FEATURE
Risk-based Remediation Guidelines Take Hold ASTM's risk-based approach to petroleum cleanups will soon be applied to chemical contamination. RONALD
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mid the widespread recognition of flaws in U.S. environmental cleanup regulations, a set of risk-based remediation selection guidelines has evolved for leaking underground petroleum tanks. Now these concepts and methods are being modified to address chemical contamination. If they meet with as much acceptance as the petroleum standards, they promise to change the cleanup of contaminated sites across the country. Regulators in 23 states have implemented or are in the process of implementing a set of risk-based corrective action standards (RBCA) for sites contaminated by petroleum spills. Regulators in 17 other states are being trained in the procedures, which were introduced in 1994 by the American Society for Testing and Materials (ASTM) (i). Like the petroleum RBCA standards, the ones in development, nicknamed "Super RBCA," combine site assessment, risk assessment, risk management, and remedial action into a single framework. Rather than aiming for a uniform goal of reducing site contaminants to natural or background levels or achieving maximum cleanup possible with current technology, the RBCA framework assesses current and potential future risks at a site and sets cleanup goals accordingly. RBCA standards were developed when state programs for underground storage tank cleanup, funded by oil and gas taxes, started facing bankruptcy as they sought to restore all sites to pristine levels. ASTM then developed a system that determined risks based on site-specific information. RBCA addresses the question of how clean is clean by matching the urgency and extent of remediation with the risk to human health, safety, and the environment. That includes consideration of future use of the site, allowing for different cleanup levels depending on whether it is to be used for industrial or residential development. Instead of calling for elimination or reduction of contamination—which can 4 3 8 A • VOL. 30, NO. 10, 1996 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
BEGLEY be costly and time-consuming—an RBCA analysis may prescribe cutting off pathways of exposure.
Three decision options RBCA proceeds in a tiered progression; the analysis moves from simple to complex only as necessary and becomes more site specific at each stage. In Tier 1, site conditions and the nature of the contamination are assessed. The site is classified by the degree of threat it poses to human health. Then, site conditions are compared with generic risk-based screening levels contained in a reference table. If site contamination exceeds those screening levels, the analysis moves to a second stage. At Tier 2, site-specific target levels of contamination are established " based on the measured and predicted attentuation of the chemical(s) of concern away from the source area(s) using relatively simplistic mathematical models" (i) and compared with site conditions. If the decision is that no additional remedial action is necessary, risk management strategies are used to monitor the site and ensure that remediation targets are maintained. If the decision is to go on to the next stage, Tier 3, the level of sophistication and cost rises, and a complete risk assessment is conducted. This gives another set of target levels and leads to another decision about how to proceed. When RBCA standards were established, it was anticipated that almost one-half of all site assessments would end at Tier 1, with fewer than onequarter going to Tier 3. By increasing site assessment costs and the sophistication of the risk assessment only as needed, RBCAs should save money and time in comparison with many current regulations. "RBCA has given us a system that helps us allocate key resources where they're most needed to protect human health, safely, and the environment, and achieve it in the most cost-effective way," said Curtis Stanley, staff hydrogeologist with Shell Development Co. and member of the ASTM groups that developed the RBCA petroleum and chemical standards. 0013-936X/96/0930-438A$12.00/0 © 1996 American Chemical Society
