Effluent Monitoring

Besides effluent discharge limits, permits usually include effluent monitoring requirements. Fundamentally, permitting authorities require monitoring of pollutants limited in the permit so that the permittee can demonstrate compliance with its limits. If the monitoring demonstrates noncompliance, then the data can be used as the basis for an enforcement action.

The permittee must retain records for all monitoring information (which includes maintenance and calibration records, strip charts, reports, etc.) for at least 3 years from the date of sampling (sewage sludge data must be maintained for 5 years).

Monitoring may also serve to provide data about treatment efficiency and to characterize effluents for permit reissuance. Instream monitoring (above and below the outfall) may also be useful to assess impacts of the discharge, but is infrequently required.