− | Underdrains comprise a length of perforated [[pipe]] embedded into a layer of [[reservoir aggregate]]. They are an optional component of [[bioretention]] systems, [[stormwater planters]], [[bioswales]] and [[Stormwater Tree Trenches |stormwater tree trenches]]. Their design varies according to the drainage requirements of the installation, and the available maintenance access. [[Underdrain]] perforated pipes should be located below the frost line to reduce the threat of ice clogging. Ontario provincial standard drawings of frost penetration depth are available from the [https://www.library.mto.gov.on.ca/SydneyPLUS/TechPubs/Portal/tp/opsViews.aspx Ministry of Transportation] as OPSD 3090.100 for northern Ontario <ref> Ministry of Transportation. 2010. Foundation Frost Penetration Depths for Northern Ontario. OPSD 3090.100. Nov 2010. Rev.1. https://www.library.mto.gov.on.ca/SydneyPLUS/TechPubs/Portal/tp/opsViews.aspx </ref> and OPSD 3090.101 for southern Ontario <ref> Ministry of Transportation. 2010. Foundation Frost Penetration Depths for Southern Ontario. OPSD 3090.101. Nov 2010. Rev.1. https://www.library.mto.gov.on.ca/SydneyPLUS/TechPubs/Portal/tp/opsViews.aspx </ref>. | + | Underdrains comprise a length of perforated [[pipe]] embedded into a layer of [[reservoir aggregate]]. They are an optional component of [[bioretention]] systems, [[bioswales]] and [[Stormwater Tree Trenches |stormwater tree trenches]] and a required component of [[stormwater planters]]. Their design varies according to the drainage requirements of the installation, and the available maintenance access. [[Underdrain]] perforated pipes should be located below the frost line to reduce the threat of ice clogging. Ontario provincial standard drawings of frost penetration depth are available from the [https://www.library.mto.gov.on.ca/SydneyPLUS/TechPubs/Portal/tp/opsViews.aspx Ministry of Transportation] as OPSD 3090.100 for northern Ontario <ref> Ministry of Transportation. 2010. Foundation Frost Penetration Depths for Northern Ontario. OPSD 3090.100. Nov 2010. Rev.1. https://www.library.mto.gov.on.ca/SydneyPLUS/TechPubs/Portal/tp/opsViews.aspx </ref> and OPSD 3090.101 for southern Ontario <ref> Ministry of Transportation. 2010. Foundation Frost Penetration Depths for Southern Ontario. OPSD 3090.101. Nov 2010. Rev.1. https://www.library.mto.gov.on.ca/SydneyPLUS/TechPubs/Portal/tp/opsViews.aspx </ref>. |