The Murray Bridge Abattoir is located 1.2km from the River Murray proper on the western edge of Mobilong Swamp. The Abattoir disposes of 0.7 to 0.8 Ml of effluent on each week day and until recently, all effluent was poured down four drainage wells. The Engineering Water Supply Department feared possible pollution to the River Murray and requested the Mines Department to investigate the hydrogeology of the area. Groundwater in the area is very saline, generally exceeding 13000 mg/l and it is unlikely that it will ever be regarded as a resource. Hydrological information around the abattoir area is very limited and it is not possible to accurately calculate the hydraulic gradient and rate of groundwater movement at this stage. However it does appear that the hydraulic gradient slopes towards the River Murray. The drainage wells penetrate the permeable Mannum Formation limestone (Tertiary age) which has an hydraulic link with the river. Drainage at the abattoir has been in operation for at least 8 years and it appears that after the initial 9-12 months period, the volume of effluent disposed of down drainage wells would equal the volume of effluent displaced into the river. Preliminary calculations suggest that the quality of River Murray water could deteriorate rapidly under severe drought conditions. Further work is required to predict possible concentrations of deleterious constituents under various drought conditions. Disposal of effluent by irrigation of pastures commenced recently and if the odour is acceptable to the residents of Murray Bridge, irrigation should be expanded as it is a more acceptable and predictable form of effluent disposal. The Agriculture and Fisheries Department should be consulted to advise on irrigation practices and the area of land required for effective uptake of pollutants by the plants under irrigation. A drilling program is planned to establish observation wells to define the hydraulic gradient and test groundwater quality.