Murray Bridge Abattoir's effluent is being disposed through drainage wells into unconfined aquifers which are hydraulically connected to the Murray River. Six rotary wells encircling the abattoirs area, proved the regional hydraulic gradient to be towards the Murray River. Calculations show that the effluent travel time to reach the river is about 10 years. Biological contaminants are naturally reduced to harmless levels in the subsurface within 2 weeks, and the time-constant chemical pollutants will be diluted by normal river flow to insignificant levels. Consequently the possibility of pollution to the Murray River by sub-surface effluent disposal is thought to be very remote. The continued use of drainage wells as a standby for the recently introduced irrigation system appears quite acceptable.