Section 160.15 - Establishment of preventive action limits(1) The department shall establish by rule a preventive action limit for each substance for which an enforcement standard is established, as follows: (a) For any substance of public welfare concern, the preventive action limit shall be 50 percent of the concentration established as the enforcement standard.(b) For any substance of public health concern, the preventive action limit shall be 20 percent of the concentration established as the enforcement standard.(c) Notwithstanding par. (b), for any substance that has carcinogenic, mutagenic or teratogenic properties or interactive effects, the preventive action limit shall be 10 percent of the concentration established as the enforcement standard.(2) The department may establish a preventive action limit for a substance which is lower than the level specified under sub. (1) if the department concludes, to a reasonable degree of scientific certainty, based on significant technical information which is scientifically valid, that a more stringent level is necessary to protect public health or welfare from the interactive effects of the substance. In evaluating whether the evidence provides a sufficient basis for a more stringent level, the department shall consider the extent to which the evidence was developed in accordance with generally accepted analytical protocols and may consider whether the evidence was subjected to peer review, resulted from more than one study and is consistent with other credible medical or toxicological evidence.(3) Notwithstanding sub. (1), the department may establish by rule preventive action limits for indicator parameters used in monitoring waste storage, treatment or disposal facilities regulated by the department such as biochemical or chemical oxygen demand, alkalinity, hardness, conductivity and pH, if enforcement standards are not established under s. 160.07 or 160.09 for the indicator parameters. In establishing preventive action limits for indicator parameters, the department shall consider the background water quality and the potential for the indicator parameters to show that preventive action limits under sub. (1) may be exceeded.