Unless you were there when they poured the concrete and know for certain what is in it, I would tread very carefully. There is no real standard for rebar and wire mesh or anything else they could have buried in it. The work I've bid out has been some drive way and sidewalk removal. I got dumpster prices, figured an average weight of 4 inch thick concrete, 50 lbs a square foot, and figured how many dumpsters I needed. The dumpsters can only be filled half full due to the weight. Took my normal rate $65 an hour, added the breaker rental and added 20% to everything. I was told I was too high. I would rather be too expensive and have some room than to bid short and try to bump somebody half way thru the job. An example of what can happen, my uncle had a decent sized construction company and was removing some docks and piers on the river for the city that had originally been put in place in the early 1900's. They were told verbally that it had nothing in it, the bid sheet read that it was clean but the bidder was responsible for confirming this for themselves. They were using a 300 series Kobelco excavator with a large hydraulic breaker for the unit, about half way thru the project they hit large power line buried in several feet of concrete and it exploded the tip of breaker, destroying it. Beware.
