Superfund: How States Establish and Apply Environmental Standards When Cleaning Up Sites
Released: 1996-04-09T00:00:00

Letter

Background

Under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), which created the Superfund program in 1980, the Environmental Protection Agency (EPA) assesses uncontrolled hazardous waste sites and places those posing the greatest risks to human health and the environment on the National Priorities List (NPL) for cleanup. As of September 1995, this list included 1,232 sites.

Cleanup standards and the degree of cleanup needed for Superfund sites are discussed in section 121(d) of the CERCLA statute, as amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA). This section requires that Superfund sites be cleaned up to the extent necessary to protect both human health and the environment. In addition, cleanups must comply with requirements under federal environmental laws that are legally “applicable” or “relevant and appropriate” (ARAR) as well as with such state environmental requirements that are more stringent than the federal standards. Furthermore, Superfund cleanups must at least attain levels established under the Safe Drinking Water Act and the Clean Water Act, where such standards are relevant and appropriate as determined by the potential use of the water and other considerations.

The federal standards most frequently considered relevant and appropriate for groundwater cleanups at Superfund sites are set under the Safe Drinking Water Act. This act establishes standards, called maximum contaminant levels (MCL), for certain contaminants in water delivered by public drinking water systems. As of March 1996, the MCLs included numeric limits on about 70 contaminants. The MCLs take into account estimates of the human health risks posed by contaminants. They also consider whether it is technically and economically feasible to reduce the contamination to a level that no longer poses a health risk. Although MCLs are legally applicable to drinking water systems, section 121(d) of CERCLA generally requires that they be considered relevant and appropriate standards for cleaning up contaminated groundwater that is a potential source of drinking water. For example, the MCL for benzene is 5 micrograms per liter. This concentration would generally be the cleanup level for benzene in groundwater that is a potential source of drinking water unless the state has promulgated a more stringent standard or other requirement that is relevant and appropriate.

There are few federal standards for contaminants in soil that are considered potentially applicable or relevant and appropriate except those for certain highly toxic contaminants, most notably polychlorinated biphenyls (PCB) and lead. Under the Toxic Substances Control Act, EPA sets requirements for cleaning up PCB contamination. In addition, EPA has issued guidance for cleaning up lead in soil.

Early in its investigation of a site, EPA determines, on the basis of the contamination present and the conditions at the site, which chemical-specific and other standards may be considered applicable or relevant and appropriate. As EPA proceeds with the selection of a cleanup method, it adjusts the list of standards to be considered on the basis of information gained during its investigation. Among the potential standards considered are any state environmental standards that are more stringent than the federal standards for the same contaminants.

In addition to numeric standards for specific contaminants, some states have set more generalized standards or policies that may have to be considered when cleaning up Superfund sites. For example, some states have established “antidegradation” policies for groundwater that could require more stringent cleanups than cleanups based on health risks. These policies are intended, among other things, to protect the state’s groundwater as a potential source of drinking water.

If federal or state standards do not exist for a given contaminant, the party responsible for cleaning up a Superfund site may use a site-specific risk assessment to help establish a cleanup level for that contaminant. A risk assessment evaluates the extent to which people may be exposed to the contaminant, given its concentration and the physical characteristics of the site. For example, the type of soil and the depth of the groundwater may affect whether and how quickly waste will migrate and reach a population. A risk assessment uses exposure and toxicity data to estimate the increased probability, or risk, that people could develop cancer or other health problems through exposure to this contamination. A risk estimate can be used along with the proposed waste management strategy to help determine the extent of the cleanup necessary at a site.

EPA has published guidance for conducting risk assessments, a set of documents referred to collectively as the Risk Assessment Guidance for Superfund. These documents outline the well-established risk assessment principles and procedures that can be used to gather and assess information on human health risks. The documents also include information on mathematical models that can be used to estimate health risks at a site, given the contaminants present and the means of exposure to them. In addition to this guidance, EPA maintains an Integrated Risk Information System (IRIS), an on-line database on the toxicity of numerous chemicals, and publishes the Health Effects Assessment Summary Tables (HEAST), another source of information on contaminants’ toxicity. EPA uses this guidance in conducting baseline risk assessments at Superfund sites, which it uses in deciding whether the human health and environmental risks posed by the contaminants are serious enough to warrant cleaning up the sites. Some states also use EPA’s risk assessment guidance in setting their standards for specific chemicals.

