Contaminated Sites – Course 2: Laws, Regulations and Risk

This module introduces the Resource Conservation and Recovery Act, the primary federal law governing hazardous and nonhazardous waste management in the United States. We cover the origin of RCRA, signed into law in 1976 and amended by HSWA in 1984, and explain the cradle-to-grave approach that tracks hazardous waste from generation through transportation, treatment, storage, and final disposal. We introduce the four goals of RCRA: protecting human health and the environment, conserving energy and natural resources, reducing waste generated, and ensuring environmentally sound waste management. We cover the regulatory structure of RCRA's ten subtitles including Subtitle D for nonhazardous solid waste, Subtitle C for hazardous waste, and Subtitle I for underground storage tanks, and note that RCRA regulations are found in Title 40 of the CFR Parts 239 through 282. We clarify the important point that solid waste under RCRA is not limited to physically solid materials but includes liquids, semisolids, and containerized gaseous materials.

This module covers the EPA's hazardous waste identification process in full detail. We begin with Subtitle D and the framework for nonhazardous solid waste management under state and local authority, covering the open dumping ban, landfill design criteria, location restrictions, financial assurance, and corrective action requirements. We then work through the four-step hazardous waste identification process: determining if the material is a solid waste, checking if it is excluded from regulation, determining if it is listed or characteristic, and checking if it has been delisted. We cover the four EPA hazardous waste lists in detail: the F-list for nonspecific source wastes, the K-list for source-specific wastes, and the P-list and U-list for discarded commercial chemical products. We then work through the four characteristic properties. Ignitability using waste code D001 and SW-846 test methods 1010A, 1020B, and 1030. Corrosivity using waste code D002 and SW-846 test method 1110A. Reactivity using waste code D003 and narrative criteria including explosion potential, toxic gas generation, and sulfide or cyanide gas production. And toxicity, which we cover in detail through the Toxicity Characteristic Leaching Procedure, SW-846 test method 1311, explaining the 48 to 72 hour extraction process and the regulatory levels for all 40 toxic chemicals in the TCLP table. We close with the three special regulatory provisions: the mixture rule, the derived-from rule, and the contained-in policy.

This module covers the three links in the RCRA cradle-to-grave chain: generators, transporters, and treatment storage and disposal facilities. We begin with the three generator categories based on monthly waste generation rates: Large Quantity Generators producing 1,000 kilograms or more of hazardous waste per month with a 90-day on-site accumulation limit, Small Quantity Generators producing between 100 and 1,000 kilograms per month with a 180-day limit, and Conditionally Exempt Small Quantity Generators producing less than 100 kilograms per month. We note the 2009 statistics of approximately 460 TSDFs, 18,000 transporters, and 14,700 LQGs on record. We then cover the Uniform Hazardous Waste Manifest, EPA Form 8700-22, explaining how it tracks waste movement from generator to TSDF and the three required elements: generator and transporter information, DOT hazard description, and waste quantity and container type. We then cover TSDFs as the final link in the chain, explaining the general facility operating standards and technical standards governing design, construction, operation, maintenance, and closure. We close with underground storage tanks under Subtitle I, covering the definition of a UST system, the risk posed by leaking USTs to drinking water for nearly 50 percent of the U.S. population, and the three strategies for minimising LUST problems: regulatory compliance, prevention and timely detection, and effective response and cleanup.

This module introduces Applicable or Relevant and Appropriate Requirements and explains how they form the regulatory framework for establishing cleanup goals at CERCLA sites. We begin by defining the distinction between applicable requirements, which are standards a private party would have to comply with by law if acting outside of CERCLA authority, and relevant and appropriate requirements, which address problems sufficiently similar to those at the CERCLA site that their use is well suited to the particular situation. We cover the three categories of ARARs: chemical-specific ARARs, which are health or risk-based numerical values expressed as acceptable contaminant concentrations at the site; location-specific ARARs, which restrict activities in environmentally sensitive areas including floodplains, wetlands, and habitats for endangered species; and action-specific ARARs, which are technology or activity-based requirements that govern how a selected remedial alternative must be achieved. We then cover Section 121 of CERCLA and the cleanup standards determination process, explaining the role of risk assessment in establishing protectiveness, the use of MCLs as generally acceptable cleanup levels for drinking water, the cancer risk range of 10 to the negative 4 to 10 to the negative 7 for carcinogens, and the role of to-be-considered materials when ARARs are unavailable or insufficient. We also explain when more stringent standards are required, such as when multiple contaminants create additive effects.

This module covers the specific federal environmental laws that serve as ARARs for CERCLA remedial actions, working through water quality, air quality, and several other statutes. We begin with RCRA requirements for hazardous waste and groundwater, explaining when RCRA corrective action requirements apply to Superfund sites and how MCLs are used as protection levels for drinking water aquifers, with Alternate Concentration Limits available where cleanup is not practicable or cost-effective. We then cover the Clean Water Act, explaining the NPDES permit system and how both on-site and off-site discharges from CERCLA sites must meet substantive NPDES requirements including discharge limitations, monitoring requirements, and best management practices. We cover the Safe Drinking Water Act and the use of MCLs and MCLGs as cleanup standards for groundwater and surface water, and explain when more stringent standards are warranted. We then cover the Clean Air Act requirements relevant to remedial activities, covering the six criteria pollutants under the NAAQS, the 187 hazardous air pollutants under NESHAPs, and New Source Performance Standards. We close with the Toxic Substances Control Act and its relevance to CERCLA actions through regulations covering PCBs, PFAS, lead, mercury, and asbestos, followed by a brief overview of other potential ARARs including NEPA, the Endangered Species Act, the Wild and Scenic Rivers Act, and standards for radioactively contaminated sites.

