Stormwater Management Requirements for Land Development Proposals

Quick Reference Guide for Identifying MTO SWM Requirements

This document is user oriented. MTO documentation requirements are grouped to reflect different stages in the land development planning and design process. Each grouping is subdivided into different tasks that the drainage practitioner may need to undertake. As a result, the user does not have to read the entire document; instead the drainage practitioner only needs to scan the groupings and select the task that is most appropriate. It is the drainage practitioner's responsibility to determine the applicability of the different tasks, and to execute them in an appropriate sequence. Selection of the most appropriate tasks should be based on the suitability to each particular land development proposal, and will depend on the scale and nature of each land development proposal.

Where a proposed land development will be discharging stormwater surface runoff to a receiving drainage system (including the highway drainage system) any potential impacts to the receiving drainage system or the highway drainage system must be examined. When doing so, consider the level of detail required in the analysis.

Since this document is to be used throughout the province, the tasks presented below, and subsequently outlined within the document, must be comprehensive enough to be applicable to the entire range of land development proposals submitted to MTO. Review These Points before Proceeding.



Task Summary

Organization and Sequence of Tasks buttonFigure 1: Organization and Sequence of Tasks (Document Map) provides an illustration of MTO drainage requirements as they are subsequently grouped in this document. Figure 1 also presents the tasks that are associated with each grouping.

A brief explanation of the document structure is provided below.

Table 1: Identifying Drainage Issues

Category Issue Relevance to MTO
Status of Land Development Proposal Preliminary or Detail Stormwater Management Report
  • Review of the plan to either set Draft Plan or Site Plan Conditions of Approval; or to approve and issue a permit for the proposed land development.
Status of Land Development Proposal Conformance with the approved land use designations (as per Official Plan or Secondary Plan)
  • If the land use designation must be changed to accommodate the proposed land development, it is too soon in the Municipal Approval Process for MTO to conduct a review of the SWM report.
Status of Land Development Proposal Drainage related Conditions of Approval (i.e. Draft Plan or Site Plan proposals) placed on the proposed land development
  • MTO will not approve works that will contravene another agency's Conditions of Approval.
  • Conditions of Approval imposed by MTO must be addressed or adhered to.
Status of Land Development Proposal Status with other regulatory agencies
  • MTO will not approve works that will contravene another agencies' authority or mandate (e.g. MNR, MOE, conservation authorities, Department of Fisheries and Oceans, municipalities etc.).
Status of Land Development Proposal Previous permits issued by MTO for this proponent or for this site
  • If MTO has approved a land development proposal in the past, how does the present one differ?
  • Have any changes to the MTO drainage practice occurred since the last permit or approval was granted?
Previous Drainage Studies Conformance to a previous drainage study (e.g. watershed, subwatershed or master drainage plan, etc.)
  • What criteria and other elements are relevant to this submission and are they adhered to?
  • Was the previous drainage study endorsed by MTO?
  • Are the design objectives, goals, design criteria and other elements as promoted by the study acceptable to MTO?
Previous Drainage Studies Conformance to previous highway studies (e.g. preliminary design reports)
  • MTO will not approve works that will conflict with existing or future highway works.
Need for Water Quality Treatment Regulatory water quality issues
  • Has MOE, MNR, CA or the municipality issued requirements for water quality treatment?
  • MTO will not approve a land development proposal that will contravene the authority or mandate of these agencies.
Identify Fish Habitat Issues Regulatory fish habitat requirements*
  • Has MOE, MNR, DFO or the CA issued requirements for fish habitat that are to be addressed by the proponent?
  • MTO will not approve a land development proposal that will contravene the authority or mandate of these agencies.
  • Any proposed fish habitat mitigation work must not impact the highway drainage system.

* Note: The resolution to fish habitat issues is outside the scope of this document. Refer to the MTO Regional Environmental Section, or the appropriate regulatory agency.

