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KOTA STONE MINING – ENVIRONMENTAL ISSUES A. Hussain Mining industry is one of the most important and old industry supporting thecountry’s economy. The present trend is to opt for opencast mining in place of underground mining. At present country’s 25 lakh hectare area is under mining leaseconditions, out of which ninety percent area is subject to opencast mining techniques.In general, all the mines affect their surrounding environment to a little or moreextent, but opencast mining in particular lead to complex nature of environmentalproblems. In these circumstances it became imperative to mine planners and operatorsto plan and execute mining programmes in such fitting manner so that the impact ofmining on the local environment is brought to a negligible state or preferably to azero level. This requires a careful planning as well as more attentive work executionon day to day basis. Impact on the local environment is more aggravated and complexin case of small mines exploiting minor minerals such as marble, granite Kota Stone,sandstone and other type of building stone quarries. Kota and Jhalawar districts of Rajasthan have been subsisted with about 100million tonnes of splitable type of decorative grade flooring limestone, better knownas Kota stone. A typical chemical composition of Kota stone is given in table-A Table – A Kota Stone Chemical Composition S. No. Chemical Constituent Percentage (weight) 1 Calcium Oxide 37.30 2 Magnesium Oxide 4.13 3 Sodium Oxide 1.21 4. Potassium Oxide 0.40 5. Aluminium Tri Oxide 1.37 6. Ferrous Oxide 0.86 7. Titanium Di Oxide 0.05 8. Silica 24.90 9. Loss on Ignition 32.94 These deposits are part of vindhyan range of sedimentary rocks, overlain by sandstone cappings. In general Kota stone mining areas are free from sand stone coveringsand the entire profile consists of different grades of lime stone beds. The floor gradelimestone is available in a variety of different colors including blue, green, brown orspotted type. Color pattern is governed by the chemical composition where mainplayers are iron, Titanium and Aluminium. Kota stone formations outcrop in varieties of colours, predominantly blue, green,brown or their combinations etc. At place calcitic veins are are distinctly criss-crossing the deposits. Soil subsoil and non splittable lime stone layers are overlyingthese deposits. 1
The kota stone deposits are located between latitudes N 24o 32’ and N 24o 48’ and longitudes E 75o 50’ and E 76o 05’ and it is covered on topo sheet No 45/D/13. 45/D/14, 54 D/1 and 54 D/2. The various Kota Stone laminations are nomenclatured locally in an uniform language. Geologically Speaking, Kota Stone is part of Semi Series of lower Vindhyan group. The local nomenclature are well understood and prevailing from the inception of the mining in this area. The regional stratigraphic sequence of the deposit is given in table-B Table-B Regional Stratigraphic Sequence (A) Upper Vindhyan 1. Bhander Series 2. Rewa Series 3. Kaimur Series 4. Semi Series (B) Lower Vindhyan 1. Suket Shales 2. Nimbahera Lim Stone 3. Jhalrapatan Sand StoneThe Kota Stone deposits are spreaded over 150 square kms area and the total probablereserves up to minable limits is about 100 million tones. A fair area-wise distribution isgiven in Table-C Table-C Area wise Kota Stone ReservesS/No Area Minable Reserves in Million Tonnes1. Chechat 30.002. Pipa Kheri- Nayagaon Belt 2.003. Suket- Atraliya Sahravada- Kukra Belt 4.004. Suket- Dingsi . 10.00. Pampakheri, Atraliya Dhabadeh, Belt5. Dhabadeh- Teliya Kheri 10.00 Sahravada, Kukada, Belt6. Manpura- Dhani 4.00 Extending Jhalawar district7. Jagankheri – Kumbhkot 30.00 Laxmipura- Satalkheri Pipakheri, Belt8. Julmi- Belt 5.00 2
9. Atraliya Deposit 5.00 Total 100.00 The workable lime stone beds ameanable to splitting are located at a depth rangefrom 15.0 mtrs to 25.0 mtrs from the surtace and form part of anticlinal- syniclinal typeof sedimentary laminated structures. Strike and Dip of the deposit is primarily location specific, but generally thedeposit dip at 7.5 percent away from the anticlinal – synclinal common axis. Thelimestone bed is divided into five prominent sacks which are separated from each otherby clay partings. Thickness of Laminations in each sacks increases with depth and texturealso improves. However the lamination thickness and texture improves with higher Silicafractions in the sacks, as given in table-D. Table-D. Silica Percentage in Different Sacks S. No. Sack Average Silica Quality Considerations Percentage 1. Top Kota Stone 18.00 Thin laminations with rough Sack texture 2. Middle Sack 20-22 Aggregated lamination thickness increases better texture 3. Third Sack 22-24 Product size have larger portion of thick laminations and very good texture. 4. Fourth Sack 24-27 Thick laminations and very good texture Stratigraphic profile also varies from place to place and can be divided into threecategories depending upon the type of waste material overlying the workable deposits,viz.1. Overburden Comprising soil, sub-soil and mixed calcareous - like chechat area.2. Overburden Comprising soil, sub-soil and Basalt rock-like Pipakheri, Zulmi area.3. Overburden Comprising soil; sub-soil to a large extent underlain by a narrow band of calcareous rocks-like Jhalwar district deposits. The stratigrapic rock profile of all three deposits are shown in Table-E. Table-E Stratigraphic Rock ProfileS. No. Rock Thickness in Mtrs. Chechat Group Pipakheri Jhalawar Group District Mines1. Top Soil/Sub Soil 0.00 – 2.50 0.00 – 1.50 10.00 – 11.002. Overburden Comprising 10.00 – 25.00 - 3.00 – 4.00 mixed calcareous Rocks3. Basalt - 10.00 – 12.00 Nil4. Top Sack 4.00 – 5.00 4.00 – 5.00 - 3
