Ash pond

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A coal-fired power plant with surface impoundments William H. Zimmer Power Station aerial 2017a.jpg
A coal-fired power plant with surface impoundments

An ash pond, also called a coal ash basin or surface impoundment, [1] is an engineered structure used at coal-fired power stations for the disposal of two types of coal combustion products: bottom ash and fly ash. The pond is used as a landfill to prevent the release of ash into the atmosphere. Although the use of ash ponds in combination with air pollution controls (such as wet scrubbers) decreases the amount of airborne pollutants, the structures pose serious health risks for the surrounding environment. [2]

Contents

Ash ponds use gravity to settle out large particulates (measured as total suspended solids) from power plant wastewater. This technology does not treat dissolved pollutants. [3] The ponds generally have not been built as lined landfills, and therefore chemicals in the ash can leach into groundwater and surface waters, accumulating in the biomass of the system. [4] [5] [6]

Design

Ash ponds are generally formed using a ring embankment to enclose the disposal site. The embankments are designed using similar design parameters as embankment dams, including zoned construction with clay cores. The design process is primarily focused on handling seepage and ensuring slope stability.

Failure of a pond's earthen embankment can cause ash spills on adjacent land and rivers, with serious environmental damage, as evidenced in the 2008 Kingston Fossil Plant spill in Tennessee [7] and the 2014 Dan River coal ash spill in North Carolina. [8]

Disposal methods

The wet disposal of ash into ash ponds is the most common ash disposal method, [9] but other methods include dry disposal in landfills. Dry-handled ash is often recycled into useful building materials. Wet disposal has been preferred due to economic reasons, but increasing environmental concerns regarding leachate from ponds has decreased the popularity of wet disposal. [9] The wet method consists of constructing a large "pond" and filling it with fly ash slurry, allowing the water to drain and evaporate from the fly ash over time. [10]

The flow of water through the fly ash and into ground water is controlled by using low-permeability clay layers and cutoff trenches/walls. Low-permeability clays have permeability on the order of 10−7 cm/s. Vertical flows through the foundation are controlled by siting fly ash ponds on areas of thick clay or rock layers that provide suitably low permeability through the base of the pond. Areas with high sub-surface permeability can be improved by importing suitable clay. Horizontal flows through the embankment are controlled using clay zones within the embankment. Cut off trenches and cut off walls are used to connect the embankment clay zones and the foundation clay layers. Cut off trenches are trenches that are dug into the selected low-permeability sub-surface layer and backfilled with clay to key the embankment clay zone into the sub-surface. Cut off trenches are generally used when the low permeability foundation layer(s) are near surface. Cut off walls are similar to cut off trenches, but are generally much deeper and narrower, and use either slurry or grout instead of clay.

Health and environmental impacts

Not all substances present in coal will burn, and hence the non-combustible material is present in more concentrated amounts in coal ash than in coal itself. Substances commonly found in coal ash include arsenic, barium, beryllium, boron, cadmium, nickel, lead, mercury, molybdenum, selenium and thallium. Elevated levels of radioactivity may also be present. [11] Many of these substances, especially heavy metals, can have negative effects on humans when ingested. Because of biomagnification, the concentration of unwanted chemicals in animals can increase up a food chain (similarly to mercury in tuna). Coal ash, a product of combustion, concentrates these elements and can contaminate groundwater or surface waters if there are leaks from an ash pond. [12]

Countries

Australia

Coal ash accounts for almost one-fifth of the waste generated in Australia. There are no national regulations requiring recycling of coal ash. [13] About 47% of coal ash was recycled in 2020. [14] Coal ash in New South Wales is typically stored in landfills ("dry emplacements") or ash ponds ("ash dams"). [15] Coal ash storage is regulated by the state Environment Protection Authority and its Dams Safety Committee, which publishes standards for dam design and environmental monitoring. [16]

