Towards ensuring high quality in construction, each piece of work must be carried out according to detailed procedures that are made available in advance. There should be an independent quality assurance agency with good participation of utility personnel to carry out quality checks at pre­identified stages or hold points. There should be formal procedures in place to deal with non-conformances from approved construction specifications, drawings and procedures, and the hierarchical levels at which their disposi­tion is to be decided shall be identified in advance. It is most appropriate to establish a formal mechanism for communicating such changes to the commissioning group and the O&M group and to associate them in the NPP construction activities to the extent feasible. This helps in making them thoroughly familiar with the as-constructed plant. Also it is frequently nec­essary to make mid-course changes in construction on account of factors such as unexpected interferences encountered while laying piping and cables or non-availability of specified materials. The O&M group must properly assess the impact of such modifications and the need for modifying operating and maintenance procedures or carrying out additional checks during commissioning.