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*easier access for construction, repairs or maintenance of the area.
*easier access for construction, repairs or maintenance of the area.
Where diverting flows around the facility is not possible, and its location requires that it be used as a temporary runoff detention basin, protection measures can prevent fine sediment from migrating into the subgrade. During construction, the area should only be excavated to 75 cm above the final post-construction base of the facility. This layer of native soil will retain fine particles so that they will not migrate down into the subsoils. To prevent compaction during bioretention construction, heavy equipment should not enter the footprint of the bioretention area. For more detailed guidance, see the LID Construction Guide <ref> Credit Valley Conservation. 2012. LID Construction Guide. https://cvc.ca/wp-content/uploads/2012/01/CVC-LID-Construction-Guide-Book.pdf </ref> and the Erosion and Sediment Control Guide for Urban Construction <ref> Toronto and Region Conservation Authority. 2019. Erosion and Sediment Control Guide for Urban Construction. https://sustainabletechnologies.ca/app/uploads/2020/01/ESC-Guide-for-Urban-Construction_FINAL.pdf </ref>.
Where diverting flows around the facility is not possible, and its location requires that it be used as a temporary runoff detention basin, protection measures can prevent fine sediment from migrating into the subgrade. During construction, the area should only be excavated to 75 cm above the final post-construction base of the facility. This layer of native soil will retain fine particles so that they will not migrate down into the subsoils. To prevent compaction during bioretention construction, heavy equipment should not enter the footprint of the bioretention area. For more detailed guidance, see the LID Construction Guide <ref> Credit Valley Conservation. 2012. LID Construction Guide. https://cvc.ca/wp-content/uploads/2012/01/CVC-LID-Construction-Guide-Book.pdf </ref> and the Erosion and Sediment Control Guide for Urban Construction <ref> Toronto and Region Conservation Authority. 2019. Erosion and Sediment Control Guide for Urban Construction. https://sustainabletechnologies.ca/app/uploads/2020/01/ESC-Guide-for-Urban-Construction_FINAL.pdf </ref>.
==Inspection and Maintenance==
Bioretention requires regular, routine inspection and maintenance of the landscaping as well as periodic inspection of other parts of the facility. Routine maintenance should include weeding, pruning, and mulching, similar to other landscaped areas, as well as the removal of trash, debris and sediment accumulated in pretreatment areas, inlets and outlets. Watering may be needed until plant establishment (first 2 years). <br>
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Inspections should occur twice annually (spring and late fall) and after major storm events. Inspect for vegetation density (≥ 80% coverage), damage by foot or vehicle traffic, erosion, debris and sediment accumulation, and damage to pretreatment devices.<br>
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Cleanouts and access points should be provided to allow clean-out of the underdrain and overflow pipe. Camera inspection of these pipes should be conducted every 5 years to ensure pipes are free of roots, sediment and debris. Hydraulic flushing or root removal may be needed to clear debris or obstructions.
==Performance==
==Performance==