Detailed Survey
The presence of rock or underground obstacles such as existing sewers, water lines, electrical or telephone wires, tunnels, foundations etc. have significant effect upon the cost of construction. Therefore, before selecting the final lines and grades for sewers necessary information regarding such constructions is collected from various central and state engineering departments.
Besides the location of underground structure, a detailed survey regarding paving characteristics of the streets, the location of all existing underground structures, the location and basement elevations of all buildings, profile of all streets through which the sewer will run, elevations of all streams, culverts, and ditches, and maximum water elevations therein are also made. The above details are noted on the map. The scale of the map may vary depending upon the details desired.
Manual on Sewerage and Sewage Treatment recommends the following scales for various plans and drawings depending upon the detailed information desired.
(a) Index Plan - 1 : 100,000 or 1 : 200,000
(b) Key Plan and general layout - 1 : 10,000 or 1 : 20,000
(c) Zonal Plans - 1 : 2,500 or 1 : 5,000
(d) Longitudinal sections of sewers - 1 : 500 or 1 : 2,250 or 1 : 2,500
(e) Structural drawings - 20 or 1 : 50 or 1 : 100 or 1 : 200