Variance

{
  "id": "MLC-T-ENV-029530",
  "term": "Variance",
  "field": "Environment",
  "definition": "1. State or USEPA permission not to meet a certain drinking water standard. The water system must prove that: (1) it cannot meet a Maximum Contaminant Level, even while using the best available treatment method, because of the characteristics of the raw water, and (2) the variance will not create an unreasonable risk to public health. The state or USEPA must review, and allow public comment on, a variance every three years. States can also grant variances to water systems that serve small populations and which prove that they are unable to afford the required treatment, an alternative water source, or otherwise comply with the standard.\n\n2. State or EPA permission not to meet a certain drinking water standard. The water system must prove that: (1) it cannot meet a MCL, even while using the best available treatment method, because of the characteristics of the raw water, and (2) the variance will not create an unreasonable risk to public health. The State or EPA must review, and allow public comment on, a variance every three years. States can also grant variances to water systems that serve small populations and which prove that they are unable to afford the required treatment, an alternative water source, or otherwise comply with the standard.\n\n3. Any mechanism or provision under Sections 301 or 316 of the CWA or under 40 CFR Part 125, or in the applicable \"effluent limitations guidelines\" which allows modification to or waiver of the generally applicable effluent limitations requirements or time deadlines of the CWA. This includes provisions which allow the establishment of alternative limitations based on fundamentally different factors.\n\n4. A State with primacy may relieve a public water system from a requirement respecting an MCL by granting a variance if certain conditions exist. These are: 1) the system cannot meet the MCL in spite of the application of best available treatment technology, treatment techniques or other means (taking costs into consideration), due to the characteristics of the raw water sources which are reasonably available to the system, and 2) the variance will not result in an unreasonable public health risk. A system may also be granted a variance from a specified treatment technique if it can show that, due to the nature of the system's raw water source, such treatment is not necessary to public health.\n\n5. A measure of the spread of the values in a distribution. The larger the variance, the larger the distance of the individual cases from the group mean.\n\n6. Government permission for a delay or exception in the application of a given law, ordinance, or regulation.\n\n7. Mathematically, the sample variance is the sum of squares of the differences between the individual values of a set and the arithmetic average of the set, divided by one less than the number of values. For a finite population, the variance s² is the sum of squares of deviations from the arithmetic mean, divided by the number of values in the population where μ is the true arithmetic mean of the population.\n\n8. A measure of the variability or precision of a set of observations.\n\n9. Measure of variability, standard deviation squared.\n\n10. (Law) Government permission for a delay or exception in the application of a given law, ordinance, or regulation.\n\n11. Any mechanism or provision under CWA sections 301 or 316 or under 40 CFR Part 125, or in the applicable effluent limitations guidelines, which allows modification to or waiver of the generally applicable effluent limitation requirements or time deadlines of the CWA. This includes provisions, [that] allow the establishment of alternative limitations based on fundamentally different factors or on CWA sections 301(c), 301(g), 301(h), 301(i), or 316(a).\n\n12. Any mechanism or provision under section 301 or 316 of CWA or under 40 CFR part 125, or in the applicable “effluent limitations guidelines” which allows modification to or waiver of the generally applicable effluent limitation requirements or time deadlines of CWA. This includes provisions which allow the establishment of alternative limitations based on fundamentally different factors or on sections 301(c), 301(g), 301(h), 301(i), or 316(a) of CWA.\n\n13. Permission granted for a limited time (under stated conditions) for a person or company to operate outside the limits prescribed in a regulation. [CARBB 2000]",
  "subject": "Water",
  "references": [
    "Safe Drinking Water Act Glossary",
    "Drinking Water Glossary; Drinking Water Glossary 2009",
    "National Pollutant Discharge Elimination System (NPDES) Glossary",
    "Drinking Water Technical & Legal Terms",
    "Program Evaluation Glossary",
    "Terms of Environment",
    "Radon Glossary of Terms",
    "Environmental Modeling and Assessment Program (EMAP) Master Glossary",
    "Benchmark Dose Software (BMDS) Glossary of Terms",
    "EPA 2005b",
    "NPDES Permit Writers Glossary; NPDES Permit Writers Manual Glossary",
    "40 CFR 122.2 (CFR 2013)",
    "MRA Thesaurus"
  ],
  "url": "https://mlchart.com/terminology/environment/variance/"
}