Site Modeler help, creating a ditch

Hi all,

I am trying to create a ditch by using site modeler along the south and east side of  the parking lot.

Here is the info:

1) parking lot has -1% slope from northwest to southeast corner, hence water flows from northwest to southeast and i need to create ditchs along the south and east boundary.

2) currently i am have to create an alignment just along thoes the east ans south boundary, import geometry from my parking lot along the horizontal alignment as a vertical, then create a corridor just with a ditch on one side and targeting the existing surface. Also i have to sombine these 2 surfaces after.

I am wondering if there is a way to create it just by using site modeler without using roadway designer? ( i knew in pad design, there is a complex slope option, but it will only generate a drain ditch when in cut, i need in both cut and fill situation)

Thank you in advance!