R 325.10707a Invalidation of total coliform samples.

Rule 707a. (1) A total coliform sample result may be invalidated by the department in 1 or more of the following instances: (a) A laboratory determines that analytical results are invalid due to any of the following situations: (i) In the absence of gas, any turbid culture in the mtf or p-a techniques. (ii) Confluent growth. (iii) Any sample that is inoculated 30 hours or more after it was collected. (iv) Improper sample analysis caused a total coliform positive result. If a sample is invalidated under this subdivision, the water supply shall collect another sample from the same location as the original sample within 24 hours of being notified until a valid result is obtained. The department may waive the 24-hour time limit on a case-by-case basis. (b) The department, on the basis of the results of repeat samples, determines that the total coliform positive sample result, which is from a sample tap that is approved in the sample siting plan, is isolated to that specific sample location. An invalidation under this subrule may occur only if the repeat samples from the same sampling location are total coliform positive and all other repeat samples are total coliform negative. (c) Substantial evidence suggests that a total coliform positive result is due to use of an unapproved sample location or documented gross deviation from accepted sample collection procedures that clearly could be expected to contaminate the sample itself and the result does not reflect water quality in the distribution system. The water supply shall still collect all required repeat samples from approved sites on the sample siting plan. (2) The decision to invalidate a total coliform positive sample shall be in writing and available to EPA and the public. (3) A total coliform positive sample shall not be invalidated solely because all repeat samples are total coliform negative.