This is a departure from previous approaches aimed at reducing contamination as much as possible without regard to risk, which led to seemingly endless cleanup operations that drained remediation funds. The redevelopment of brownfields has been one of RBCA's successes, according to Ravi Arulanantham, toxicologist at the San Francisco Bay Regional Water Quality Control Board. He has trained California regulatory staff in RBCA methods and has seen the results at contaminated sites. "RBCA is about working smarter versus working harder. There is no net benefit to society by regulating at unattainable levels of cleanup. I believe in another year or two, this is the way California will go, because it gives us the same level of protection." Arulanantham says the brownfields sites "would never have been cleaned up because the system was so unpredictable. Whether you were at a high- or lowrisk site, the goal was to clean to pristine levels. The responsible party would never know when this process would end. Now I can give them some predictability. Once they get a stable plume, they can go into a risk management mode and walk away." Strong appeal—unproven track record RBCA's proponents say it is too early in the process to fully assess its success. It is a testament to RBCA's appeal, however, that regulators and industry in nearly every state have bought into the system without waiting to see what kind of track record it develops. Expectations are running high. Managers of Iowa's leaking underground storage tank remediation program anticipate that by using the RBCA approach they will judge that 25% of the 4600 sites do not need remediation, for a potential saving of more than $80 million. EPA has been promoting RBCA to the states and working with them to evaluate its performance. "The gains have been more conservative than we thought they would be, but we're early in the process," reported Lisa Lund, acting director of EPA's Office of Underground Storage Tanks. "The states are being cautious with this and using it more conservatively." EPA had predicted that 30-40% of underground storage tank sites would stop at Tier 1, but the actual figure so far is 15%. Industry is similarly hesitant. "It's a little bit early in the process to say what the impacts of RBCA have been," said Bruce Bauman, research program coordinator with the American Petroleum Institute. "It has certainly helped everyone to prioritize their sites and has allowed companies, through discussions with their regulators, to stop active remediation at sites where the risks are low. It has saved money in that way." Mobil projects that widespread implementation of RBCA at its petroleum leak sites will save 1520% in cleanup costs. According to Mark Malander,
States faced with extensive underground petroleum storage tank cleanups are turning to a set of decision-making guidelines developed by the American Society for Testing and Materials. Twenty-three states have adopted or are in the process of implementing the risk-based standards. Photo courtesy IT Corporation.
remediation consultant with Mobil Business Resources Corp., "The big savings is that, when using site-specific cleanup levels, sites with active remediation would go down to a monitoring mode." Using RBCA, the company looked at 49 petroleum contamination sites in Texas and found that 28 of them required no action, 13 required monitoring leading up to closure, and 8 called for active remediation. Without the risk-based, site-specific assessment, 20 sites would have required active remediation. Mobil is working with the Florida Department of Environmental Protection to project the costs of several RBCA options the state is considering. Malander said of the overall RBCA experience, "What we're seeing so far is that RBCA has the potential to save the industry and the states significant amounts of money. However, the key to the cost savings is the VOL. 30, NO. 10, 1996 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 4 3 9 A
Initial Site Assessment Conduct site investigation and organize available information regarding principal chemical(s) of concern, extent of contamination, and potential migration oathwavs and receptors.
Site Classification and Initial Response Action Classify site per specified scenarios and implement appropriate initial response action. Reclassify site as aoproDriate.
Risk-based Corrective Action Standards Interim Remedial Action Conduct partial source removal or other action to reduce the risk(s).
Identify reasonable potential sources, transport pathways, and exposure pathways. Select appropriate Tier 1 risk-based screening levels (RBSLs) from "look-up table." Compare these values with site conditions.
/
Uhemical(s) of concern concentration \ e x c e e d RBSLs? ,,
Remediation to Tier 1 RBSLs practicable?
Interim remedial action appropriate?
Collect additional site data as needed and conduct assessment per specified procedures. Compare Tier 2 site-specific target levels (SSTLs) with site conditions.
x Chemical(s) of \ concern concentrations \ _ e x c e e d SSTLs?*/
Remediation to Tier 2 SSTLs practicable?
Interim remedial action appropriate?
Collect additional site data as needed and conduct assessment per specified procedures. Compare Tier 3 site-specific target levels (SSTLs) with site conditions.
/ Chemicai(s| of \ ^ concern concentrations . X e x c e e d SSTLs? y^
Interim remedial ^ action appropriate? .,
Remedial Action Program Identify cost-effective means of achieving final corrective action goals. Implement the preferred alternatives.
Continued monitoring required?
Compliance Monitoring Conduct monitoring program as needed to confirm that corrective action goals are satisfied.
