What does this mean?
Also when you say the concreter "broke" into the existing stormwater pipe - do you mean he accidentally broke it or he didn't seal it properly when he tapped into it?
The clay has a surface area of 500-800 square meters per gram of soil approx.A massive amount of area able to exchange water /minerals etc.
The concretor punched a hole in the existing storm water pipe and put his pipe from the new drain on top of it and didn't seal it .