Every year, America’s coal-fired power plants produce about 140 million tons of coal ash, making coal combustion residuals (CCR) the second-largest waste stream in the country. That’s a lot of solid waste, and it’s waste that contains high levels of arsenic, lead, selenium and other cancer-causing substances that America’s community leaders would rather not have in their local earth, water, and air. In fact, recent publicly available data on CCR shows that as many as 535 coal ash ponds in the U.S. don’t have a simple HDPE liner to prevent toxic chemicals from seeping into groundwater that could make its way into drinking water. For decades, many coal ash ponds have been contained with low-permeability clay and clay cut-off trenches and walls. Because federal and state CCR regulations have been relatively lax over the years, very few coal ash ponds incorporate High Density Polyethylene (HDPE) geomembrane liners, leachate collection systems, or the types of flow controls commonly found in municipal solid waste landfills and landfill closure systems.
In fall 2017, the Virginia office of AECOM, a well-regarded global infrastructure engineering firm, released a public report summarizing the best practices in CCR/coal ash containment, citing “closure-in-place” as the prevailing choice when considering all factors, from community impacts to overall costs. These best practices were laid out in the report’s executive summary, which reads in part:
“As of September 2017, there were approximately 500 ash ponds in the United States covering a total of more than 23,500 acres and storing a total of more than 1 billion cubic yards (CY) of CCR material. Closure-in-place is being pursued for more than 93% of ponds with CCR volumes greater than 5 million CY and 75% of ponds between 1 and 5 million CY and more than 80% of ash ponds larger than 20 acres. Closure by removal has generally been reserved for low volume (less than 1 million CY) and small acreage (less than 20 acres) ash ponds. Currently, there are approximately 140 ash ponds in the southeastern United States (Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, and West Virginia). Of these ponds, more than 92% with CCR volumes greater than 5 million CY and more than half of ponds with between 1 and 5 million CY are being closed in place. Sixty-seven percent (67%) of ash ponds with CCR volumes of less than 1 million CY are being closed by removal. Similarly, more than 70% of ash ponds with more than 100 acres and more than 55% between 20 and 100 acres are being closed in place. More than 65% of the smaller ash ponds (less than 20 acres) are being closed by removal.”
(Source: Senate Bill 1398 Response, Coal Combustion Residuals Ash Pond Closure Assessment, Nov. 2017. AECOM Engineering.)
Suitable for both capping and lining CCR landfills, HDPE geomembrane is a polyethylene thermoplastic made from petroleum with a high strength-to-density ratio that is resistant to many solvents and can withstand higher temperatures (120 °C/ 248 °F) for short periods, making it an excellent barrier material to contain and cap coal ash waste, including bottom ash, sluiced bottom ash and fly ash, flue gas desulfurization (FGD) wastewater, and other CCR waste products. HDPE is also one of the world’s most-produced plastic products, accounting for nearly half of the 99.6 million tons of polyethylene-based plastics forecasters expect to be produced worldwide in 2018.
When searching for an experienced installer of HDPE geomembrane for coal ash containment or CCR ash pond capping, you would be well-served to look into U.S. HDPE installation companies with broad experience and millions of square feet of verifiable installations of HDPE and other geosynthetic, geomembrane, and geotextile materials, especially installations concerned with protecting earth, water, and air from contaminants, such as those found in large landfill and containment and closure projects, mining heap-leach pads and energy waste or wastewater containment projects. Specific recent experience in CCR containment and coal ash pond lining is also something to look for.
While much of America’s coal ash waste is located in the eastern portion of the U.S., CCR containment can be needed wherever coal is burned. For example, in 2016-2017, Nevada and eastern California’s electric power utility NVEnergy hired International Lining Technology to install 500,000 square feet of 60ml HDPE geomembrane with a geocomposite product on top to contain the 91-acre coal ash landfill that had been created by the Reid Gardner Generating Station, a 557-megawatt power station near Moapa, Nevada that closed in March of 2017.