1. GEOLOGICAL AND ENVIRONMENTAL INVESTIGATIONS OF BRIDGE PROJECTS

2. Geological and environmental investigation of bridges
How the impact is different from a hazard
Purpose of construction of bridges
Geological impact of construction of bridges
Environmental impact of construction of bridges
Geological and environmental investigations
Measures to reduce the impact of construction of proposed bridges

3. How the impact is different from a hazard
A proposed bridge and road project may have various impacts. All these can be predicted well in advance at the time of preparation of Environmental Impact Assessment (EIA) report.
Various Impacts of the bridge are
Impact on Environment
Impact on Economy
Impact on Culture
Impact on Society.

4. PURPOSE OF BRIDGES
To have connectivity between two sides of stream/ river/ two land masses
Elevated bridges/ flyovers to ease traffic
To have different mode of transport in the same location – rail, road, sea link
Transportation - Reduce distance between two locations , reduce the travelling time (bus, rail)
Public utility purpose – , gas pipe line, diesel/ petrol/ crude oil pipe line, cables
Transportation of water - aqueduct

6. Geological impact of construction of bridges
If weak rocks are occurring in the location of proposed bridge , appropriate design that suits to weak rocks need to be chosen. If any failure in identification of weak rocks /assessment of load bearing capacity ,it may lead to damage.
If faults are not identified before, further displacement of blocks may takes place

7. ENVIRONMENTAL IMPACT OF BRIDGES
land requirements increase and creates small pockets of land which affect the drainage of the larger catchment.
cutting and filling of soil & vegetation, diversion of routes create short to long term impacts on the land environment which is intrinsically linked to soil and water.
Fly ash is being promoted as an alternate filling & dressing material, despite its toxic nature which can become dangerous for human health and resources to which it comes in contact
Afflux i.e. effect of structures over river which increases the flood level in immediate upstream of the bridge as a result of obstruction to natural flow of river which reduces its effective waterway.

8. ENVIRONMENTAL IMPACT OF BRIDGES

9. ENVIRONMENTAL IMPACT OF BRIDGES
If one bridge is constructed across the river it may not have significant impact but when series of bridges are constructed it will have impact on raise in flood level, meandering of river.( tens of bridges constructed across Yamuna in Delhi area)
Environmental Impact of the bridge is less when compared to road project. Bridge is a part of road project

10. Loss of forest land Loss of Green Cover/tress, shrubs wooden material
Loss of tribal culture/ forces migration of tribals to remote areas
Loss of forest produce
- nuts, leaves , spices, gum, fruits, honey, plant based medicines, fiber, timber, fire wood etc.
Impact on climate, rain fall,/ micro climatic changes
Loss of carbon absorption capacity
Loss of bio diversity
Reduction in cleaning capacity of pollutants

11. Loss of forest land
Loss of educational benefits Loss of tourism Loss of aesthetic effect Forest reduces run off and increases infiltration Reduction in infiltration will leads to reduction in availability of groundwater Contributes to floods Loss of ecological benefits In accessible areas in forest will have access to human beings

12. Loss of forest produce nuts leaves spices gum fruits honey
plant based medicines
fiber, timber, fire wood etc.

13. Impact on climate and rain fall
Loss of forest cover results in reduction in co2 absorption capacity in turn capacity to give O2 also comes down
Increase in temperature in adjoining areas
Microclimate changes

14. Loss of forest land

15. Loss of wild life
Loss of shelter to wild life will lead to migration of wild animals
Loss of bio diversity
Species may become extinct
Livelihood of tribal will get effected

16. Geological and environmental investigations
The purpose of geological and environmental investigation is to identify a suitable site for construction of bridge
- bridge should be safe
- cost of construction should be economic
- cause less damage to the natural and man
made environment
We need to identify at least two or more locations, evaluate and finally select the location having minimum damage to the environment , safe and economic.

17. Geological investigations
Utilize remote sensing, geological, topographical maps and hydrological maps, for selection of bridge site.
Identify the geological structures – folds, faults and assess stability of rocks by carrying out drilling at the proposed location.
Carry out geotechnical investigations to check the settlement/ load bearing capacity of the ground and accordingly go for appropriate design

18. Geological investigations
Fault areas are unsafe for bridge
Identify the rocks occurring along the proposed location.

19. Geological and Geotechnical investigations

20. Environmental investigations
Detailed investigations are essential to assess the impact of the proposed high projects on natural and man made environment
Impact on forestland
Impact on agricultural land
Wild life
Economy
Ecological
Aesthetic
Social
Cultural

21. Measures to reduce the impact of bridge
Utilize latest technologies available such as remote sensing, geological, topographical maps and hydrological maps to arrive the location suitable for construction of bridge.
Select the location that cause minimum damage
Preferably avoid passing the bridge /route through forests to the possible extent
If required the bridge and road to pass through forest , go for compensatory afforestation
Carry out geotechnical investigations to check the settlement/ load bearing capacity of the ground and accordingly go for appropriate design.

22. Measures to reduce the impact of bridges
resettlement and rehabilitation and compensation in a appreciable manner
We need to identify at least two or more locations, evaluate and finally select the location having minimum damage to the environment , safe and economic.