Chapter-2
Proposed Mining and Sources of Pollution
2.0 PROPOSED MINING AND SOURCES OF POLLUTION
2.1 Introduction
This chapter deals with the geology of the mining lease area, exploration details, evaluation of the deposit, estimation of reserves, method of mining, machinery, phase wise mineral extraction details, details on infrastructure, various sources of pollution and the control measures.
2.2 Description of the Mines
The general and technical details of the mining operations are given in
Table-2.1.
TABLE-2.1
DESCRIPTION OF MINES
Sr. No.
/Parameter
/Description
/I
/General Mine Features
1 / LatitudeLongitude / 19o18' N to 19o22' N
82o57’ E to 82o59' E in Toposheet 65 I/15
2 / Site and its surroundings / Site is a hillock with plateau top, ground slope varies between 1:40 and 1:5 and at few places slopes are steeper than 1:10.
3 / Pre mining landuse / Barren and waste land
4 / Distance from proposed refinery / 16.0-km (Aerial)
5 / Streams / Nallahs / Nil on plateau top, except a few rain-fed run-off channels
6 / Nearest stream / river / Khandabindha nallah, a major tributary of Indravati River (0.5-km, N of plateau bottom)
II /
Mine Technical Features
1 / Method of mining / Opencast mechanised mining2 / Proposed Production from the mine lease / 3.0 MTPA (Before expansion);
8.5 MTPA (Total after proposed expansion)
3 / Expected total Overburden / 153.42 Million Tonnes
4 / Total ML area / 1388.74-ha
5 / Mineable Reserves / 194.5 Million Tonnes
6 / Extent of mechanization / 100%
7 / Type of Blasting / Deep hole blasting with delay detonators
8 / Type of drilling / Down the hole drilling
9 / Power requirement / 3000 kW
10 / Source of Power / From CPP of alumina plant
11 / Water requirement / 720 m3/d (Before expansion)
2000 m3/d (Total after expansion)
12 / Water source / San river water
13 / Waste water Generation
a / Domestic waste / 40 m3/d (Total after expansion)
b / Industrial waste / 220 m3/d (Total after expansion)
C / Mine water discharge / Nil
14 / Waste Water Treatment
A / Sanitary waste / The sanitary waste from the mine service yards is treated in Sewage Treatment Plant
b / Industrial waste / Vehicle wash water and workshop wastewater will be treated in oil water separator and sent to STP
15 / Noise Levels / Maintenance of HEMM to keep the noise levels <85 dB(A)
16 / Ground vibration / Within the safe limits
17 / Solid waste generation / Overburden – 6.2 MTPA
18 / Fire Fighting System / Adequate fire fighting systems will be provided on all HEMM
19 / Stripping ratio
(ore : overburden) / 1.4 : 1
2.3 Geology and Hydrogeology
2.3.1 Physiography
Baphlimali plateau forms a part of Eastern Ghat hills. The plateau top is generally flat and the elevation varies from 990-m to 1093-m. The plateau is devoid of vegetation in most part. The ground elevation in the plains is about 750-m.
2.3.2 Existing Drainage
The Baphlimali plateau top has a relatively flat relief with slopes towards the fringes of the plateau.
The plateau top has no streams or nallahs, except the run-off of rainwater during monsoon. A number of springs originate from the foothills of the plateau at about 100-150m below the plateau top. The streams originating from the foothills of the Baphlimali Plateau have been assessed for its quality and quantity. These streams originating from Baphlimali either join Khandabinda nallah on north or San nallah on the south of the deposit.
River Indravati, the main water course in the region, flows in SW direction on the W side of the deposit at a distance of 7.5-km. The Khandabinda nallah, a major tributary of Indravati River, flows at about 0.5-km in N. San nallah is flowing at about 7.5-km in S direction from the plateau.
Surface water flow measurements indicate that the flow is gradually decreasing from December to April. Earlier, flow measurements indicate that the flow in these streams decreases further and the minimum flow is observed during first or second week of May. However, the streams are perennial in nature.
Quality of both surface water and groundwater is good without high concentration of pollutants. The pre mining surface drainage pattern of the mine lease area is shown in surface map under Figure-2.1.
