Friday, 3 August 2012

Urban Water and Your Property Part Two: Drainage

Last week we shared a blog post written by former manager of Toronto Water and current EAC volunteer, Mike Price, on urban water and your property that focused on incoming water. Part two of the post, also contributed by Mike, examines considerations for urban homeowners around water that leaves your property, also known as drainage. 

The water leaving a typical urban property leaves via surface flow or underground pipes. The surface flow during a rainfall event will take with it all surface pollutants used on, or deposited on, the surface. The underground pipes can be: 

    -  Sanitary sewer containing sanitary waste and maybe weeping tile water depending on the municipality
   -  Storm sewer containing rain water and maybe weeping tile wate
   -  Combined sewer where all liquids are put into one pipe

Current Issues regarding municipal waste water treatment
·    -  Surface waters, lakes, rivers and oceans, are becoming contaminated from human activities, resulting in polluted recreational waters, damage to fish and shellfish, and changes in the whole ecosystem. 
·     - Storm sewer flows are not treated but empty into the nearest waterway
·     - Sanitary sewage takes huge amounts of power to pump and treat before release into the environment
·     - Combined sewers are prone to surcharging and overflow during heavy rainstorms causing surface water pollution
·      - Sanitary sewers and especially combined sewers are prone to backing up and causing basement flooding in heavy rainstorms
·      -  Previous drainage design criteria often required roof drains and weeping tiles be connected to the sewers (thus adding clean water to be expensively treated at sewage treatment plants)

Current solutions for Urban drainage dischargers
     To assist with the big picture - sanitary waste solution:

 -   Reduce flows to municipal sanitary sewer by installing water efficient fixtures
 -   Reduce flows to municipal sewers by disconnecting roof downspouts from the sewer
-    Reduce flows to municipal sewers by installing sump pump for weeping tile water and discharge the clean water to the ground for irrigation
 -   Consider ‘grey-water’ reuse such as flushing toilets
 -   Consider a sewer backflow preventer to mitigate against basement flooding

    To assist in implementing storm water management techniques:

 - Rainwater harvesting (methods listed earlier)
 - Eco-gardening
             - Minimize need for water
             - Reduce lawn area  
             - Move to drought tolerant lawn grass
             - Leave grass clippings on the lawn
             - Use ‘push’ lawnmower to reduce pollution
             - Eliminate pesticides and fertilizers on lawns
             - Use shade trees
             - Xeriscaping garden designs
             - Mulch gardens to retain water
             - Discharge roof water via ‘chains’ to garden
             - Consider natural ponds to capture rainwater
             - Decrease paved areas, increase porous areas
   - Don’t wash the car in the driveway
  - Don’t dump any soapy water, waste oil or chemicals down the storm drain (it goes straight  to the nearest creek!)
- Pick up animal feces 


  1. You can also try to store and manage waste materials properly, so that they do not flow into storm sewers during a storm. This would include removing litter and pet waste and covering dirt piles. Make sure your garbage is secured and has a dry place to be stored. Also, landscape your property with plants that are native to where you are living.

    Monica Barnes

  2. We all know how climate change become worser today, which is the cost of unbalance temperature and responsible for every dying plant every day, that's why it is more advisable to use xeriscaping.