As a producer, you are responsible for ensuring that animal mortalities are not disposed of in a liquid manure, storm water, or process wastewater storage or treatment system that is not specifically designed to treat animal mortalities.
Mortalities can be managed by performing one of the following:
Incineration requires a permitted facility with an air curtain burner. Open burning is not allowed.
Composting. If mortalities will be composted, the facility shall comply with Ecology Publication No: 05-07-034 “On-Farm Composting of Livestock Mortalities”.
Natural decomposition. A livestock animal that dies on private or state rangeland from causes other than a significant infectious or contagious disease agent may be left to decompose naturally on that property as long as the carcass:
> 1,325 ft any surface water, well, or sinkhole and from any public roadway or residence not owned by the owner
Is out of public view; and on the land with the property owner's permission.
Burial. If the producer intends to bury the mortalities they may do so in accordance with WAC 246-203-121 which requires:
disposal within 72 hrs,
burials be surrounded by 3 ft of earth on all sides,
burials are at least 100 ft from surface water or wells.
Outside seasonal flooding areas or 100-year flood plain
Rendering. Utilization of a rendering company to remove mortalities.
In accordance with WAC 16-25, for animals dying of disease or unknown causes, the distance from wells or surface water is increased to 300 ft when disposing of mortalities via burying.
Livestock that have died from a reportable disease must be disposed of in consultation with the state veterinarian.
WA State Vet 360-902-1878
Sources: Chapter 16-25 WAC Disposal of Dead Livestock