Extra over and above the rate of item No. 29.2, 29.4, 29.5 ( a to e) for lowering sub-soil water level from its natural level, as decided by the Engineer-in-charge, by every 0.30 m depth (upto requisite depth), including cost of bore holes machinery and carrying out the work in safe manner complete in all respects. For pipe sewers having i/d above 760 mm