(a) Any discharge authorized by a SPDES permit shall be subject to such requirements for monitoring the intake, discharge, waters of the State or other source or sink as may be reasonably required by the department to determine compliance with effluent limitations and water quality standards that are or may be effected by the discharge; including the installation, use, and maintenance of monitoring equipment or methods (including, where appropriate, biological monitoring methods), and if imposed shall be included as provisions of the SPDES permit.

(b) Any discharge authorized by a SPDES permit that is not a minor project (as defined in Part 621 of this Title); which the regional administrator requests, in writing, be monitored; which contains toxic pollutants for which effluent limitations have been established by the administrator pursuant to section 307(a) of the act and 40 CFR parts 129 and 405-471 inclusive (see section 750-1.25 of this Subpart); or to which the department applies this section; shall, upon inclusion of such requirements in the SPDES permit, be monitored by the permittee for at least the following:

(c) Each effluent flow or pollutant required to be monitored pursuant to subdivision (b) of this section shall be monitored at intervals to be determined by the department as sufficiently frequent to yield data that reasonably characterizes the nature of the discharge of the monitored flow or pollutant. Variable effluent flows and pollutant levels may be required to be monitored at more frequent intervals than relatively constant effluent flows and pollutant levels, which may be required to be monitored at less frequent intervals.

(d) Each permittee subject to the requirements of subdivision (b) of this section shall submit reports to the department summarizing the results of the monitoring required under subdivision (b) of this section at the end of each month, unless otherwise specified by the department. For permittees discharging to surface waters, these reports shall be submitted, at a minimum, annually.