Final Verification

Once the results of wet and dry weather sampling indicate that a drain is clean, final verification sampling will begin. Final verification sampling consists of 7 grab samples taken at the outlets of 20 of the largest drains in the drainage district. These samples will be taken within a 45-day period and include at least one wet weather sample. For a drain to be declared clean, the E. coli count from six of the seven samples must be less than 3,000 colonies/100 ml, and only one sample can be as high as 4,000 colonies/100 ml.

To the knowledge of the Bear Creek team, this standard for final verification sampling have never been sought in an urban watershed. It is possible that the standard will not be achieved in every instance. Once all reasonable methods have been employed to find the sources of E. coli in a drain, bacterial source tracking methods may be employed to determine the origin of the contamination.