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The large amounts of water extracted along with the gas in coalbed methane operations can boost stream levels and benefit fish and wildlife, but the often contaminated water can also cause significant ecological harm, according to a report soon to be issued by the U.S. Fish and Wildlife Service.
In an analysis of the potential for ecological benefits of CBM water in Wyoming's Powder River Basin, where CBM development has skyrocketed in recent years, FWS concluded that it could be used to create or enhance wetlands and generally increase the available water for fish and wildlife. But the quality of the water is often poor, containing salts and other impurities, potentially resulting in the contamination of waterways and wildlife.
In the Powder River Basin, water in the coal seams must be pumped out to release the methane.
"Obviously, more water has benefits to fish and wildlife, but there can also be negatives," said Pedro Ramirez, an environmental contaminants specialist with FWS. Ramirez presented the findings of the study at a coalbed methane conference in Denver, Colo., March 30, organized by the Strategic Research Institute.
FWS collected water samples from five areas where produced water had been discharged and from seven pools where produced water had been impounded. Researchers also collected samples from eight wetlands that had received produced water and tested fish tissues as well.
They found that levels of several contaminants, including selenium, lead and cadmium, exceeded acceptable thresholds. For instance, selenium levels at some sites were 3.9 parts per billion, almost twice as high as the 2 parts per billion limit that scientists have established for protecting aquatic life.
'All sorts of problems'
Selenium in produced water bioaccumulates in the food web, potentially putting a whole spectrum of species at risk, Ramirez said. "It can create all sorts of problems, especially in fish larvae and bird eggs," he said, explaining that the contaminant can cause deformities or kill embryos.
FWS also found high levels of chromium in fish collected from the sites. Chromium concentrations in fish were more than 24 parts per million. Four parts per million is considered harmful. "These fish obviously exceed those levels," he said.
Other contaminants found in produced water include sodium (salt), copper, lead and arsenic.
Sodium that accumulates in evaporation ponds can harm birds that visit the ponds, Ramirez said. In pools with high levels of sodium, salt crystals will form on the birds' feathers. When the birds attempt to clean it off, the salt goes to the brain, and they will suffer neurological damage, he said.
"They can't hold up their heads, and they end up drowning," he explained.
In addition to effects on water quality, producers and regulators should consider potential effects on fish and wildlife, he said. "When you're disposing CBM water, these are the things FWS is concerned about," he told the crowd of largely industry representatives.
One industry attendee questioned whether there were background levels of selenium in the soil that may have skewed FWS's results in some areas. Ramirez agreed that the study was "limited" and said selenium can occur in soils and that further study is needed to clarify how much selenium is coming from the produced water pumped to the surface and how much is in the soil.
Ramirez suggested that producers avoid discharging produced water containing high levels of selenium or sodium into containment ponds.
Producers and water management companies are developing new ways to dispose of produced water, including treating it using various technologies before releasing it onto the surface.
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