annual repair maintenance of residential and non residential buildings at regional centre nsg rajarhat kolkata during 2020 21 sh cleaning and disinfection of water tanks chamber manhole sewerage line etc a r m o residential and non residential buildings at regional centre nsg rajarhat kolkata during 2020 21 sh cleaning and disinfection of water tanks chamber manhole sewerage line etc , cleaning of terrace/loft water storage tank ( inside surface area ) upto 2000 litre capacity at all heights with coconut brushes , duster etc . , removal of silt , rubbish from the tank and cleaning the tank with fresh water disinfecting with bleaching powder @ 0 . 5gm per litre capacity of tank , including marking the date of cleaning on the side of tank body with the help of stencil and paint and disposing of malba , all complete as per direction of engineer-in-charge . ( the old date already written on tank should be removed with paint remover or black paint and if date is not written with the stencil or old date is not removed deduction will be made @ rs . 0 . 10 per litre if during cleaning any gi fittings or ball cock is damaged that is to be repaired by contractor at his own cost and nothing extra will be paid on this account ) , cleaning and desilting of gully trap chamber , including removal of rubbish mixed with earth etc . and disposal of same , all as per the direction of engineer-in-charge . , cleaning of under ground sump , over head r . c . c . tank ( independent staging ) including disposal of slit and rubbish , all as per direction of engineer-in-charge . the cleaning shall consist following operations:- ( i ) tank shall be emptied of water by pumping & bottom shall be cleaned of slit and other deposits . ( ii ) entire surface area of the sump shall then scrubbed thoroughly with wire brush etc . and pressure washed with water . ( iii ) chlorination of rcc internal surface by liquid chlorine . ( iv ) the treated surface shall be dried using air jetting and all loose particles shall be removal from the surface . ( v ) finally the surface shall be treated with ultraviolet radiation etc . as per direction of engineer-in-charge .