Thanks for the comments,
I am not sure of the lumber sizes...next time I go down I will take some measurements. The main beams are really BIG, perhaps 12 inches x 8 inches. The cross boards are about 10 - 12 inches wide by 2 to 3 inches tall if I recall correctly. Everything was rough-cut direct from a mill. The support beams underneath are cross ties. I will post exact sizes this week.
The bridge cost me $900 in material and my contractor built it in about 2 days. He claimed that it is sturdy enough to support his CAT D8 - not sure about that, but it is rock solid.
I had a choice of building a bridge or installing a large culvert and choose the bridge. I my opinion it is less likely to have maintenance issues and will move a LOT of water if necessary. Plus the bridge seemed to have a little more character.
