The Tennessee Valley Authority’s own testing – in 1981 and 1995 – revealed its coal ash contained radioactive materials and toxic heavy metals, a USA TODAY NETWORK-Tennessee investigation shows.

For more than two decades following that testing, TVA didn’t tell plant workers and contract laborers about those radioactive materials and toxic heavy metals, the ongoing investigation shows.

And when 7.3 million tons of that coal ash gushed from a busted dike in December 2008 at the Kingston Fossil Plant in Roane County and into the Clinch and Emory Rivers, TVA didn’t tell emergency responders or the workers tasked with cleaning it up, a report by TVA's Office of the Inspector General showed.

Even now, amid allegations members of the Kingston disaster clean-up workforce were poisoned by long-term exposure to its coal ash, TVA contends in a letter to two Tennessee congressmen that its coal ash is safe.

“Years of scientific and regulatory review, including by the EPA, have confirmed that coal ash should be deemed and regulated as nonhazardous,” TVA Chief Executive Officer Bill Johnson wrote in a March letter to U.S. Reps. Tim Burchett, R-Knoxville, and Steve Cohen, D-Memphis.

“The known trace elements, some of which can cause illness where sufficient concentration and exposure conditions exist, have not been thought to be present at high enough levels in coal ash to harm people given known exposure pathways and the safety measures required at the recovery project site,” the letter continued.

TVA internal records obtained

The Kingston coal ash spill remains the nation’s largest human-caused environmental disaster in U.S. history, bigger than the Exxon Valdez and Deepwater Horizon oil spills. A decade later, more than 40 TVA and contract laborers who cleaned up the spill are dead and more than 400 are dying from what they say is exposure to the toxic elements in coal ash.

USA TODAY NETWORK-Tennessee has been investigating the claims of workforce poisoning since early 2017. The news organization has now interviewed hundreds of workers, obtained and reviewed video and photo evidence of worker conditions and obtained and analyzed hundreds of government, court and TVA records on the spill and the clean up.

TVA tested its coal ash in 1981, and that testing revealed TVA’s coal ash contained radium-226 at levels at least three times and as much as eight times higher than naturally-occurring levels in soil and other radioactive metals including uranium and thorium, according to documents reviewed by USA TODAY NETWORK-Tennessee.

The study showed an average radium content in its coal ash at or exceeding the Environmental Protection Agency's safe drinking water standards for a single dose.

Independent testing of coal ash at the Kingston spill site from June 2009 to March 2010 showed radium levels exceeding the EPA's safe drinking water standards by nearly double the maximum allowable limit, documents show.

Workers in the Kingston clean up were exposed to coal ash as much as 70 hours per week.

Exposure to radium over a long period heightens the risk of diseases, including lymphoma, bone cancer, and hematopoietic (blood-formation) diseases, such as leukemia and aplastic anemia, according to the EPA. These effects, the EPA says, take years to develop after exposure.

Many of these diseases have been diagnosed in the Kingston cleanup workers.

TVA did some more testing of its coal ash in 1995, revealing levels of arsenic, cadmium, chromium and selenium considered unsafe under public drinking water standards, records show.

Michael Sutton, a TVA manager in its coal ash division, wrote about both the 1981 and 1995 test results in a 2001 report obtained by USA TODAY NETWORK-Tennessee.

TVA didn’t list any of those dangerous ingredients in the Material Safety Data Sheet, known as an MSDS, on coal ash that was provided to laborers at all of its coal-firing plants in Tennessee in 2001, records show.

TVA’s 2001 MSDS said its coal ash contained only seven ingredients, with crystalline silica — the cause of a condition known as black lung in coal miners — listed as the only potential threat to a worker’s health.

The fact sheet listed “trace” amounts of arsenic as the only other toxic ingredient. It made no mention of heavy metals or radioactive material.

TVA gave that same 2001 MSDS to emergency responders, including the U.S. Coast Guard, the EPA and various state regulatory officials, in the hours following the spill, records show.

Jacobs Engineering, TVA’s disaster cleanup project manager, used the same 2001 MSDS ingredient list in a 2009 EPA-approved master safety and health plan that governed worker safety requirements for the disaster cleanup operation.

TVA and Jacobs did not update either the MSDS or the master safety and health plan until after workers began complaining of illnesses linked to the components TVA had found in its coal ash decades earlier.

TVA's current MSDS and the final master safety and health plan approved for the cleanup in 2013 still doesn't list radium-226 as an ingredient in coal ash, a review shows.

