A few questions for everyone out there. 1. When you're installing 4" corrugated drain pipe, and you are going to be driving over it with machines or trucks, how deep do you go to make sure that it will not get crushed? Mostly I'm talking about when you have to spread dirt and run a soil conditioner to prep a yard. 2. Or does anyone prep first, then trench? 3. Perforated or solid? 4. Does anyone bother to clean the "crumbs" out of the trench before laying the pipe? If this has already been discussed ad nauseam, please refer me to the thread, otherwise I'd like to hear from as many people as possible. Thanks!