Keith you must of got unlucky with your contractors, you would need to carry out a service clearance before starting work, which detects most underground services that could be in the way such as Power and telephone cables, Water Mains, Gas mains and even sewers if they have water laying in them. If they are dry just run a load of water down the waste outlet and you should get a signal using Cable Avoidance Tools (CATs), and Signal Generators (gennys)Although nothing is 100% as cables can be turn off at the time of the clearance. Plastic pipes may have no water in then so are dry. The same with small sewers.Finally, how well trained the person was carrying out the clearance
Paul Allen ● 4322d