So to boil it down (no pun intended): The collectors are posing a public safety hazard by either parking illegally or running in traffic, in an area already known for fatal accidents. Second, the water itself is questionable, with several agents detected that can pose a problem for human beings.

Seems like the logical answer would be to short-term increase traffic enforcement over the area, in the mid-term remove the pipe and plug the hole to prevent use, and in the long-term improve the highway and remove the problem.