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Wisconsin's groundwater law

Wisconsin's groundwater law, Ch. 160, Wis. Stats., established the framework for a comprehensive approach to protect public health and welfare and the environment. The intent of this law is to minimize the concentration of polluting substances in groundwater through the use of numerical standards in all groundwater regulatory programs. The law applies to all groundwater in the state and is used by all state agencies in their regulatory programs that may impact groundwater.

Current standards

State groundwater standards (NR 140)

Under Ch. 160, DNR must establish state groundwater quality standards based on recommendations from the Department of Health Services (DHS). The state groundwater standards are in NR 140, Wis. Adm. Code.

NR 140 is updated periodically to include standards for new substances or revisions as needed for existing standards. Setting new groundwater standards is a continual process based on a priority list of substances established by DNR and other state agencies.

For each substance, two numerical standards are set - an Enforcement Standard (ES) and a Preventive Action Limit (PAL).

Enforcement Standard (ES)

Chapter NR 140 groundwater quality ES recommendations are developed by DHS based on existing "federal numbers," such as public drinking water maximum contaminant levels (MCLs), or through a statutorily prescribed process that incorporates drinking water exposure assumptions, established health based "acceptable daily intake" levels and, for carcinogenic substances, a calculated "one in a million" cancer risk level.

If an established groundwater ES is exceeded at a regulated facility, practice or activity, a response action is required to achieve compliance with the ES. Chapter NR 140 response actions include operational changes, design or construction modifications and, potentially, prohibition or closure of a facility, practice or activity.

Preventive Action Limit (PAL)

A ch. NR 140 PAL, in accordance with ch. 160, Wis. Stats., is set at a percentage of an established ES concentration. PAL groundwater quality standards are used as design standards for facilities, practices and activities regulated by the state that can affect groundwater. They are also the level at which a regulatory agency may investigate the source of a substance in groundwater and require response actions to minimize the substance concentration and prevent exceedance of an ES.

Current groundwater standards

Setting new standards

Setting new groundwater standards (updating NR 140)

Wisconsin's groundwater standard setting process is subject to the requirements of the state rulemaking process. The main steps in setting standards that are unique to promulgation of groundwater quality standards are as follows.

  1. A list of substances which are detected in groundwater or have a reasonable probability of entering groundwater is generated in one of two ways:
    1. each regulatory agency submits to the DNR a list of those substances which are related to facilities, activities and practices within its authority to regulate and which are detected in or have a reasonable probability of entering the groundwater resources of the state; or
    2. any person may petition a regulatory agency to add or delete a substance from the list.
  2. DNR and DHS determine which substances on the priority list are of public health concern and which are of public welfare concern. DHS develops recommendations for health-related substances. DNR develops proposed standards for substances which are not health-related but cause aesthetic or other effects. Background documents for all substances are prepared for rulemaking.
  3. The DNR proposes revisions to Chapter NR 140, Wis. Adm. Code, and seeks hearing authorization from the Natural Resources Board.
  4. Public hearings are held by DNR to seek public comments on proposed standards.
  5. DNR makes a final determination on proposed standards based on DHS recommendations, new information from state and federal sources and public comments.

Amendments to groundwater standards

Learn more about efforts to update NR 140 groundwater quality standards.

Applying standards

Applying groundwater standards

Chapter NR 140 groundwater quality standards are used as design standards for facilities, practices and activities regulated by the state that can affect groundwater. These activities include: contamination site cleanup, authorized discharges of treated liquid and solid waste, use of approved agricultural chemicals, regulation of solid waste landfills and beneficial use of industrial byproducts. NR 140 groundwater quality standards also apply to bottled drinking water in Wisconsin, and they are used to determine eligibility for the private water supply Well Compensation Grant Program, administered under ch. NR 123, Wis. Adm. Code.

Regulatory programs

Once rules are adopted, regulatory agencies must review their existing rules regulating facilities, activities and practices which may be sources of substances that have new standards. If existing rules are inadequate to prevent standards from being exceeded, the regulations governing these facilities, activities and practices must be revised (s. 160.19, Wis. Stats.). If standards have been exceeded, agencies must require site-specific actions and must review the adequacy of their rules (s. 160.21-26, Wis. Stats.). This assures that all groundwater gets the same level of protection regardless of which agency is responsible for regulating the activity.

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