Act does not cover groundwater pollution or complex hydrological networks; the precedent suggesting this in fact discusses interconnected larger waters, and federalism and practical enforcement concerns dictate a narrower reading of the regulated bodies of water.
Prudential abstention is not available to the court where a citizen cause of action is directly created by a statute that makes use of factors that would suggest abstention.
http://www.opn.ca6.uscourts.gov/opinions.pdf/18a0213p-06.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.