Netherlands

Ash ponds are not allowed in the Netherlands, as they are a type of landfill. Instead, all coal ash is recycled in the Netherlands. [17]

Turkey

In 2021 inspections were criticized and said to be insufficient. [18] : 75 

United States

In the United States, coal ash is a major component of the nation's industrial waste stream. [19] As of 2012 there were over 470 operational coal-fired power plants in the US, and approximately 60 percent of US coal ash was disposed in surface impoundments and landfills. The US had 310 active on-site landfills in 2012, averaging more than 120 acres in size with an average depth of over 40 feet, and more than 735 active on-site surface impoundments, averaging more than 50 acres in size with an average depth of 20 feet. [20] In 2017, 38.2 million short tons (34.7×10^6 t) of fly ash, and 9.7 million short tons (8.8×10^6 t) of bottom ash were generated. [21] As of July 2022, 225 coal-fired power plants were operational in the United States. [22]

A 2019 report by the Environmental Integrity Project states that for U.S. coal-fired plants with available monitoring data, 91 percent of them have contaminated groundwater with "unsafe levels of toxic pollutants." [23]

In 2018 an environmental justice advisor to the US Environmental Protection Agency (EPA) stated that the increased toxic exposures from ash ponds will have disproportionate adverse health effects on low-income and minority communities. [24]

Historically, due to few federal and state regulations concerning ash ponds, most US power plants do not use geomembranes, leachate collection systems, or other flow controls often found in municipal solid waste landfills. [10] In 1980 the U.S. Congress defined coal ash as a "special waste" that would not be regulated under the stringent hazardous waste permitting requirements of the Resource Conservation and Recovery Act (RCRA). [25] Congress also directed EPA to study the coal ash problem and decide whether further regulation would be appropriate. In 2000, EPA stated that coal fly ash did not need to be regulated as a hazardous waste. [26] [27]

Following a 2008 failure that caused the Tennessee Valley Authority's Kingston Fossil Plant coal fly ash slurry spill, EPA began developing regulations that would apply to all ash ponds in the US. EPA published a Coal Combustion Residuals (CCR) regulation in 2015. The agency continued to classify coal ash as non-hazardous (thereby avoiding strict permitting requirements under RCRA Subtitle C), but with new restrictions:

  1. Existing ash ponds that are contaminating groundwater must stop receiving CCR, and close or retrofit with a liner.
  2. Existing ash ponds and landfills must comply with structural and location restrictions, where applicable, or close.
  3. A pond no longer receiving CCR is still subject to all regulations unless it is dewatered and covered by 2018.
  4. New ponds and landfills must include a geomembrane liner over a layer of compacted soil. [28]

Some of the provisions in the 2015 CCR regulation were challenged in litigation, and the United States Court of Appeals for the District of Columbia Circuit remanded certain portions of the regulation to EPA for further rulemaking. [29]

EPA also published an effluent guidelines (wastewater) regulation in 2015 pursuant to the Clean Water Act. [30] The regulation limits discharges of toxic metals from power plants, including ash ponds and other wastestreams. The Agency estimated that the regulation would reduce the industry's metals discharges of 1.4 billion pounds annually. [31] In October 2020 EPA published a final rule that reverses some provisions of the 2015 wastewater regulation. The revised regulation extends the compliance deadline for some power plants, and exempts some others completely from the more stringent 2015 requirements. [32] [33] The 2020 rule has been challenged in litigation. [34] In March 2023 EPA published a proposed rule that would reverse some aspects of the 2020 rule and tighten the wastewater limitations for some facilities. [35]

EPA published a proposed RCRA rule on August 14, 2019 that would use location-based criteria, rather than a numerical threshold (i.e. impoundment or landfill size) that would require an operator to demonstrate minimal environmental impact so that a site could remain in operation. [36]

