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| *Begin the drainage time calculation by dividing the area of the practice (''A<sub>p</sub>'') by the perimeter (''P''). | | *Begin the drainage time calculation by dividing the area of the practice (''A<sub>p</sub>'') by the perimeter (''P''). |
| *To estimate the time (''t'') to fully drain the facility: | | *To estimate the time (''t'') to fully drain the facility: |
− | :<math>t=\frac{nA_{p}}{f'P}ln\left [ \frac{\left (d_{T}+ \frac{A_{p}}{P} \right )}{\left(\frac{A_{p}}{P}\right)}\right]</math> | + | :<math>t=\frac{nA_{p}}{f'x}ln\left [ \frac{\left (d_{T}+ \frac{A_{p}}{x} \right )}{\left(\frac{A_{p}}{x}\right)}\right]</math> |
| {{Plainlist|1=Where: | | {{Plainlist|1=Where: |
| *''n'' is the porosity of the filter media, | | *''n'' is the porosity of the filter media, |
| *''A<sub>p</sub>'' is the area of the practice (m<sup>2</sup>), | | *''A<sub>p</sub>'' is the area of the practice (m<sup>2</sup>), |
| *''f''' is the design infiltration rate (mm/hr), | | *''f''' is the design infiltration rate (mm/hr), |
− | *''P'' is the perimeter of the practice (m), and | + | *''x'' is the perimeter of the practice (m), and |
| *''d<sub>T</sub>'' is the total depth of the practice, including the surface ponding depth (m).}} | | *''d<sub>T</sub>'' is the total depth of the practice, including the surface ponding depth (m).}} |
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