39. Subject to the provisions of Part III, before the Engineer undertakes the execution of any repairs under section 18 or of any work other than any new work of which the estimates, specifications and plans have been prepared and deposited in the Engineer's Office for public inspection as provided in sections 7 and 8, he shall prepare the specifications and estimates of the expenses to be incurred in respect of such repairs or work including such proportion of the establishment charges as the Government or the Authority shall direct.