Brownfields_Content Page_Contaminated soil and sediment

Contaminated soil and sediment

The need to clean up contaminated soil is generally determined by comparing the concentrations of contaminants in samples to the respective cleanup standard (the residual contaminant level or RCL). The RCL is a calculated value that considers the toxicity of the contaminant and the amount of exposure to the contaminant that is expected to occur.

Soil with contaminants at concentrations above the RCL must be remediated or addressed by maintaining a cap or barrier over the contaminated soil (referred to as a performance standard). § NR 720.05, Wis. Admin. Code states, "Remedial actions conducted by responsible parties to address soil contamination shall be designed and implemented to restore the contaminated soil to levels that, at a minimum, meet the residual contaminant levels or performance standards for the site or facility determined in accordance with this chapter."

Questions regarding the development or use of RCLs may be addressed to Erin Endsley. 

Soil Residual Contaminant Level Spreadsheet

Guidance: Soil Residual Contaminant Level (RCL) Spreadsheet (RR-0151) [XLS] provides RCLs developed in accordance with ch. NR 720, Wis. Admin. Code (Soil Cleanup Standards), using the results from U.S. EPA's RSL web calculator using NR 720 default target risk criteria. The RCL spreadsheet is periodically updated and includes several worksheets:

  • An overview page with a how-to for comparing site data to RCL worksheets and when to conduct cumulative risk calculations.
  • RCLs for the direct contact pathway and groundwater protection pathway.
  • Cumulative cancer risk calculations for carcinogenic polycyclic aromatic hydrocarbons (cPAHs) for both non-industrial and industrial land uses.

Contaminated Soil Quick Reference Table

Guidance: Contaminated Soil Quick Reference Table (RR-106)[PDF] is a table of RCLs for common compounds. The values in this table do not consider cumulative effects as required in § NR 720.12(1), Wis. Admin. Code, and is intended for quick reference only.

Health Information

The Wisconsin Department of Health Services (DHS) provided advice to the DNR that exclusively using cumulative cancer risk to assess carcinogenic PAHs in soil is reasonable and protective, and recommended using the U.S. Environmental Protection Agency (EPA)'s most current default values in determining RCLs: Response to the Remediation and Redevelopment (RR) Program's Request to Reassess the Residual Contaminant Levels (RCLs) for Polycyclic Aromatic Hydrocarbons (PAHs), 2016, Department of Health Services.

RCL Options

Alternative Options For RCLs

Alternate approaches for assessing the need to address soil contamination at a site may be permitted under ch. NR 720, Wis. Admin. Code. Alternative approaches that may be approved by the DNR are described below.

Questions regarding alternative options for RCLs may be addressed to Erin Endsley.

Background Concentrations

One approach is to use the background concentration of the contaminant as the RCL. The background concentration of a contaminant may be used as the standard for determining the need to conduct a cleanup when its value is greater than the RCL calculated from default toxicity and exposure values.

The DNR assigned background concentrations for numerous inorganics (e.g. lead, arsenic, barium) commonly found in soil. The background threshold values for several inorganics are listed on Guidance: Soil Residual Contaminant Level (RCL) Spreadsheet (RR-0151) [XLS].

For contaminants without an assigned background threshold value, the background concentration must be determined on a site-specific basis using a DNR-approved and appropriate method (§ NR 720.07(3), Wis. Admin. Code).

Average Soil Concentrations

Using averaged contaminant concentrations to determine whether or not the calculated RCL has been exceeded is an optional approach that is most appropriate when the contaminant is widespread, and concentrations are relatively consistent and close to its RCL. Averaging is not appropriate as the only method at sites where areas of significantly high concentrations of soil contamination are present (relative to the RCL), or to address hot spots or source areas on a property.

This alternative approach requires approval from the DNR (§ NR 720.07(2)(b), Wis. Admin. Code). Because this approach is not approved by the DNR in all situations, the DNR recommends submitting the proposed sampling plan and analysis methodology for review and approval as early in the project as possible.

