Streamlining the risk assessment process By DAWN NELSON The Environmental Company Risk assessment is not a new concept as an alternative to stringent, nonsite-specific standards for determining cleanup action at hazardous waste sites. But the traditional use of this tool has been a fairly comprehensive, arduous process based on hypothetical situations without regard to actual site conditions and the feasibility of a remedy. It has been burdened with regulatory constraints and inflexibility where assessments conform to a predetermined set of standards. In the traditional realm, regulatory agencies typically rely on worst-case scenarios, conservative assumptions, and stringent, sometimes unrealistic, cleanup levels because risk regulations are often designed to cover all possible scenarios at a particular site and are based on outdated science. Scientists sample for petroleum compunds in groundwater and subsurface soil near some fuel pipelines in Texas. Photo by The Environmental Co. As a result, a tool with much promise for improving cleanup strategies and reducing costs often leaves responsible parties and regulatory agencies in opposing, antagonistic relationships. Cleanup of sites becomes costly, time-consuming and ineffective. Because of increasingly tight budgets to address contamination, there is an increasing need for innovative, practical and cost-effective approaches to risk assessment that result in scientifically sound, corrective solutions and are directly integrated with the remedy selection process. Many regulatory agencies are working to incorporate this concept into existing regulations and responsible parties are making it an integral part of their environmental management program. With more streamlined risk assessment approaches becoming an obvious trend, considerable cooperation is needed between the responsible party and the lead agency to make these approaches work in reality. Much skepticism exists on both sides of the fence. Responsible parties view the regulatory agencies as inflexible and unrealistic, while regulatory agencies often view responsible parties as uncooperative and potentially irresponsible if left to their own devices. In our firm's experience, however, agencies and responsible parties, often with the assistance of third parties, are willing to come together to develop a practical and responsible approach that is specific to a particular site if communication is frequent and consistent. This scenario serves as a partnership or team approach which allows participants to make mutually acceptable decisions about appropriate risk assessment methodology and corrective action. In applying practical and cost-effective risk assessments to solve corrective action issues, the most important elements in the assessment are: 1) Use of tiered assessment methodology; 2) Selection of site-specific land use scenarios; and 3) Development of risk-based cleanup levels. It is also imperative to remain focused on the project objectives and align the risk assessment goals with the overall project goals. By following these concepts and establishing a platform of cooperation and candid communication, risk assessments can be conducted in a manner that focuses on the priorities of a remedial project. The key to practical and streamlined risk assessments is developing risk-based cleanup levels in a phased or tiered fashion. The fundamental premise of a tiered approach is that one can begin at a simple screening step and proceed to different levels of complexity, if necessary, to achieve cost-effective and health protective cleanup levels. This flexibility is more cost- effective than traditional approaches because remedies are based on cleanup levels that are tailored to project needs and site- specific conditions and risks. Additionally, the two phases, risk assessment and remedy selection, are brought together to form a more unified and effective study. This provides a practical bridge between the risk assessment and remedy selection phases of a project with a mutual goal of developing final cleanup levels (which may be the same values developed during the risk assessment). The American Society for Testing and Materials (ASTM) has a risk-based corrective action (RBCA) standard for petroleum release sites which exemplifies this tiered approach. Each tier in the RBCA methodology consists of assessing risks and costs and a decision on whether to proceed to successive tiers. The level of risk assessment in the tiered process spans from a qualitative or screening assessment in the first tier to a full-scale quantitative risk assessment in the third tier. The first tier, typically consisting of predetermined conservative risk-based concentrations, is designed to be simple so that a responsible party can quickly determine the potential magnitude of the contamination. If site concentrations are below these values, the party can generally conclude that the site in question is not a threat to human health or the environment. If concentrations exceed the screening levels, parties can elect to proceed to the next tier where additional site data are usually collected and a limited site-specific risk assessment is performed using more realistic land use scenarios and exposure modeling. The goal of this second tier is to derive cleanup levels that are more tailored to site conditions. It may also be determined that an interim action would be more cost-effective and would eliminate the need for further assessment. Sites making it to the third tier are usually very complex and require extensive fate and transport modeling and sophisticated risk assessment techniques. By collecting enough site data to satisfy the needs of each tier in a progressive manner, building upon the data base of the previous tier, and making objective decisions at each step, the cost and time of collecting unnecessary data and performing comprehensive risk assessments on relatively simple sites can be avoided. The Environmental Company is part of a team which is currently taking advantage of this tiered concept at hazardous waste sites, one in particular is located in Oregon. The Oregon Department of Environmental Quality (ODEQ) has traditionally limited the risk-based corrective action (RBCA) approach to petroleum sites, but the responsible party and the agency have committed to evaluating the site in a RBCA-like manner not only for the purpose of deriving cleanup levels during the risk assessment, but, more significantly, for evaluating distinct areas of the site in separate investigation phases. The commitment is based on the premise that the responsible party will provide interim progress updates and both the party and agency will maintain frequent communication. The project managers set up regularly scheduled meetings and established a system of interim reports in which the agency has an opportunity to comment on the approaches being proposed before any significant work is conducted. For example, a preliminary report that outlined a phased approach to evaluating site contamination and risks was prepared for ODEQ. The agency commented on our methodology and, based on discussions held in successive meetings, we adjusted some specific risk assessment elements. Overall, the agency approved our phased approach which entails evaluating distinct areas of the site separately in phases (e.g., phase one represents evaluation of a contained volume of contaminated soil), performing a screening level assessment, and developing remediation goals rather than generating risk estimates. The advantage in evaluating distinct areas separately is that if, for example, groundwater samples collected directly below soil contamination in the first phase reveal no contaminant migration, then it will be unnecessary to proceed to phase two, which is an extensive characterization and evaluation of the groundwater. Additionally, remediation goals are being derived for different possible remedy scenarios in the risk assessment so that remedies could be evaluated concurrently and the cleanup levels are based on reality. This process brings together the risk and remedy evaluations, with the benefit of eliminating redundant steps, expediting the corrective action, and reducing study costs. Several states have used the American Society of Testing Materials standard as a basis for developing their own risk-based corrective action regulations and guidelines. Examples of states using this approach include Oregon, Alaska, Hawaii, Texas, California, and Arizona. Washington state is developing a tiered approach to specifically evaluate potential risks to ecological receptors under the Model Toxics Control Act (MTCA). MTCA Methods A, B, and C, generally focused on human health risks, are not considered a tiered approach. These methodologies also establish a distinction between development of cleanup levels as part of a risk assessment and the actual levels to which sites will be remedied (although they may be the same at some sites). So, in effect, one has to perform two risk assessments at some sites to arrive at a final remediation or cleanup level. In addition to Oregon, The Environmental Company has worked on projects in Texas and Hawaii using a practical approach to evaluating risks at sites located in these states. We relied on regulations and guidances that both states have developed for assessing risks through tiered assessments and risk-based corrective action. By being objective about the problems present at the sites, treating our clients as partners, and maintaining open dialog with the lead agencies, we are able to accomplish practical and cost-effective risk evaluations. In one project, the client assumed that it was required to do a comprehensive baseline risk assessment, but by carefully reviewing the regulations, communicating with the regulatory agency, and evaluating the project objectives, we determined that a full-scale assessment was not necessary. We proceeded with a straightforward two- tiered method for evaluating potential ecological and human health risks. We came in under budget and prepared a well-received report that documents our innovative and practical approach to addressing environmental concerns at the site. Dawn Nelson is the senior toxicologist for the Environmental Company Inc., a full-service environmental consulting firm based in Issaquah.