While both parties await the findings of a study on what causes the low fish viability in Moon Brook, Rutland City has filed suit against the Environmental Protection Agency (EPA) over whether the EPA can regulate storm runoff entering the stream. The EPA blames runoff. The city disagrees. Under less pressing circumstances, the city would not have filed until the study was released and both parties had had a chance to digest it. However, waiting too long pushes against a six-year cutoff for the city to appeal federal rulings on the waterway. The city’s argument relies on a 2013 ruling that stormwater runoff into Accotink Creek in Fairfax County, Va., is not a pollutant. If the EPA can require Rutland to block stormwater from reaching Moon Brook, that decision would cost the city millions of dollars as well as blocking future development.