Bird mortality in oil field wastewater disposal facilities.

Commercial and centralized oilfield wastewater disposal facilities (COWDFs) are used in the Western United States for the disposal of formation water produced from oil and natural gas wells. In Colorado, New Mexico, Utah, and Wyoming, COWDFs use large evaporation ponds to dispose of the wastewater. Birds are attracted to these large evaporation ponds which, if not managed properly, can cause wildlife mortality. The U.S. Fish and Wildlife Service (USFWS) and the U.S. Environmental Protection Agency (EPA) conducted 154 field inspections of 28 COWDFs in Wyoming from March 1998 through September 2008 and documented mortality of birds and other wildlife in 9 COWDFs. Of 269 bird carcasses recovered from COWDFs, grebes (Family Podicipedidae) and waterfowl (Anatidae) were the most frequent casualties. Most mortalities were attributed to oil on evaporation ponds, but sodium toxicity and surfactants were the suspected causes of mortality at three COWDFs. Although the oil industry and state and federal regulators have made much progress in reducing bird mortality in oil and gas production facilities, significant mortality incidents continue in COWDFs, particularly older facilities permitted in the early 1980's. Inadequate operation and management of these COWDFs generally results in the discharge of oil into the large evaporation ponds which poses a risk for birds and other wildlife.