Actually it's 8.5 but it is a secondary MCL and it is not that uncommon to see it busted.
I get a different number for the alkalinity. At 20 °C pOH = 14.165 - 10.61 = 3.555 so OH- concentration is about 10^-3.355=.2786 and it would take that much acid to neutralize it. In ppm as CaCO3 .2786*50 = 13.9. Another 2.5 ppm of acid would be required to establish the H+ concentration at pH 4.3 giving a total of 16.4 for the 4.3 alkalinity of a solution which contains only strong base. Since my number was different I started pouring over my spreadsheet looking for inconsistencies and didn't find any but I did find another mistake so I'm happy this came up.
I said in #3 that one ought to be able to measure alkalinity at home more accurately that with a drop count kit and that got me wondering what it might take starting from scratch or starting from scratch except that one owns a pH meter. Doesn't look too bad ($50 - $102). I put some comments and links to the necessary equipment/materials at http://www.wetnewf.org/pdfs/measuring-alkalinity.html