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Line 1: <p>The depth of an infiltration facility is dependent on the native soil infiltration rate, porosity (void space ratio) of the [[Reservoir gravel|gravel storage layer]] and the targeted time period to achieve complete drainage between storm events. The depth of the reservoir for designs <em>without an underdrain</em> can be calculated using the following equation:</p> <strong>d = (q × t<sub>s</sub>)/ V<sub>r</sub></strong><br><p>Where: <br> d = Stone reservoir depth (mm) <br> q = Infiltration coefficient for native soils (mm/hr) (See [[Infiltration#Planning|Infiltration]] for details on measurement and safety factors) <br> V<sub>r</sub> = Void space ratio for aggregate (typically 0.35 for clear angular stone) <br> t<sub>s</sub> = Time to drain (48 hour recommended) <br></p><p>Notes: <ul> <li>The infiltration coefficient (q) used above should incorporate a safety correction factor </li> <li>On highly permeable soils (e.g., infiltration rate of ≥ 45 mm/hr), a maximum depth of 2 m is recommended to prevent soil compaction and loss of permeability from the mass of overlying stone and stored water.</li> <li>For designs that include an underdrain, the above equation can be used to determine the maximum depth of the stone reservoir below the invert of the underdrain pipe.</li> </ul></p><p>The ratio of impervious drainage area to infiltration area should be between 5:1 and 20:1 to limit the rate of accumulation of fine sediments and clogging.</p>[[category: Infiltration]][[category: modeling]]
Infiltration: Sizing and modeling (view source)
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