DEMOLITION AND RECONSTRUCTION OF OHT AT INS MANDOVI

Demolition and dismantling of the existing 15.00 meter high staging Reinforced Cement Concrete (RCC) overhead water tank structure of 75000 gallon capacity, including top dome, ring beams, cylindrical container walls, floor slabs, galleries, walkways, internal/external staircases, chajjas, balconies, staging columns, braces, and ground-level or underground foundations, raft, and footings.Work shall be executed at all heights, depths, lifts, and leads, strictly conforming to safety standards (IS 4130 or equivalent) and structural stability requirements complete all as specified and as directed by Engr-in-Charge The scope of work is fully comprehensive and explicitly includes the following interconnected operations:- Scaffolding & Protection: Providing, erecting, maintaining, and dismantling heavy-duty, design-approved cup-lock or tubular steel staging and scaffolding up to the maximum required height. This includes installing catch platforms, heavy-duty safety industrial nets, and 100% enclosure with green debris/dust-prevention netting to completely isolate the hazard zone.

Controlled Dismantling & Lowering: Executing top-down demolition using specialized techniques such as diamond wire saw cutting, core drilling, high-reach hydraulic pulverisers, or controlled mechanical breakers. The item includes the safe, controlled lowering of severed concrete blocks, pipes, and heavy structural components to the ground using mechanical cranes, winches, or pulleys, strictly prohibiting the unconfined free-fall drop of debris. Foundation & Ground Breaking: Demolition of the massive ground-level column pedestals, underground foundations, and raft down to a minimum depth of 1.00 meter below the existing natural ground level using heavy hydraulic excavators equipped with rock breaker attachments.

Material Segregation & Scrap Management: Breaking down large demolished concrete chunks at ground level to transportable sizes (under 150 mm). This includes gas cutting, separating, straightening, cleaning, sorting, and systematically stacking all salvaged reinforcement steel bars, structural steel sections, and internal/external GI/CI/MS piping assemblies at a designated on-site location. (Note: Salvaged scrap material shall be credited as per contract conditions). Dust & Environmental Control: Operating continuous water-sprinkling systems, water tankers, or industrial mist cannons throughout the demolition cycle to achieve total dust suppression and comply with environmental pollution control norms. Site Safety & Perimeter Protection: Erecting and maintaining a 3.00-meter-high temporary corrugated GI sheet barricading wall around the entire operational footprint, complete with high-visibility reflective caution tape, night-warning LED blinkers, hazard signage, and dedicated safety watchmen/traffic marshals

Removing all unserviceable muck, concrete debris, and demolition slush from the site by Manual/ Mechanical loading, handling, and The scope explicitly covers sorting, loading onto commercial tipper trucks, and transportation/ carting away of all waste materials completely outside defense land to an authorized dumping ground or registered waste recycling plant located at a lead distance beyond 30 Km from the site. This includes securing defense gate passes, tracking via transit slips, paying all tipping fees/taxes, and leaving the entire defense site completely cleared, leveled, dressed, and safe for subsequent use complete all as specified and as directed by Engineer-in-Charge

Material and labour for providing, assembling, testing and commissioning approved make factory manufactured Hot Pressed Moulded Sheet Moulding Compound (SMC/GRP) Panel Water Storage Tank having net storage capacity of 341 KL (Approx. Size 12.00 m × 10.00 m × 3.00 m), complete in all respects, erected over RCC staging at approximately 15.00 m height, including all labour, materials, tools and plants, lifting arrangements, transportation, loading, unloading, testing and commissioning as specified herein. The tank shall be manufactured from hot pressed moulded food grade SMC/GRP panels suitable for storage of potable water and shall conform to the requirements of IS 14399:1996 (Part I & Part II) or latest revision, IS 17243 (where applicable), IS 2062, IS 800, IS 875 (Part 1, Part 2 & Part 3), IS 1893, IS 3370 and all other relevant BIS Specifications/Codes as amended up to date. The tank shall be modular in construction consisting of interchangeable panels of sizes 1000 mm × 1000 mm, 1000 mm × 500 mm and 1000 mm × 2000 mm, factory moulded under hydraulic hot press and assembled at site strictly in accordance with the approved manufacturer's design and recommendations.

The SMC panels shall be manufactured from premium quality unsaturated polyester resin reinforced with alkali-free glass fibres and shall be UV stabilised, corrosion resistant, fungus resistant, weather resistant, non-toxic and suitable for storage of potable water. The minimum panel thickness shall not be less than 18 mm for bottom panels and bottom corner panels, 16 mm for first tier side wall panels, 14 mm for intermediate side wall panels, 12 mm for top tier side wall panels and 10 mm for roof panels. Wherever the manufacturer's approved structural design requires thicker panels based on hydrostatic pressure, wind load, seismic load or any other design requirement, thicker panels shall be provided without any extra cost to the Government. Under no circumstances shall panel thickness less than those specified above be accepted.

The tank shall be supplied in ready-to-assemble condition and assembled at site using minimum Grade 8.8 High Tensile Hot Dip Galvanized or Olive Green coated nuts, bolts and washers together with minimum 75 mm wide × 3 mm thick food-grade butyl rubber sealing tape/gasket placed continuously between adjoining panels to ensure complete watertightness throughout the service life of the tank. The sealing tape shall be non-toxic, non-shrinkable and suitable for potable water applications.

The external structural support system shall consist of Hot Rolled Mild Steel ISMC 150 or ISMB 150 sections as minimum size, conforming to IS 2062 Grade E250, or larger sections wherever required by the approved structural design. The structural framework shall comprise vertical supports, horizontal stiffeners, tie rods, diagonal bracings, gusset plates, cleats, anchor brackets and all necessary structural members required to safely withstand the hydrostatic pressure of the fully filled tank together with dead load, live load, wind load and seismic load. The spacing of vertical supports shall be as per manufacturer's approved design but shall not exceed 6.50 metres centre-to-centre. The vertical supports shall extend above the roof level of the tank to facilitate safe movement and inspection over the tank roof.

All structural steel members forming part of the tank shall conform to relevant BIS Specifications and shall receive proper surface preparation followed by one coat epoxy zinc phosphate primer and two coats high-build epoxy paint of approved shade. Wherever hot dip galvanizing is specified, the galvanizing shall have a minimum zinc coating of 610 g/m² (approximately 85 microns) after fabrication.

The rate shall include supply, fixing and commissioning of FRP lockable manhole, FRP internal ladder, FRP external ladder extending from the base of the tank to the roof level, manual type water level indicator, air vent fitted with stainless steel insect-proof screen, inlet, outlet, overflow, scour, drain and vent nozzles complete with puddle flanges, all necessary gaskets, brackets, sealants, fasteners, anchor bolts and accessories required for complete installation and satisfactory operation of the tank.