There are around one million off mains drainage systems in England and Wales and when you venture outside Scotland’s central belt a very high proportion of rural and semi-rural properties North of the boarder are served by septic tanks and sewerage treatment plants. What may surprise some people is that sometimes these huge tanks can just raise out of the ground.
Auger are asked to look at this scenario more frequently than you would expect. The cause is ground water, and if you imagine trying to hold a balloon underwater you’ll get the idea. The majority occur when tanks are emptied in winter, when the ground water table rises in conjunction with the tank being emptied. Emptying the tank doesn’t mean emptying all of the liquid waste, it means removing the solids from the base of the tank. Leaving some liquid waste in the tank will often avoid the issue of it floating if ground water is high, and it need s to be emptied in the winter months. Installing tanks to manufactures specifications for wet ground conditions will avoid the risks of this occurring. Surrounding the bottom of the tank in concrete will not always suffice, and it is often necessary to secure the tank to a concrete base foundation and/ or form a concrete collar around the top of the tank.
The difference in these types of claims compared to a damaged tank with a broken baffle, or a failed drainage field is the urgency. With a damaged tank or drainage field, the homeowner still has a useable system; all be it they have to get the tank emptied more regularly. With a tank raising out of the ground, it is not only sudden and unexpected, but there is no effective system and waste will just be running into the hole below the tank, and the area will be unsafe and contaminated. This is what happened to a customer in Lanark recently. They had use of a shared Klargester sewerage treatment plant, which was emptied and almost immediately raised 3 feet above ground level.