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No Further Action
How RBCA works Tier 1 analysis assesses site conditions and contamination. The main compounds of concern, extent of contamination, and potential exposure pathways to affected populations are all identified. The site is then classified as an immediate threat, short-term threat, long-term threat (greater than two years), or no demonstrable threat. Then, site conditions are compared with conservative risk-based screening levels (RBSL) contained in a reference table. At that point, it is decided whether to institute remediation, do nothing, or move on to a Tier 2 analysis. Tier 2 replaces the non-site-specific, generic RBSLs with site-specific target levels (SSTLs) and compares them with conditions at the site. Generating the SSTLs requires more involved data collection and analysis. Screening-level predictive models may be used. During Tier 1, the implication is that an exposed individual is located at the point of contamination. In Tier 2, default exposure assumptions may be replaced with alternative exposure points such as site boundaries, which usually result in a lower risk estimate. Again, a decision is made about which way to proceed. If no further action is deemed necessary risk management procedures are established for monitoring to ensure that site remediation targets are kept Tier 3 raises the level of sophistication up to and including a full risk assessment. Toxicity information, probabilistic evaluations, and complex analysis of chemical fate and transport may all be considered. This gives another, even more sitespecific, set of SSTLs, which leads to another decision about how to proceed. In practice, a Tier 1 analysis can help determine which compounds at a site actually pose a threat and through which potential pathways of exposure they do so. An RBCA reference table of contaminants and site conditions gives guidance on what degree of risk might be posed. The location of contamination and its potential pathways might include surface soil, subsurface soil, or groundwater, all of which can be compared with expected land use. That further narrows down specific risks.
policy decisions each state makes regarding their corrective action program," such as determining what degree of cleanup they decide is acceptable.
"Super RBCA" for chemical cleanups The still-evolving ASTM guidelines for chemicalcontaminated sites are currently in review and expected to be completed as early as next year; they will expand the RBCA framework of tiered decision making to cover the wide variety of situations involving hazardous chemicals. The initiative offers the promise of the risk-based approach, but the states still face tough decisions about how to handle chemical contamination. It requires that each state and EPA grapple with often-controversial details such as determining relevant exposure pathways and adopting toxicological values. "It's easier to address underground storage tanks.
The sites have similar characteristics, so the standards are easier to write," commented Paul Johnson of the University of Arizona-Tempe, lead author of the original ASTM standard and co-chair of the group drafting the chemical contamination protocol. "It is important to understand that the standards prescribe a way to go about handling a site; they do not prescribe what chemicals to look at or what values to adopt. That is up to the states." Pennsylvania has proposed regulations stemming from the state's Land Recycling and Environmental Remediation Standards Act, passed in July 1995, which was designed to put contaminated industrial sites back into productive use. The proposed regulations establish an RBCA-like assessment of almost 500 regulated substances. They allow remediators to choose whether to do a cleanup to background levels, to statewide health standard levels, or to site-specific cleanup levels, using a 1 in 100,000 cancer risk factor. The Pennsylvania regulations also address a major issue in the chemical RBCA standards: ecological risk. Largely ignored by the petroleum standards, the ecological risk posed by contaminated sites is of growing importance in state regulations. The ASTM guidelines being developed call for determining whether a pathway to ecological exposure is present at a site. If it is, a site-specific ecological risk assessment is recommended. The chemical standards feature the tiered methods of the original RBCA process but cover thousands of organic and metallic chemicals. Although the standards will probably be used first at voluntary cleanup sites, EPA staff from the Superfund and Resource Conservation and Recovery Act (RCRA) corrective action programs are closely watching the success of the standard. The RBCA approach may influence pending revisions to Superfund and RCRA, according to Bill Gulledge, vice president of Environmental and Commercial Insurance and chair of ASTM's subcommittee on environmental regulatory performance standards. "We saw Congress considering changes to RCRA and Superfund, and we felt that the provisional chemical standard would be good input." "In principle, it's possible to build RBCA into the reauthorization of Superfund," said Larry Froebe, manager of risk assessment and toxicology with International Technology Corporation. The process, he says, is effective in getting sites back into use. As more state and federal policy makers and their constituents demand greater consideration of risk in regulatory decision making, RBCA and similar approaches can be expected to become even more popular. Whether or not a given risk-based approach follows the ASTM model, "it's where we're all headed," Froebe believes.
References (1) American Society for Testing and Materials. Standard Guide for Risk-based Corrective Action Applied at Petroleum-Release Sites; ASTM: West Conshohocken, PA, ,995 (E1739-95))
Ronald Begley is a freelance journalist based in Richmond, Va. He is former Washington bureau chief at Chemical Week magazine. VOL.30, NO. 10, 1996/ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 4 4 1 A
