Changes

*Based on case studies reviewed, primary outlet trenches without groundwater interaction may provide summer temperature cooling of the warmest flows by roughly 1 to 3⁰C if the trench storage volume is equal to or greater than 5% of the runoff volume discharged from the pond during the 25 mm event.

*Based on case studies reviewed, primary outlet trenches without groundwater interaction may provide summer temperature cooling of the warmest flows by roughly 1 to 3⁰C if the trench storage volume is equal to or greater than 5% of the runoff volume discharged from the pond during the 25 mm event.

==Infiltration Systems==

===Infiltration Systems===

Infiltration systems may be used as an alternative to cooling trenches for mitigating the thermal effects of pond outflows in areas not constrained by water tables and space.  As with cooling trenches, these may be installed on the main pond outlet or a secondary outlet.  Since water tables at the pond outlet are often high, large void chambers may be more suitable than trenches as they provide greater storage per unit depth.   

Infiltration systems may be used as an alternative to cooling trenches for mitigating the thermal effects of pond outflows in areas not constrained by water tables and space.  As with cooling trenches, these may be installed on the main pond outlet or a secondary outlet.  Since water tables at the pond outlet are often high, large void chambers may be more suitable than trenches as they provide greater storage per unit depth.