For LT2 Schedules 1, 2 and 3, if the lab failed to analyze the sample properly, for example by failing to conduct the proper number of dilutions, a resample is required. If the result was obtained via correct analytical methods with acceptable QA/QC, no resample is required. The result should be entered into the DCTS as TNTC, or as >2419 for Colilert Quantitray.
For LT2 Schedule 4 systems, a numerical result is required to calculate mean annual E. coli concentration, for comparison to the trigger levels. Therefore, the system should resample when the result for the initial sample is TNTC. Note that for Colilert, a result of >2419 is acceptable but means that the system has exceeded the trigger levels regardless of the results for all of the other samples, if the system is conducting biweekly sampling (26 samples for the year). If this is the case, the result should be entered into the DCTS, and the system may elect to discontinue E. coli monitoring and proceed directly to Cryptosporium monitoring.