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Contaminant Issues - Oil Field Waste Pits

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Commercial Oil Field Waste Disposal Facilities

Commercial and centralized oil field wastewater disposal facilities (COWDFs), like oil field waste pits, pose a significant risk to migratory birds and other wildlife because they use large evaporation ponds (either passive or with aeration) to dispose of and treat oil and gas exploration and production wastes. Commercial oilfield wastewater disposal facilities are operated for profit and receive wastewater from one or more oil and gas operators. A centralized oilfield wastewater disposal facilities is owned and operated by the same oil and gas company that operates the wells generating the wastewater disposed of into the facility. COWDFs that dispose of wastewater through deep well injection generally do not pose a risk to wildlife.

commercial oil field

There are 72 COWDFs in Region 6 (30 in Colorado, 16 in Utah and 26 in Wyoming )(#'s as of October 2011). COWDFs are hazardous to wildlife as they accumulate significant quantities of oil on the surface of very large pits or evaporation ponds without effective wildlife exclusionary devices. Generally, COWDFs are operated in the following manner. Wastewater is initially disposed of into a receiving pit and the greatest amount of oil tends to float to the surface in that pit. Water from receiving pits is often sent to another pit or series of pits for evaporation or other management.

The following management practices make COWDFs a risk to the environment and migratory birds:

  • no site security such as fencing and locking gates to prevent unauthorized entry and the unauthorized disposal of wastes at the facility other than oil field produced water

photo of a vacuum truck disposing water into COFWDF
Vacuum truck disposing water into COWDF

  • accumulation of oil on the evaporation ponds

waste pond
Oil-covered evaporation pond.

  • oil and water separation occur in the main evaporation pond
  • skim ponds or open topped separation tanks are not equipped to prevent entry by birds and other wildlife

oil bird

Grebe carcasses in a COFWDF evaporation pond.

  • presence of visible sheens on thesurface of evaporation ponds visible sheen
  • concentrations of salts in the evaporation ponds may eventually cause hypersaline conditions which could pose a risk to migratory birds and cause mortality
  • surfactants or other chemicals present in the wastewater can cause birds to become waterlogged and cause mortality

Mirgatory bird mortality has been documents in oil field wastewater disposal facilities due to the presence of oil, paraffin, and sheens in the evaporation ponds. The presence of visible sheens on wastewater ponds are just as deadly to birds that come in contact with them. A light sheen will coat the bird's feathers with a thin film of oil. Although a sheen of oil on the bird may not immediately immobilize the bird, it will compromise the feathers' ability to insulate the bird. Furthermore, the affected bird will ingest the oil when it preens its feathers and suffer chronic effects. The bird could suffer mortality depending on the severity of the chronic effects and the amount of oil ingested.. Any oil or sheens remaining in the ponds in between the removal actions has the potential of coating birds or other wildlife coming into contact with it. Mortality or morbidity may result depending on the amount of oil coating the animal, the species, prior condition of the animal, the amound of stress incurred by the animal after oiling, and weather conditions.

Oily sludges remaining at the bottom of the impoundments as well as oil in the bank soil can seep onto the pond surface, especially during the summer when warm temperatures can mobilize the oil. Additionally, rainfall events or snowmelt will wash oil from the banks back into the pond. The chronic oiling can only be prevented by cleaning the banks, removing the oil-soaked soils and the bottom sludge.

High concentrations of salts can also pose a risk to migratory birds.  Birds entering ponds with hypersaline water can ingest the brine and die from sodium toxicity.  Salt toxicosis has been reported in ponds with sodium concentrations over 17,000 milligrams per liter (parts per million) (Windingstad, R.M. et al. 1987.  Salt toxicosis in waterfowl in North Dakota. Jour. Wildlife Diseases 23(3):443-446).  Ingestion of water containing high sodium levels can also pose chronic effects to aquatic birds, especially if a source of freshwater is not available nearby.  Aquatic birds ingesting hypersaline water can be more susceptible to avian botulism ( Cooch, F. G. 1964.  A preliminary study of the survival value of a functional salt gland in prairie Anatidae.  Auk 81:380-393).  During cooler temperatures, sodium in the hypersaline water can crystallize on the feathers of birds landing in these waterbodies.  The sodium crystals destroy the feathers' thermoregulatory and buoyancy functions causing the bird to die of hypothermia or drowning.  Sodium intoxication can cause neurological impairment resulting in the bird's inability to hold its head upright (Meteyer CU, Dubielzig RR, Dein FJ, Baeten LA, Moore MK, Jehl JR Jr and K Wesenberg. 1997. Sodium toxicity and pathology associated with exposure of waterfowl to hypersaline playa lakes of southeast New Mexico. J. Vet. Diagn. Invest. 9: 269-280).  The bird's head will droop into the water and cause it to drown.

If the evaporation pond is receiving produced water from oil or natural gas wells, oil and gas production chemicals, such as corrosion inhibitors and surfactants, could be present in the produced water and could pose a risk to migratory birds.  When a bird comes into contact with water containing surfactants, the surfactant will reduce the surface tension of the water; thus, allowing water to penetrate through the feathers and onto the skin.  This compromises the insulative properties of the feathers and subjects the bird to hypothermia (Stephenson, R. 1997. Effects of oil and other surface-active organic pollutants on aquatic birds.  Environmental Conservation 24(2):121-129).  The loss of water repellency by the feathers due to reductions in surface tension will cause the bird to become water logged and the loss of buoyancy will cause the bird to drown.


For more information, contact Pedro ‘Pete’ Ramirez, Jr. (

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