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Managing Properties with Residual Contamination

Continuing Obligations to Protect Public Health and the Environment

What is Residual Contamination and What Does it Require?

Wisconsin, like most states, has changed its cleanup standards over the years to allow some residual contamination to remain after a cleanup of contaminated soil or groundwater. Residual contamination means that some contamination remained above state standards when a cleanup was completed and approved.

When the state approves a cleanup with residual contamination, it must ensure long-term protection of public health and the environment in accordance with s. 292.12(2), Wis. Stats. and other applicable laws. This is done by establishing continuing obligations in the state’s closure letter, which is the cleanup approval document. About 12 percent of properties with residual contamination also have continuing obligations that include land use controls (sometimes called institutional controls). Owners of property with land use controls must obtain state approval in order to change them.

When the state approves a cleanup that leaves residual contamination, DNR will add the property to a database on the Internet established in accordance with s. 292.12(3), Wis. Stats. This database is DNR’s GIS Registry.

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Complying with Continuing Obligations

A. Requirements for all properties with residual contamination

  1. The property owner must obtain prior approval from DNR to construct or reconstruct a water supply well, if, and when, such work is planned. The approval ensures that the well will be properly constructed to protect it from the residual contamination. Well drillers may assist property owners in completing the GIS Registry Site Well Approval Application (Form 3300-254).
  2. If those who own or occupy these properties disturb the area of residual contamination, they are responsible for proper sampling, handling and treatment or disposal of the contamination. For example, if they dig up contaminated soil they must treat or dispose of it legally. This is generally done with the assistance of a private environmental consultant.

B. Additional Requirements for Properties with Residual Contamination and Land Use Controls

A property has a land use control if:

  • the state’s closure letter, found in the GIS Registry, requires monitoring or maintenance of specified physical conditions, or requires written state approval before changing specified physical or land use conditions; or
  • the letter was written before June, 2006 and requires a deed restriction. In this case the land use control is defined in the deed restriction, which is also in the GIS Registry.

When are land use controls required?

There are three situations where land use controls are used in Wisconsin:

  1. Where the state requires installation or maintenance of:
    • a passive protective barrier, such as pavement, over a contaminated area, or
    • an active venting system to prevent volatile contaminants from entering a structure.
  2. Where a structural impediment restricted full investigation or cleanup of the contamination and the state requires more action after the impediment is removed. One example would be a requirement to complete an investigation of contaminated soil when a building is demolished that had previously restricted sampling under the foundation.
  3. Where the state imposed other limits to ensure appropriate use of the property. One example would be a requirement to complete additional cleanup if the land use changes from industrial to residential or commercial.

What are the continuing obligations for properties with land use controls?

Land use controls mean that the property owner must do the following, unless this responsibility has been contractually accepted by someone else:

  1. Periodically inspect the physical conditions specified in the closure letter, maintain them and record these maintenance activities; and
  2. Obtain prior written approval from the state before changing the physical conditions.

C. Other requirements for groundwater monitoring wells that need to be properly abandoned

Sometimes a person responsible for completing a cleanup is not able to locate and properly abandon a groundwater monitoring well. Typically this happens when vehicles such as snow plows destroy the above-ground portion of the well. This poses an environmental risk because the open pipe into the soil provides an easy route for pollutants at the surface to reach the groundwater.

Owners of properties that are included in the GIS Registry due to “lost” monitoring wells have these responsibilities.

  1. Properly abandon the groundwater monitoring well in accordance with Chapter NR 141.25, Wis. Admin. Code, as soon as the well can be located.
  2. Conduct proper sampling, handling and treatment or disposal of contaminated soil if any area of residual contamination is disturbed.
  3. Obtain prior approval from DNR to construct or reconstruct a water supply well, if such work is planned, in order to protect the well from contamination.

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Locating Continuing Obligations in Wisconsin’s GIS Registry

DNR’s GIS Registry is Wisconsin’s map-based system to find properties with continuing obligations due to residual contamination. This information may be helpful to property owners, purchasers, lenders, local government officials and others.

The GIS Registry includes portable document format (PDF) copies of certain maps, data tables and the state’s closure letter, as well as links to more information in DNR’s on-line database. A good source of information is the state’s closure letter. This letter states that no additional environmental cleanup is needed in the specified area, closes the state’s active file and includes specific information about how to manage the residual contamination.

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For more information about this page, contact:

Mark Gordon, 608.266.7278

Last Revised: Thursday December 06 2007