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mLine 51:
Line 51: − − − − *A minimum of 150 mm reservoir gravel should be laid beneath the perforated pipe. − *A minimum of 300 mm reservoir gravel should be laid over the perforated pipe. An exception would be where a small bioretention installation is being made in a stormwater planter and no compaction of the reservoir material is undertaken. Otherwise this material is required to protect the pipe from the compaction processes. − *A layer of 75 - 100 mm pea gravel may then be included on top of the reservoir gravel to provide a smoother surface and reduce tearing to the geotextile. − *A layer of geotextile is usually then used to prevent migration of fines into the underdrain/reservoir space. − A pair of small wells are recommended to inspect and periodically flush accumulated sediment from the underdrain pipe.
→Underdrains for non-exfiltrating practices
*To promote infiltration the base of the gravel reservoir and the underdrain pipe should be horizontal to optimize distribution of the water within.
*To promote infiltration the base of the gravel reservoir and the underdrain pipe should be horizontal to optimize distribution of the water within.
*Where drainage or conveyance to a downstream facility is a greater priority, the base of the reservoir and the underdrain pipe may have a gradient of up to 1-2%.
*Where drainage or conveyance to a downstream facility is a greater priority, the base of the reservoir and the underdrain pipe may have a gradient of up to 1-2%.
==Maintenance and inspection==
==Maintenance and inspection==