Don't be afeared of steel...
Here's a bridge I built over a finger of my pond. It's 52 feet long...and I spent about $100 on it. All I had to buy was the cable, clamps and that angle iron for the hand rail. Just wish they would part with some more of the stuff.
This is actually modular warehouse shelving. Each section spans 13 feet, and it comes in widths from about 30" to 48". My buddy tells me that when Wal Mart moves or upgrades they basically give this stuff away as well. I got it from my employer, but ever since, when I'm at auctions, I look pretty close for the stuff.
Could've put a wood deck on it, easy enough, but got quarry screen for nothing. I've painte it since, so it looks better. Buried the legs in the ground about 30" with sakrete. Prolly didn't need the sakrete...it'll stand longer than I do.
[img]http://images.snapfish.com/3454%3B%3A8%3B23232%7Ffp335%3Enu%3D323%3B%3E756%3E465%3EWSNRCG%3D3233327%3B45569nu0mrj[/img]
In a lifetime, the average driver will honk 15,250 times. My wife figures I'm due to die any day now...