Leaching Tests

An alternate approach of establishing RCLs based on the protection of groundwater is the use of leaching tests. Information on using this method to calculate site-specific RCLs is provided in Guidance on the Use of Leaching Tests for Unsaturated Contaminated Soils to Determine Groundwater Contamination Potential (RR-523).

This alternative approach requires approval from the DNR (§ NR 720.07(2)(b), Wis. Admin. Code). Because this approach is not approved by the DNR in all situations, the DNR recommends submitting the proposed sampling plan and analysis methodology for review and approval as early in the project as possible.

Soil Performance Standards

Remedial actions conducted by responsible parties to address soil contamination shall be designed and implemented to restore the contaminated soil to levels that, at a minimum, meet the residual contaminant levels or performance standards for the site or facility determined in accordance with § NR 720.05(2), Wis. Admin. Code. The following guidance documents provide information on how to establish and maintain a performance standard so that the residual contaminants in soil do not pose a threat to public health, safety or welfare or the environment.

Management

SOIL MANAGEMENT (NR 718, WIS. ADMIN. CODE)

Once excavated, contaminated soil and other solid wastes must be managed in compliance with the solid waste rules outlined in Ch. 292, Wis. Stats., and chs. NR 500 to 538, Wis. Admin. Code. Compliance with these rules typically requires contaminated material that is generated from environmental cleanup sites be transported offsite to be disposed at facilities licensed to accept that waste (operating licensed landfills). Contaminated material may be managed at other locations under certain circumstances, as described below.

1. Exempt soil management

Contaminated soil excavated as part of a response action conducted under ch. 292, Wis. Stats., and chs. NR 700 to 799, Wis. Admin. Code, may qualify to be managed as “exempt soil” if the contaminants it contains meet certain criteria. Generally, exempt soil will only be impacted by metals and/or polycyclic aromatic hydrocarbons (PAHs) at concentrations below approved background concentrations or residual contaminant levels. Exempt soil may be managed without prior department review and approval if its use does not violate the location criteria listed in ch. NR 504.04 (4), Wis. Admin. Code, which in part, prohibits placement within a floodplain, causing adverse impacts to wetlands, taking an endangered species or causing an environmental standard to be exceeded.

2. Obtaining an exemption through NR 718 to manage contaminated soil or other solid waste

The Remediation and Redevelopment (RR) Program may grant an exemption to the solid waste rules through ch. NR 718, Wis. Admin. Code, so that the material generated from response action sites may be managed somewhere besides a licensed facility. Obtaining this exemption typically requires that the generator provide the DNR a description of the material management activities that will take place, the material that will be reused, and whether any continuing obligations will be imposed at the completion of the activity to ensure that the reused material does not pose a risk to human health or the environment.

Excavated contaminated sediment may be managed as an "other solid waste." Once excavated, it may be managed within the project area or at the adjacent upland properties with an exemption through ch. NR 718, Wis. Admin. Code. Other management options must comply with the solid waste rules.

3. Low-Hazard exemptions granted by the Waste and Materials Management Program

An exemption obtained through ch. NR 718, Wis. Admin. Code cannot be used to manage contaminated soil somewhere other than a site or facility, or to manage nonsoil solid waste somewhere other than the site it was excavated from. A low-hazard exemption may be obtained through the Waste and Materials Management Program (WA) to manage waste at a location other than a licensed facility where an exemption through ch. NR 718, Wis. Admin. Code, cannot be used.

4. Importing fill soil to sites applying for the voluntary party liability exemption (VPLE)

Soil of unknown quality that is imported onto sites enrolled in the VPLE program represent a potential source of environmental contamination that must be investigated prior to attaining a certificate of completion (COC). Applicants in the VPLE program should ensure that soil and other fill materials brought onto their sites are from a known source and do not contain contaminants that would be a concern if used.

5. Contained out determinations

Hazardous waste cannot be managed with an exemption through NR 718, Wis. Admin. Code, or through a low-hazard exemption. Contaminated soil may be considered a hazardous waste if it contains a listed hazardous substance at a concentration greater than a health-based standard. A “contained-out” determination may be made on soil containing a hazardous waste to determine if concentrations warrant managing the material as a hazardous waste or as a solid (nonhazardous) waste. Contained out determinations for soil contaminated with chlorinated volatile organic compounds (VOCs) such as trichloroethene (TCE) is further detailed in “Contained-Out” Values for PCE, TCE and Vinyl Chloride (RR-969).

