Probably a third hand story at this point but what I was told from someone that worked there for a long time is that at one point, the winch that raised the cesium source got jammed in the up position. Obviously this was a problem because no one could approach it. They brought in a marksman who somehow shot the winch or rope or whatever which dropped the source back into it's pig.

I will say that this experiment only exposed the plot of land to radiation, not contaminated it. Unless the source was broken or eroded, there would be no detectable radiation on that land once the source is sealed up.

That's not to say BNL hasn't contaminated the land, it is a Superfund site. They do a lot of medical experiments there (they invented the PET scan) but medical waste hasn't always been disposed of properly like now. They had "glass holes", a hole in the ground where you'd chuck in your contaminated labware.