Stormwater Management Report
Stormwater Management Reports for Ontario Development Projects
We prepare comprehensive, P.Eng.-stamped stormwater management reports for Site Plan Approvals, plans of subdivision, and commercial redevelopment — satisfying MOE guidelines, Conservation Authority requirements, and municipal engineering standards across Ontario.
Know What You Need
Stormwater Brief vs. Stormwater Management Report
Not every project requires the same level of stormwater analysis. The City or Conservation Authority will specify which document is required based on your project's size, location, and drainage impact. Understanding the difference upfront prevents costly revisions.
Stormwater Brief
A simplified analysis for smaller or lower-risk projects where the municipality accepts a less detailed submission.
Typically required when:
- Minor additions or alterations with limited new impervious area
- Small residential infill projects outside regulated areas
- Projects where drainage patterns are largely unchanged
- Municipalities that accept a brief for projects below a defined threshold
Stormwater Management Report
A comprehensive engineering study required for larger or higher-risk projects with significant drainage impacts.
Typically required when:
- Site Plan Approval applications for commercial, industrial, or multi-residential development
- Plans of subdivision creating new lots and roads
- Projects within or adjacent to Conservation Authority regulated areas
- Developments that increase impervious area beyond municipal thresholds
- Sites requiring stormwater management facilities such as detention ponds or underground storage
Regulatory Framework
Engineering Standards & Regulatory Bodies We Address
Ontario MOE Stormwater Management Planning and Design Manual
The primary provincial guideline governing stormwater quantity control (2-, 5-, 10-, 100-year storm events) and water quality treatment levels (Basic, Normal, Enhanced Level 1 and 2) for Ontario development projects.
Conservation Authority Requirements
Conservation Halton, TRCA, Credit Valley Conservation, GRCA, and other Conservation Authorities require stormwater reports for sites within regulated areas. We coordinate CA permit applications concurrently with municipal submissions.
Municipal Engineering Design Standards
Each municipality — Burlington, Oakville, Hamilton, Mississauga, Brampton, and others — has its own engineering design standards specifying storm sewer sizing, overland flow routes, and SWM facility design criteria.
Halton Region & Other Upper-Tier Municipalities
Regional municipalities impose additional stormwater requirements for developments requiring Regional approval or servicing allocation, including water quality and quantity targets beyond base municipal standards.
Process
Our Stormwater Report Process
Pre-Submission Consultation
We review your site, proposed development, and applicable municipal and Conservation Authority requirements to confirm the scope of stormwater analysis required before any design work begins.
Existing Conditions Hydrology
We delineate pre-development drainage areas, calculate existing runoff rates and volumes for all design storm events, and establish the baseline your post-development design must match or improve upon.
Proposed Drainage Design
We design the post-development drainage system — storm sewers, catchbasins, overland flow routes, and SWM facilities — to control peak flows and volumes to pre-development levels.
Water Quality Analysis
We size and design stormwater quality controls (oil-grit separators, bioretention, enhanced filters, or detention facilities) to achieve the required MOE treatment level for your site.
Report Preparation & Stamping
We compile the full stormwater management report — including all calculations, drainage area maps, facility design, and supporting drawings — and stamp it with a P.Eng. seal for submission.
Municipal & CA Submission
We submit the report package to the City and Conservation Authority, respond to technical comments, and revise as needed to achieve approval and keep your project on schedule.
Deliverables
What We Deliver
Stormwater Management Report
Stamped P.Eng. report documenting pre- and post-development hydrology, drainage design, SWM facility sizing, and water quality analysis in accordance with MOE guidelines and municipal standards.
Drainage Area Maps
Pre- and post-development drainage area delineations showing catchment boundaries, flow paths, and areas used in hydrological calculations.
Hydrological Calculations
Rational method or SCS/SWMHYMO modelling for 2-, 5-, 10-, and 100-year storm events demonstrating post-development flows do not exceed pre-development conditions.
SWM Facility Design
Detailed design of detention ponds, underground storage chambers, bioretention cells, oil-grit separators, or other facilities required to achieve quantity and quality targets.
Erosion & Sediment Control Plan
Construction-phase erosion and sediment control measures to prevent sediment migration to watercourses, as required by the Conservation Authority and municipality.
Municipal Submission Package
Complete stamped report and drawing package formatted to the applicable municipal engineering standards and submitted through the City's permit or Site Plan portal.
FAQ
Frequently Asked Questions
When is a full stormwater management report required instead of a brief?
A full stormwater management report is typically required for Site Plan Approval applications, plans of subdivision, commercial or industrial development, and any project that significantly increases impervious area or is located within a Conservation Authority regulated area. Smaller residential projects may qualify for a stormwater brief — we assess your project scope and confirm which document the City and Conservation Authority will accept.
What storm events does a stormwater management report need to address in Ontario?
Ontario's MOE Stormwater Management Planning and Design Manual requires analysis of the 2-year, 5-year, 10-year, and 100-year storm events for quantity control. The specific return periods required depend on the receiving system — minor system (storm sewers) and major system (overland flow) are analysed separately. Water quality treatment is assessed using the 25mm design storm for Enhanced Level 1 protection.
What water quality treatment level is required for my project?
The required treatment level depends on the sensitivity of the receiving watercourse and the municipality's standards. Enhanced Level 1 (80% total suspended solids removal) is the most common requirement for development adjacent to sensitive watercourses. Basic or Normal protection may be acceptable for sites discharging to municipal storm sewers with no direct watercourse connection. We confirm the applicable level during pre-submission consultation.
Do I need a Conservation Authority permit in addition to a municipal approval?
If your site is within a Conservation Authority's regulated area — typically within 30 metres of a watercourse, wetland, or floodplain — a CA permit is required in addition to the municipal Site Plan Approval or building permit. We coordinate both submissions concurrently to minimise delays. Conservation Authorities in Ontario include Conservation Halton, TRCA, Credit Valley Conservation, GRCA, and others depending on your location.
How long does stormwater management report review take?
Review timelines vary by municipality and Conservation Authority. As part of a Site Plan Approval, stormwater review typically takes several months depending on project complexity, comment cycles, and the municipality's current workload. We prepare thorough, submission-ready reports to minimise back-and-forth with reviewers and keep your project on schedule.
Can you prepare stormwater reports for projects across Ontario?
Yes. We prepare stormwater management reports for projects across the Greater Golden Horseshoe and broader Ontario, including Burlington, Oakville, Hamilton, Mississauga, Brampton, Milton, Halton Hills, and surrounding municipalities. We are familiar with the engineering standards and Conservation Authority requirements applicable to each jurisdiction.
Need a Stormwater Management Report?
Contact our team for a free consultation on your project's stormwater requirements.
Contact Us
Start Your Stormwater Management Report
Tell us about your project and site. We'll confirm the scope of stormwater analysis required and provide a clear timeline for your report.