Approximately 37% of the electrical power used in the United States is generated by coal-fired power plants. Air pollution control systems installed on coal-fired power plants collect solid byproducts of coal combustion, which are commonly referred to as coal combustion products (CCPs). Common CCPs include fly ash, bottom ash, boiler slag, and flue gas desulfurization (FGD) residuals. Disposing CCPs in landfills or similar waste containment facilities is costly and land intensive, and many CCPs have useful engineering properties. Consequently, CCPs are often used beneficially in other products or applications, most notably as construction materials. Beneficial use of CCPs has many positive benefits in the context of sustainability including an annual reduction in greenhouse gas emissions by 11 million tons, fossil fuel consumption by 17 TJ, and water consumption by 121 GL, amounting to more than $11 billion (US) in total economic benefits.
Field water quality data collected from roadways where fly ash or bottom ash was used as embankment fill or as a stabilizing agent in the base or subgrade was assessed for any potential risk of ground water and surface water trace element contamination. Trace element concentrations (e.g. As, Cd, etc.) were obtained for seven roadways in Minnesota, Wisconsin, Indiana, and Georgia, spanning the applications of fly ash base and subgrade stabilization, fly ash fill, and bottom ash fill.
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