Inspection chamber in sewage drain

For civil engineers,

There is a high drain connection work is under progress in my location. Few days ago, a contractor visited my house and asked me to construct 2ftX2ft inspection chamber inside the premise for connection with high sewage drain. Now I found that there is another inspection chamber being construct outside my premise building(at road) and these are finally being joined with manholes.

My question is, what is the need of 2 inspection chamber just inside and outside the premise building?