Section 85(2)(a) in The Mumbai Municipal Corporation Act, 1888
(a)when the [city engineer] [The words 'city engineer' were substituted for the words 'executive engineer' by Bombay 19 of 1930, Section 6.] or the executive health officer [or the hydraulic engineer] [These words were inserted by Bombay 2 of 1911, Section 4(a).] is granted leave of absence for a period exceeding one month, the appointment of a person to act for him shall be made by the corporation;