If a lab uses a sensitive testing method (i.e., reports an exact number of total coliforms) and the water test results are not 0 total coliforms and 0 E.coli, will an operation autofail an audit?

It depends on what the water is used for. Review the Water (for Fluming and Cleaning) and Ice section within the CanadaGAP audit checklist. Water uses highlighted in yellow in question L3A of the audit checklist will result in an autofail if at least one good (0 total coliforms, 0 E. coli) water test is not available.