Changes

<h3>Drawdown time</h3>

<h3>Drawdown time</h3>

The design of infiltration facilities should be checked for [[drawdown time]]. Target drawdown time is between 48-72 hours.  

The design of infiltration facilities should be checked for [[drawdown time]]. Target drawdown time is between 48-72 hours. <br>

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

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

<math>t=\frac{nP}{qx}ln\left [ \frac{\left (d+ \frac{P}{x} \right )}{\left(\frac{P}{x}\right)}\right]</math>

<math>t=\frac{nP}{qx}ln\left [ \frac{\left (d+ \frac{P}{x} \right )}{\left(\frac{P}{x}\right)}\right]</math>