TVA, Jacobs dispute basis of safety questions

TVA has declined to answer a list of questions about its coal ash, its testing, its safety materials, its treatment of workers before, during and after the 2008 spill, its response to the 2008 spill and cleanup or its potential responsibility for the alleged poisoning of members of the Kingston spill workforce through long-term exposure to the toxic ingredients in its coal ash.

“That TVA disagrees with you about the facts or what conclusions might be drawn from them reflects TVA’s (and EPA’s and many others’) more complete understanding of the recovery effort,” the utility wrote in a statement. “TVA has and will continue to provide factual and truthful information regarding coal ash and the Kingston recovery project.”

One of Jacobs' attorneys, Theodore J. Boutrous Jr., declined to answer questions about whether TVA told the firm about its 1981 study and what it revealed about TVA's coal ash when TVA contracted with Jacobs to oversee the cleanup in early 2009.

"There was extensive testing of water, soil, and air at the Kingston Site in the immediate aftermath of the spill by a number of government agencies and companies, including the TVA, the Tennessee Department of Environment and Conservation, and the EPA," Boutrous wrote.

"To the extent your question suggests that anyone — including Jacobs — would rely only on a 1981 study or the referenced MSDS in setting safety standards at the site, that is incorrect," he continued.

Many of the results of that early independent testing cited by Boutrous were later tossed out as invalid because of problems with the laboratories chosen by TVA and Jacobs, according to a report by TVA's Office of the Inspector General.

Once Jacobs took over testing in mid-2009, the firm monitored workers' exposure to silica, but not to any of the toxic chemicals, heavy metals or radioactive isotopes TVA's study revealed was contained in its coal ash, EPA records show.

Jacobs' safety manager Tom Bock testified he repeatedly told workers the coal ash in which they were immersed was safe enough to eat daily, an assertion not supported by science.

Bock also testified he ordered protective dust masks destroyed when workers who complained of sicknesses and breathing troubles sought to wear them, a trial transcript shows.

Lawsuit remains pending

The Kingston coal ash spill destroyed a half-dozen homes, roads and infrastructure and remains the largest manmade environmental disaster in U.S. history — larger than the 1989 Exxon Valdez oil spill in Alaska and 2010 Deepwater Horizon oil spill in the Gulf of Mexico.

Investigation:Complete coverage of USA Today Network-Tennessee's ongoing probe

TVA’s Office of the Inspector General would later conclude TVA was at fault for the dike failure, ignored failure warning signs and treated coal ash — which contains at least 26 toxins, heavy metals and radioactive metals — as a substance as safe as household garbage in its handling of the material and worker safety measures.

The EPA put TVA in charge of cleaning up its own mess in January 2009, within three weeks of the spill. TVA hired Jacobs, a global project management contractor, to help on the effort.

TVA ratepayers paid more than $1.3 billion for the clean up. Jacobs was paid more than $64 million of that total for its project management.

In 2013, 57 workers and their relatives filed a lawsuit in U.S. District Court in Knoxville against Jacobs, alleging the firm’s safety managers lied about the dangers of coal ash and denied them adequate protective gear. The number of plaintiffs in the case later rose to just more than 100, including family members of deceased workers, after USA TODAY NETWORK-Tennessee launched its probe in 2017.

A jury in November 2018 ruled Jacobs breached its contract with TVA and its duty of care to protect the workers. The jury also ruled Jacobs’ breach was capable of causing the sicknesses claimed by the workers.

Chief U.S. District Judge Tom Varlan has ordered Jacobs to try to negotiate a settlement, noting many of the sickened workers do not have health insurance.

Jacobs says it thinks the rulings that led to the mediation order are incorrect and plans to appeal, Boutrous wrote in a statement released last month.

"The trial in the first phase of this case was fundamentally flawed and unfair, and it should not stand," Boutrous said. "There has been no finding of liability in these cases, and Jacobs stands by the quality of its work in assisting TVA with the management of the Kingston cleanup. Jacobs takes pride in working on some of the world’s toughest challenges and in protecting the safety of all those who work on its projects.”

The verdict means the workers can now pursue damages against Jacobs if they can prove they were poisoned by the coal ash. Jacobs is suing subcontractors under indemnity agreements built into the firm’s contract with TVA and invoking a separate indemnity agreement with TVA to recoup any damage awards and the firm’s legal bills.