Were doing a class project at the university i go to and were pouring a concrete pad. The pad is for two grain bins and it will be a 22ftx22ft. There is a gutter down spout that comes out and will run through the dead center of the pad. Thats ok just run the drain pipe through the pad. The problem is when it gets past the pad and runs on out into the parking lot where its gravel and heavy farm machinery will be traveling we need something solid so it it is not crushed. We cant just bury the pipe deeper cause were working on completely flat ground and a 30ft s40 steal pipe cost $450 dolars and we are working with a tight budget. Any ideas of a cheaper material piping?