The public anxiety over entombing coal ash in Lee and Chatham counties comes down to this: a sheet of plastic that’s no thicker than two credit cards stuck together.
That’s the thickness of the plastic liners that will be installed in two landfills to safeguard the environment from the nasty stew contained within. The coal ash heading to Lee and Chatham counties is laced with arsenic, lead, selenium and other heavy metals.
According to the company building the landfills, the plastic liners are virtually indestructible and will last more than 500 years. That prediction comes from Duke Energy’s landfill construction firm, Kentucky-based Charah, in a recent filing with the U.S. Army Corps of Engineers.
But after years of studies, many engineers discount estimates of liner durability as simplistic. Industry engineers have calculated that a landfill liner could last anywhere from a few decades to 1,000 years before it springs a leak, depending on a host of factors.
Yet on one thing the experts agree: No landfill liner will last forever.
“All lining systems should be designed on the assumption that there will be leakage in the lining system,” said Ian Peggs, a materials scientist in Florida who has studied the issue for years. “Ultimately the whole thing will fall apart.”
Local opponents of the proposed landfills say the statistical risk of liner failure is simply too great, and they’re asking state regulators not to issue a construction and operating permit for the landfills. They shudder at the prospect of their communities sharing living space, possibly for centuries, with two enormous earthen crypts together holding 20 million tons of toxic industrial waste that does not decay.
“I totally understand the need to move this coal ash that’s leaking into rivers all over the state,” said Elaine Chiosso, the Haw Riverkeeper. “I just think it’s insane to hope those liners will last basically forever.”
The N.C. Department of Environment and Natural Resources is expected to decide on the permits in the coming weeks. At recent public hearings in Sanford and Pittsboro on the proposed landfills, scores of residents pleaded with state environmental regulators to deny the permits. Opponents cited the risk of groundwater contamination, years of truck caravans and sunken property values.
Peggs, president of I-Corp International in Florida, has a high degree of confidence in liner systems, as long as they are properly installed and carefully monitored. But he said liners are prone to leaks because of substandard landfill design and damage during installation. He recently presided over a discussion session dedicated to liner leakage at the February geosynthetics industry conference in Oregon, where experts hashed out the perennial conundrums of leak detection, leak prevention and leak probabilities.
A temporary fix
More than 150 million tons of coal ash currently steep at 14 sites in North Carolina. These ash repositories have no liners and are contaminating local groundwater, some reaching drinking wells. In response to the environmental crisis, the state legislature last year required Duke Energy to move ash from four sites that lawmakers deemed high-priority to lined landfills by August 2019, putting the electric utility on a hurry-up schedule.
Landfills reinforced with liners are generally considered the safest way of storing society’s garbage, whether the waste is generated by households or heavy industry. Lined landfills are endorsed by the U.S. Environmental Protection Agency and by some environmental organizations for coal ash storage.
Last week, Duke announced plans to bury more than 10 million tons of coal ash in three lined landfills at the utility’s Dan River power plant in Eden, Sutton plant in Wilmington and Robinson plant in Hartsville, S.C. Environmental groups praised the move because the power company plans to confine the ash on Duke’s property, and away from sources of water.
In Lee County, local officials have agreed not to challenge the landfill in their community in exchange for a $12 million payment from Duke Energy. The proposed landfill would be built at the abandoned Colon clay mine in Sanford.
Chatham County officials are still reviewing the industrial waste project that will take up to eight years to fill with 12 million tons of ash. The site in Moncure would be built at the former Brickhaven clay mine.
In the first phase of Duke’s coal ash cleanup, estimated to take up to 18 months, Duke would move 2 million tons from Wilmington and nearly 1 million tons from Gaston County to be buried in Brickhaven or Colon or both. It’s not clear how the sites will be used once they are covered over with vegetation. The Brickhaven landfill covers 145 acres and the Colon landfill, 118 acres.
“The mines reclaimed with ash as structural fill will provide valuable, usable land in these counties that can be suitable for commercial and economic development,” said Scott Sewell, Charah’s chief operating officer, in an emailed statement. “The land also will be suitable for agricultural use or green space. Specific plans have not yet been determined.”
But even ardent supporters call landfills a temporary fix, until a better solution is discovered or the coal ash is dug up and recycled.
“In my opinion, some of the landfill stuff is more-or-less kicking the can down the road,” said geotechnical engineer Stacey Smith at the Smith & Gardner firm in Raleigh, which has worked on hundreds of landfills. “It puts it in a holding spot until additional research allows us to reuse these materials as a resource.”
Ed Mussler, who heads up the permit review branch at the N.C. Department of Environment and Natural Resources, believes dry landfills reinforced with liners can protect society for an indefinite period of time. He characterized the plastic liner as just one component in a multi-layered protective system.
