What storm drain?
It just runs across the paddock and into a trench carved out along the boundary, called a swale I think, and it's my job to dig out the weeds and allow drainage.
You don't (or didn't) need a plumber unless you were connecting to mains water and a lot of mud brick builders did their own legal plumbing providing it was from a water tank.
This is my pet peeve with council telling me what I can and cannot do, bit like state gov with their business advisory service, a public servant telling me how to be a success,Ha.