least thirteen water samples per month should be submitted for microbiological testing, with the samples being drawn from "the point at which the treated water enters the distribution system". A longstanding standard at the Walkerton PUC, however, was to comply with an earlier governmental requirement of nine samples per month. Employees were instructed to collect four weekly samples from each of the three wells that served Walkerton. This meant that even in an ideal month, the PUC typically submitted one fewer sample than required by law; in practice, it was more common for eight or nine samples to be submitted than for thirteen to be. In addition, the samples that were submitted often had their points of origin mislabelled; for the sake of convenience, testing employees might draw two samples from one location but label the bottles as having come from two locations, or draw a water sample from the water supply of their own home rather than from within distribution points of the system. As a result, not all water sources were being tested adequately, and there was little regularity to which ones were tested when. Multiple Ministry of the Environment (MOE) documents dating to throughout the 1990s note that Walkerton's sampling practices were lacking. Walkerton was placed on a list of non-compliant municipalities in 1997, but removed shortly thereafter after assurances from Stan Koebel that compliance would improve. Nevertheless, a 1998 inspection verified that eight or nine samples were still the standard of collection in Walkerton. The PUC was again warned about noncompliance, and again Stan Koebel agreed to improve testing practices. MOE reports throughout the 1990s also noted that the PUC was inadequately chlorinating water that ran through the Walkerton system. Best practices dictated that chlorine residual levels after fifteen minutes of contact between the chlorine and the water be maintained at 0.5 mg/L, with that level verified through daily testing; this would indicate that the water was being adequately purified of potentially harmful microorganisms. Inspections of the Walkerton system in 1991, 1995, and 1998 showed chlorine residual levels in the Walkerton system of between 0.12 mg/L and 0.4 mg/L, with a mean level of 0.27 mg/L. According to the later Walkerton Inquiry, "Stan Koebel testified that he generally set the chlorinator to slightly less than 0.5 mg/L and that Frank Koebel would lower it to approximately 0.3 mg/L several times a month." Both men felt that