Following a court remand, EPA published its "CCR Part A" final rule on August 28, 2020 requiring all unlined ash ponds to retrofit with liners or close by April 11, 2021. Some facilities may apply to obtain additional time—up to 2028—to find alternatives for managing ash wastes before closing their surface impoundments. [37] [38] [39] EPA published its ""CCR Part B" rule on November 12, 2020, which allows certain facilities to use an alternative liner, based on a demonstration that human health and the environment will not be affected. [40] Further litigation on the CCR regulation is pending as of 2021. [41]

On January 11, 2022 EPA announced an enforcement action involving ash ponds at certain coal-fired plants in Indiana, Ohio, Iowa and New York. The agency's proposal would deny the plants' requests for extensions beyond the 2021 deadline and would require them to close their ash ponds ahead of their proposed schedules. EPA sent warning letters to four additional plants. [42] [43] EPA received a total of 57 extension requests. In November 2022 the agency announced its initial final determination on an extension request, denying a request submitted by a plant in Ohio. As of 2023 EPA has published proposed determinations for additional plants and the review process is ongoing. Each proposed determination is subject to a public comment period. [44]

Remediation

Remediation options include "capping, dewatering and/or stabilizing, consolidating into a new landfill, disposing off site, converting to wetlands, or any combination of these options." [45]

There are some initiatives, such as a 2015 initiative by Duke Energy, to excavate existing ash ponds to reduce the environmental effects of coal-burning power facilities on the surrounding environment. [46] [47]

See also

Related Research Articles

<span class="mw-page-title-main">Hazardous waste</span> Ignitable, reactive, corrosive and/or toxic unwanted or unusable materials

Hazardous waste is waste that has substantial or potential threats to public health or the environment. Hazardous waste is a type of dangerous goods. They usually have one or more of the following hazardous traits: ignitability, reactivity, corrosivity, toxicity. Listed hazardous wastes are materials specifically listed by regulatory authorities as hazardous wastes which are from non-specific sources, specific sources, or discarded chemical products. Hazardous wastes may be found in different physical states such as gaseous, liquids, or solids. A hazardous waste is a special type of waste because it cannot be disposed of by common means like other by-products of our everyday lives. Depending on the physical state of the waste, treatment and solidification processes might be required.

<span class="mw-page-title-main">Landfill</span> Site for the disposal of waste materials

A landfill site, also known as a tip, dump, rubbish dump, garbage dump, trash dump, or dumping ground, is a site for the disposal of waste materials. Landfill is the oldest and most common form of waste disposal, although the systematic burial of the waste with daily, intermediate and final covers only began in the 1940s. In the past, refuse was simply left in piles or thrown into pits; in archeology this is known as a midden.

<span class="mw-page-title-main">Industrial waste</span> Waste produced by industrial activity or manufacturing processes

Industrial waste is the waste produced by industrial activity which includes any material that is rendered useless during a manufacturing process such as that of factories, mills, and mining operations. Types of industrial waste include dirt and gravel, masonry and concrete, scrap metal, oil, solvents, chemicals, scrap lumber, even vegetable matter from restaurants. Industrial waste may be solid, semi-solid or liquid in form. It may be hazardous waste or non-hazardous waste. Industrial waste may pollute the nearby soil or adjacent water bodies, and can contaminate groundwater, lakes, streams, rivers or coastal waters. Industrial waste is often mixed into municipal waste, making accurate assessments difficult. An estimate for the US goes as high as 7.6 billion tons of industrial waste produced annually, as of 2017. Most countries have enacted legislation to deal with the problem of industrial waste, but strictness and compliance regimes vary. Enforcement is always an issue.

<span class="mw-page-title-main">Incineration</span> Waste treatment process

Incineration is a waste treatment process that involves the combustion of substances contained in waste materials. Industrial plants for waste incineration are commonly referred to as waste-to-energy facilities. Incineration and other high-temperature waste treatment systems are described as "thermal treatment". Incineration of waste materials converts the waste into ash, flue gas and heat. The ash is mostly formed by the inorganic constituents of the waste and may take the form of solid lumps or particulates carried by the flue gas. The flue gases must be cleaned of gaseous and particulate pollutants before they are dispersed into the atmosphere. In some cases, the heat that is generated by incineration can be used to generate electric power.

