I picked up the phone and was told that there had been an explosion at the Cinema Centre in Canberra and that a man had been killed. We were asked to investigate. The picture below shows the Old Cinema Centre in the centre of the picture and the Dendy Cinema Centre of today in the top right hand corner and a petrol station was located opposite but to the left.
I had mapped the excaavation on which the Cinema was built shortly after my arrival in Canberra. In the north wall there was a depression in the top of weathered clayey mudstone that was filled with gravel and water was leaking from the gravel during and after rain. After the Cinema was built water ponded behind the north wall and algae grew in the sump inside the building.
The management realised that there was ponding of water and drilled a hole in the wall to allow the water to enter the sump and then pumped into the stormwater drain.
During rain the water level rose until it flowed through the hole into the sump; however. Petrol also flowed in through the hole.
The plumber was called in to install a pump to remove the water. When the plumber lit his blowtorch the pertol exploded; he was knocked unconcious and fell into the sump and drowned in three inches of water.
Having identified the problem, a number of observation holes were drilled and all contained petrol. The obvious source of the petrol was from the Service Station opposite. X-ray diffraction tests showed that the petrol in the holes was similar to that at the Service Station, but had lost some of its aromatic components.
A three foot diameter hole was driklled into the gfravel in front of the Cinema; the hole was backfilled with clay and the hol.e in the wall was sealed.
The next task was to remove the petrol. A three foot diameter hole was drilled nearby and a skimmer installed in the hole. The skimmer is a cylinder of stainless steel with the bottom set in the groundwater. The cylinder is rotated and petrol that adheres to the staiknless steel is wiped off into a container. Although many gallons of petrol were removed petrol has been adsorbed by the clay soilthroughout the sujrrounding area and forty five percent of petrol adsorbed by the clay cannot be removed.
The foundations of buildings between the Cinema and Lake Burley Griffin will intercept petrol contaminated groundwater.
At the inquest in the Coroner’s Court, our report was presented. Steve, a hydrogeologist representing Mobil denied that the petrol came from the Seervice Station, but the Coroner accepted the results of our work and recommended that the remedial work be continued.
Steve and I went off to the Ainslie Pub for a beer.
E.G. Wilson, 14/7/2015