Monitoring the leaks
Below the plastic liner proposed by Charah would sit a 2-foot layer of clay, which would hold back water for 50 years, Mussler said. The top of the landfills would be protected by 6-foot soil buffers, each buffer placed over another plastic liner, Mussler said.
The landfill bottom would also contain a leachate collection system to pump water out for removal and treatment. The whole setup is designed to let water drain out of the ash and to prevent new water from getting in, what’s known in the industry as a hermetically sealed “dry tomb.”
“If no water gets in, no water can get out,” said Mussler, the permitting branch supervisor in the agency’s solid waste section. “If after 30 years you’ve got no water coming out of the landfill, you’ve got a pretty good issue.”
But critics say the design has many holes.
In Charah’s application, the two landfills would be monitored for 30 years, with no plans for subsequent monitoring. Left to fend for themselves, the man-made mounds would be exposed to rain, wind, erosion, forests and other natural forces, said Morton Barlaz, a solid waste specialist who heads N.C. State University’s Department of Civil, Construction & Environmental Engineering.
“If you put a final cover on and walk away after 30 years, then you will have a problem at some time,” Barlaz said. “You will probably have to do annual maintenance on the final cover for a very long time – or in perpetuity.”
Only three landfills in the state are monitored for leaks. The three, including one coal ash dump, are double-lined along the bottom and have state permits allowing up to 500 gallons of water per acre per day to leak, said DENR spokeswoman Cathy Akroyd.
That amount of leaking is “very high” for double-lined landfills, said Abigail Beck, a Vermont-based engineer and director of Liner Integrity Services at TRI Environmental.
The EPA recommends only 100 gallons per day be allowed to leak, while New York state allows just 20 gallons and Michigan only five gallons, Beck said.
Most landfills in the country, including North Carolina, use single liners. The single liners don’t have leakage limits because the detection systems typically are placed above the liner at the bottom of the ash. The thinking is if water can be detected entering the landfill, engineers can fix the problem and keep the ash dry.
“This goes straight to the heart of the irony of single-lined landfills, where the leakage cannot be measured, so it therefore cannot be controlled,” Beck said in an email. “If they leak, the groundwater gets contaminated, and there is no way to know it will happen until it is too late.”
Beck believes it is possible to build a leak-proof landfill using a two-liner system.
The single-liner technology is the design Charah has submitted for the proposed Lee and Chatham county landfills. Ellen Lorscheider, a solid waste section chief at DENR, acknowledged that a breach in a single liner “would take years to show up” in groundwater.
Founded in 1987, the Kentucky company began operations here in 2001 and now has 120 employees in the state managing eight active projects, including the construction of the Asheville Airport Structural Fill. In all, Charah has 50 long-term coal ash management contracts at 34 power plants in 18 states, according to a company fact sheet.
Landfills contamination in North Carolina
There are 44 lined landfills in the state that store municipal solid waste, another nine hold coal ash. The landfills date back to the nationwide adoption of liner technology in the early 1980s. The most recent was built in 2012.
Some of the landfills – including three lined coal ash landfills – have groundwater contamination, but the contamination has not been traced to liner failure. Two municipal solid waste landfills, in Cabarrus County and in Buncombe County, are currently being assessed to determine the cause of elevated groundwater contamination readings, said Ellen Lorscheider, solid waste section chief at DENR.
Liner problems often start during installation, when the sheets are accidentally cracked, torn or punctured.
That happened at a Duke Energy landfill at Belews Creek Steam Station in Stokes County, which in April 2008 began receiving gypsum, a byproduct of coal-burning power plant emissions. Monitoring wells at that landfill registered high levels of iron, sulfate and total dissolved solids in groundwater, prompting reviews by Duke Energy.
Duke’s June 2014 assessment report, submitted to DENR, describes tears to the liner edge in multiple places, caused by heavy equipment traffic. The report notes that in one area the damage occurred at elevations above the waste. The damage was repaired in 2011, the report said.
Groundwater samples were collected in August 2013 and analyzed by the Duke Energy Analytical Laboratory. Duke forwarded the data to its contractor, HDR Engineering in Charlotte. Contamination showed up in multiple monitoring wells.
HDR blamed the high sulfate readings on contaminated groundwater at a single monitoring well located just five feet from the road used by trucks to deliver the gypsum. HDR said the contamination was likely caused by gypsum falling from the trucks, said DENR hydrogeologist Elizabeth Werner.
HDR also said high rainfall caused excessive surface runoff and infiltration of gypsum into the groundwater. HDR’s assessment is ongoing.