Facility owners must keep a copy of all DMRs for how long?

• A. 1 Year
• B. 2 Years
• C. 3 Years
• D. 5 Years

Answer: (C)

Discharge monitoring records are kept for a three-year window. The DMRs, along with the supporting monitoring data used to prepare them, must be retained for three years from the date the sample was collected. This ensures data is available for regulatory audits and permit compliance checks. While some state rules or internal policies might require longer retention, the standard federal requirement is three years.