Looks like I need a Culvert to drain the runoff from rain and snow between my Pole Barn and the house drive. I figured I will grade to a drain and pour a concrete slab with a funnel to a drain. Then a tube under the lane to Daylight. How could I even guess how large the tube needs to be? I'm guessing it'll be 60-80 feet long. I can figure Square footage if that would do me any good. But it looks to me that it will be just a guess whatever I do. Any ideas? Also how deep below grade will this need to be? I will have have heavy equipment crossing at times. Dump truck, Excavator, Tractors, you know all the cool Man Toys.