increased runoff and storm water pollution. 

Although LID works that service residential lands may be exempt from requiring an environmental permission, if they are being installed within an area that is required to obtain an approval for the storm water management works, then the LID works must be included in the site plan for SWM works. This is because they impact how the storm water management system is designed and operated.

Provincial plan areas

SWM works in the following areas may be subject to additional requirements that may impact the design of the works: 

The LEP should review these plan policies to determine if there are design criteria or restrictions that are relevant for SWM works in these areas. For example, Oak Ridges Moraine Conservation Plan prohibits SWM works with new rapid infiltration basins and new rapid infiltration columns.

Assessment of monitoring section

The assessment of monitoring section is where a LEP must document their analysis of whether monitoring of the discharge from the works is necessary. For example, a LEP may document that monitoring of the discharge is necessary to reduce the potential for an adverse effect to be caused by the effluent from the works. LEPs should consider all the information collected during the site assessment and any other information the LEP considers relevant.

For SWM works where the LEP has determined monitoring is necessary, the assessment of monitoring section must include a monitoring plan that documents:

  • the list of parameters subject to monitoring and effluent objectives
  • sampling and analysis methods, methods and protocols for sampling, analysis and recording should follow the Protocol for the sampling and analysis of industrial or municipal wastewater
  • monitoring locations
  • the frequency and duration of monitoring, for example, semi-annual samples for initial 2 years of operation of the works
  • an explanation for why the duration of monitoring is appropriate
  • corrective actions to address any exceedances of the objectives

The ministry’s local district office must be notified of any exceedances of effluent objectives immediately, in writing, within 7 calendar days and include corrective actions undertaken.

When determining the list of parameters to be monitored, if the activity is a significant drinking water threat, the LEP may consider including the parameters that are associated with a relevant issue contributing area.

Operations and maintenance manual section

A LEP must prepare and include an Operations and Maintenance (O & M) Manual in the SWM report to support the owner or operator of the SWM works in keeping the works functioning properly. Preventative maintenance can reduce costs and prevent the potential for adverse effects from poorly functioning SWM works.

The O & M Manual must include procedures, best practices and an inspection and repair program to identify corrective maintenance needs in a timely manner. Best practices must be consistent with any manufacturer’s recommendations.

Below is a list of maintenance activities that a LEP can consider when preparing this section of the SWM report:

  • methods or tests to detect when maintenance is necessary
  • cleaning to avoid obstructions of the inlet and outlet of the works and a reduction in the capacity of the works
  • maintenance and cleaning procedures to verify that sediment, debris and excessive vegetation are removed from the works to prevent the excessive build-up of:
    • sediment
    • oil/grit
    • debris or decaying vegetation
  • procedures for pond sediment clean out, dewatering and management as applicable

The O & M Manual must identify the frequency of inspections, which cannot be less than once per year and must include an inspection as soon as practical following a significant storm event. Under Ontario Regulation 137/25, a significant storm event means the occurrence of 25 millimetres or more of rain at a location in a 24-hour period. The frequency for inspections that are not specific to significant storm events should take into consideration recommendations by the manufacturer of the treatment devices and input received from others.

In addition, the LEP must provide contingency plans and procedures in the O & M Manual to be implemented during abnormal situations, for example, when a spill occurs into or from the works or the works are bypassed, including:

If the works include low impact development works (LID), LEPs should include best management practices for the operation and maintenance of LID works in the O & M Manual of the SWM report. LID works must also be operated and maintained in the same manner as other components of SWM works that are registered in the EASR, as failure to operate and maintain these LID systems could lead to a failure of the SWM works.

If the assessment of monitoring section includes a monitoring plan, the O&M Manual must contain best practices for maintaining and operating the monitoring and sampling equipment, including procedures for routine physical inspection and calibration of equipment.

If the storm water management works have been determined to be a significant drinking water threat, the LEP should consider operational procedures to reduce the threat.

Erosion and sediment control plan section

A LEP must include an erosion and sediment control plan (ESC plan) in the SWM report. The ESC plan must be implemented during the construction of the works and when construction is undertaken at the property where the works are located. The purpose of the ESC plan is to document preventative measures to be taken to reduce erosion during construction activities and to prevent excessive run-off of sediment from entering the SWM works or from being discharged off site during construction activities.

The ESC plan should be reviewed and updated, if necessary, each time construction activities are undertaken at the property where the SWM works are located.

The erosion and sediment control plan must follow the requirements in Ontario Regulation 137/25 and should include procedures for removing temporary erosion and sediment control measures and reinstating disturbed areas.

The following guidance documents may be relied upon to prepare the ESC plan:

Updates to the SWM report

After registration, if changes are made, a SWM report can be updated or an addendum with the updated information can be uploaded to accompany the SWM report.

The SWM report must be uploaded in the registry upon registration and must be kept up-to-date and made available to persons engaging in the activity.

When changes are proposed for the works or the catchment area, a LEP must update the SWM report or add an addendum before the changes are made. A LEP may update the full report or develop an addendum to the report. Any update or addendum must be completed by a LEP and dated, signed and sealed as per Ontario Regulation 137/25 and uploaded to the registry. An addendum is considered to be part of the SWM report.