Mapping is a great tool for better understanding a system and synthesizing research. I wanted to better understand the water system in Pittsburgh to know where we get our water, where the sewage goes, where contaminates are coming from, and how it's getting into our water supply.
Though this process I've discovered a whole category of sewage called nonpoint. Nonpoint contaminates are one where the origin is ambiguous, hard to pinpoint or naturally accruing. The contaminates could be from old mines, agricultural over-spray, or whatever the rain water washes off the street. They will be there and are hard to remove from the system as we don't know where they are originating from, but are also not a big problem as levels are low and do not cause large fluctuations in the quantity of contaminates detected.
The large list of chemicals may appear to be scare but it is important to note that sewage is 99% water and non of these chemicals are at dangerous levels. However, some are getting close and are constantly being monitored by the EPA.
This does raise a few important issues. Although Pittsburgh's water supply is clean, what is done in Pittsburgh heavy influences the communities down stream. Being at the origin of the Ohio River, Pittsburgh has a heavy influence on the heath and well-being of over three million people. CSO dumping sewage into the river during storms will heavy tax the water filtration plants down stream that source from the Ohio River. It seams now that the actions in Pittsburgh have a much larger influence then I thought before.
Side note: I wonder how much of this stuff makes it to my tap?