I have an easement to enter an adjacent property to access my east side, for agricultural purposes. It's one of those things that I just don't want to "wear it out." It also involves me driving around the block to get over there. It would just be much simpler to access my piece via a bridge of some sort... Then I'm not relying on someone else to get over there.Yes that is a good size structure and you will need a pretty good size crane to set it. Plus you have to have a good enough road to get the crane and pieces to it. The other issue if if there is a lot of silt in that stream, you will have to excavate that out and place rock to support the culvert. To do it right, you will probably need to dig some test holes and have a Geotech engineer look at it for foundation recommendations. My guess and this is only a guess as I haven't had any quotes for something that size in that short of distance is that you are probably looking at for 15 LF of culvert 12'x16' size with some sort of wingwalls may be 40-50k. You would also need rip-rap to prevent erosion, and you will have to pump the stream flow around it. Even if you did the work yourself and then rent a crane, I would guess you may end up with 75-100k in it depending on how much additional work is required and how much equipment you own. My price may be a little high as I am used to see culverts with highway load ratings. Although if I was going this route I would something that I could take a loaded dump truck across.
If you want to check into the bridge cost look at ADM Welding. http://admwelding.com/ THey make temporary/ permanent bridges for construction, gas lines, etc. Instead of a crane you may be able to use a large excavator to set it. You would still need abutments which can be an issue with the silt. I know they sometimes have used bridges for sale too.
I think you are looking at a pricey solution here though no matter what way you go. I have to wonder for occasional use if the cost would be worth it. If you can get a concrete truck to both sides, what is the major need to cross the stream? Not being critical just trying to understand why you are wanting a crossing there.
Thanks for the insight!