This Chapter Incorporates Both Qualitative and Quantitative Description of Various Environmental

4.0IMPACT ASSESSMENT

4.1Introduction

This chapter incorporates both qualitative and quantitative description of various environmental impacts of the proposed opencast bauxite ore mine. ‘Environmental Impact’ can be defined as any alteration of environmental conditions or creation of a new set of environmental conditions, adverse or beneficial, caused or induced by the action or set of proposed actions under consideration.

The opencast mining operations in general cause environmental degradation and if adequate control measures are not taken to prevent/mitigate the adverse environmental impacts, these operations may cause irreversible damage to the eco-system. The environmental parameters most commonly affected by mining activities are:

• Topography and drainage;
• Climate;
• Land Environment;
• Air quality;
• Water resources and quality including Hydrology;
• Noise levels and ground vibrations;
• Soil quality;
• Flora and Fauna; and
• Socio-Economic conditions.

Various environmental impacts, which have been identified due to the mining activities, are discussed in the following sections without mitigation measures.

4.2Impact on Topography and Drainage

4.2.1Impact on Topography and Visual Impacts

The proposed mine lease lies on the Baphlimali hill, which has a maximum height of 1093-m above MSL. The average height of the plateau from the immediate surroundings is about 150-m and the height of the plateau from the plains is about 250-m.

There will not be any significant adverse changes in the topography as the excavation will be confined to the top of the hill. Change in landscape of plateau top is only on account of lowering of profile by 10-12m, compared to the height of 200-m of the hill. But the general topography shall be maintained.The overburden generated upto fourth year of operations will be dumped temporarily for initial seventeen years of working at designated dump sitesand simultaneous backfilling is proposed from fourth year onwards, without any additional dumping. The dumped overburden also will be re-handled and used for backfilling from seventh year onwards and there will not be any dump after seventeenth year of operation.

The existing topography may be changed only in terms of height and no adverse visual impacts are envisaged. At the foot of the hill, there will not be any topographical changes.

4.2.2Impact on Drainage

The plateau is almost flat with gentle slopes towards fringes of the plateau. There will be no interception of the groundwater, since the ground water table (100 to 150-m) is much deeper than the bottom of the bauxite floor (20 to 30-m). Hence, there will not be any mine water generation during mining activities.

There are no streams present in the mine lease area, except a few rain-fed runoff channels. There will not be any diversion of surface water streams, other than these channels. These runoff channels may be diverted ahead of the overburden dump. The drains will be made along the contour lines to prevent entry of rainwater in the active mine lease area. Drainage within the mine is channelised into backfilled areas and directed into sumps or water reservoirs, where in the water will seep down to the substratum, owing to removal of impervious laterite and bauxite layer on top (the porosity of laterite is 19.8% while the porosity of bauxite and Khondalite is about 25%). Therewill be no significant impact on the existing drainage pattern.

4.3Impact on Climate

4.3.1Temperature

The average monthly minimum and maximum temperatures have been monitored at the proposed site and also analyzed based on the data from nearest IMD station at Koraput. The trend of temperatures shows a regular cyclic pattern. The temperature pattern indicates a regional behaviour and is not likely to be affected by the proposed bauxite mining. The proposed plantation will however moderate any local temperature hikes due to operation of mining machinery and blasting.

4.3.2Rainfall

The proposed mining operations are not expected to have any adverse effect on the rainfall pattern of the area.

4.3.3Wind Speed

The wind speeds in any area are dependent on the generation of elevation and depressions in the region. The controlling factors for wind speed lie much beyond the small area considered for the proposed mining. Thus, the proposed mining activities are not likely to contribute to any variation in wind speed in the area.

4.3.4Humidity

The relative humidity in the area is not likely to change because of the proposed mining, as it will not cause any changes in the prevailing temperatures and rainfall of the region.

4.4Impact on Land Environment

4.4.1Impact on Land Use Pattern

The plateau is a barren land without any major vegetation. No agricultural activities including ‘Podu’ cultivations are under way in core zone area. The present land use in buffer zone is presented in Section-3.9 of Chapter-3. No adverse impact is anticipated in land use of buffer zone due to the proposed mining operations, as all the concerned activities will be concentrated in the core zone only.

The proposed mining operations will impact the land usage of about 1388.74-ha of land. However, the mining activities will disturb in land aesthetics to about 850-ha of land only during the entire mine life. The remaining land (538.74-ha) will be changed in land usage, but will remain undisturbed. The land use at each stage is given in Table-4.1.

