Missouri wastewater treatment facilities must possess a valid operating permit to discharges to waters of the state. The permit defines conditions and limitations specific for that facility under the Missouri Clean Water Law and the National Pollutant Discharge Elimination System. Department staff members sample discharges defined in the facility’s operating permit. Samples may be collected as 24-hour timed-interval composite samples using an automatic wastewater sampler, or a one-time grab sample. Field measurements, such as pH and temperature, are also documented. Samples are collected and returned to the department's Environmental Services Program laboratory to be analyzed for water quality parameters included in the facility's permit.
Data from a sampling event may be used for:
- Quality assurance or quality control purposes
- Check the accuracy of the facility’s monthly discharge monitoring reports
- Support determinations of compliance with the conditions established in the Missouri Clean Water law, state regulations, operating permit or limitations contained in an administrative order or court order
- Support other findings for the purpose of enforcement actions