<span class="mw-page-title-main">Tailings</span> Materials left over from the separation of valuable minerals from ore

In mining, tailings or tails are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are different from overburden, which is the waste rock or other material that overlies an ore or mineral body and is displaced during mining without being processed.

<span class="mw-page-title-main">Resource Conservation and Recovery Act</span>

The Resource Conservation and Recovery Act (RCRA), enacted in 1976, is the principal federal law in the United States governing the disposal of solid waste and hazardous waste.

<span class="mw-page-title-main">Industrial wastewater treatment</span> Processes used for treating wastewater that is produced by industries as an undesirable by-product

Industrial wastewater treatment describes the processes used for treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater may be reused or released to a sanitary sewer or to a surface water in the environment. Some industrial facilities generate wastewater that can be treated in sewage treatment plants. Most industrial processes, such as petroleum refineries, chemical and petrochemical plants have their own specialized facilities to treat their wastewaters so that the pollutant concentrations in the treated wastewater comply with the regulations regarding disposal of wastewaters into sewers or into rivers, lakes or oceans. This applies to industries that generate wastewater with high concentrations of organic matter, toxic pollutants or nutrients such as ammonia. Some industries install a pre-treatment system to remove some pollutants, and then discharge the partially treated wastewater to the municipal sewer system.

<span class="mw-page-title-main">Municipal solid waste</span> Type of waste consisting of everyday items discarded by the public

Municipal solid waste (MSW), commonly known as trash or garbage in the United States and rubbish in Britain, is a waste type consisting of everyday items that are discarded by the public. "Garbage" can also refer specifically to food waste, as in a garbage disposal; the two are sometimes collected separately. In the European Union, the semantic definition is 'mixed municipal waste,' given waste code 20 03 01 in the European Waste Catalog. Although the waste may originate from a number of sources that has nothing to do with a municipality, the traditional role of municipalities in collecting and managing these kinds of waste have produced the particular etymology 'municipal.'

<span class="mw-page-title-main">Bottom ash</span> Solid residue of combustion in the lower part of an industrial oven

Bottom ash is part of the non-combustible residue of combustion in a power plant, boiler, furnace or incinerator. In an industrial context, it has traditionally referred to coal combustion and comprises traces of combustibles embedded in forming clinkers and sticking to hot side walls of a coal-burning furnace during its operation. The portion of the ash that escapes up the chimney or stack is, however, referred to as fly ash. The clinkers fall by themselves into the bottom hopper of a coal-burning furnace and are cooled. The above portion of the ash is also referred to as bottom ash.

<span class="mw-page-title-main">Coal combustion products</span>

Coal combustion products (CCPs), also called coal combustion wastes (CCWs) or coal combustion residuals (CCRs), are categorized in four groups, each based on physical and chemical forms derived from coal combustion methods and emission controls:

<span class="mw-page-title-main">Coal-fired power station</span> Type of thermal power station

A coal-fired power station or coal power plant is a thermal power station which burns coal to generate electricity. Worldwide there are over 2,400 coal-fired power stations, totaling over 2,000 gigawatts capacity. They generate about a third of the world's electricity, but cause many illnesses and the most early deaths, mainly from air pollution.

<span class="mw-page-title-main">Health and environmental impact of the coal industry</span>

The health and environmental impact of the coal industry includes issues such as land use, waste management, water and air pollution, caused by the coal mining, processing and the use of its products. In addition to atmospheric pollution, coal burning produces hundreds of millions of tons of solid waste products annually, including fly ash, bottom ash, and flue-gas desulfurization sludge, that contain mercury, uranium, thorium, arsenic, and other heavy metals. Coal is the largest contributor to the human-made increase of carbon dioxide in Earth's atmosphere.

