4. The authorised development is to be carried out within the parameters shown and described on the framework plans and in carrying out the authorised development the undertaker may—
(a)deviate laterally from the lines or situations of the authorised development shown on the works plans to the extent of the limits of deviation shown on those plans; and
(b)in respect of the rail works deviate vertically from the levels shown on the rail alignment plans to the extent of the limits of vertical deviation shown on those plans.