(1) No new work or appliance, the estimated cost of which exceeds such amount as may be fixed by the Central Government in this behalf, shall be commenced or provided by a Board, nor shall any contract be entered into by a Board in respect of any such new work or appliance until a plan of and estimate for, such work or appliance has been submittted to, and approved by, the Board; and, in case the estimated cost of any such new work or appliance exceeds such amount as may, from time to time, be fixed by the Central Government in this behalf, the sanction of the Central Government to the plan and estimate shall be obtained before such work is commenced or appliance provided.
     (2) Nothing in sub-section (1) shall be deemed to require the further sanction of the Central Government in any case where the actual expenditure incurred does not exceed by more than ten per cent. the estimated cost so sanctioned.