Science & Technology
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Section 17: Air - Waste Characteristics & Targets
The air migration pathway for evaluating HRS scores evaluates the likelihood of release of hazardous substances into the atmosphere and how many people and sensitive environments could be exposed to hazardous substances carried in the air.
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Section 16: Air - Likelihood of Release
Learn about the air migration pathway for evaluating HRS scores and the likelihood of hazardous gas and particulate substance release.
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Section 15: Surface Water - Ground Water to Surface Water Component
Learn about surface water targets, which can be threatened by the release of contaminated ground water.
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Section 13: Surface Water - Human Food Chain Threat
Learn about how surface water releases can threaten the human food chain.
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Section 12: Surface Water - Drinking Water Threat
Learn about how surface water releases can threaten the safety of drinking water.
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Section 11: Surface Water - Likelihood of Release
Learn about the surface water pathway, the most complex pathway for evaluating Hazard Ranking System (HRS) scores.
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Section 10: Ground Water - Waste Characteristics & Targets
Learn about the waste characteristics factor category in the ground water pathway, which is made up of two components: the toxicity/mobility of the most hazardous substance associated with the site and the hazardous waste quantity at the site.
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Section 9: Ground Water - Likelihood of Release
Learn how EPA evaluates an identified aquifer's likelihood of release factor category for the purpose of scoring the ground water pathway.
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Section 8: Ground Water - Aquifers
Learn about issues surrounding aquifers, the basic unit of evaluation in the HRS ground water pathway.
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Section 7: Targets
Learn about targets, the third factor category in the HRS pathway score equation. Targets are the people, resources, or sensitive environments that could be affected by the site.
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Section 6: Likelihood of Release
Learn about the likelihood of Release (LR) factor category, which is evaluated based on the factors of observed release and potential to release.
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Section 5: Waste Characteristics
Learn about the calculation process for substance-specific factors, the chemical characteristics of the hazardous substances found at a site that are available to migrate from the site sources.
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Section 4: Source Characterization
Learn about source characterization for Superfund sites. Although the Hazard Ranking System (HRS) is designed to score releases and sites, sources and areas of observed contamination play a crucial role in determining HRS pathway scores.
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Section 3: HRS Structure
Read about the the four pathways for evaluating a Hazard Ranking System (HRS) score: ground water migration, surface water migration, soil exposure, and air migration.
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Section 2: Site Assessment Process
Learn about the multi-step process leading to the final National Priorities List (NPL) listing decision, which begins when a site is discovered and listed in CERCLIS.
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Section 1: Regulatory Context of the HRS
Learn about the regulatory context of the Hazard Ranking System (HRS), the primary tool that EPA uses to place sites on the National Priorities List (NPL).
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Nitrogen Dioxide (NO2) and Sulfur Dioxide (SO2) Secondary Air Quality Standards
The Clean Air Act requires EPA to set national ambient air quality standards (NAAQS) for six pollutants considered harmful to public health and the environment
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Nitrogen Dioxide (NO2) Primary Air Quality Standards
The Clean Air Act requires EPA to set national ambient air quality standards (NAAQS) for six pollutants considered harmful to public health and the environment
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Carbon Monoxide (CO) Air Quality Standards
The Clean Air Act requires EPA to set national ambient air quality standards (NAAQS) for six pollutants considered harmful to public health and the environment
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WATERS GeoViewer
This landing page provides information about the EPA GeoPlatform hosted WATERS GeoViewer.