Evaporation ponds or retention ponds exist at in situ leach (ISL) uranium mining operations for the collection of wastewaters. Evaporation ponds are designed to keep toxic pond sediments contained and submersed at all times.
Evaporation ponds at Crowe Butte Uranium ISL mine, near Chadron Nebraska, estimated to be larger than three football fields each. Photo courtesy of Buffalo Bruce.
Due to the nature of ISL mines, there are high volumes of solutions being handled at any one time. These are stored temporarily in a retention pond, before the solutions are treated or injected into disposal wells or the water evaporated and the remaining solids removed and disposed of. (http://www.sea-us.org.au/pdfs/isl/no2isl.pdf)
The most common problem with evaporation/retention ponds are they “often leak and contaminate the underlying groundwater.” (http://www.nap.edu/openbook.php?record_id=1770) If the ponds were to leak and seepage were to escape from the facility, the toxic solutions would contaminate the underlying soil and potentially reach the water table and impact on groundwater resources. (http://www.sea-us.org.au/pdfs/isl/no2isl.pdf)
Wastewater ponds have caused problems for wildlife. As evaporation takes place, waste waters become more concentrated with salts and heavy metals. The U.S. Fish and Wildlife service states these wastewaters of hazardous substances “attract and kill migratory birds and other wildlife.” (http://www.fws.gov/mountain-prairie/contaminants/contaminants3.html)
Air quality near mining wastewater retention ponds is of concern. On December 18, 2008 a Moab Times article announced Utah’s Grand County Council passed a “groundbreaking” ordinance to protect the county’s air quality. Craig Bigler reported, “The ordinance sets standards for permitting and monitoring evaporation pond facilities for the disposal of produced water from oil and gas wells.” While Bigler specified oil and gas evaporation ponds as the target of this ordinance (http://www.grandcountyutah.net/pdf/bc/Ordinances/ord_476.pdf), the same concerns exist with uranium mining evaporation ponds: nearness to existing residences, irrigated farm lands, or intermittent streams; ground water depth, flow rates, and direction of flow; and wind patterns at the evaporation pond site. Uranium mining evaporation ponds have one added hazard: the presence of radioactive isotopes.
The uranium ore body targeted by miners contains not only uranium but also dozens of radioactive decay products, which include radium, radon gas, and polonium-210. (http://www.medicalnewstoday.com/articles/58088.php)
During uranium exploration and mining, huge quantities of radon gas are also released into the air, and dissolved in surface waters. The US Surgeon General has determined that radon is the second leading cause of lung cancer after cigarette smoking; tens of thousands of Americans die every year from exposure to radon gas.
When radon gas is released from a uranium mine, it deposits solid radioactive fallout including polonium-210 on the ground for hundreds of miles downwind from the mine site. Even during exploration, each drill-hole acts as a chimney which vents radon gas into the air from deep underground.” (http://pacificfreepress.com/content/view/2064/81/)
Radon gas emission is a health concern at any uranium mine, including ISL operations where “radium and radon are transported in the mining and processing solutions to the surface. When at the surface and the solutions are pumped to the retention pond, appreciable quantities of radon can thereby be released (Kasper et al., 1979). The radon gas can be transported in the direction of prevailing winds significant distances away from the mine, where radon will decay to a stable solid due to it’s very short half-life.” (http://www.sea-us.org.au/pdfs/isl/no2isl.pdf)
Radon gas can travel a thousand miles in just a few days, with a light breeze. As it travels low to the ground (it is much heavier than air) it deposits its "daughters" -- solid radioactive fallout -- on the vegetation, soil and water below. (http://www.ccnr.org/uranium_deadliest.html#daughters)
The areas of Weld and Larimer Counties nearest Powertech’s proposed uranium mine are familiar with wind. In his book, Colorado Weather Almanac, Meteorologist Mike Nelsen characterizes Colorado as being notorious for its wild winter winds. “Seasonally, hurricane force winds blow across the Front Range of the Rocky Mountains, and wind speeds approaching 150 mph- equivalent to a category 4 hurricane – have been measured at the National Center for Atmospheric Research in Boulder” (Colorado Weather Almanac, Page 65). Colorado’s wind season begins mid-November and lasts until mid-April when it blows into thunderstorm season. Thunderstorm season has earned Weld County the title of tornado capital of America.
Severe storms have damaged mining ponds. Winds have caused ponds to overtop when conditions exceeded the pond design’s wind rating, earth quakes can damage the pond, and mining ponds have overflowed in unusually heavy rainfall. Click here to see a map of wind directions from Powertech’s proposed uranium mine area.
The topography of Powertech’s proposed uranium mine is “generally flat to rolling prairie with occasional steep-sided, flat-top mesas. The whole area is incised by intermittent streams flowing southeasterly and flowing only during spring melt or from summer thunder storms.” (http://www.powertechexposed.com/Centennial43-101.pdf)
In June 2007 a thunderstorm’s runoff from the flattop mesa where Powertech proposes to mine uranium filled this pond on Jay and Robin Davis’ property. Flooding of the pond is a yearly occurrence and, by late September, the pond has typically dried up.
In this area, spring melts and summer thunderstorms fill ponds and flood ravines. Cities, towns, farms, and ranches down stream from these intermittent flows rely on this storm runoff. Heavy rains and flash floods are common during Colorado summers. Mike Nelson writes, “It is not uncommon during the middle and late summer for a thunderstorm to produce 3 to 6 inches of rain in just a few hours’ time. This kind of downpour cannot completely soak into the soil, so it runs off into ditches, dry washes, and low-lying areas.” (Colorado Weather Almanac)
Flooding and uranium mining don’t mix well for downstream residents. Due to their low-lying relief, flooding of a mine site can be of significant concern, both in terms of environmental management and operational issues. Flooding can give rise to many problems at an ISL mine that is poorly designed or equipped to handle such events. These might include a breach of the retention pond and associated wastes, flow into wells that are improperly sealed at the surface (especially monitoring wells), integrity problems for pipes across creeks due to debris flow in the creek during a flood event, erosion of surface soils, and damage to site equipment. Perhaps the most serious possibilities are a breach of the retention pond or water flow into any of the extensive series of wells involved in ISL, as this will lead to a local rise in groundwater pressures and exacerbate the potential for and early detection of excursions, and possibly interfere with groundwater quality monitoring. (http://www.sea-us.org.au/pdfs/isl/no2isl.pdf)
The area of Powertech’s proposed uranium mine near Nunn has a history of heavy rains and flooding. To see a photo gallery of recent storms click here.