Section 166(4) in West Bengal Municipal (Building) Rules, 2007
(4)(a)A private bridge must be constructed as and where necessary to the satisfaction of the Municipality so as to leave sufficient waterway to pass the maximum discharge of the channel spanned by the bridge.(b)The invert of the channel under a private bridge must be laid to the same slope as that of the channel;(c)When a pocket for the deposit of debris is cut in the hillside above a private bridge, it must be lined with masonry walls unless constructed on solid rock.
