Changes

==Calculate drawdown time==

==Calculate drawdown time==

[[file:Hydraulic radius.png|thumb|Three footprint areas of 9 m².<br>

[[file:Hydraulic radius.png|thumb|Two footprint areas of 9 m².<br>

From left to right x = 12 m, x = 14 m, and x = 16 m]]

Perimeter = 12 m (left) Perimeter = 20 m (right)]]

To calculate the time (''t'') to fully drain the facility:  

To calculate the time (''t'') to fully drain the facility:  

:<math>t=\frac{V_{R}A_{p}} {q'P}ln\left [ \frac{\left (d+ \frac{A_{p}}{P} \right )}{\left(\frac{A_{p}}{P}\right)}\right]</math>

:<math>t=\frac{V_{R}A_{p}} {q'P}ln\left [ \frac{\left (d+ \frac{A_{p}}{P} \right )}{\left(\frac{A_{p}}{P}\right)}\right]</math>