(1) Unless otherwise indicated in this subpart or in Appendix A, the general standards outlined below are applicable to all surface waters of the state at all times.
(2) They apply specifically with regard to substances attributed to discharges, nonpoint sources, or instream activities as opposed to natural phenomena.
(b) Waters may, on occasion, have natural background levels of certain substances outside the limits established by these criteria, in which case these criteria do not apply.