Master Plan

• Preparation of Base Map
• Rehabilitation of Existing system
• Proposed Sewerage Zones and Population projection of Zones
• Trunk Mains & Outfall Sewer
• Sewage Pumping Stations
• Sewage Treatment Plants(technology options and least cost analysis)
• Connection of house sewer to sewerage system
• Low Cost Sanitation
• Assessment of requirement for Engineering Survey and investigations for DPR

Preparation of Base Map

For planning sewerage system a map showing all roads, railways, drains, rivers, water bodies, contours (atleast 1 m interval) ward boundaries, physical features, existing water supply and sewerage system etc is required. Some times different maps are available for different areas and different features. All these maps should be integrated into one map (Base Map) with different layers for different features.

Rehabilitation of Existing System

Make assessment of condition of existing sewerage system. Assess rehabilitation possibilities and compare option of rehabilitation versus developing new system.

Proposed Sewerage Zones & Population Projection of Zones

Broadly, the drain area of each STP defines zone area of that STP. As such no. and location of STPs proposed should be decided judiciously. Each zone can be further divided in sub zones as per main physical features, phasing of development of sewerage system, topography etc.

Trunk Mains & Outfall Sewer

Design the trunk main and outfall sewers. See the alignment of trunk/outfall sewer in field and revise design if any site problems.

Sewage Pumping Stations

Assess need and location of SPS. Avoid pumping station if possible. Assess land required and try to put it on available government land.

Sewage Treatment Plants (Technology Options and Least Cost Analysis)

Decide ways to dispose effluent. Compare life cycle costs on present value basis for different processes. Find out land required for each type of process. Decide treatment process.

Connection of House Sewer to Sewerage System

In past the general practice is that main sewers are laid by utility and connection from house to sewer Man hole is done by the house owner at his own cost. However the problem in this system is that

• People already having septic tanks are not willing to incur cost to connect their waste to sewers,
• When connection is made in future road is broken. Man hole masonry material goes in the man hole and blocks the flow. The roads are not repaired immediately and as such public feels inconvenience. As such good practice is that connection pipe from house to sewer man holes is also laid under the project by the utility. This will ensure quick connectivity and increase flows in sewer network and sewage treatment plants.

Low Cost Sanitation

Determine low cost sanitation or onsite sanitation required. Target should be to have 100% sewerage/onsite sanitation for BPL and in slum areas. The city should become open defecation free.

Assessment of Requirement for Engineering Survey & Investigations for DPR

To cut costs, master plan should be prepared from available maps. However for DPR one should have topographical map, scale at least 1:2500, showing levels at road junctions and 25 m interval. Underground strata up to 10 meter depth, soil bearing capacity, permeability at STP site and map of existing sewerage system etc should also be known. Based on available information and required information assessment be made of requirement for Engineering Surveys and investigations.