GEM-2 image of a former liquid disposal site
The area surveyed was a former liquid waste disposal site. The site included 13 unlined lagoons constructed from sand. Discharges to the lagoons included primary septic waste and brewery waste, with unknown quantities of other wastes also discharged. Operations at the site began in the mid 1950's and continued until 1981. Soil contamination has been present at this site for approximately 40 years and leaching from this site over time has caused a plume of contaminated groundwater to migrate from the site.
Ground water beneath the lagoon and areas up to 1300 metres to the south east show elevated levels of nutrients and heavy metals (Cadmium, Chromium, Copper, Nickel, Zinc, Arsenic etc). A previous magnetic survey located approximately buried metallic objects within the area. The general direction of groundwater flow is away from the site, with a regional gradient to the north.
GEM2 Survey
The survey was designed to achieve two tasks. The first of these was to confirm the locations of the buried metallic objects as there had been some disturbance of these objects when a fire passed through the area several years earlier. The second objective was to determine the extent of soil contamination within the compound and its immediate surrounds. The survey was completed in less than a day and represents an area of some 8.8 hectares.
Results
The survey located 43 metallic objects within the area and their positions correlated well with the previous magnetic survey. It also clearly identified the lagoons used for liquid waste disposal as well as detecting a site of leakage between two adjacent lagoons. Of most concern was the detection of a site of leakage out of the disposal area. Further investigation revealed that this had occurred some 15 years earlier yet traces of this event were still detected. These features are labelled in the accompanying image.
