Specifications Part 1 - Water Supply, Sewerage and Tube Well Works

S.NoTypes of tubewellTable No.- 17.2Dia of boreDia of casingPermissible limit ofverticality in 30 mdepth (all in onedirection)1. Shallow Up to 30 cm 15 cm 15 mm2. Shallow & deep37.2 cm or 40cm20 cm 30 mm3. Deep 45 cm or more 25 cm or more 50 mm17.12 Casing pipe:-17.12.1 Pipe or casing pipe-Blind pipe or casing pipe is provided in non-aquifer-portionand below housing pipe and up to slotted pipe. The casing pipe of specifieddiameter shall be lowered up to a minimum depth of 9 meters below groundlevel to prevent pathogen bacteria from entering in to the well and there byprevent the water from possible pollution. If the collapsible strata in overburdencontinue beyond 9 meters depth than the casing pipe shall be lowered up torock level and embedded ink rock in a depth of 0.15 meter. The casing pipeshall also be extended above ground level in a height of about 0.3 meter. Pipematerial shall conform to IS: 1239 (Part-I) 1990 mild steel tube, tubular andother wrought steel fittings/ IS: 12818: 1992 Unplasticized PVC screen andcasing pipes for tube wells17.12.2 Slotted pipe:-The screen or slotted pipe should be provided against the required thickness ofaquifer in order to allow ground water to be pumped into the tube well. Thelength of the slotted pipe should be decided by the thickness of the aquiferportion needed to be tapped and normally the screen should be providedagainst coarsest and bottom most aquifer layer. The upper one and unwantedaquifer layers should be made up by smallest feasible dia casing pipe. Pipematerial shall conform to IS: 1239 (Part-I) 1990 mild steel tube, tubular andother wrought steel fittings/ IS: 12818: 1992 Unplasticized PVC screen andcasing pipes for tube wells17.13 Gravel Packing:-17.13.1 The term gravel packing is used to the placing of uniform gravel adjacent to thewell screen. The thickness of the pack ranges from 75mm to 150 mmdepending upon design.17.13.2 The gravel selected for packing tube wells shall be consist of hard quartz withan average specific gravity of not less than 2.5. The quartz shall be of subrounded to rounded grains with minimum angular features. The gravel shall befree from impurities, such as shale, mica, felspar, clay, sand, dirt, loan,hematite and organic materials.17.13.3 The main purpose of gravel pack is to enable water bearing formation to yieldsand free water to its maximum capacity.Urban Administration & Development Department Page 203