Water pollution from shallow coal-bed methane production is muddying the reputation of the world's cleanest fossil fuel.
Natural gas burns clean, and the drilling rigs required to mine the gas from coal beds in Wyoming's Powder River Basin are small. But groundwater flowing into the normally arid plains as the gas is extracted—in some instances at least 18,000 gallons of water a day at each well—is causing big complaints.
Residents and landowners in the area say the deluge of sodium-rich well water is eroding topsoil and destroying native plants in dry creek beds and on the plains, changing the region's ecology.
Rancher Ed Swartz's family has owned property in the Basin for three generations. Even though three other ranches lie between his land and the mining operations, Swartz said the salty water from the mines is hurting his alfalfa hay crop, which he feeds his cattle in the winter.
In the past two years, he said, "salty water coming down the creek has killed all the native vegetation that grows at the bottom of the creek. And it's being replaced with salt-tolerant grasses and reedy-type grasses, which are not very palatable to the cattle."
"You see a bunch of bare, dead branches sticking up over there," he added. "I don't want to lose deciduous trees. You can't plant them back, and that salt water is killing them."
Huge Loss of Water
The loss of underground water is an inevitable by-product of shallow coal-bed methane production. The gas is held in place by water pressure. Releasing the gas from coal aquifers that lie less than 1,000 feet (300 meters) below the ground requires pumping out the water.
Tom Doll of Barrett Resources Corporation, which is drilling 40 to 70 methane wells per month in the Powder River Basin, said water production at the wells varies, but the average is 11 to 12 gallons a minute for each well. But, he added, "we have some that range as high as a hundred gallons a minute in areas west where the coal is deeper."
Even at the minimum output, at least 18,000 gallons of water per well are being dumped onto the surface land every day. And Barrett is just one of about a hundred companies drilling for methane in the area.
Some people have proposed re-injecting the water back into the aquifer. That could be tougher than it sounds.
"It's like squeezing an orange and putting a straw in it," said Wyoming geologist Walter Merschat of Scientific Geochemical Services. "You can draw all the juice out of it through the straw, but try to squirt the juice back into the orange."
"It's very difficult, and it's the same with the aquifer," he said.
When the water is removed from the aquifer, the rock collapses and becomes more compact, which closes up the holes and spaces that would be needed to pump the water back in.
"Now, almost in a wink of time, we're pumping hundreds of millions of gallons of water out of that coal," said Merschat. "And it's almost impossible—if it is possible—to get the water back in, in a short period of time."
Studies Underway
Based on current levels of annual rainfall and snowmelt, Merschat said it would take a century to two centuries to replenish the aquifers.
"If it takes that long to replace the water, what right does anyone have to alter an aquifer system like that for our future generations?" said Merschat.
The high salt content of the water also changes the chemistry of the soil, said Merschat. The salt causes the clay to swell, making it impermeable to water. That affects vegetation because the roots of plants and trees can't get the water they need.
Some help may be on the way.
The University of Montana's Biological Station at Yellow Bay has been called on to investigate water pollution caused by the methane wells in Powder River Basin. And this week, the governors of Wyoming and Montana—states in which the gas-rich Powder River Basin lies—signed an agreement to monitor the pollution and its effects.
If studies show that the water pollution is affecting the region's water quality, legislation may be enacted requiring the mines to restrict the amount of salt and other minerals in the methane-related water.
Meanwhile, there is continued concern that in the short term, the region's habitats may be changed dramatically as water collects and forms ponds and reservoirs.
Watch television coverage of this story on National Geographic Today, only on the National Geographic Channel, 7 p.m. ET/PT in the United States.
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