STORMWATER MANAGEMENT BRIEF

The purpose of a Stormwater Management Brief is to outline the detailed Stormwater Management Plan for the development. When preparing the Stormwater Management Brief, we use the Rational Method or Visual OTTHYMO software to simulate existing drainage conditions.     

Stormwater Management Brief may recommend an on-site stormwater quality control under post-development conditions for any portion of the site that exceeds the pre-development storm drainage. Stormwater Management Brief ensures that stormwater flows are controlled to pre-existing rates on site, up to the 100-year event.   Stormwater management brief may outline the design of the major system to accommodate runoff exceeding the capacity of the minor system for flows up to and including the 100-year storm or Regional storm event, whichever is larger.  

A stormwater management brief includes Pre and Post-drainage area plans showing proposed conditions and identifying the drainage pattern of the site.   Stormwater Management brief may outline the design of infiltration systems to retain stormwater and control the post-development peak flow rates up to the 100-year storm event to the pre-development peak flow rates. 

 Typical stormwater management criteria included in a Stormwater Management Brief for a proposed development are 

• Water Quality – Provide sufficient treatment measures to meet the Ministry of the Environment, Conservation and Parks, (MECP) Enhanced (80% TSS Removal) criteria and promote the at-source removal of potential contaminants. 

• Water Quantity – Provide sufficient water quantity control to maintain post-development peak flow rates up to the 100-year storm event to the existing flow rates or the target discharge rate allowed for the Site in the design of the downstream receiving systems. 

• Erosion and Sediment Control – Provide appropriate erosion and sediment control during construction/area grading to protect adjacent properties from potential siltation.  

  We prepare a Stormwater Management Brief to identify the stormwater management measures including stormwater quality and quantity controls for proposed development to support the site grading and drainage plans.
  If additional hard area footprints are proposed, it will produce additional runoff and we need to direct the additional stormwater runoff to a suitable outlet and demonstrate that there will not be any negative impact on adjacent properties.  
If the majority of the rear yard is proposed to be hardscaped, percolation will not be feasible and the stormwater flows will drain onto the adjacent properties.  
If impervious coverage and an elevated water table depth are present, a Low Impact Development (LID solution is not applicable and we need to design an engineered solution for the stormwater.

 Stormwater Management brief typically manages the Post-development storm drainage using a combination of minor (storm sewers) and major (overland) systems.    For Site Plan Applications (SPA) and building permits, municipalities may require a Stormwater Management brief to calculate the pre and post-development stormwater flow calculations and identify how on-site drainage will be managed.    

For Additional Information please contact

• Miaoyi Xue, P.Eng,
• Joo Min Park, MEng, P.Eng.
• Edgar Labuac, P.Eng
• Weiming Lin, B.Eng
• Rui Cong Xia, B.ASc(Civil)

LAND & BUILDING EXPERTS

Land Line: 416 332 1743After Hours / Text Messages: 416 727 8336

Email: landbuildex@gmail.com