The Bases States Used in Developing Standards

States that have set environmental standards have made decisions about what levels, or concentrations, of chemical contaminants can remain at hazardous waste sites after cleanups. We analyzed the processes that the states in our survey said they went through, as well as the factors that they said they took into consideration, in developing their soil and groundwater standards. In this section, we first summarize (1) the extent to which the states based their soil standards on estimates of the human health risks posed by contaminants at the sites and (2) the methods that the states used to estimate these risks. We then report on the factors other than health risks that the states said they considered when developing their soil standards. Since the bases for the states’ standards for groundwater differed somewhat from those for soil, we summarized the information on groundwater standards separately. Finally, since federal drinking water standards are frequently used as cleanup standards for groundwater, we compared the states’ groundwater standards to the federal standards for the same contaminants to determine the extent of their correspondence.

We have included the information we obtained from the 33 states in our survey. In all, 21 of the 33 states had set their own standards for either soil or groundwater, or for both media. (See table 2.1.)

Thirteen of the 21 states had set their own soil standards, and 20 had set some groundwater standards that were in addition to or different from the MCLs for drinking water, as discussed in the remainder of this section.

Consideration of Health Risks in Setting Soil Standards

All 13 of the states with soil standards indicated that they considered risks to human health when developing their standards. The number of chemical-specific standards per state ranged from about 10 to nearly 600. All but one of these states generally relied on EPA’s guidance for estimating health risks from contaminants (Missouri had developed its soil standards before EPA issued its guidance). These states said that they had used EPA’s guidance, either alone or in combination with their own methodologies and policies, to estimate health risks. (See table 2.2.) For example, Pennsylvania said that it had used EPA’s guidance to estimate the toxicity of contaminants and its own model to estimate how much contamination from the soil might travel into groundwater. These estimates are two of the major components in the health risk calculation. uses at Superfund sites, which extends from 1 in 10,000 to 1 in 1 million. As shown in table 2.2, eight states chose the more stringent risk level of 1 in 1 million for individual carcinogens in soil, while five states chose the somewhat less stringent risk level of 1 in 100,000. For noncarcinogens in soil, 11 states used the same measure that EPA uses at Superfund sites, while 2 states used a somewhat more stringent measure.

Consideration of Other Factors in Setting Soil Standards

Ten of the 13 states considered factors in addition to health risks when setting their soil standards. As a result, their standards could be either more or less stringent than those based solely on estimates of health risks. These other factors included the following:

Chemical levels that occur naturally in the environment. In some locations, certain contaminants may exist naturally in the soil in concentrations differing from those that would be allowed under standards based on risks to human health. For such contaminants, the states typically set their standards at the naturally occurring levels rather than at the levels based solely on risk. In some cases, this practice would result in less stringent cleanups than would be necessary to meet the risk-based standards. However, since some chemicals do not occur naturally in the environment, this practice would in some instances result in more stringent cleanups than would otherwise be required.

Detection limits and practical quantification limits. When the concentrations of some contaminants that could remain in the soil without posing health risks fell below the levels that can be accurately measured or detected by current technology, the states said that they typically adopt less stringent, but measurable, concentrations as their standards.

Secondary, or aesthetic, criteria. Some chemicals cause unpleasant odors or other problems at levels that do not pose human health risks. The states may set their standards for these chemicals below risk-based levels to protect the public from such problems.

Consideration of Health Risks in Setting Groundwater Standards

Twenty of the 33 states we surveyed said that they had set some chemical-specific standards that would limit the concentrations of various toxic chemicals that could be present in groundwater at Superfund sites. These states not only adopted some of the existing federal standards, such as MCLs, but also set some standards in addition to or different from them.