2.3.3 Geology
2.3.3.1 Regional Geology
The lateritisation of the east coast bauxite deposits was developed at the expense of gneisses and schists. The dominant rock assemblage in the region, comprise khondalites (quartz-garnet-potash-feldspar-sillimanite gneisses with or without graphite) and its variants. These are high grade metasediments of argillaceous, arenaceous and calcareous nature. The other group includes charnockites (hypersthene-diopside granulites) and its equivalents, porphyritic granite gneisses etc. of Precambrian age. The general stratigraphic succession is as follows:
Recent alluvium and soil / RecentFerruginous and aluminous laterite and bauxite (on hill tops) / Tertiary
------Unconformity------
Garnetiferous porphyritic granodiorite and gneiss with later leuco-granite (Charnockite suite) / Precambrian
Garnetiferous quartizite, graphite sillimanite - garnet B quartz gneiss (Khondalite suite)
2.3.3.2 Geology of the Deposit
The deposit occupies the crest of Baphlimali Parbat, a hill in the Eastern Ghats. The hill is essentially composed of khondalites with charnockites occurring in the south-eastern part of the hill. The formations have NE-SW trend and steep south-easterly dips of 50-80 degrees.
The important characteristics in the profile of Baphlimali deposit are summarised below:
· Top soil is mostly lateritic in nature varying between 0-2m in thickness and covers almost 50% of the plateau area.
· The laterite is more ferruginous and siliceous at the top where it is hard and has cloggy, cavernous look. It gradually becomes more soft with depth where it is aluminous in nature grading into bauxite. The clay bearing areas and clayey laterites, occurring on the surface, are marked by growth of dwarf - palms.
· The bauxite shows gradational contact with overlying laterite and has a fairly sharp contact with the underlying partially leached parent rock.
· Roof of bauxite, due to gradational contact with overlying laterite, is a chemical boundary and thus becomes a function of cut-off grades adopted by the user.
· Floor of bauxite has a sharp contact with underlying partially lateritised Khondalite (PLK)/partially Kaolinised Khondalite (PKK). The undulations on bauxite floor are rapid and sharp as compared to those on the roof.
· There are some occurrences of PLK/PKK mixed bauxite and also aluminous laterite patches within the bauxite column as inside waste.
· The average thickness of overburden and bauxite globally for the deposit is estimated to be 9.84-m and 11.51-m respectively.
· There is a gradual decrease in hardness and compactness of bauxite from top to bottom.
There are few small patches of no-ore zones (non mineralised areas) which have been confirmed by drilling. These no-ore zones are formed either due to exposures of Khondalite on the surface or due to non-enrichment of alumina in the entire lateritic/ bauxitic column.
· Geomorphology - Surface Features
The laterite cover occupies the crest of the hill between 990-m and 1093-m RL with a relief of about 103-m, Baphlimali is characterised by a relatively flatter profile when compared to other bauxite plateau in the east coast region. The ground slope varies between 1:40 and 1:5. Slopes steeper than 1:10 are rare. Nearly half of the peripheral length of the plateau (29.5 km) is marked by scarps (2-17 m height) with an average of 8-m. The scarps are better developed in the eastern side where the maximum thickness of bauxite has been observed. The scarps are generally aligned sub-parallel to the strike of the formation. The ground slopes do not show any diagnostic relationships with ore characteristics. However, they may be broadly correlated as follows:
The surface of the plateau is largely covered with lateritic soil. There are, however, a few impersistent narrow exposures of pisolitic laterite (essentially ferruginous) dissecting the capping at places and a few weathered khondalite exposures restricted to the high topographical zone. Some partially lateritised khondalite patches (PLK) could be seen with laterite exposures. Most of the scarps expose only the partial thickness of the laterite/bauxite column and a few others do expose the PLK/weathered khondalite.