TABLE-4.1

LAND USE IN MINE LEASE AREA AT DIFFERENT STAGES

Note: *: Topsoil will be stored within the area to be excavated and concurrently used for reclamation of the back-filled area. Accordingly, it is not quantified separately.

A perusal of the above table shows that about 67.0-ha area will be disturbed during first five years of operation, which will progressively increase to 850.0-ha by the end mine life. This will lead not only to land degradation but also cause soil erosion as well as visual impact if appropriate control measures are not adopted. However, the greenbelt proposed in and around the mining area will ensure protection of soil due to erosion.

4.4.2Land Degradation

There is no forest area present in the mining lease area and also there are no endangered or rare flora and fauna species exist in the ML area or buffer zone. The plateau top is a barren land without any vegetation. The land degradation is expected during mining activities of excavation, overburden dumps, soil extraction etc.

The mining technique has been so chosen such that only 80 to 100-ha of area is under mining at any given point of time. Land reclamation and plantation is a major mitigating measure to nullify the impact on land. From fourth year of mining operations, the generated overburden will be simultaneously backfilled. The topsoil will be excavated will be utilized in the tree plantation. By the seventh year of operations, all the dumped overburden during the initial four years of operations will be re-handled and used for backfilling. A safety zone of 15-m width will be maintained all along periphery of the mine lease boundary.

At the end of the life of the mine, the original topography can be regained but with a decrease in plateau top level by about 10-m. The area will have a bowl shape. This will minimize the impact of the mining on the land degradation.

4.5Impact on Air Quality

The air pollution impact of bauxite mines depends on the intensity of bauxite extraction operations, mode of transport and mode of screening of bauxite. The intensity of operation is directly related to the rate of production of bauxite from mining. Production details are reported in Chapter-2. Similarly drills, shovels, dumpers of different capacities are engaged mainly for extracting and transporting the bauxite from these mining areas. The details of the equipment are given in Table-2.8 of Chapter-2.

Majority of the heavy machinery is operated on diesel. The proposed mining activity is likely to contribute additional Suspended Particulate Matter (SPM), Dust from area sources and Oxides of Nitrogen (NOx) and hydrocarbons from automobile exhaust. The existing baseline concentrations of pollutants are within the limits prescribed by CPCB.

Air pollution sources at the proposed mine can be classified into three categories, viz., area sources, line sources and instantaneous point sources. Extraction of bauxite by various activities in mining area is considered as an area source. Transportation of bauxite and overburden within the mine lease area is considered as line sources. Semi Mobile crusher is considered as point source and blasting activity can be considered as considered as instantaneous point sources.The sources of pollutants from mining activities are given in Table-4.2.

TABLE-4.2

SOURCES OF POLLUTANTS

4.5.1Impacts from Area Sources

As discussed above, the area sources include mine pit and its activities covering drilling, blasting, hauling, loading/unloading and stockpiles.

In the proposed project, drilling will be done with latest drill machines with provisions for dust extraction thus the likelihood of dust emission from drilling activities is meagre.

The blasting will be carried out only during 12 noon to 2 pm during the daytime when normal wind conditions prevail and temperature inversions are not likely to occur. The gaseous emissions like Oxides of Nitrogen from the blasting activity will be instantaneous and will prevail for shorter duration. Hence, the impact due to blasting will be instantaneous and there will not be any long-term adverse impacts.

Similarly, the excavator operations, loading and unloading operations will cause dust generation. The dust generated will be confined to the area of operation of the excavator and will not have any adverse impact on the community. The gaseous emissions from these operations will also be negligible and limited to the mine pit only.

A temporary overburden dump will be created, which is another source of dust generation. However, regular sprinkling of water will be taken-up to minimize the dust generation.

The dust emissions from the above areas will be fugitive in nature and maximum during summer season (when the wind velocities are likely to be high) and almost nil during the monsoon season. The dust emissions are likely to be confined to the mine premises only. The quantification of these fugitive emissions from the area sources is difficult as it depends on lot of factors such as dust particle size, specific gravity of dust particles, wind velocity, exposed area, moisture content of the material, surface compactness of the exposed area and ambient temperatures etc.

• Air Pollution Impact Prediction through Modelling

The impact of the mining activities on air quality has been assessed by using USEPA approved area source model called Fugitive Dust Dispersion Model (FDM). Fugitive Dust Dispersion Modelling (FDM) techniques were used to find the dust emissions due to the proposed mining operations. At any given point of time, mining will be carried out in an area of about 100-ha. The bench height of the bauxite mining will be about 10-m.The SPM emission factor of 0.6 gm/ha/hr has been assumed in the mining activities.

