joint groundwater report - Texas Commission on Environmental ...

ability to remove or treat all contaminants to background concentrations. Economic feasibilities include thehigh cost of sophisticated treatment technologies and the long time periods required to retrieve the affected<strong>groundwater</strong> for treatment. In many cases contaminated <strong>groundwater</strong> cannot be restored to its original quality,and significant costs are incurred at many sites in the recovery and treatment of <strong>groundwater</strong>. It may not betechnically possible or cost-effective in all cases to clean <strong>groundwater</strong> to its original quality.Recognizing this situation, the state's policy requires that <strong>groundwater</strong> be kept reasonably free ofcontaminants that would interfere with present uses or impair future uses of <strong>groundwater</strong>. In response, theTNRCC has developed an approach which focuses on protection of <strong>groundwater</strong> for high quality uses,including human health, and which addresses the cost of available remediation technologies. The TNRCC,which has primary jurisdiction for the regulatory protection of <strong>groundwater</strong>, is implementing a risk-basedapproach in setting cleanup levels that is based on sound science, flexibility, and common sense.This risk-based approach takes into consideration the actual or reasonable potential for public andenvironmental exposure to contaminants in the determination of the timing, type, and degree of siteremediation. Risk assessment is the process used to quantify the potential adverse effects to human health dueto exposure to chemicals. A risk assessment process was first proposed by the National Academy of Sciencein the 1983 publication: Risk Assessment in the Federal Government: Managing the Process. The basicprocess proposed by the National Academy of Science is the foundation for most published risk assessmentguidance documents developed by state and federal regulatory agencies.The risk assessment process consists of four steps: hazard identification, dose-response assessment,exposure assessment, and risk characterization. The objective of hazard identification is to determine whetherthe available chemical-specific scientific data describe a causal relationship between exposure to the chemicaland adverse human health effects. The dose-response assessment quantifies the relationship between the dose(amount of chemical that the organism is exposed to) and the response (adverse health effects). The objectiveof the exposure assessment is to analyze site-specific information to estimate the most likely dose to potentialhuman receptors. The risk characterization uses information from the previous three steps to estimate adversehuman health effects. The risk characterization answers the question "How much risk does the situationpose?" This is followed by the risk management step which answers the question "What should be done withthe risk that has been quantified?"Depending on the level of the risk and the current regulatory policies, risk management may involve noaction,engineering solutions such as soil and <strong>groundwater</strong> remediation, or institutional controls such as deedrestrictions or limiting access to the site. Thus, risk-based decision-making can be protective of human healthand the environment, and offers a scientifically sound and administratively effective way to respond to thepressures for timely action at large numbers of sites and the efficient use of both public and private resources.The TNRCC's Office of Waste Management has incorporated risk-based corrective action into its rules andpolicies.The Groundwater Classification System has been incorporated into rules of the industrial solid wasteprogram of the Industrial and Hazardous Waste Division and the Pollution Cleanup Division of the TNRCCfor closures and remediations of hazardous and non-hazardous waste sites and areas of contamination. Therules, known informally as the Risk Reduction Rules, were promulgated in Title 30, <strong>Texas</strong> AdministrativeCode, Chapter 335, Subchapters A and S, with an effective date of June 28, 1993. These rules specify threerisk reduction standards, or levels of cleanup, for contaminated media including <strong>groundwater</strong>.Standard 1 calls for cleanup to background conditions regardless of the <strong>groundwater</strong> classification. Standards2 and 3 allow for consideration of the potential use of <strong>groundwater</strong> as a human drinking water resource based15