<span class="mw-page-title-main">Hazardous waste in the United States</span>

Under United States environmental policy, hazardous waste is a waste that has the potential to:

<span class="mw-page-title-main">Kingston Fossil Plant coal fly ash slurry spill</span> 2008 environmental disaster in Tennessee, US

The Kingston Fossil Plant coal fly ash slurry spill was an environmental and industrial disaster that occurred on December 22, 2008, when a dike ruptured at a coal ash pond at the Tennessee Valley Authority's Kingston Fossil Plant in Roane County, Tennessee, releasing 1.1 billion US gallons of coal fly ash slurry. The coal-fired power plant, located across the Clinch River from the city of Kingston, used a series of ponds to store and dewater the fly ash, a byproduct of coal combustion. The spill released a slurry of fly ash and water which traveled across the Emory River and its Swan Pond embayment onto the opposite shore, covering up to 300 acres (1.2 km2) of the surrounding land. The spill damaged multiple homes and flowed into nearby waterways including the Emory River and Clinch River, both tributaries of the Tennessee River. It was the largest industrial spill in United States history.

<span class="mw-page-title-main">Big Sandy Power Plant</span>

The Big Sandy Power Plant is a 268 megawatt (MW), natural gas power plant owned and operated by Kentucky Power Company, a subsidiary of American Electric Power (AEP), on the shores of the Big Sandy River near Louisa, Kentucky. It was established in 1963. It was formerly a coal-fired power plant, but was converted to natural gas in 2016.

Solid waste policy in the United States is aimed at developing and implementing proper mechanisms to effectively manage solid waste. For solid waste policy to be effective, inputs should come from stakeholders, including citizens, businesses, community-based organizations, non-governmental organizations, government agencies, universities, and other research organizations. These inputs form the basis of policy frameworks that influence solid waste management decisions. In the United States, the Environmental Protection Agency (EPA) regulates household, industrial, manufacturing, and commercial solid and hazardous wastes under the 1976 Resource Conservation and Recovery Act (RCRA). Effective solid waste management is a cooperative effort involving federal, state, regional, and local entities. Thus, the RCRA's Solid Waste program section D encourages the environmental departments of each state to develop comprehensive plans to manage nonhazardous industrial and municipal solid waste.

Water in Arkansas is an important issue encompassing the conservation, protection, management, distribution and use of the water resource in the state. Arkansas contains a mixture of groundwater and surface water, with a variety of state and federal agencies responsible for the regulation of the water resource. In accordance with agency rules, state, and federal law, the state's water treatment facilities utilize engineering, chemistry, science and technology to treat raw water from the environment to potable water standards and distribute it through water mains to homes, farms, business and industrial customers. Following use, wastewater is collected in collection and conveyance systems, decentralized sewer systems or septic tanks and treated in accordance with regulations at publicly owned treatment works (POTWs) before being discharged to the environment.

<span class="mw-page-title-main">Health effects of coal ash</span>

Coal ash, also known as coal combustion residuals (CCRs), is the mineral residue that remains from burning coal. Exposure to coal ash and to the toxic substances it contains may pose a health risk to workers in coal-fired power plants and residents living near coal ash disposal sites.

<span class="mw-page-title-main">2014 Dan River coal ash spill</span> Ecological disaster in North Carolina

In February 2014, an Eden, North Carolina facility owned by Duke Energy spilled 39,000 tons of coal ash into the Dan River. The company later pled guilty to criminal negligence in their handling of coal ash at Eden and elsewhere and paid fines of over $5 million. The U.S. Environmental Protection Agency (EPA) has since been responsible for overseeing cleanup of the waste. EPA and Duke Energy signed an administrative order for the site cleanup.

<span class="mw-page-title-main">Allen Fossil Plant</span>

The Allen Fossil Plant was a 741-megawatt (MW), coal power plant located south of Memphis, Tennessee. It generated electricity from 1959 to 2018. At the time of its closure, the plant was operated by Tennessee Valley Authority (TVA).

