160.25(1)(b)(b) A regulatory agency shall impose a remedial action for a specific site which is reasonably related in time and scope to the substance, activity or practice which caused the enforcement standard to be attained or exceeded at the point of standards application.

160.25(2)(2) If a facility is subject to regulation under chs. 283 or 289 to 292 and if the concentration of a substance in groundwater attains or exceeds an enforcement standard at a point of standards application, the department shall require remedial actions for a specific site in accordance with rules promulgated under s. 160.21 as are necessary to achieve compliance with the enforcement standard at the point of standards application.

160.25(3)(3) If nitrates or any substance of aesthetic concern only attains or exceeds an enforcement standard, the regulatory agency is not required to impose a prohibition or close a facility if it determines that:

160.25(3)(a)(a) The enforcement standard was attained or exceeded, in whole or in part, because of high background concentrations of the substance; and

160.25(3)(b)(b) The additional concentration does not represent a public welfare concern.

160.25(5)(a)(a) A regulatory agency shall consider the existence of background concentrations of naturally occurring substances in evaluating response options to the noncompliance with an enforcement standard for that substance. A regulatory agency may not order remedial action under sub. (1) or (2) at a site where the background concentration of a substance is determined to be equal to or greater than the preventive action limit, unless the regulatory agency determines 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.

160.25(5)(b)(b) Paragraph (a) does not apply to a substance which is carcinogenic, teratogenic or mutagenic in humans.

160.25(6)(6) If the concentration of a substance in groundwater attains or exceeds an enforcement standard 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 those 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.

160.255(2)(2) Notwithstanding s. 160.19 (1), (2) and (4) (b), a regulatory agency is not required to promulgate or amend rules that define design or management criteria for private on-site wastewater treatment systems to minimize the amount of nitrate in groundwater or to maintain compliance with the preventive action limit for nitrate.

160.255(3)(3) Notwithstanding s. 160.19 (3), a regulatory agency may promulgate rules that define design or management criteria for private on-site wastewater treatment systems that permit the enforcement standard for nitrate to be attained or exceeded at the point of standards application.

160.255(4)(4) Notwithstanding s. 160.21, a regulatory agency is not required to promulgate rules that set forth responses that the agency may take, or require to be taken, when the preventive action limit or enforcement standard for nitrate is attained or exceeded at the point of standards application if the source of the nitrate is a private on-site wastewater treatment system.

160.255(5)(5) Notwithstanding ss. 160.23 and 160.25, a regulatory agency is not required to take any responses for a specific site at which the preventive action limit or enforcement standard for nitrate is attained or exceeded at the point of standards application if the source of the nitrate is a private on-site wastewater treatment system.

160.257(1)(a)(a) “Aquifer storage and recovery system” means all of the aquifer storage and recovery wells and related appurtenances that are part of a municipal water system.

160.257(1)(b)(b) “Aquifer storage and recovery well” means a well through which treated drinking water is placed underground for the purpose of storing and later recovering the water through the same well for use as drinking water.

160.257(1)(c)(c) “Municipal water system” means a community water system, as defined in s. 281.62 (1) (a), that is owned by a city, village, town, county, town sanitary district, utility district, public inland lake protection and rehabilitation district, or municipal water district, or by a privately owned water utility serving any of the foregoing.