When coal is burned to generate electricity, it leaves a solid residue — coal ash. Our operations have produced 28% less coal ash since 2005 as we generate more electricity with cleaner energy sources, including natural gas, wind and solar. As a result, we’ve reduced the number of sites where we store or dispose of coal ash on our properties. This progress will continue as we transition away from coal and fulfill our industry-leading vision of providing 100% carbon-free electricity by 2050.
We operate in states that have effectively regulated storage and disposal activities for decades. These local rules specify construction and operating standards for facilities where we store and dispose of coal ash, and they ensure routine inspections and groundwater monitoring. In addition, the U.S. Environmental Protection Agency began regulating coal ash as a nonhazardous waste in 2015 under its Coal Combustion Residuals (CCR) Rule, which establishes national minimum standards for the design, operation and closure of these facilities.
Coal combustion residuals or byproducts are generically referred to as coal ash. Fly ash, bottom ash and slag are common terms that describe different types of coal ash. Coal ash is mainly made up of rocks, minerals and other noncombustible, natural materials that are present in coal when it is mined from the earth. Less than 1% of coal ash contains trace elements, which are also found in soil and naturally exist in our environment.
Over the years, many studies have evaluated the environmental impact and safety of coal ash. The results support the classification of coal ash as a nonhazardous waste, but also confirm the importance of responsibly managing, storing, disposing and reusing coal ash.
Our?generating plants consume more than 23 million tons of coal a year, producing approximately two million tons of coal ash annually. Xcel Energy currently has nine active coal ash facilities, including three impoundments or ponds and six landfills. Since the adoption of EPA’s CCR Rule, we have closed 15 ponds that were no longer used. We removed the ash from these ponds and are now completing the required groundwater monitoring that is part of the closure process.
Each coal-fueled plant is unique in the amount and type of ash it produces and how the ash is reused or disposed. More than half of our coal operations are located in arid regions where groundwater is scarce or at a greater depth — a favorable geologic condition that minimizes the possibility of environmental impacts.
More than 80% of the coal ash from our operations is permanently disposed in landfills in a dry form. The Sherburne County (Sherco) Generating Plant is our only plant with a pond that stores wet coal ash. Coal ash from the plant is sluiced to this 100-acre pond, which was designed with state-of-the art features for managing water and protecting the environment. When this pond is full, it will be capped with an engineered, protective cover system, and a special collection system will continue to dry the pond after it is closed. EPA inspected the pond in 2009 during a nation-wide review and found that it meets stringent safety requirements. We would expect all our coal ash storage and disposal facilities to receive similar findings because of our high standards around safety and protecting the environment.
Nearly 20% of the coal ash produced at our plants is reused for beneficial purposes, including 100% of the coal ash produced at our Texas coal-fueled plants. Reuse offers many environmental, engineering and economic benefits, such as:
EPA and other federal agencies encourage the reuse of coal ash through a framework of engineering standards, material specifications, procurement guidelines and other programs. Many uses of coal ash are further regulated by state and local governments.
Our practice is to responsibly reuse this material whenever possible and appropriate. Currently, when we sell coal ash produced at our plants to third parties, our contracts allow only encapsulated beneficial use or un-encapsulated beneficial use in quantities less than 12,400 tons in non-roadway applications. Our contracts also require that third parties responsibly manage the coal ash and follow all federal, state and local requirements.
The most common use of our coal ash is as a cement or concrete additive and for manufacturing protective coatings. Bottom ash from our plants is mainly used for construction within lined disposal facilities, as a cement or concrete additive, and for manufacturing roof shingles and sand blasting grit.
Some ash also is used in power plant air emission-control equipment. Rather than using raw material in control equipment, such as limestone, coal ash can be used as a sorbent to capture sulfur dioxide from stack emissions.
The design and operation of Xcel Energy’s coal ash facilities adheres to local, state and federal standards. We also incorporate operating practices that minimize the potential for precipitation to come in contact with the ash. These include:
EPA’s CCR Rule provides two options for closing landfills and ponds — either removing the coal ash from the facility or installing an engineered cover system or cap over the facility. Generally, our landfills will be closed with the ash in place, with the current natural or engineered liner system, and an engineered cap installed. How we close our ponds will vary, depending on what is best for each site’s conditions.
To confirm that our design and operating practices are effective, we install wells to test groundwater and monitor performance. Regulations and individual plant permits determine the number and location of wells. State or local requirements generally specify that groundwater monitoring systems include wells located up- and down-gradient of the facilities to assess the quality of groundwater entering and leaving the site, which can help in identifying sources that may influence groundwater. EPA’s CCR Rule requires well placement as close as possible to the landfill or pond.
The U.S. Environmental Protection agency regulates the disposal of coal ash under the Coal Combustion Residuals Rule, published in April 2015. The following are documents that Xcel Energy is required to provide under the new rule:
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