The number of chemical-specific standards per state ranged from about 30 to nearly 600. While the remaining states that we surveyed had not developed any of their own groundwater standards, the federal MCLs are typically used as Superfund cleanup standards for groundwater.

Nineteen of the 20 states had based their groundwater standards, at least in part, on estimates of the human health risks posed by exposure to chemical contaminants. (See table 2.3.)

In the remaining state, none of the officials currently involved in implementing the standards could provide historical information on how the standards had been developed. Sixteen of the states had calculated their own health risk estimates when setting the standards for at least some of the contaminants. Three of the states had not predominantly developed their own estimates but had instead adopted standards developed by others, including some or all of the MCLs, that were based on estimates of health risks.

All 16 states that had developed formulas for calculating human health risks had used guidance from EPA on how to estimate such risks, either alone or in combination with their own procedures and formulas. (See table 2.4.) In setting their standards, 13 of these states used a risk level of 1 in 1 million for individual carcinogens, while 3 states used the less stringent risk level of 1 in 100,000. For individual noncarcinogens, 15 states used a measure that was as stringent as EPA’s, while 1 state used a more stringent measure.

Consideration of Other Factors in Setting Groundwater Standards

All but 2 of these 16 states said that they had considered factors in addition to human health risks when setting their groundwater standards. Taking such factors into account can affect the concentration of a chemical that a state will allow to remain under its standard. As a result, a standard may be either more or less stringent than one based solely on human health risks. may require more stringent cleanups than would be required solely on the basis of risk.

Differences Between the States’ Groundwater Standards and the Federal MCLs

Because the federal MCLs are typically used as cleanup standards for groundwater used as drinking water at Superfund sites and many of the states based some of their own groundwater standards on the federal MCLs, we compared the states’ standards for contaminants to the corresponding MCLs. We found that if a federal MCL existed for a chemical that was included in a state’s standards, the state usually set its standard at this level. However, a majority of the states had standards for a few chemicals that differed from the MCLs. These standards tended to be more stringent than the MCLs.

The states offered a variety of explanations for why their standards were more stringent than the federal MCLs. Two states set more stringent levels for certain contaminants if they could detect the contaminants at levels below the MCLs. Several states reported that some of their standards were more stringent because these standards had not been adjusted, as the MCLs had been, for other factors, such as cost or technical feasibility.

Some states’ standards may also have been more stringent because the states had antidegradation policies for groundwater. For example, Wisconsin mandates that the environment be restored to the extent practicable. Consequently, it has set “preventive action limits” for contaminants in groundwater that may be used to determine the extent of the cleanup required at Superfund sites unless it can be shown that meeting such limits would not be technically or economically feasible. All of the preventive action limits are more stringent than the corresponding federal MCLs. They limit the concentrations of chemicals that can cause cancer to one-tenth the concentrations allowed under the MCLs, and they limit the concentrations of chemicals that can cause other health effects to one-fifth the concentrations allowed under the MCLs. However, the state allows exemptions for contaminants that occur naturally at levels exceeding the preventive action limits.

Nearly all of the states had only a few, if any, standards for contaminants that were less stringent than the corresponding federal MCLs. However, under SARA, only those numeric standards that are more stringent than the federal standards are to be considered as cleanup levels at Superfund sites.

The Flexibility States Provided in Applying Standards to Cleanups

Even though the states have set environmental standards, they have found that applying these standards uniformly to all sites may not be effective because conditions can vary from one hazardous waste site to another. As a result, sites may pose different levels of health risks and may, therefore, require different degrees of cleanup. We examined whether the states (1) allow the level of cleanup determined to be necessary under their standards to be adjusted to take into account site-specific conditions and (2) set different standards for different uses of the land or groundwater (e.g., set more stringent cleanup standards for land that could be used for residential than for industrial purposes). Overall, the states provided more flexibility in applying their soil standards than their groundwater standards.

Flexibility to Adjust Cleanup Levels Based on Soil Standards to Account for Site-Specific Conditions

Eight of the 13 states that had soil standards indicated that they allow the extent of the cleanup deemed necessary under their standards to be adjusted for site-specific factors. For example:

Georgia’s risk reduction standards include the option of determining cleanup target concentrations for contaminants on the basis of site-specific risk assessments.

