3.2 Requirement of Transmission Line Routing
3.2.1 The alignment of the transmission line shall be most economical from the point of view
of construction and maintenance.
3.2.2 Routing of transmission line through protected / reserved forest area should be avoided.
In case it is not possible to avoid the forests or areas having large trees completely, then
keeping in view of the overall economy, the route should be aligned in such a way that
cutting of trees is minimum.
3.2.3 The route should have minimum crossings of Major river, Railway lines, National / State
highways, overhead EHV power line and communication lines.
3.2.4 The number of angle points shall be kept to a minimum.
3.2.5 The distance between the terminal points specified shall be kept shortest possible,
consistent with the terrain that is encountered.
3.2.6 Marshy and low lying areas, river beds and earth slip zones shall be avoided to
minimize risk to the foundations. & Towers
3.2.7 It would be preferable to utilize level ground for the alignment.
3.2.8 Crossing of power lines shall be minimum. Alignment will be kept at a minimum distance
of 300 m from power lines to avoid induction problems on the lower voltage lines.
3.2.9 Crossing of communication line shall be minimized and it shall be preferably at right
angle. Proximity and parallelism with telecom lines shall be eliminated to avoid danger
of induction to them.
3.2.10 Areas subjected to flooding such as nalla shall be avoided.
3.2.11 Restricted areas such as civil and military airfield shall be avoided. Care shall also be
taken to avoid aircraft landing approaches.
3.2.12 All alignment should be easily accessible both in dry and rainy seasons to enable
maintenance throughout the year.
3.2.13 Certain areas such as quarry sites, tea, tobacco and saffron fields and rich plantations,
gardens & nurseries which will present the Owner problems in acquisition of right of way
and way leave clearance during construction and maintenance should be avoided.
3.2.14 Angle points should be selected such that shifting of the point within 100 m radius is
possible at the time of construction of the line.
3.2.15 The line routing should avoid large habitations, densely populated areas to the extent
3.2.16 The areas requiring special foundations and those prone to flooding should be avoided.
3.3 For examination of the alternatives & identification of the most appropriate route, besides
making use of informations / data / details available / extracted through Survey of India
Topographical maps and computer aided processing of NRSA’s satellite imagery, the
contractor shall also carry out reconnaissance / preliminary survey as may be required for
verification & collection of additional informations / data / details.
3.4 The contractor shall submit his preliminary observations & suggestions along with various
informations / data / details collected and also processed satellite imagery data,
topographical map data marked with the alternative routes etc. The final evaluation of the
alternative routes shall be conducted by the contractor in consultation with Owner’s
representatives and optimal route alignment shall be proposed by the Contractor. Digital
terrain modeling using contour data from topographical maps as well as processed satellite
data shall be done by the contractor for the selected route. A fly through perspective using
suitable software(s) shall be developed for further refinement of the selected route, if
required. Site visit and field verification shall be conducted by the contractor jointly with the
Owner’s representative for the proposed route alignment.
3.5 Final digitized route alignment drawing with latest topographical and other detail / features
(altitude / longitude) including all rivers, railway lines, canals, roads etc upto 8 kms on both
sides of selected routé alignment shall be submitted by the contractor for Owner’s approval
along with report containing other informations / details as mentioned above.
4.0 Detailed Survey :
4.1 The detailed walk over survey shall be carried out using GPS, total stations, digital
theodolites etc. along the approved route alignment. As an alternative, the contractor may also
use ALTM (Airborne Laser Terrain Modeling) techniques of equal or better accuracy for the
detailed survey and plotting on topo sheet to fix up angle point.
4.1 Soil resistivity, along the route alignment shall be measured in dry weather by four
electrode method keeping inter – electrode spacing of 50 mtrs. For calculating soil
resistivity formula 2πar (where a=50 m and r=megger reading in ohms) shall be adopted. In
case of soil characteristics changes within 2 to 3 km, values shall have to be measured at
intermediate locations also. Megger reading and soil characteristics should also be
indicated in the soil resistivity results.
4.2 Route Marking
The route of the transmission line shall be recorded using GPS of positional accuracy less
The co-ordinates of all the angle points as well as other important crossings, landmarks etc.
shall be recorded using GPS for easy relocating.
At the starting point of the commencement of route survey the co-ordinates shall be
recoded. The co-ordinates of the location of the survey instrument shall also be recorded.
Further, the co-ordinates at prominent position at intervals of not more than 750 meter
along the transmission line to be surveyed upto the next angle point shall also be recorded.
Wherever the line alignment crosses the EHT line, Railway line, P&T line or roads, the
contractor shall record co-ordinates on the points of crossing. Wherever line route
alignment passes over permanent land marks such as rock, boulders, culverts etc. suitable
white paint marks with directional and GETCO markings shall be made and co-ordinates
4.3.1 The complete profiling along the route shall be carried out using surveying equipments
viz. total stations, GPS, digital theodolite, long range scanners etc. Reference levels at
every 20 meters along the route are to be recorded. R/Ls at other undulations along the
route as well as in the route plan and other enroute details viz. crossings, building &
structures, trees & other infrastructure etc shall also be recorded. Areas along the route,
which in the view of the contractor, are not suitable for tower spotting, shall also be
4.3.2 The complete profiling details shall be digitized and the data shall be prepared & stored
in the format compatible to computer – aided tower spotting software.
4.3.3 A printed / plotted output of the digitized profiling shall be submitted by the contractor to
Owner’s site-in-charge for review before taking up computer- aided tower spotting.