Brownfields_Content Page_Residual contamination

Residual contamination

Wisconsin, like most states, allows some residual contamination to remain after a cleanup of contaminated soil or groundwater. Residual contamination means that some contamination remained above state standards after an environmental cleanup was completed and approved.

In order to protect public health, the DNR will often place a "continuing obligation" on property where there is some environmental contamination. Continuing obligations are legal requirements that apply to a property even after the ownership changes. Continuing obligations are sometimes called "environmental land use controls" or "institutional controls."

When the state approves a cleanup with residual contamination, it ensures long-term protection of public health and the environment in accordance with a s. 292.12(2), Wis. Stats. [PDF exit DNR], and other laws. The state does this by establishing continuing obligations in the "closure" letter, which is the state's cleanup approval document. Because Wisconsin does not require removal of all contamination, it is common for approved cleanups to have continuing obligations.

Continuing obligations

Continuing obligations are certain actions for which property owners are legally responsible. They still apply after a property is sold - each new owner becomes responsible for them.

The state provides notice to the public by adding the property and related continuing obligation information to the DNR's Wisconsin Remediation and Redevelopment Database (WRRD) on the internet established in accordance with s. 292.12(3), Wis. Stats [PDF exit DNR].

The two most common continuing obligations are:

  1. proper management of contaminated soil if it is excavated; and
  2. obtaining approval for construction of water supply wells.

Other property-specific obligations may include:

  • keeping clean soil and vegetation over contaminated soil;
  • keeping a cover of pavement, soil, asphalt or an engineered cover over contaminated soil or groundwater;
  • notifying the state if a structural impediment (e.g., building) that restricted the cleanup is removed, the owner may then need to conduct additional state-approved environmental work;
  • operating and maintaining a vapor mitigation system;
  • maintaining industrial land use for sites where industrial soil standards were applied for closure; or
  • maintaining a specific use of the property, as defined in the closure letter, and notifying the state before changing that use.

Property owners with property-specific obligations must obtain the state's permission before changing the portion of the property where these requirements apply.

For more information, please read Continuing Obligations for Environmental Protection (RR-819) [PDF].

How to comply with continuing obligations

  1. If owners, right-of-way (ROW) holders or occupants disturb 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.
  2. The property owner must obtain prior approval from the DNR to construct or reconstruct a water supply well, if such work is planned. This 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 application for this approval (GIS Registry Site Well Approval Application (Form 3300-254) [PDF]).
  3. Some properties have additional requirements. There is a property-specific continuing obligation if:
    • the state's closure letter requires monitoring or maintenance of specified physical conditions, or requires written state approval before changing specified physical or land use conditions; or
    • the state's closure letter was written before June 2006 and requires a deed restriction. In this case the continuing obligation is defined in the deed restriction.

Property-specific continuing obligations due to residual contamination

  • When the state determines that the nature of the residual contamination requires installation and maintenance of:
    • a passive protective barrier such as pavement over a contaminated area; or
    • an active vapor mitigation system to prevent volatile contaminants from entering a structure.
  • When a structural impediment restricted full investigation or cleanup of the contamination and the state requires more action if the impediment is removed. One example is completing an investigation of contaminated soil after a building that had restricted sampling under the foundation is demolished.
  • When the state imposed other limits to ensure appropriate use of the property. For example, the owner may be required to complete additional cleanup if the land use changes from industrial to residential or commercial.
  • Sometimes, when a vapor mitigation system is required, a dewatering system may also be needed in order for the vapor mitigation system to be effective.

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 the conditions of the continuing obligations and record these maintenance activities.
  2. Obtain prior written approval from the state before changing the physical conditions if there is a property-specific continuing obligation. This preapproval does not apply to a general requirement to properly handle contaminated soil, which may be done under the guidance of a private environmental consultant.

Continuing obligations during a cleanup

The state may impose a continuing obligation before a cleanup is completed when the cleanup is expected to take a long time. For example, a person responsible for an unlicensed landfill may be required to construct and maintain an "engineered cap" over the landfill while continuing to monitor the groundwater quality and methane emissions. The obligation to maintain the cap is established in the state's approval of the cleanup plan, called a remedial action plan. Like other continuing obligations, this requirement also applies to new property owners.

Abandoning groundwater monitoring wells

Sometimes a person responsible for completing a cleanup is not able to locate and properly abandon a groundwater monitoring well, usually because the top has been broken off. The open pipe provides an easy route for pollutants at the surface to reach the groundwater. In addition to any other continuing obligations in the state's closure letter, these property owners must properly abandon the monitoring well in accordance with Chapter NR 141.25, Wis. Adm. Code [PDF exit DNR], as soon as the well can be located.

Finding continuing obligations at Wisconsin properties

The RR Sites Map application has a layer called "Continuing Obligations Apply" to assist users in finding properties affected by either residual contamination and/or continuing obligations. This is intended to help property owners, purchasers, lenders, local government officials and others. A user can navigate to a property and use the identify tool to find out more information about a site, including a link to the Bureau for Remediation and Redevelopment Tracking System (BRRTS) on the Web (BOTW) database. Documents available on BOTW may include the site closure letter, property maps and contaminant data. The state's closure letter would contain any continuing obligations or responsibilities for the site.