to rash driving, and corrosion due to atmospheric conditions and biological wastes. In October 2008, 6 high-tech surveillance cameras were placed to monitor the entire long and wide structure from the control room. Two of the cameras were placed under the floor of the bridge to track the movement of barges, steamers and boats on the river, while the other four were fixed to the first layer of beams — one at each end and two in the middle — to monitor vehicle movements. This was in response to substantial damage caused to the bridge from collisions with vehicles, so that compensation could be claimed from the miscreants. Corrosion has been caused by bird droppings and human spitting. An investigation in 2003 revealed that as a result of prolonged chemical reaction caused by continuous collection of bird excreta, several joints and parts of the bridge were damaged. As an immediate measure, the Kolkata Port Trust engaged contractors to regularly clean the bird droppings, at an annual expense of . In 2004, KoPT spent to paint the entirety of of the bridge. Two coats of aluminium paint, with a primer of zinc chromate before that, was applied on the bridge, requiring a total of 26,500 litres of paint. The bridge is also considerably damaged by pedestrians spitting out acidic, lime-mixed stimulants (gutka and paan). A technical inspection by Port Trust officials in 2011 revealed that spitting had reduced the thickness of the steel hoods protecting the pillars from six to less than three millimeters since 2007. The hangers need those hoods at the base to prevent water seeping into the junction of the cross-girders and hangers, and damage to the hoods can jeopardize the safety of the bridge. KoPT announced that it will spend on covering the base of the steel pillars with fibreglass casing to prevent spit from corroding them. On 24 June 2005, a private cargo vessel M V Mani, belonging to the Ganges Water Transport Pvt. Ltd, while trying to pass under the bridge during high tide, had its funnel stuck underneath for three hours, causing substantial damage worth about 15 million to the stringer and longitudinal girder of the bridge. Some of the 40 cross-girders were also broken. Two of four trolley guides, bolted and welded with the girders, were extensively damaged. Nearly of of the track were twisted beyond repair. The damage was so severe that