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Table 2: Analyzing the Receiving Drainage System

Category Issue Relevance to MTO
Components Identify the receiving drainage system
  • Have all the components of the highway drainage system been identified?
  • Have all other components of the receiving drainage system been identified?
Obtaining an Outlet Obtaining an outlet to the highway drainage system
  • Does the developer have the right to drain the site through the highway drainage system?
  • Does MTO have the right as a landowner to refuse to accept the drainage from the proposed land development?
  • Will the riparian rights of other landowners be compromised by the proposed land development?
  • MTO will not approve works that will conflict with existing or future highway works.
  • Is there an alternative outlet?
Regulating Criteria Identify criteria that will regulate the components of the receiving drainage system (including the highway drainage system)
  • MTO drainage policy and criteria must be satisfied.
  • Drainage policy and criteria of regulatory agencies must be followed.
Existing Drainage Problems Identify existing drainage problems on upstream or downstream riparian property
  • Liability assumed by MTO if the property of any upstream or downstream landowner is damaged by drainage from the proposed land development.
Existing Drainage Problems Identify existing drainage problems on the highway right-of-way
  • Erosion at bridge or culvert crossing or in roadside ditches.
  • Capacity problems in the highway storm sewer resulting in highway flooding.
  • Capacity problems at a highway bridge or culvert.
Assessing Impacts to the Receiving Drainage System Upstream or downstream flooding
  • Increased water surface elevations in the receiving drainage system.
Assessing Impacts to the Receiving Drainage System Upstream or downstream erosion problems
  • Increased stream velocities causing stream channel erosion.
Assessing Impacts to the Receiving Drainage System Highway flooding
  • Potential for surcharge of the highway storm sewer system that could cause highway flooding.
  • Exceedence of the roadside ditch capacity causing highway flooding.
Assessing Impacts to the Receiving Drainage System Highway overtopping
  • Potential for overtopping of highway at bridge or culvert.
Assessing Impacts to the Receiving Drainage System Erosion in the highway right-of-way
  • Increased flow in the roadside ditch drainage system causing erosion.

 

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Table 3: Checking the Capacity of the Highway Drainage System

Potential Impact to Highway Relevance to MTO
Capacity of highway bridge or highway culvert
  • Stormwater runoff discharging from the proposed land development causes the bridge/culvert capacity to become exceeded.
Capacity of highway surface drainage system (roadside ditch, storm sewer, or major system)
  • Stormwater runoff discharging from the proposed land development causes the capacity of the highway surface drainage system to become exceeded.
  • The design of the highway surface drainage system may limit the rate at which stormwater runoff from the proposed land development may enter into the into the highway surface drainage system.
Capacity of highway stormwater management detention facility
  • Stormwater runoff discharging from the proposed land development causes the capacity of the stormwater management detention facility to become exceeded.
  • The design of the highway stormwater management detention facility may limit the rate at which stormwater runoff from the proposed land development may enter into the into the highway stormwater management detention facility

 

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Table 4: Mitigating Impacts to the Receiving Drainage System

Mitigative Method Relevance to MTO
Stormwater management controls
  • Level of water quantity control required: over control of runoff; under control of runoff; or post to pre-development control of runoff.
  • Level of water quality control.
  • Method of control.
  • Any impacts to the highway drainage system must be mitigated.
Modifications to the receiving drainage system
  • Conformance with MTO drainage practice.
  • Conformance with the drainage practices of the regulatory agencies.
  • Any impacts to the receiving drainage system must be mitigated.
Modifications to the highway drainage system
  • Purpose of the highway right-of-way.
  • Planned shared use.
  • Drainage works by an outside party constructed within the highway right-of-way.
  • Conformance with MTO drainage practice.
  • Conformance with the drainage practices of the regulatory agencies.
  • Any impacts to the highway drainage system must be mitigated.
Erosion protection works
  • Conformance with MTO drainage practice.
  • Conformance with the drainage practices of the regulatory agencies.
  • Any impacts to the receiving drainage system (including the highway drainage system) must be mitigated.

 

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Table 5: Finalizing Construction and Operation Issues

Issue Relevance to MTO
Sediment and erosion control during construction
  • Accumulation of sediment in the highway drainage system, highway water crossing or in drainage systems downstream of the highway, caused during the construction of the proposed land development.
Operation and maintenance responsibilities, and ownership of the drainage works
  • Ownership of drainage works (e.g. legal agreements with municipality or the developer, conditions registered through site plan approval,).
  • Long term operation and maintenance costs for the drainage system associated with the proposed land development.

 

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