Article type: Municipal infrastructure capacity guide
Focus: Water capacity, sanitary capacity, storm connection capacity, and municipal engineering review
Service area: Ontario-wide
Primary services: Site Servicing Plans, Functional Servicing Reports, and Stormwater Management Reports
Before a development application is submitted, the municipality needs confidence that the proposed site can be serviced without creating unacceptable pressure on existing infrastructure.
That means more than showing a watermain, sanitary sewer, or storm connection on a drawing. The submission must explain existing conditions, calculate the proposed demand, review available downstream capacity, and identify any upgrades or controls required to support the development.
A clear capacity review is often a key part of site plan control, zoning, official plan, consent, subdivision, and building permit applications across Ontario.
What infrastructure capacity means in a development application
Infrastructure capacity is the ability of existing and proposed systems to safely serve a development under the applicable municipal criteria.
The review generally covers:
- Water demand and available pressure
- Fire flow, where required
- Sanitary wastewater flow and downstream sewer capacity
- Storm drainage and municipal storm connection capacity
- Allowable release rates
- Connection sizing and constructible routing
- Treatment plant, pumping station, or trunk infrastructure considerations
- Impacts on upstream and downstream conditions
- Required municipal or Conservation Authority approvals
The exact requirements vary by municipality, development scale, land use, and application type. A capacity conclusion should therefore be based on current municipal servicing standards, available record information, pre-consultation comments, and project-specific design criteria.
Ontario’s O. Reg. 588/17 identifies water, wastewater, and stormwater management as core municipal infrastructure asset categories. A development submission must demonstrate how the proposed project fits within the performance and servicing expectations of the local system.
Start with an existing municipal infrastructure review
The first step is to understand what exists and what information is available.
A professional review may include:
- Municipal watermain, sanitary sewer, and storm sewer mapping
- Pipe sizes, materials, inverts, slopes, and connection points
- Available record drawings and as-built information
- Existing service locations and easements
- Water pressure or hydraulic model information, where available
- Existing drainage patterns and outlet conditions
- Known flooding, surcharge, backup, or capacity concerns
- Approved developments that may already rely on the same infrastructure
- Municipal master servicing plans and applicable engineering standards
This review establishes the boundary of the capacity analysis. It also helps identify issues before the site plan, building layout, or grading design becomes too advanced to change easily.
A municipality may require the applicant to discuss the limits of the downstream analysis with engineering staff before the report is prepared. The City of Hamilton Functional Servicing Report guideline, for example, identifies the need to evaluate local and trunk infrastructure, water distribution systems, wastewater systems, stormwater facilities, grading, and required upgrades.
Confirming water capacity
Water servicing analysis should show that the proposed development can receive adequate domestic water service and, where applicable, fire protection.
The review typically includes:
Water demand calculations
The proposed use, floor area, number of units, population, fixture demand, or equivalent development assumptions are used to calculate water requirements.
Depending on the municipality and project type, the analysis may consider:
- Average day demand
- Maximum day demand
- Peak hour demand
- Domestic service demand
- Irrigation or process demands, where applicable
- Pressure zone and elevation constraints
The calculations should identify assumptions clearly and relate them to the proposed land use. A municipal engineer should be able to trace the calculation from the development plan to the recommended service size.
Fire flow review
Fire flow is reviewed where required by municipal criteria, building use, building size, or fire protection requirements.
The review may require:
- Available fire flow information
- Watermain pressure and hydraulic conditions
- Hydrant locations
- Building classification and configuration
- Required fire flow criteria
- Fire department or municipal requirements
- Watermain sizing recommendations
The final conclusion should state whether the existing system can support the proposed demand and fire flow or whether additional analysis, looping, upsizing, or municipal improvements are required.
Confirming sanitary capacity
Sanitary capacity analysis demonstrates that the proposed development can discharge wastewater without exceeding the capacity of the connecting sewer or downstream system.
A sanitary review generally includes:
- Proposed population or equivalent population
- Average and peak sanitary flow
- Infiltration and inflow allowances, where applicable
- Sanitary service connection size
- Pipe slope and capacity
- Outlet sewer capacity
- Downstream sewer capacity
- Pump station or treatment plant considerations
- Existing and approved future development demands
The analysis should not stop at the property line. Where required, it should follow the sanitary system far enough downstream to demonstrate that the proposed flows will not create a capacity deficiency.
The conclusion may identify:
- Available reserve capacity
- Percentage of capacity used by the proposed development
- Required downstream upgrades
- Service sizing recommendations
- Phasing or timing considerations
- Additional confirmation required from the municipality or system owner
A Functional Servicing Report brings this information together with the proposed servicing strategy and provides clear conclusions for municipal review.