Using these inputs, the FDM modelling has been carried out and found that the short-term Ground Level Concentrations for SPM at the boundary of the ML area will be about 56.7-µg/m3. This will be further reduced farther from ML area. However, the safe zone of 15-m around the mining operations will act as a parapet wall to dust dispersions. This will also reduce the dust dispersions.

The nearest settlement from the ML boundary is Durmushi located at a distance of about 0.5-km in SW direction. The expected GLCs at this location will be
<10- µg/m3 and hence, it can be observed that the mining will be insignificantly affect the AAQ of the study area (10-km around the ML Boundary).

4.5.2Line Sources and their Impact

Transportation of bauxite/waste from the mine pit to the primary semi mobile crusher unit/ dump site will be covered under line source. There will be a total of 12 dumpers operating for transportation. The width of the main haul road is about 15-m. The crushed ore will be transported to alumina refinery by conveyor belts. The conveyor system will be adequately covered and barricaded and will also be elevated. The conveyor belt is so designed that any obstruction will immediately stop the system. A round the clock patrolling is also proposed.

The likely contribution from the dumpers plying on the haul roads has been computed by using CALINE3 model. The modelling has been carried out for Oxides of Nitrogen and Carbon Monoxide. The emission factors specified by Indian Institute of Petroleum (IIP), Dehradun have been used for the modelling. The modelling for dust has not been carried out as there are no specified emission factors for particulate matter by IIP.

The contribution of dumper movement within the mine quarry area will be as follows:

The maximum concentration (1-hourly) due to the dumper movement will occur within 20-m on either side during stability Class-A conditions.

It can be observed that the contribution from the dumper movement on the haul road will be confined to the mine area only and will not have any adverse impact on the community.

The dumper movement will cause emission of particulate matter. However, this will be fugitive in nature and will be restricted to the proximity of the haul road only.

Further, the truck wheels are likely to cause pollution in terms of dust. However, with the inception of truck washing system, this is going to be minimized.

The control measures as suggested in Chapter-5 will be implemented to reduce the dust pollution.

4.5.3Impact due to Instantaneous Emission Sources and their Impact

Blasting is the major source of instantaneous emission sources. Blasting in the mining will be conducted through deep blast holes and will be carried out between 12 pm to 2 pm only. There will not be any secondary blasting, as rock breaker will be used to reduce the size of the ore/boulders.

SPM and NOx emissions are envisaged during these blasting operations. But these are kept under control by sprinkling of water on haul roads.

The large quantity of dust will be wind borne due to blasting but due to the proposed greenbelt around the mine, the spread of dust will be arrested. Even though blasting generates NOx, it will be instantaneous and intermittent.

4.5.4Point Emission Sources and their Impact

For the expanded mining operations, two semi mobile primary crusher units are proposed for crushing the bauxite. The dust emissions are controlled by wet scrubbing. The crushers will be connected to stack whose particulate emissions will be controlled less than 150 mg/Nm3.

DG Sets could be another type of point emission source.The power requirement of the mine area will be sourced from the alumina refinery located at the Doragurha. The DG set (500-KVA) will be installed only as a stand by arrangement and will be used only during power interruption. Hence the emissions from the DG set will be intermittent in nature and hence, were not considered for the dispersion modelling.

The contributions of primary crushers on the air quality impact are assessed using ISC-ST3 dispersion model.

The SPM emission factors for crushing plant are as follows:

Stack Height:30-m

Exit Velocity:15.0 m/sec

Exit Temp:60 oC

Stack Diameter:0.50 m

Exit Dust Load:150 mg/Nm3 (Max)

ISCST3 short-term model has been run based on the hourly meteorological data generated at the site. The overall contribution from the primary crusher on air pollution is assessed and found that the incremental concentrations of SPM will be about 1.6 µg/m3, occurring at a distance of about 1.5-km from the crusher location.

It can be observed that the emissions from the crusher house will be maintained within stipulated norms.

4.5.5Fugitive Emissions

The fugitive emissions are mainly generated while loading the ore/overburden at mine face, transportation of ore from mine face to crusher and while unloading of bauxite/overburden at crusher/dump site. Automatic water sprinklers will be installed. Pressurized water will be sprinkled. The dust on haul roads will be suppressed through regular water sprinkling. The fugitive emission generated during drilling will be controlled by using dust collectors to the drilling machines.