Minnesota characterized its standards as “quick reference numbers,” rather than fixed limits, that are considered when determining how extensively to clean up a site. Thus, cleanup levels can be tailored to local conditions. For example, if exposure to contaminants in soil were reduced or eliminated because the soil was inaccessible, the cleanup levels would not need to meet the standards. Alternatively, if multiple contaminants with the same toxic effect were found at the same location, the cleanup level for each individual contaminant might be more stringent than the standard.

Pennsylvania said that it has developed interim standards pending final regulations for about 100 soil contaminants but considers these to be “worst case” numbers that can be adjusted to reflect site-specific conditions. contaminated soil. Alternatively, under certain conditions, some states allow cleanups to be based on site-specific risk assessments. Three of these states also said that they permitted less stringent cleanup levels than those based on their standards if meeting them was not technologically feasible or if naturally occurring levels of chemicals in the local environment were higher than the levels set by the standards. However, the use of such alternatives was the exception rather than the rule.

Some of the states also indicated that even if they do not provide much flexibility in applying their standards, they may permit flexibility in determining how to achieve the required level of protection. For example, instead of requiring costly incineration of contaminated soil to meet its standards, a state may allow the area to be covered with a clay cap so that people cannot come into contact with the contaminants.

Different Soil Standards for Different Land Uses or Exposures

The states may also provide flexibility by establishing different standards for different projected uses of the land at a site. Ten of the 13 states with soil standards told us they had set such standards. For example, Michigan said that it had defined soil standards for three types of land uses: residential, industrial, and commercial (with two subcategories). Generally, the more stringent standards apply to residential property, since people are more likely to be exposed to contaminants for a longer period of time on residential property than on other types of property.

Flexibility to Adjust Cleanup Levels Based on Groundwater Standards to Account for Site-Specific Conditions

While most states allowed flexibility in their cleanup levels for soil, the states were less flexible in setting cleanup levels for groundwater. The degree of flexibility largely depended on whether the groundwater was considered a potential source of drinking water. place a notice in deed records to inform future property owners of any contamination left on the property. Cleanups under the third standard must also use federal MCLs when available, but for contaminants without corresponding MCLs, site-specific risk-based cleanup levels can be determined on the basis of the site’s projected use. The third standard also requires deed notification.

The remaining 16 states indicated that, in general, for groundwater used as drinking water or considered potentially usable as drinking water, their standards were fixed limits that must be achieved during cleanup. Most of these states did say, though, that they allowed certain limited exceptions to their standards or the use of a site-specific risk assessment under some circumstances. For example, if the contaminated water came from an area where the contamination would not immediately threaten communities, a state might let the contamination be reduced naturally over time rather than require that it be cleaned up immediately.

The states gave various reasons for the relative inflexibility of their groundwater standards for drinking water. First, some of the states said that they were mirroring the federal MCLs for drinking water, which are also fixed limits. Some of the states also noted that, as discussed in section 2, they consider groundwater that may possibly be used as drinking water as a valuable resource that needs to be conserved.

Different Standards for Different Uses of Groundwater

Although the states in our survey told us that their standards for groundwater used as drinking water are relatively fixed, some states also reported that they provided some degree of flexibility by not classifying all groundwater as drinking water. They also set less stringent standards for groundwater that would not be considered a potential source of drinking water. For example, Connecticut’s groundwater classification system acknowledges that in certain areas, such as those that have had long-term industrial or commercial use, the groundwater would not be a suitable source of drinking water unless it were treated. The state does not usually require that the groundwater in such areas be cleaned up to the standards for drinking water. Also, some states do not classify groundwater as drinking water if it has a high mineral content or if it is located in a geological formation that does not yield much water. agricultural purposes, groundwater of special ecological significance (e.g., supporting a vital wetland), and groundwater in urban, industrial, or commercial areas.