Confirming storm connection capacity
Storm capacity has two connected parts: the site’s stormwater management strategy and the receiving municipal or private drainage system.
A complete review should address:
- Existing and proposed drainage areas
- Pre-development and post-development flows
- Minor system design
- Major system and overland flow routes
- Storage requirements
- Allowable release rates
- Outlet control sizing
- Water quality treatment
- Erosion protection
- Downstream storm sewer, channel, or watercourse capacity
- Flooding and safe drainage during major events
A Stormwater Management Report should explain how runoff will be collected, controlled, treated, and safely released.
Allowable release rates
Municipalities may restrict the amount of stormwater that can be released from a site. The allowable release rate may be based on:
- Existing conditions
- Municipal storm sewer capacity
- Pre-development discharge
- Approved watershed or drainage criteria
- Flood control requirements
- Erosion control requirements
- Conservation Authority direction
- Site-specific municipal comments
Where post-development runoff exceeds the allowable release rate, the design may require storage, an orifice, control structure, inlet restriction, flow splitter, or another practical control.
The design should also confirm that the control can be constructed, maintained, and coordinated with grading, landscaping, access, utilities, and building elevations.
Downstream capacity
A storm connection is not automatically acceptable because a municipal sewer is located at the frontage.
The review should consider whether the receiving infrastructure has adequate capacity under the applicable design conditions. It should also confirm that the proposed outlet will not create unacceptable surcharge, flooding, erosion, or impacts on adjacent properties.
Where the site drains to a watercourse, valley, wetland, or regulated area, Conservation Authority requirements may apply. These requirements can affect stormwater quality, water balance, erosion protection, outlet design, and floodplain constraints.
What belongs in the capacity submission
A municipal engineer typically expects a coordinated package, not isolated calculations.
The submission may include:
- Existing infrastructure plan
- Proposed water servicing plan
- Sanitary drainage plan
- Storm drainage and catchment plan
- Site grading plan
- Stormwater Management Report
- Functional Servicing Report
- Water demand and fire flow calculations, where required
- Sanitary flow and capacity calculations
- Stormwater storage and release calculations
- Service sizing recommendations
- Erosion and Sediment Control Plan
- Utility and easement coordination
- Clear conclusions and upgrade recommendations
The drawings should use clean layouts, coordinated design, and constructible routing. The reports should present clear calculations, practical controls, and conclusions that directly address the municipal review criteria.
How to reduce capacity-related review comments
Capacity comments often result from missing information rather than complex engineering problems.
Before submission:
- Confirm the current municipal criteria
- Review pre-consultation comments
- Obtain the best available record information
- Coordinate the site plan, grading, servicing, and SWM design
- Explain all design assumptions
- Show proposed service sizes and connection points
- Distinguish existing, proposed, and future infrastructure
- Address downstream impacts directly
- Identify any deficiencies instead of omitting them
- State what upgrades or approvals are required
- Coordinate Conservation Authority requirements where relevant
- Ensure reports and drawings are sealed where required
Municipal approvals move more efficiently when the reviewer can understand the development, follow the calculations, and confirm that the proposed infrastructure is practical to build and operate.
Reliance Engineering provides approval-focused capacity reviews
Reliance Engineering prepares Site Servicing Plans, Functional Servicing Reports, and Stormwater Management Reports for development projects across Ontario.
Our work connects existing municipal infrastructure review with water demand calculations, sanitary flow calculations, storm drainage strategy, allowable release rates, connection sizing, and downstream capacity discussion.
We provide:
- Clean layouts
- Coordinated design
- Constructible routing
- Clear calculations
- Practical controls
- Municipal experience
- Approval support
- Permit-ready drawings
Before you submit your development application, request a consultation to confirm whether your water, sanitary, and storm servicing strategy is complete.
Request a Consultation with Reliance Engineering
Professional credentials and contact information
Naresh Ochani, P.Eng. M.Eng.
Reliance Engineering Canada Limited
PEO Certificate of Authorization: 100548882
6850 Millcreek Dr, Mississauga, ON L5N 2H4
Phone: 647-385-6418
Email: [email protected]
Office hours: Monday–Friday 9:00 AM–5:00 PM; Saturday 12:00 PM–2:00 PM; Sunday Closed.
Related resources
- Site Servicing Plans
- Stormwater Management Reports
- Functional Servicing Reports
- Site Plan Approval Drawings
- Erosion and Sediment Control Plans
- Contact Reliance Engineering
