Gas line pigging and blowing out procedure

[DUISENM69]

I work in the construction of Combined Cycle Power plant. We have two suppliers of natural gas and our gas pipeline consists of 24' main line and two 16' branches from suppliers and one 16' branch to our facility. Our EPC contractors are going to pig only main line and blow out the branches by 7 bar compressed air. Is it enough to be sure that the branches are clean?
The second question. Our contractor insists that acceptance craiteria for blowing out will be visual observation of blown air. Should I insist on using target plates?

Thanks,