5. Middle Sack 2.50 – 3.00 2.50 – 3.00 -6. Third Sack 3.00 – 4.00 3.00 – 4.00 3.00 – 4.007. Fourth Sack 1.25 – 2.00 1.25 – 2.00 1.25 – 2.00 Semi mechanized mining method is usually adopted, where the overlying wastematerial is removed with the help of hydranlic excavators having bucket size 0.5 to 0.9cu. meter and tippers of 10.0 to 15.0 mt bucket capacity. Hard overburden is drilled with125 mm size water-hole drilling portable rigs. The drilling pattern in the soft rocks ismaintained at 4.0 x 4.5 mtrs, while in Basalt it is narrowed down to 3.0 x 3.0 mtrsMixture of conventional cartridged explosives and ANFO is used for blasting. In Basaltthe charging factor is kept at the rate of 1.25 kg per foot of drilled hole length, while inother cases it is 0.8 kg/foot of drilled length of hole. Radiat blasting techniques is used inthe sensitive areas, while at other places 17 ms relays are used to provide relief betweendetonating rows. The workable tables are given 150 mm to 450 mm deep cut channels at aninterval of 0.6 mtrs distance with the help of electric motor driven Jhirri machines. Semi-Skilled artisans, cut and size different length of slabes from these bays and stack atdesignated places, from where the slabes are loaded into trucks and transported to salesstock, maintained at quarry top. This entire operation is manually operated. A general statement of Kota Stone production from 1996-97 to 2011-12 is givenin Table-F Table-F Year wise Kota Stone Production (Figures are approximate) S. No. Year MT. 1 1996 - 97 10.00 2 1997 - 98 21.00 3 1998-99 22.00 4 1999 - 2000 20.00 5 2000-01 21.00 6 2001 – 02 22.00 7 2002-03 23.00 8 2003 – 04 30.00 9 2004-05 28.00 10 2005 – 06 35.00 11 2006-07 30.00 12 2007 – 08 40.00 13 2008 – 09 45.00 14 2009-10 40.00 15 2010 – 11 50.00 16 2011 - 12 55.00 The average yield of acceptable quality of Kota Stone per hectare land area isabout 1.00 lakh M.T, and with the current trend of yearly production level, 55.0 to 60.0hectare land is brought under stone mining each year. In all cases this land belongs tofarming sector and is completely degraded as far as agriculture is concerned. In a rough 4
estimate, till date almost 900 hectare prime agriculture land has been lost to Kota Stonemining alone in Kota and Jhalawar districts. Damage to land surface from sand stonemining is not included in this assessment. In addition to the environmental problem cropping up due to permanent loss ofprime agricultural land, there is one more dimension to this activity i.e. formation ofwaste dumps over agricultural land. Most of the mining leases are of 4.0 Ha to 25.0 Hasize areas, where side by side pit reclamation is not possible. The angle of repose of theblasted overburden is almost 380, which requires a sizable space in the operative sections,apart from productive platforms, facility recess, and water sink and other utility Space.As a result, large quantity of blasted wastes are dumped over prime agricultural tracts,specially purchased for making these waste Dumps. The quantum of problem can beunderstood by the figure that 2.5 cum waste has to be stripped off and dumped in thedump-yards for each metric tonne of Kota Stone production. Capacity of the dump-yardsretaining waste material depends upon many factors such as size, shape, angle of reposeetc, but on an average 1.0 Hq area dump-yard may hold about 1.75 lakh m3 wastematerial taking into account angle of repose, optimum square shape and space for haulroads and benches etc. The present trend of production level is likely to generate about 138 lakh m 3 ofwaste material every year. Presently only 35 percent of this bulk quantity is filled back inthe mined out areas, leaving behind 90.00 lakh m3 waste dumped over prime agriculturalland, requiring 45.0 to 50.0 hectare fresh land for dumping waste generated in a year. Asper our estimates around 1800 lakh m3 waste material is dumped in random formationscovering about 900 to 1000 hectare area. The third dimension to this problem is of the disposal of the fine slurry releasedfrom the cutting polishing industries. Every year about 2.5 to 3.0 lakh mt of stone polishis discharged into local convenient places. This affects about 5 to 10 hectares land everyyear. In total both Kota and Jhalawar district are loosing about 120-150 Hectare primeagriculture land every for facilitating Kota Stone mining, which is quite alarming. In addition to this one more point needs immediate attention. Kota Stone is alocalized non-renewal natural resource and its limited reserves may not last anotherfifteen years with the current policy of liberalized lease sanctioning process and increasedproduction level. This aspect needs introspection from the point of sustainable growthand regulation. The mining in these districts is loosing valuable top - soil at the rate of 8.0 to 8.50cu.mtrs per year, which is another loss to eco-system. To overcome the environmental problems as highlighted above, followingmeasures are recommended.1. Fresh mining leases should be considered exclusively on the land presently occupied by the old waste dumps.2. Mine-owners should be pressed to dumps their waste generations into nearby old abandoned quarries.3. The case agreements should have special provisions to force con-current refill after an initial grace period to facilitate development and space for such refills.4. Cutting polishing industries should be forced to dump their slurry into old mined out areas or in the active dumps. Any violation should be penalized. 5
5. Top soil should be mined out separately and conserved for reclamation purposes. (A.HUSSAIN) 6