Environmental considerations for the disposal of PBB-contaminated animals and wastes.

Accidental contamination of livestock feed in 1973 by polybrominated biphenyls (PBB) led to the destruction of over 30,000 animals in Michigan. Animal carcasses of mostly dairy cattle along with some beef cattle, hogs, sheep and rabbits destroyed under the Federal Food and Drug Administration guidelines were disposed on the land at an environmentally safe site in Kalkaska County, Michigan. The geology and hydrology of the disposal site on state-owned land is considered favorable for the disposal of contaminated carcasses and to prevent any migration of PBBs into ground and surface waters of the area. Materials underneath the site are predominantly sand with layers of silts and clays of glacial origin. The vertical isolation from the surface to the water table is over 90 ft, and the horizontal isolation to the privately owned properties and surface water bodies is well over 1.5 mile in all directions. The site design provides necessary safeguards for minimizing surface water infiltration into disposal trenches and maximizing the protection to the environment. A series of water wells in the direction of flow are established for monitoring groundwater quality for years to come. A 40-acre Gratiot County landfill located near St. Louis, Michigan, has received 269,000 lb of wastes containing 60 to 70% PBBs between 1971 and 1973. PBB wastes are intermixed with general refuse at various depths predominantly in the eastern half of the landfill. Phase I of the hydrogeological investigation shows that the landfill is situated immediately above the groundwater aquifer and a divide. Recently drilled test wells show traces of PBBs in the aquifer in all directions. Additional studies are planned in the near future for corrective measures and monitoring.