Since you are already talking to the right people (EPA) you probably already know this from the EPA web site:
The MCL for nitrates has been set at 10 ppm, and for nitrites at 1 ppm, because EPA believes, given present technology and resources, this is the lowest level to which water systems can reasonably be required to remove this contaminant should it occur in drinking water.
MCL is the legally enforceable maximum level allowed in drinking water supplies at the treatment plant - it might change by the time it gets to your tap, but they should help investigate that. What level are you measuring??
72g bowfront planted, CO2, 4x - T5HO, Eheim 2213 and 2217, 2 angels, pristella tetras, blue tetras, betta, albino bristlenose pleco, albino cories. Sword, vals, hygros, ludwigias, java moss and fern, anubias
2g Mac-quarium. Clown gravel, fluorescent plastic plants, and 2 guppies.