If I've said it once here, I've said it a million times...forget QC, at least til you understand it's very real limitations. QC is completely dependent on your neighbors data. If ALL were to the same standard, things would be much more representative of actual conditions, but usually, it's not. Some locales may have "good" data to compare with, however, most likely do not as a whole. Pay attention to your own PWS..and know that it's "where it should be". You'll save yourself a lot of meaningless, worthless headaches.