This module introduces the fundamental concepts of environmental risk assessment and the planning and scoping stage that precedes the four formal steps. We begin by defining risk as the chance of harmful effects to human health or ecological systems resulting from exposure to a stressor, and explain the three factors that determine the level of risk: how much of a contaminant of concern is present in the environmental medium, how much exposure a person has with the contaminated medium, and what the inherent toxicity of the contaminant is. We introduce the four-step risk assessment process with a visual process flow diagram: hazard identification, dose-response assessment, exposure assessment, and risk characterization. We cover the applications of risk assessment in site remediation, including determining safe levels for contaminants, estimating current and future risks under a no-action alternative, and selecting the best cleanup alternative through risk-based remediation. We then cover the planning and scoping stage in detail, including the selection of receptors such as individuals, the general public, and sensitive subgroups including children, pregnant women, and the elderly, the categories of environmental hazards, point and nonpoint and natural sources, exposure pathways through air, water, soil, food, and consumer products, and the three exposure routes of ingestion, inhalation, and dermal contact. We also cover the body's reactions to environmental hazards and the four categories of toxic effect timing: acute, sub-chronic, chronic, and intermittent.

This module covers the first two formal steps of risk assessment and introduces the core engineering equations used throughout the rest of the section. We begin with hazard identification, explaining how it determines whether exposure to a stressor can cause adverse human health effects and introduces the five EPA weight of evidence categories for carcinogenicity: human carcinogen, probable carcinogen, possible carcinogen, not classifiable, and evidence of noncarcinogenicity. We then cover dose-response assessment, explaining the relationship between dose and adverse health effects, the concept of the threshold dose, and the two types of dose-response relationships. For nonlinear dose-response we cover the No-Observed-Adverse-Effect Level, the Lowest-Observed-Adverse-Effect Level, and the Reference Dose expressed in milligrams per kilogram per day, as well as the Reference Concentration for inhalation risks. For linear dose-response we introduce the cancer slope factor and the cancer risk formula. We then introduce the Hazard Index equation for non-carcinogenic effects and the cancer risk equation for carcinogens. We cover the Average Daily Dose equation in full, explaining each term: concentration, intake rate, absorption factor, exposure factor, and body weight. We then derive the Exposure Factor equation from frequency of exposure, exposure duration, and averaging time, noting the critical distinction that averaging time equals exposure duration for noncarcinogens but equals a lifetime of 70 years for carcinogens. We close with all standard EPA default values for body weight, exposure duration, water intake, soil ingestion, and air intake rates for infants, children, and adults.

This module is entirely devoted to fully solved engineering calculation examples covering all four exposure pathways, matching the style and depth of the worked examples in the textbook. We begin with water ingestion dose calculations, working through Example 3.3 step by step for both adults and children exposed to 10 milligrams per litre of methylene chloride in drinking water, demonstrating how the lower body weight of children produces a higher dose per kilogram despite a lower absolute intake rate. We then work through soil ingestion dose calculations in Example 3.4, first calculating the exposure factor for a child on site three days per week for 40 weeks per year over four years, and then applying the ADD equation with appropriate unit conversions. We then work through soil dermal contact dose calculations in Example 3.5, covering how different age groups require separate exposure factor calculations due to different soil adherence rates, and how the total ADD is summed across the 0 to 1 and 1 to 6 year age periods. We then work through inhalation dose calculations in Example 3.6, calculating the daily average dose of PM10 at the NAAQS standard for both adult males and adult females using their respective air intake rates, and explaining why the results differ. Throughout all examples, units are tracked carefully and all assumptions including AF equals 1 and EF equals 1 for worst-case scenarios are clearly stated and justified.

This final module brings together the full risk assessment framework through a worked example on the hazard index and allowable concentrations, covers risk characterization and risk management, and closes with a complete set of practice problems. We begin with Example 3.7, working through the calculation of the hazard index for toluene-contaminated groundwater with an oral reference dose of 0.2 milligrams per kilogram per day and a safety factor of 20, demonstrating that setting the allowable average daily dose below the RfD produces an HI below 1. We then calculate the maximum allowable toluene concentration in drinking water separately for adults and children, showing why the lower child concentration of 0.16 milligrams per litre governs as the compliance limit despite both having the same allowable daily dose per kilogram. We then cover risk characterization as the final step of the assessment, explaining how it synthesises information from all previous steps and serves as the first input to the risk management process. We introduce risk management and how it incorporates economic and social factors alongside the scientific risk assessment results to determine how risks should be managed, and cover risk communication as an essential practice for contaminated site remediation projects. The module closes with all seven practice problems from the textbook chapter covering cancer risk calculation, exposure factor determination, water and soil ingestion doses, soil dermal contact, inhalation dose, and hazard index with allowable concentration limits, giving students the opportunity to apply every equation covered in the section.