References

  1. ↑ U.S. Environmental Protection Agency (EPA), Washington, D.C. "Hazardous and Solid Waste Management System; Identification and Listing of Special Wastes; Disposal of Coal Combustion Residuals from Electric Utilities." Proposed rule. Federal Register,75 FR 35130, June 21, 2010.
  2. ↑ Erickson, Camille (October 7, 2019). "Mixing water, Powder River Basin coal ash dangerous to human health, new research finds". Casper Star-Tribune. Casper, WY.
  3. ↑ "Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category". EPA. 2018-11-30.
  4. ↑ Brooke, Nelson (June 5, 2019). "New Interactive Maps of Groundwater Pollution Reveal Threats Posed by Alabama Power Coal Ash Pits". Black Warrior Riverkeeper. Birmingham, AL.
  5. ↑ Springer, Patrick (March 13, 2019). "Report: Unsafe coal ash contamination found in North Dakota groundwater". Bismarck Tribune. Bismarck, ND.
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  7. ↑ Dewan, Sheila (2008-12-23). "Water Supplies Tested After Tennessee Spill". The New York Times.
  8. ↑ "Case Summary: Duke Energy Agrees to $3 Million Cleanup for Coal Ash Release in the Dan River". Enforcement. EPA. 2017-03-15.
  9. 1 2 McLaren, R. J. & A. M. DiGioia (1987). "The Typical Engineering Properties of Fly Ash". In Woods, R. D. (ed.). Geotechnical Practice for Waste Disposal. Reston, VA: American Society of Civil Engineers.
  10. 1 2 Kessler, K. A. (1981). "Wet Disposal of Fossil Plant Waste Case History". Journal of the Energy Division. American Society of Civil Engineers. 107 (2): 199–208. doi:10.1061/JDAEDZ.0000063.
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  12. ↑ Schlossberg, Tatiana (2017-04-15). "2 Tennessee Cases Bring Coal's Hidden Hazard to Light". The New York Times.
  13. ↑ Millington, Ben (2019-03-09). "Coal ash has become one of Australia's biggest waste problems — and a solution is being ignored". ABC (Australian Broadcasting Corporation) News. Newcastle, NSW.
  14. ↑ National Waste Report 2020 (PDF) (Report). Docklands, Victoria: Australia Department of Agriculture, Water and the Environment. 2020-11-04. p. 36.
  15. ↑ "Coal ash dams". Sydney NSW: Environment Protection Authority, New South Wales (EPA/NSW). 2021-09-21.
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  18. ↑ Çaltı, Nuray; Bozoğlu, Baran; Aldırmaz, Ahmet Turan; Atalar, Gülşah Deniz (2 June 2021). Özelleştirilmiş Termik Santraller ve Çevre Mevzuatına Uyum Süreçleri [Privatized Thermal Power Plants and Environmental Legislation Compliance Processes] (Report) (in Turkish). İklim Değişikliği Politika ve Araştırma Derneği. Archived from the original on 9 October 2021. Retrieved 27 July 2021.
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  20. ↑ "Frequent Questions about the 2015 Coal Ash Disposal Rule". EPA. 2021-10-13.
  21. ↑ 2017 Coal Combustion Product Production & Use Survey Report (PDF) (Report). Farmington Hills, MI: American Coal Ash Association. 2018. Archived from the original (PDF) on 2019-05-07. Retrieved 2019-05-19.
  22. ↑ "Number of operational coal power plants worldwide as of July 2022, by country/territory". Energy. New York: Statista. July 2022.
  23. ↑ "Coal's Poisonous Legacy". Washington, D.C.: Environmental Integrity Project. 2019-03-04.
  24. ↑ McKenna, Phil (2018-03-15). "EPA Environmental Justice Adviser Slams Pruitt's Plan to Weaken Coal Ash Rules". New York: Inside Climate News.
