Locust wood is the fastest way to dull a chainsaw blade. If you cut it at night you can see sparks cut from the wood. It will take a lot of time to clean up everything but you are doing a great job of it.
Locust will dull a chain quicker than any other wood also. Makes for a hot fire tho. Wish I was in better shape, would like to help out but my body is too broken to help myself, mush less others. Blessings be upon you and those who came to help.
As for your bridge -- the quotes are for a commercial grade repair that will hold vehicles over a certain weight -- such as a fuel/propane truck used in refilling your tanks -- a fire truck/ambulance answering an emergency call -- etc. It might be in your town's/county's/state's regulations under construction codes. I suspect, the cost is not only for the repair but also upgrading what is left of your bridge. It is really difficult to get around these regulations if you plan on renting out your property on the other side of the river because that falls under health and safety regulations. Older bridges are grandfathered as long as the structure is not compromised -- so you can replace decking/railings but do not have to replace the underlying structure (I Beams, concrete supports, etc). Do not despair just yet. Give a call to the university closest to you that awards degrees in Civil Engineering. Within the CE Department, there should be a Prof who can give you insight or quote the regs chapter and verse. Have all the information on hand -- width, length, height -- was there a culvert there originally -- what is on the other side and its use. Take pictures and gather any old pictures if you have them. Also check to see if there are professionals who are willing to do parts of the job at reduced rates or even free. Check with your neighbors -- did they lose their bridges? Is there a way to give them access to your bridge (deeded right away) -- so they could chip in on the repair of your bridge? Do they access their property over old roads and might give you a deeded right away. I have watched your video -- River Property and Cabin Dreams -- was the old RV on the side where the bridge is out? The old concrete 20x20 structure -- which side of the river is it located? I swear I could see a roof line to the left thru the trees but maybe that is off the main road. And to end this epic post -- you should be allowed to construct a "temporary" foot bridge to access your property on the other side of the river.
I think the marble piece has been there longer than this flood. The way the tree grew around it my guess would be maybe 20-30 years ago when the tree was smaller someone put it there to come back for it and now you have found it.
looks like sycamore to me...unless it's honey locust...Black Locust is hard stuff like steel when seasoned...super thick bark also...then white with a very dark heartwood