40 CFR § 270.31 - Requirements for recording and reporting of monitoring results.
All permits shall specify:
(a) Requirements concerning the proper use, maintenance, and installation, when appropriate, of monitoring equipment or methods (including biological monitoring methods when appropriate);
(b) Required monitoring including type, intervals, and frequency sufficient to yield data which are representative of the monitored activity including, when appropriate, continuous monitoring;
(c) Applicable reporting requirements based upon the impact of the regulated activity and as specified in parts 264, 266 and 267. Reporting shall be no less frequent than specified in the above regulations.