Bauxite is considered to have been derived by the in-situ chemical weathering of the khondalites. It occurs as a gently dipping or near horizontal blanket capping over partially lateritised or weathered khondalite. Both laterite and bauxite show relict foliation
The average thickness of ore body is arrived at by weighting the thickness of the bauxite zone indicated by exploration points spaced at regular grid intervals against their areas of influence. Narrow discrete partings of non-ore intervening with bauxite have been included in bauxite for practical considerations. Where thickness is so high as to convert the quality of material into non-ore if combined with bauxite, only one subzone, generally the top one, has been accepted as bauxite. The reserves of zone below the non-ore partings have been estimated separately. The various lithounits adopted for the current exercise are as follows:
DETAILS OF LITHOTYPES
Litho Unit Number / Lithology / Thickness Range (m) / Average Thickness (m) /1 / Soil and soil mixed laterite / 0-2 / 0.5
2 / Hard Laterite with very high slilica / 2-5 / 3
3 / High silica aluminous laterite / 2-3 / 2
4 / Low silica aluminous laterite / 1-2 / 1
5 / Bauxite / 6-41 / 13
6 / PLK/PKK mixed with bauxite / Deeper / -
7 / PLK/PKK and Khondalite / Deeper / -
The detailed description of different lithotypes is as follows:
Lithounits 1 and 2 essentially form a part of overburden at the top. Lithounit 3 is predominantly occurring as overburden below the lithounit 2. However, there are few occurrences of lithounit 3 within the ore column as inside waste. Lithounit 4 occurs equally as inside waste within ore column and as bottommost layer of overburden just above the ore-roof. Lithounit 5 is typical bauxite and forms more than 90% of the ore column. Lithounit 6 invariably occurs just below the ore column within one to two meter horizon. However, there are few instances of lithounit 6 occurring as inside waste within the ore column. Lithounit 7 is essentially a bottom waste below the lithounit 6 and thus is not significant from point of view of mining/ wining the ore.
From the above it is obvious that litho units 1, 2 & 7 are not expected to mix with ore during mining. Thus litho units 3, 4, 5 and 6 are important for defining ore column and mineable column in individual drill holes.
2.4 Exploration and Exploitation
Drilling is the most important exploration activity undertaken during this exploration, especially since most of the deposit is covered under capping of soil. The pattern and type of drilling for proving a given deposit depends on the topography, shape, size, extent, compositional variation, attitude of beds and structure of the deposit. Taking these parameters into consideration, scientific drilling was adopted.
The lease area has been extensively explored in detail by Geological Survey of India (GSI) (during 1976-77), Mineral Exploration Corporation Limited (MECL) (during 1978-81), INDAL (during 1992) and MECL (during 1998-99) to establish mineral reserves. Details of exploration carried in the lease area are described below:
TABLE 2.2
SUMMARY OF TOTAL EXPLORATION WORKS
Sr. No. / Agency / Year / Summary of Works1 / GSI / 1976-77 / Drill holes: 52
Meterage : 1445.65
No. Of drill hole samples : 1240
2 / MECL / 1978-81 / Drill Holes : 530 (504 vertical + 26 inclined)
Meterage : 17843.55 (16758.15 vertical + 1085.40 inclined)
No. of Samples : 21837
Deep pits : 33
Meterage : 955.40
61 m3 of trenching
341 samples studied for petrology & minerology
Moisture and Density determinations
3 / INDAL / 1992 / Redrilling of 30 holes by vacuum suction located on MECL bore hole points, meterage 792
Resampling of 6 nos. of MECL pits
4 / MECL / 1998-99 / Drill holes : 45
Meterage : 1228
No. of samples : 1209
2.4.1 Exploration as done by MECL
Based on the resource evaluation studies done by GSI, MECL planned and executed detailed exploration programme at the instance of Govt. of India. The methodology followed by MECL has been described in the following sections.
2.4.1.1 Method of Exploration done by MECL
a) Topographical Surveying
Triangulation and levelling survey was carried out over the entire bauxite plateau and a network of 26 Triangulation stations was laid down. All GSI bore holes were also connected to these stations.
A central axial line and cross-section lines at every 200 m interval (or less in selected areas) were laid from the nearest triangulation station. The survey grid was connected to Survey of India Triangulation Station T-10 at 1093.22 m (Topo Sheet No. 65 I/15). The base plan for geological mapping was developed on 1:2000 in three parts covering the entire plateau top.