Investigation of leakage through the left abutment of Aroona Dam was requested by the Director and Engineer in Chief, Engineering and Water Supply Department, in a letter dated 5th February, 1971 to the Director of Mines. Aroona Dam is situated in Aroona Gorge about 8 miles south-west of Leigh Creek and supplies this township and the open cut coal fields with water. The dam wall is 65ft high and the total capacity of the reservoir in 1948 was 1650 million gallons, however due to inflow of silt into the reservoir the total capacity in 1970 was reduced, to 1200 million gallons. Considerable leakage (estimated at about 8 million gallons a month) from the reservoir occurs through the left abutment of the dam, and two diamond drill holes were drilled (Fig.l) to a-depth of 51.2ft. (DH.1) and 70ft. (DH.2) and water pressure tested, to determine the frequency of open joints, the occurrence of permeable sandstone beds in the quartzite, the possible occurrence of shear zones, the water gradient through the ridge (Fig.2) and the average permeability of the ridge. During a previous investigation of the leakage (Johnson 1962) four diamond drill holes were drilled, water pressure tested and logged. The positions of these holes (AL1 AL2 AL3 and A14) are shown on Figure 1. Possible sites for an upstream storage dam within the reservoir were also inspected. This dam would be designed to form a settling pond in the.upper reaches, to prevent silt entering the main portion of the reservoir. The reservoir is fed by Aroona, Windy and Emu Creeks which only, flow a few times a year after heavy rains, and carry large quantities of silt into 'the reservoir. This storage dam would also be of some assistance in alleviating the high evaporation rate from the reservoir. Possible quarry, sites to provide material for construction of the dam were inspected. Prior to this report four other reports had been written on the Aroona Dam site and the leakage through the left abutment of the dam. (see Bibliography).