Brownfields_Content Page_Contaminated soil and sediment

Contaminated soil and sediment

The information on this page relates to the characterization, assessment and management of contaminated soil, sediment and other solid waste on sites or facilities being investigated or cleaned up in compliance with the requirements of chs. NR 700 to 799, Wis. Admin. Code. Please contact Remediation and Redevelopment (RR) Program staff for situations not addressed on this page and for site-specific technical questions.

Soil RCLs

Soil residual contaminant levels

The following guidance documents are available to help environmental professionals calculate residual contaminant levels (RCLs) in accordance with ch. NR 720, Wis. Admin. Code [exit DNR] (soil cleanup standards). The RR Program's spreadsheet will be periodically updated so that the RCLs will be the results from EPA's RSL web-calculator with NR 720 default parameters.

1. Instructions on using and interpreting results from the U.S. EPA's regional screening level (RSL) web-calculator and the RR Program's spreadsheet of RCLs.

2. Two versions of the RR Program's spreadsheet of RCLs with soil levels protective of the direct contact pathway and groundwater quality.

The macro-enabled version of the RCL spreadsheet has five separate worksheets while the no-macro version has four. The no macro version lacks a "DC Summary" worksheet. The use of either one will provide the same data evaluation results at the bottom of the DC RCL worksheets. The spreadsheet's overview page provides a short "how-to" and "what-to-do" with the evaluations from the RCL worksheets when preparing data summary tables.

Notes in ch. NR 720, Wis. Admin. Code, refer to "table(s) of residual contaminant levels"; these tables are worksheets in the RCL spreadsheet above. The table in the note under ch. NR 720.10, Wis. Admin. Code (RCLs based on protection of groundwater) is the "GW_RCLs" worksheet. The table in the note under ch. NR 720.12, Wis. Admin. Code (RCLs based on protection from direct contact) is either the "Non-Industrial_DC_RCLs" or the "Industrial_DC_RCLs" worksheet.

3. Modified version of the RR Program's spreadsheet of RCLs used to assess seven carcinogenic polycyclic aromatic hydrocarbons (cPAHs) on only a cumulative basis.

Using this modified spreadsheet is considered a risk assessment. Per ch. NR 722.11 (1), Wis. Admin. Code, a responsible party may request to use this modified spreadsheet to determine alternate environmental standards when attaining compliance with the RCLs is not practicable. A request to use the modified spreadsheet can be made by submitting a "request for technical assistance" using Form 4400-237 or by incorporating the request into another fee-based submittal. The DNR will review the request and either approve, modify or disapprove the planned use of the modified spreadsheet.

4. A table of the most common compounds that is intended to be a quick reference only. Note: This table does not take into account cumulative effects as required in Ch. NR 720.12(1), Wis. Admin. Code.

5. Use of leaching tests to calculate residual contaminant levels based on the protection of groundwater.

Ch. NR 720.10 (2) (b), Wis. Admin. Code,  allows leaching tests to be used as one method to calculate RCLs based on the protection of groundwater. 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). [PDF]

6. Contact information

  • Questions regarding the modified PAH calculator (item 3) can be addressed to Paul Grittner.
  • Other questions regarding the calculation or use of RCLs may be addressed to Erin Endsley.
Background information

Alternative assessments

Soil assessments

The need to remediate soil contamination is generally determined by comparing contaminant concentrations in a soil sample to a substance-specific standard (the residual contaminant level or RCL). The RCL is calculated based from variables representing 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). Alternate methods are presented in ch. NR 720, Wis. Admin. Code, for assessing the need to address soil contamination at a site: using the background concentration of the contaminant as the RCL and averaging the contaminant concentrations in multiple soil samples for comparison to the RCL.

1. Calculating the RCL based on the background concentration for the compound [Ch. NR 720.07 (3), Wis. Admin. Code].

The DNR does not generally require responsible parties to reduce contaminant concentrations at their sites below background. The background concentration of a substance may, therefore, be used as the standard for determining the need to conduct a cleanup when this value is greater than the RCL calculated from default toxicity and exposure values. The DNR has assigned background concentrations for numerous metals (such as lead, arsenic, barium, etc.) commonly detected in soil samples. An explanation on the statewide background value for arsenic is provided in Wisconsin Statewide Soil-Arsenic Background Threshold Value (RR-940) [PDF]. The background values for arsenic and other metals are listed on the various RCL spreadsheets

For substances without a DNR-approved background value, the background concentration must be determined on a site-specific basis using a DNR-approved and appropriate method.

2. Comparing the average concentration of a substance to the RCL [Ch. NR 720.07 (2), Wis. Admin. Code].

When evaluating the direct contact pathway, it may be possible to average measured soil sample concentrations to determine whether or not the calculated RCL has been exceeded. Averaging soil concentrations measured in multiple samples is most appropriate when the contaminant is widespread, and concentrations are relatively consistent and close to the RCL for that substance. Averaging is not appropriate as the sole method for addressing sites where areas of significantly high concentration of soil contamination is present (relative to the RCL), or to address hot spots or source areas on a property.

Averaging soil contaminant concentrations for comparison to RCLs, and the methods used to calculate those averages, will not be approved by the DNR in all situations. It is therefore recommended that DNR approval of the proposed sampling plan and analysis methodology be obtained as early during the project as possible. Obtaining preapproval helps ensure that the DNR will accept the results of the analysis. Soil averaging that is conducted without following an approved methodology may delay the approval of a site investigation or closure request.

3. Contact information

Questions regarding background determinations or compliance averaging can be addressed to Judy Fassbender.

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). [PDF]

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 [PDF] 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) [PDF] 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) [PDF].

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

Other

A number of guidance documents have been prepared by the DNR to address specific topics relating to soil contamination.

1. PCB soil contamination

Sites with PCB contaminated soil undergoing cleanup may need to comply with the federal Toxic Substances Control Act (TSCA) as well as the NR 700, Wis. Admin. Code rules series.

Questions regarding PCB contamination may be addressed to Angela Carey.

2. Contamination within the smear zone.

The smear zone is located between the historic high and low water table elevations. 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.

3. Biodegradation as a remedial action to address soil contamination.

Information regarding natural attenuation of petroleum contamination in unsaturated soil is provided in Naturally Occurring Biodegradation as a Remedial Action Option for Soil Contamination Interim Guidance (Disclaimers Updated September 2004) (RR-515) [PDF]. This document provides information on how petroleum contamination biodegrades in the environment, how to evaluate a site to determine the suitability of relying on natural biodegradation, and the long-term monitoring needed to evaluate the progress and effectiveness of biodegradation at a site.

For questions on contaminated soil, contact

For questions on contaminated sediments, contact