PowerPoint Presentation

[Audio] Welcome to the narrated presentation on Shallow Sewerage System. The conventional sewerage system, besides requiring huge capital investment, is often found to encounter unreasonable delays in its implementation. A group of professionals at NCPE have undertaken a pilot study in one sewerage zone of Nalgonda Municipality in Telangana, in order to demonstrate that the shallow sewer system is cost effective, permits rapid implementation, causes least public nuisance and involves minimum road digging – a perfect recipe for the success of the alternative sewerage system..

[Audio] open drains conveying sullage are liable to spread diseases, contaminate water sources, serve as breeding sites to mosquitoes, cause water logging and damage roads when they overflow. Larger municipalities avoid the unsightliness and public nuisance by adopting the conventional underground sewerage system..

[Audio] In the Conventional Sewerage System, very often, the sewer pipes are laid in the middle of the road with manholes at regular interval of 30 meter centre to centre. The house service connection is made to the nearest manhole through an inspection chamber using a 100 mm or 150 mm diameter pipe. While it is a well-established and accepted system, it is not without disadvantages..

[Audio] The most significant restrictive aspects of the conventional sewerage system are its high capital cost, deep excavation, extensive road damage and long implementation period. The damage to roads, especially narrow roads, is so extensive that it becomes necessary to re-carpet the entire width of the road. Very often the manhole covers are not flush with the road surface. These aspects of conventional sewerage system scare the policy makers to such an extent that they develop second thoughts about adopting it in their municipality..

[Audio] Municipalities find it hard to choose between unhygienic open drains and the laboriousness of the conventional sewerage system. The Municipal Commissioner of Nalgonda Municipality has requested NCPE to propose an economical, practical, low maintenance solution while avoiding damage to the roads and causing minimum disturbance to the public. NCPE has proposed the shallow depth sewerage system as it addresses all the requirements of the ULB..

[Audio] The shallow sewerage system, with smaller pipe diameter, shallower burial, narrower construction corridor and lack of manholes makes it a low cost alternative. When built with CPVC pipe, it can be easily flexed so that curvilinear routing becomes easy. It can be laid at a flatter gradient as no minimum flow velocity needs to be maintained..

[Audio] The shallow sewer system is permitted in the CPHEEO Manual under decentralized sewerage system. In 2018, the Government of Andhra Pradesh has successfully implemented it in many ULBs. It is reported that the system is working satisfactorily since then..

[Audio] As the depth is shallow, the system has to be built away from heavy vehicular loads. In Indian scenario, it is possible to lay the sewers along the property line or beneath the sidewalks. The pipeline can be encased in concrete when the depth is less than 0.8 meter and it is subjected to vehicular loads..

[Audio] The components of a shallow sewer system consists of sewer pipe, inspection chamber, house service connection and ventilation pipe. The capital cost of shallow sewer system is lowered due to reduced excavation, no road cutting and restoration, lack of manholes etc. The maintenance cost is also low as the shallow depth makes maintenance easy and cheap..

[Audio] The shallow sewerage system is designed for one of the sewerage zones of Nalgonda Municipality. Both conventional and shallow sewer designs are attempted in order to bring out the cost difference between the two systems. The first step in the design of sewerage system is to produce the topographic map, road network map and contour map. These maps are produced by undertaking DGPS and total station survey. Subsequently, the catchment map and sewerage zone map are also produced..

[Audio] The design of the conventional sewer network is done using sewerGEMS software using standard design parameters as recommended by CPHEEO. The total length of the sewer network is 84.243 kilometer and the project cost is rupees 158.03 crore..

[Audio] Design of shallow sewer network is done by using the UNCHS Habitat guidelines contained in ' Design of Shallow Sewer System', along with the CPHEEO guidelines. Sewers with burial depths of up to 1.1 m are laid along the property line at a slope of 1 in 167, and they qualify as shallow sewers. All the remaining sewers are either sub-mains or mains and are designed as conventional sewers. Each connection is provided with an inspection chamber. The total project cost is obtained as rupees 90.64 lakhs. Cost comparison with the conventional system indicates that there is a 42.64 percent overall saving. The expenditure is 13 percent excess in laying of sewers owing to the dual pipes but this is meager in compassion to the 82.65 percent saving in the road restoration works..

[Audio] NCPE believes that the shallow sewer system in combination with the conventional system can prove to be a game changer in the sanitation sector. Thank You..