In an environmental showdown with high stakes for Indiana, the Hoosier Environmental Council and five other groups filed suit last week to force the Trump administration to uphold rules ordering utilities to clean up toxic coal ash ponds by April.

The move is being watched closely here because Indiana has more of the toxic dumps than any other state, leeching carcinogens into groundwater, some of which is used for drinking water.

So when the Trump administration this summer weakened a law that regulated the heavy metal-laden waste — thereby allowing the pits to keep spewing dangerous chemicals for nearly two more years — Hoosiers were particularly at risk.

The environmental groups say that is unacceptable.

"The notion that we would leave ash sitting in groundwater where it already is or is likely to be used as drinking water supply is as far from good policy as you can get," said Tim Maloney, the Hoosier Environmental Council's Senior Policy Director.

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"These unlined impoundments pose a very significant health and environmental risk, and the preponderance of the pits are leaking," he added. "So any efforts to reduce oversight simply are not justified."

The original clean-up order, implemented in 2015 under the Obama administration, was the first ever federal regulation of the disposal of coal ash, which contains concentrated levels of cancer-causing chemicals such as arsenic and chromium. That law said that ash ponds meeting certain conditions — being that they are a known source of contamination or are within five feet of groundwater — must close and be cleaned up by April 2019.

In Indiana, that means nearly all of the roughly 85 pits in the state — storing more than 60 million cubic yards of coal ash — would need to close within six months.

Two main closure methods are accepted by the EPA: to cap the ash and leave it where it is or to remove it to a dry, lined landfill. Utilities say removal is more costly, though estimates are hard to come by. Environmental advocates and scientists argue it is the cleaner and safer option to protect against further contamination.

In March, monitoring results were released, proving that nearly all coal ash ponds around the nation are leaking toxic pollutants into groundwater.

But the amendments, rolled out in July, give coal plant owners more time to clean up certain ash ponds that are leaking: until October 2020. In other words, the ash could keep polluting the waters around it for two additional years.

"Any extension of the deadline that lets the pits operate longer clearly doesn’t meet the protectiveness requirements and certainly is an important part of our petition in this case," said Jenny Cassel, an attorney for Earthjustice, which filed the lawsuit in the U.S. Court of Appeals for D.C. on the group's behalf.

Other amendments to the 2015 rule include weakening drinking water protections by removing some contamination limits, allowing state officials to judge site compliance instead of professional engineers, and allowing state officials to end groundwater monitoring.

In its announcement of the Trump Administration's new rule, EPA said the revisions would provide utilities and states more flexibility in how coal ash is managed, and saves between $28 million and $31 million a year in regulatory costs. Utilities, which have not yet responded to this latest petition, strongly supported the July revisions.

But the possibility they could be exempt from certain pollution monitoring requirements — the same monitoring that revealed evidence of contamination — is also being challenged in last week's petition..

Coal ash contamination is the subject of another court case being played out in Tennessee, where 30 workers are dead and 250 more are sick or dying after cleaning up a spill, all from illnesses linked to toxins found in coal ash.

In that case, workers are suing the utility and firm that oversaw the cleanup, claiming they were misled about the dangers of long-term exposure to the ash and were denied protective gear. The firm, through its attorney, contends that the workers are lying and — even if they’re not — that it had no duty to protect them.

That spill, which happened 10 years ago at the Tennessee Valley Authority Kingston plant, set in motion a chain of events that led to the Obama Administration's 2015 coal ash rule.

That original rule has also been the subject of lawsuits. In fact, just one month after Trump's EPA finalized its rollback plan, the same U.S. Court of Appeals in Washington, D.C., ruled that the Obama-era regulations did not go far enough to protect the public.

One of the ways it fell short, according to the court, was that some ash pits had been improperly exempted from regulations. These pits are known as "legacy ponds," the remnants of closed and retired power plants.

Roughly a quarter of Indiana's legacy ponds, as many as 20, will now need to be appropriately closed, as well, according to Maloney.

"Federal agencies should be held accountable when they adopt arbitrary rules that don’t reflect the evidence and the environmental and health risks that coal ash poses," he said, adding that the Hoosier Environmental Council was on the initial 2015 suit, too. "We think these recent rollbacks will be vulnerable in the same way the others were under the original rule."

Maloney said he also hopes any potential future rollbacks — which the EPA has said could be expected next year — will be deterred by the court's August decision.

Given the federal uncertainty surrounding the coal ash rule, Maloney said he thinks it would be prudent for the state not to rule on any proposed closure plans, as he expects the latest rollbacks will likely be overturned.

That said, Maloney added, the states could take it upon themselves to impose stricter restrictions.

"The state can act on its own authority to have a program that gets the job done no matter what the federal agency does, and in our view that is to excavate the ash at these pits unless there is clear and convincing evidence it is not and will not cause contamination," he said.

The Indiana Department of Environmental Management has already received several closure proposals from utilities around the state, including Duke Energy and Indianapolis Power & Light.

The vast majority of those plans would cap the ash in place, or leave the ash in the unlined pits with an impermeable barrier over the top. That does nothing, however, to prevent the ash from coming in contact with groundwater and seeping toxins into it.

Instead, according to Cassel, environmental groups and public health officials recommend excavating the ash to a lined and dry enclosure.

IDEM officials have been reviewing the submitted closure plans, scrutinizing them, asking questions and raising issues. No determinations have been made on the proposals, and the agency said it is currently evaluating how the court ruling or lawsuit might impact its decisions.

"The real question is in the end, will IDEM feel empowered to make the right decision?" Maloney asked. "A policy that would put our health, environment and drinking water supply at risk is just wholly irresponsible and flawed, and that needs to change and the ash to be removed from those sites."

Call IndyStar reporter Sarah Bowman at 317-444-6129 or email at sarah.bowman@indystar.com. Follow her on Twitter and Facebook: @IndyStarSarah. Connect with IndyStar’s environmental reporters: Join The Scrub on Facebook.

IndyStar's environmental reporting project is made possible through the generous support of the nonprofit Nina Mason Pulliam Charitable Trust.