6. Contacts

Questions regarding contaminated soil and solid waste management at response action sites may be addressed to Paul Grittner. Questions regarding contained out determinations may be addressed to Angela Carey.

Fill Exemptions

HISTORIC FILL EXEMPTIONS

Without written approval from the DNR, solid waste disposal locations cannot be used for agricultural purposes, cannot have buildings constructed over the waste disposal area and cannot have the final cover or waste be excavated (Ch. NR 506.085, Wis. Admin. Code). Written approval provided by the DNR to take these actions are commonly referred to as “historic fill exemptions.” Applications for the exemption must provide information regarding the types of waste materials present, known and suspected environmental impacts, and activities that are proposed to take place at the facility.

Expedited applications, which require fewer details to complete, may be submitted when there is no significant environmental pollution at the site. The Remediation and Redevelopment Program (RR) will typically provide historic fill exemptions at sites where cleanup, remediation or redevelopment activities will result in the cap or waste being disturbed or built over.

Questions regarding historic fill exemptions can be addressed to Judy Fassbender.

Sediment

CONTAMINATED SEDIMENTS

A discharge of a hazardous substance that impacts sediments must be investigated and remediated as outlined in chs. NR 700 to 799, Wis. Admin. Code. This includes discharges that occurred on an upland property that migrated to sediments and discharges that occurred directly to the waterbody.

Guidance on Addressing Contaminated Sediment Sites in Wisconsin (RR-0124) outlines the recommended steps to investigate and clean up contaminated sediment; a brief overview of these approaches is available in DNR publication Guidance: Contaminated Sediment Fact Sheet (RR-0115).

Ch. NR 347, Wis. Admin. Code, requires the collection and analysis of sediment from a project site. The information collected can then be used to evaluate site-specific appropriate actions, including permit conditions, which are necessary to manage potential environmental risk. Guidance for Applying the Sediment Sampling and Analysis Requirements of Chapter NR 347, Wis. Admin. Code is designed to assist in the interpretation of the requirements of ch. NR 347, Wis. Admin. Code, to shape the initial information submittal required of any party who proposes a dredging project in the state of Wisconsin. This document is not designed to provide complete guidance for complex cases, such as those where large volumes of sediment with elevated levels of contaminants are present. Complex cases require more extensive review and input from staff with specialized expertise in wastewater, waste management and sediment management.

DNR’s Consensus Based Sediment Quality Guidelines: Recommendations for Use and Application (RR-088) is an interim guidance intended to assist in screening sediment quality data to help estimate the likelihood of toxicity. The values presented in the Consensus Based Sediment Quality Guidelines could be used as cleanup standards, with DNR approval, if they meet the provisions of chs. NR 700 to 799, Wis. Admin. Code, for the site.

Ch. NR 716, Wis. Adm. Code, requires a site investigation to evaluate known or potential impacts to environmental media (including sediment and surface water) and receptors (e.g., fish, bird, animal and plant life) as well as the potential pathways for migration of the contamination. The site-specific evaluation considers factors listed in Guidance: When should a site investigation enter surface water? (RR-0117).

Questions regarding contaminated sediment may be addressed to Carrie Webb.

ADDITIONAL RESOURCES ON CONTAMINATED SEDIMENTS

All of the following links exit the DNR website.

Other

PCBs In Soil

Sites with PCB contamination in soil may need to comply with the federal Toxic Substances Control Act (TSCA) in addition to chs. NR 700 - 799, Wis. Admin. Code. The U.S. EPA determines whether TSCA regulations apply.

Questions regarding PCB contamination may be addressed to Angela Carey.

Contamination in the Smear Zone

The smear zone is located between the historical high and low elevation table. Residual contamination within the smear zone is regulated as soil contamination - even if the material is occasionally saturated due to fluctuations of the water table.

For questions on contaminated soil, contact

For questions on contaminated sediments, contact