Seven of these 12 states indicated that site-specific factors can be taken into account when determining the extent of the cleanup needed for these other types of groundwater. For example, Rhode Island told us that it allows the cleanup levels for some contaminants to differ from the levels set in its standards. For example, vapors escaping from volatile organic chemicals in the groundwater could accumulate in overlying buildings and cause potential health effects. In some cases, these vapors could build up and cause threats of explosion. In setting its “urban” groundwater standards, this state conservatively assumed that the buildings would not be ventilated and that the vapors from the underlying groundwater would be trapped in the buildings. However, in deciding how extensively to clean up a site, the state allows for a consideration of site-specific factors, such as depths to groundwater. When site-specific factors are considered, the cleanup levels may not need to be as stringent as the standards alone would require.

Objectives, Scope, and Methodology

The Chairmen and Ranking Minority Members of the House Committee on Transportation and Infrastructure and its Subcommittee on Water Resources and Environment asked us to determine whether states (1) when setting numeric standards for cleanups at hazardous waste sites, based them on estimates of the human health risks posed by exposure to contamination and (2) when using standards, provide the flexibility to adjust the level of cleanup prescribed by the standards to take into account the conditions and risks found at individual waste sites.

To accomplish these objectives, we conducted a telephone survey of 33 states, receiving a response rate of 100 percent. We selected these states because they included approximately 91 percent of the sites that the Environmental Protection Agency (EPA) had included on its National Priorities List (NPL) as of April 1995. We obtained information for standards for contaminants in soil and groundwater, the two media most frequently cleaned up at Superfund sites. (See app. II for a list of the states, the number of NPL sites in each state, the types of standards in each state, and the types of authority for the standards.)

We defined standards as limits on the concentrations of toxic chemicals in soil and groundwater and included limits promulgated in a state’s laws or regulations or established as guidance or policy. We also included in our definition only standards that might be used as the basis for setting cleanup levels at a Superfund facility. Because petroleum spills are not covered under Superfund legislation, we excluded states that had established standards only for petroleum products under their separate programs for cleaning up leaking underground storage tanks. We excluded states that had simply adopted the federal standards set under the Safe Drinking Water Act or had established antidegradation policies without also setting specific numeric limits on contaminants.

The questions in our survey included (1) whether a state’s standards were derived from a risk-based formula and/or other factors, such as the naturally occurring levels of contamination in the soil and groundwater; (2) whether the formulas were based on EPA’s guidance or on the state’s own methodologies for estimating human health risks from contamination; (3) what risk levels, such as a 1-in-1-million increased probability of contracting cancer, were used in setting the standards; (4) whether the standards were set for different uses of the land or groundwater; and (5) whether the standards were considered fixed limits or the state provided flexibility to adjust the cleanup levels based on these standards to take into account specific conditions at a site. We interviewed the managers of states’ Superfund programs, technical experts in these programs, and other key officials responsible for developing and/or implementing the states’ standards. When necessary to clarify information, we contacted officials again for follow-up questions.

The data we obtained were current as of September 1995. To ensure the accuracy of our information, we provided state officials with a summary of the information we had compiled on their standards for their review. In addition, we provided copies of a draft of our report to EPA officials, including the Director of the Office of Emergency and Remedial Response and officials responsible for working with state Superfund programs, for their review and comment. They said that the report was an accurate discussion of states’ standards and provided several technical changes and clarifications on the Superfund law’s requirements for cleanups. We incorporated their changes and suggestions. We conducted our audit work from March 1995 through March 1996.

States Included in Survey and Reported Status of States’ Standards

(continued)

Major Contributors to This Report

Stanley J. Czerwinski, Associate Director Eileen R. Larence, Assistant Director Sharon E. Butler, Senior Evaluator Susan E. Swearingen, Senior Evaluator Luann M. Moy, Senior Social Science Analyst Josephine Gaytan, Information Processing Assistant The first copy of each GAO report and testimony is free. Additional copies are $2 each. Orders should be sent to the following address, accompanied by a check or money order made out to the Superintendent of Documents, when necessary. VISA and MasterCard credit cards are accepted, also. Orders for 100 or more copies to be mailed to a single address are discounted 25 percent.

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