In a joint project by the group, along with Waterkeeper Alliance, Clean Water Action, Earthjustice and the Environmental Integrity Project, Closing the Floodgates: How the Coal Industry Is Poisoning Our Water and How We Can Stop It examined the water permits of about 400 coal-fired plants.

Officials for the groups said more than half of those it reviewed allow coal ash and wastewater discharge from scrubbers into waterways.

“In the absence of any effective pollution limit, coal plants have become by far the largest source of toxic water pollution in the country, based on toxicity,” it said in the report.

Of the 274 coal plants discharging coal ash and scrubber wastewater, almost 70% – or 188, have no limits for discharges such as arsenic, boron, cadmium, lead, mercury, and selenium, the groups said.

Additionally, the project noted 102 plants – one third of that 274 – have no monitoring requirements or obligations to report discharges to the public or to regulatory agencies.

In its project, the Sierra Club also reported finding 71 coal plants that had discharged toxic water into rivers, lakes, streams and bays already declared impaired because of poor water quality.

Additionally it said more than three out of four of those coal plants, 59 in all, had no permit to limit metal discharges.

“Nearly half of the coal plants surveyed [187] are operating with an expired Clean Water Act permit [and] 53 of these power plants are operating with permits that expired five or more years ago,” the Sierra Club said in the report.

The group released the report to the public on Tuesday, holding a public conference call to answer questions and discuss specifics of its findings.

The Sierra Club said among the most troubling findings was a lack of binding federal standards to limit coal plant pollution, adding that existing standards established in 1982 did not include most of today’s worst pollutants.

According to the US Environmental Protection Agency, which itself has gotten into the fight against coal-fired plants from issues of water to greenhouse gases, has said that more than half of all toxic water pollution in the US comes from power plants.

That, the Sierra Club said, made coal-fired facilities the number one source of the nation’s water pollution.

The EPA said in the past that about 140,000 people experienced increased cancer risk annually due to arsenic in fish from coal plants, 13,000 children under seven annually were reported to have reduced IQs because of lead in fish, and about 2000 children are born with lower IQs because of mercury in fish ingested by their mothers.

“Allowing coal polluters to fill our rivers and lakes with this witches’ brew of toxic chemicals threatens public health and diminishes quality of life for Americans," Waterkeeper Alliance president Robert F Kennedy Jr said.

“The Clean Water Act is one of our nation's greatest achievements, but 40 years after this critical legislation was passed, the coal industry is still polluting with impunity, thanks to a loophole no other industry has enjoyed.”

Clean Water Action president Robert Wendelgass called for the EPA to “end the power plant industry’s free pass to pollute”

“It's time for power plants to stop using rivers, lakes, streams and bays as open sewers to dump their toxic waste,” he said.

“It's especially a travesty that we are allowing more than 70 coal plants to dump dangerous heavy metals directly into waterways that are already impaired with those very same toxics … [w]orse still, three quarters of these plants are operating without a permit to limit the amount of toxic metals they can dump in the water.”

The environmental groups said it would be working to raise awareness for its cause and the EPA’s critical new coal plant water pollution standards by holding events across the nation including a “toxic lemonade stand” in Pennsylvania and a “Miss and Mr Toxic Water Swimsuit Competition” in Missouri and a kayaking trip outside of coal plant in Oklahoma.

In the end, the environmentalists said they were seeking one goal from the EPA’s consideration of the new standards – a complete ban on all toxic discharge.