Turner, J.V., and Townley, L.R. (1997), Status of the contaminant plume near the Baldivis tailings pond, 1994-1996, Report to WMC Kwinana Nickel Refinery, CSIRO Land and Water Consultancy Report No. 97-13, 15pp., May. [Confidential]

Electrical conductivity profiles from fully screened boreholes and hydrogeochemical analyses have been used to determine the extent to which changes have occurred in the geometry and hydrogeochemistry of the contaminant plume associated with the Baldivis tailings pond. The measurements relate to the period between July 1994 and September 1996. Electrical conductivity profiles have been measured on five occasions and hydrogeochemical data collected on three occasions during this time period.

We conclude on the basis of a systematic analysis of multiple electrical conductivity profiles measured in boreholes between July 1994 and September, 1996 that the contaminant plume has remained stable and has not altered discernibly in elevation or areal distribution. Two exceptions to this conclusion are noted where fluctuations in the elevation of the interface are observed: in the vicinity of 80-13 and MR3. Between July 1995 and September 1996 the interface elevation has declined at these locations, presumably in response to pumping and groundwater recovery near these locations.

From the hydrogeochemical data that there is a slight tendency toward declining ammonium and sulphate concentrations in a few selected bores influenced by either pumping/recovery or due to their location near the margins of the contaminated zone. The behaviour of these individual bores is exceptional, and overall it is concluded that there has been very little change in the concentration of the hydrogeochemical parameters analysed over the bulk of the volume of the plume between 1994 and 1996.