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→Cooling Trenches
[[File:Cooling Trenches.jpg|450px|thumb|Close up view of a 'cooling trench'. These trenches work by outflows of warm pond water coming into contact with cooler [[stone]]
[[File:Cooling Trenches.jpg|450px|thumb|Close up view of a 'cooling trench'. These trenches work by outflows of warm pond water coming into contact with cooler [[stone]]
media (along the top of the trench) and side walls, which in turn promotes heat transfer between the two, resulting in a reduction in outflow water temperatures beign discharged to a receiving waterbody (i.e., stream) (Van Seters and Dougherty, 2019).<ref> Van Seters, T., and Dougherty J. 2019. Data Synthesis and Design Considerations for Stormwater Thermal Mitigation Measures. Sustainable Technologies Evaluation Program. Ontario. https://sustainabletechnologies.ca/app/uploads/2019/04/Thermal-Synthesis-Final.pdf</ref>. Photo Source: [[Acknowledgements: Azimuth Environmental]]]]
media (along the top of the trench) and side walls, which in turn promotes heat transfer between the two, resulting in a reduction in outflow water temperatures beign discharged to a receiving waterbody (i.e., stream) (Van Seters and Dougherty, 2019).<ref> Van Seters, T., and Dougherty J. 2019. Data Synthesis and Design Considerations for Stormwater Thermal Mitigation Measures. Sustainable Technologies Evaluation Program. Ontario. https://sustainabletechnologies.ca/app/uploads/2019/04/Thermal-Synthesis-Final.pdf</ref>. Photo Source: [[Acknowledgements|Azimuth Environmental]]]]
'''Design Considerations'''
'''Design Considerations'''
*Secondary pond outlets that drain water from 0.5 m below the permanent pool elevation to cooling trenches can help to reduce or eliminate the long duration and very warm interevent flows.
*Secondary pond outlets that drain water from 0.5 m below the permanent pool elevation to cooling trenches can help to reduce or eliminate the long duration and very warm interevent flows.
*Trenches may incorporate an infiltration function to help further reduce thermal loads if native soils and groundwater levels are suitable.
*Trenches may incorporate an infiltration function to help further reduce thermal loads if native soils and groundwater levels are suitable.
[[File:Cooling Trenches excavated.jpg|450px|thumb|Another image of a cooling trench being built with two parallel trenches that contain [[Choker layer|pea gravel]] and two sets of 200 mm perforated [[pipes]] wrapped in filter fabric. (Van Seters and Graham, 2013<ref> Van Seters, T., Graham, C. 2013. Evaluation of an Innovative Technique for Augmenting Stream Baseflows and Mitigating the Thermal Impacts of Stormwater Ponds. Sustainable Technologies Evaluation Program, Toronto and Region Conservation Authority, Toronto, Ontario. https://sustainabletechnologies.ca/app/uploads/2013/08/Cooling-trench-final-2013a.pdf</ref>. Photo Source: [[Acknowledgements|Doug McGill]]]]
'''Expected Performance'''
'''Expected Performance'''
*Performance of primary outlet cooling trenches is highly variable due to differences in cooling trench sizing, design, initial water temperature and degree of groundwater interaction
*Performance of primary outlet cooling trenches is highly variable due to differences in cooling trench sizing, design, initial water temperature and degree of groundwater interaction