For our project a underground infiltration system is planned. Now we are wondering whether a underground infiltaration system counts as a LID practice?

As a second question we are wondering whether it is possible to discharge the runoff from some parts of the project perimeters (e.g. terrace, entrance to underground parking) directly into the sewage system when we show that we can (theoreticaly) retain the whole volume on site? The runoff from the entrance to the underground parking has to be discharaged into the sewage system to be legal.