I realize that carbonate/bicarbonate is the most predominate base at any alkaline pH in most drinking water (the pronation state is not consequential). Still, I don't conflating alkalinity, pH, and carbonate because they are distinct and have different effects/meanings. In fact, pH nicely summarizes all of the relevant variables if you remember your freshman General Chemistry (and I haven't yet had enough beer to forget that!)
Anyway, I see the problem. My water report comprises two separate spreadsheets, one from "surface water" and one from "ground water." The biggest difference in the two, by far, is the mean bicarbonate concentration, which differs by a factor of four. Since it is not at all clear when they take water from the surface or the ground, there is no way to know what is coming out of the tap without measuring it. Next time I will take one of the lower numbers, and I bet Brun' Water will be spot-on for the sparge and the mash.
Thanks for the help--I'll check in again after my next brew day