What can I do if my son was walking to our community fishing dock when he slipped and fell in raw sewage that was streaming into the lake?

What are you suing for? Leaving aside for the moment the issue of liability, or whether the community is responsible for any compensation, in the legal system, you can only recover compensation for actual physical or monetary injury. So, say that you son does contract some disease or parasite--you could then potentially sue for medical costs and, if it debilitates him for some relatively prolonged period, "pain and suffering." But there is no compensation for what *could* happen, so if he isn't sickened and if you don't incur medical costs, even if you sued and won, you would not get any money.

(Yes, you could sue for the cost of tests--but you'd probably spend more on the lawsuit, because you'd need a medical expert witness, who do not work cheap--then you'd get in terms of recovering the cost of the testing.)

It's also not automatic that the community would be liable: they are only liable if at fault, which means that their worker removed the cap and left it off; or someone else removed it, the community was aware it was removed (for example,, someone called in a complaint) and despite knowing of the problem and having time to correct it, failed to do so. But say that the cap was removed by children or teens as a prank and the community was not aware (or even that a complaint was just called in, but there was no time yet to fix it): in that case, they would not be liable.