The attached sources provide the foundational standards and technical requirements for a general water supply project. The documents mention Water Quality Improvement Project.
General specification for construction water supply works
The specifications can be utilized by a contractor, technicians, and user committees to achieve quality control work and get economic efficiency and technical reliability, especially in rural and urban environments.
Project Scope and Fundamental Standards
The main purpose of this specification is to give a clear and precise description to enable competitive bid opportunities while also considering good workmanship and performance.
The materials used must be new and include recent design improvements. International standards are preferred, but the national ones of Nepal or any other applicable alternatives are also welcome as long as there is no inferior quality.
The contract is supposed to be executed on a contract basis with the project management organization supervising the works.
Site Preparation and Earthworks
The basic idea is to clear the site of all vegetation, rocks, and topsoil as instructed by the Site-In-Charge.
Excavation works should be done according to the lines and levels of the project drawings. Water should also be drained and trenches shored.
Fillings made of materials should be put in layers, preferably 15 cm, and watered and compacted to prevent future settlement.
For pipes’ backfilling, the first 30 cm layer should be free from stones.
Material Quality and Storage Protocols
Material quality is crucial and lays the foundation for this project.
Cement: high-quality Ordinary Portland Cement (NS or equivalent) is allowed. It should be stored in a weather-proof material with a raised wooden floor.
Sand: The sand should be clean river or pit sand, not containing organic matters. In the case of slow sand filters, it should meet the specifications of effective size (0.20 to 0.3 mm) and uniformity. For aggregates, chemically inert, hard, and durable should be picked with angular or rounded shapes.
Bricks and Timber: The former should be well-burnt and of regular shape, while the latter is recommended to use Sal Wood that has been preserved against decay and insects.
Concrete Works and Structural Execution
Concrete is divided into four common grades – M10, M15, M20, and M25, which stand for their compressive strength. The sources stress the need for “controlled concrete” when the mix is determined by weight and water-cement ratios.
Mixing and Placing: Mechanical mixing is advised to have a uniform consistency. The freshly mixed concrete should be placed within 30 minutes of mixing to avoid segregation.
Consolidation and Curing: It can be done by hand punning or mechanical vibration to ensure there are no air pockets and gaps around the reinforcement. The concrete should be cured for at least seven days, whereby it is continuously sprayed by water or kept wet.
Pipeline Installation and Technical Testing
The technical heart of this project lies in the pipeline. The employer will usually provide the pipes and valves, but the contractor should make sure that they are properly transported and installed. They should also be cleaned before placing them in the trench in an uphill direction and at socket ends.
The sources highlight several techniques of jointing including Tyton flexible joints, flanged joints (rubber ring), and HDPE butt-welded joints.
The project should only be finalized after having subjected the pipeline to water-tightness tests and disinfection to kill germs and make the water potable.
Measurement and Payment Framework
It is essential to use measurements as a payment basis to facilitate an amicable settlement between the employer and contractor. According to the sources, site clearance and structures’ payments include all the items of work, dewatering, and sampling costs. Excavations and concrete are mostly measured in a cubic meter, whereas shuttering and plastering are in square meters. This way, payment will be made according to the work done on-site conforming to the drawings and specifications.