  25. ↑ "Special Wastes". Hazardous Waste. EPA. 2021-07-06.
  26. ↑ EPA (2000-05-22). "Notice of Regulatory Determination on Wastes From the Combustion of Fossil Fuels." Federal Register,65 FR 32214.
  27. ↑ Luther, Linda (2013-08-06). Background on and Implementation of the Bevill and Bentsen Exclusions in the Resource Conservation and Recovery Act: EPA Authorities to Regulate "Special Wastes" (Report). Washington, D.C.: U.S. Congressional Research Service. R43149.
  28. ↑ EPA. "Hazardous and Solid Waste Management System; Disposal of Coal Combustion Residuals From Electric Utilities." 80 FR 21301, 2015-04-17.
  29. ↑ Green, Douglas H.; Houlihan, Michael (2019-04-24). "D.C. Circuit Court Remands CCR Deadline Extension to EPA". Environment, Energy, and Resources Section. Washington, DC: American Bar Association.
  30. ↑ EPA. "Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category." 80 FR 67837. 2015-11-03.
  31. ↑ "Steam Electric Power Generating Effluent Guidelines—2015 Final Rule". EPA. 2020-09-04.
  32. ↑ Dennis, Brady; Eilperin, Juliet (2020-08-31). "Trump administration rolls back Obama-era rule aimed at limiting toxic wastewater from coal plants". The Washington Post.
  33. ↑ EPA (2020-10-13). "Steam Electric Reconsideration Rule." Final rule. Federal Register,85 FR 64650
  34. ↑ "Environmental Groups File Lawsuits Against Trump Administration for Toxic Water Pollution Rollbacks". New York, NY: Waterkeeper Alliance. 2020-11-02.
  35. ↑ EPA (2023-03-29). "Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category." Proposed rule. 88 FR 18824
  36. ↑ EPA. "Hazardous and Solid Waste Management System: Disposal of Coal Combustion Residuals from Electric Utilities; Enhancing Public Access to Information; Reconsideration of Beneficial Use Criteria and Piles; Proposed Rule." Federal Register,84 FR 40353. 2019-08-14.
  37. ↑ "EPA Letting Some Hazardous Coal Ash Ponds Stay Open Longer". U.S. News. 2020-10-16.
  38. ↑ EPA. "Hazardous and Solid Waste Management System: Disposal of Coal Combustion Residuals From Electric Utilities; A Holistic Approach to Closure Part A: Deadline To Initiate Closure." 85 FR 53516. 2020-08-28.
  39. ↑ "Revisions to the Coal Combustion Residuals (CCR) Closure Regulations; Fact sheet". EPA. July 2020.
  40. ↑ EPA (2020-11-12). "Hazardous and Solid Waste Management System: Disposal of CCR; A Holistic Approach to Closure Part B: Alternate Demonstration for Unlined Surface Impoundments." Final rule. 85 FR 72506
  41. ↑ Smoot, D.E. (2020-12-11). "Groups challenge rollback of coal ash rule". Muskogee Phoenix. Muskogee, OK.
  42. ↑ Daly, Matthew (2022-01-11). "EPA moves to crack down on dangerous coal ash storage ponds". The Washington Post.
  43. ↑ "EPA Takes Key Steps to Protect Groundwater from Coal Ash Contamination". EPA. 2022-01-11. Press release.
  44. ↑ "Coal Combustion Residuals Part A Implementation". EPA. 2023-10-30.
  45. ↑ Johnson, Mark; Nillson, Kent (2014-12-01). "Construction Considerations Are Key in Closure Planning for Coal Ash Ponds". Power Magazine. Rockville, MD: Access Intelligence, LLC.
  46. ↑ "Coal Ash". Charlotte, NC: Catawba Riverkeeper Foundation. Archived from the original on 2017-03-03. Retrieved 2020-02-22.
  47. ↑ "Ash Management & Safe Basin Closure". Charlotte, NC: Duke Energy.
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