Cyanide is used in heap leach gold mining. A cyanide solution is applied to the mined out ore to extract gold. The pregnant cyanide solution is stored in pits or ponds which attract and kill wildlife.

Trona Mine Evaporation Ponds

Trona, sodium sesquicarbonate, is mined to produce soda ash that is used in the manufacturing of glass, fertilizer, detergent, and many other products. Wastewater from this process is piped to surface impoundments or ponds. The water is highly alkaline and has a very high salt concentration. Consequently, the trona ponds remain ice free longer than freshwater ponds attracting birds during the colder season. Birds landing on these ponds can become encrusted with salt and may drown. Birds that preen their feathers can become sick or die due to ingesting too much salt. Birds may also suffer from cold stress as the salt crystals reduce the insulating ability of the feathers.

Photos of a trona pond and salt-encrusted bird.

Coal-fired Power Plant Evaporation Ponds (FGD Ponds)

Some coal-fired power plants use soda liquor from trona (soda ash) processing plants, alkaline fly ash, sodium carbonate or lime to neutralize the acidity of water used in their flue scrubbers. The water in the scrubbers reduces sulfur dioxide emissions from the power plant.

Water used in the scrubbers is recycled several times then discharged into a nearby evaporation pond. This Flue Gas Desulfurization (FGD) liquor is high in sodium, chloride, sulfates, carbonates and bicarbonates. As in the trona mine evaporation ponds, the FGD ponds have very high salt concentrations. Birds landing on these ponds can become encrusted with salt and may drown. Birds that preen their feathers can become sick or die due to ingesting too much salt. Birds may also suffer from cold stress as the salt crystals reduce the insulating ability of the feathers.

Acidic Water Impoundments

Process water in some industries such as phosphate fertilizer processing plants becomes acidic with a pH less than 2. The acidic process water is stored in open impoundments that attract migratory birds.

Birds landing in these acidic ponds can ingest this water which causes severe trauma to their gastrointestinal tracts and eventual death. The acidic water also removes natural oils from the birds’ feathers causing them to die by drowning or hypothermia. 

Solutions

Gold mines are covering cyanide pits with netting to exclude wildlife and prevent mortality.

Some mines are using high density polyethylene balls to cover the cyanide pits and render them unattractive to migratory birds.

Trona mines and phosphate processing plants are currently hazing birds with manned airboats. The airboat crews also recover debilitated birds from the ponds and rehabilitate and release them back into the wild. This method is time and labor intenstive and, although it reduces mortality, it does not eliminate it. Techniques to discourage use of these industrial impoundments by animals are constantly being developed. and improvements in technology for processing natural resources is ongoing. For example, many of the trona plants are switching to a dry process to dispose of their wastes. This eliminates the use of water and therefore the ponds. Additionally, some coal-fired power plants have developed radar-activated bird deterrent systems to discourage migratory birds from using FGD evaporation ponds.