Section 160.23 - Implementation of responses for specific sites; preventive action limits(1) If the concentration of a substance in groundwater attains or exceeds a preventive action limit at a point of standards application, the regulatory agency shall assess the cause of the increased concentration, taking into account background concentrations, if known, and other known or suspected contributors in the area and shall evaluate the significance of the concentration of the substance and shall implement responses for a specific site designed to: (a) Minimize the concentration of the substance in the groundwater at the point of standards application where technically and economically feasible;(b) Regain and maintain compliance with the preventive action limit, unless, in the determination of the regulatory agency, the preventive action limit is either not technically or economically feasible, in which case, it shall achieve compliance with the lowest possible concentration which is technically and economically feasible; and(c) Ensure that the enforcement standard is not attained or exceeded at the point of standards application.(2) A regulatory agency shall take responses with respect to a specific site in accordance with rules promulgated under s. 160.21.(4) The regulatory agency may not impose a prohibition on the substance or the activity or practice which uses or produces the substance unless the regulatory agency: (a) Bases its decision upon reliable test data;(b) Determines, to a reasonable certainty, by the greater weight of the credible evidence, that no other remedial action would prevent the violation of the enforcement standard at the point of standards application;(c) Establishes the basis for the boundary and duration of the prohibition; and(d) Ensures that any prohibition imposed shall be reasonably related in time and scope to maintaining compliance with the enforcement standard at the point of standards application.(6)(a) A regulatory agency shall consider the existence of the background concentration of a naturally occurring substance in evaluating response options to the noncompliance with a preventive action limit for that substance. Before a regulatory agency may order a remedial action under sub. (2) or issue a prohibition for a specific site where the background concentration of a substance is determined to be equal to or greater than the preventive action limit, the regulatory agency shall determine that the proposed remedial action will result in the protection of or substantial improvement in groundwater quality notwithstanding the background concentrations of naturally occurring substances.(b) Paragraph (a) does not apply to a substance which may be carcinogenic, teratogenic or mutagenic in humans.(7) If the concentration of a substance in groundwater attains or exceeds a preventive action limit at a point of standards application and if a waste facility subject to the waste management fund incurs costs for repairing environmental damage which arises from these occurrences which are not anticipated in the plan of operation and which poses a substantial hazard to public health or welfare, those costs may be paid as provided under s. 289.68.(8) An action under this section with respect to a specific site does not constitute a major state action under s. 1.11(2).1983 a. 410; 1989 a. 56; 1995 a. 227.