How prevalent is organized crime still in construction within the U.S?

Great topic. They are still there and are always plotting some comeback but RICO has kept them in check. I can't speak to development but when I was in PE, I had a mob situation at a portco that I had to deal with at a company in NJ.
 

This firm had a trash vendor that was massively overcharging them. This discrepancy was brought up to the vendor and they fixed their accounting and provided a refund. However,  the overcharging problem came back after a couple months. At this point, we started looking for a new vendor. Word got out to the existing trash company and they had a guy follow an hourly worker home and threaten him. This poor hourly dude had no decision making power and the portco just ended up giving him a different role and hired more security at their facility. We eventually changed vendors and nothing dangerous materialized. 

There were a couple key aspects of this situation that helped the company avoid conflict. Firstly, it was sufficiently large to the point that the vendor didn't know who target. Secondly, the company had enough resources and was able to hire additional security to ensure the safety of their employees. These aspects combined deterred the vendor from going after higher level people and you could infer that the company had more power than some shitty trash business trying to strong arm a sizable company. If it was a smaller operation, I think the vendor could have been a much bigger problem.