SCIENTIFIC STUDY OF SOIL EROSION AND PREVENTIVE MEASURES
FOR GIDI ‘C’ OPENCAST PROJECT (0.6 MTY)
OF CENTRAL COALFIELDS LIMITED
SEPTEMBER, 2012
SLOPE STABILITY CELL ENVIRONMENT DIVISION CENTRAL MINE PLANNING & DESIGN INSTITUTE LTD. (A Subsidiary of Coal India Ltd.) GONDWANA PLACE RANCHI – 834008
SCIENTIFIC STUDY OF SOIL EROSION AND PREVENTIVE MEASURES
FOR KARMA OPENCAST PROJECT (0.6 MTY)
OF CENTRAL COALFIELDS LIMITED
SEPTEMBER, 2012
SLOPE STABILITY CELL ENVIRONMENT DIVISION CENTRAL MINE PLANNING & DESIGN INSTITUTE LTD. (A Subsidiary of Coal India Ltd.) GONDWANA PLACE RANCHI – 834008
INDEX
Chapter Name of Chapter Page No
1 Background 1 - 2
2 Project Profile 4 - 11
3 Soil Erosion 12 - 27
4 Control Measures 28- 38
5 Cost & conclusion 39- 41
CMPDI Prevention of soil erosion
CHAPTER - I
Background
1.0 Purpose
CCL had submitted a proposal to concern department for the release of 237.300Ha. of forest land for the Gidi ‘c’ open-cast project to MoEF, GoI through DFO, East Division, Hazaribagh. Stage – II clearance has been accorded by MoEF vide letters no. 8 -114/2003 -FC- dated 30.10.08 of Sr. Assistant Inspector General of forest MoEF, Govt. of India with certain conditions.
As per clause no. 3 (I, II, III, IV & V) of the said letter the user agency has to comply with;-
Preparation of a scheme for the proper mitigation measures to minimize soil erosion and choking of stream and shall be implemented; Planting of adequate drought hardy plant species and sowing of seeds to arrest soil erosion; The area shall be reclaimed keeping in view of the international practice or stabilizing the dump grading/benching so that the angle of repose (normally less than 280 at any given point) are maintained; The top soil management plan should be strictly adhered; The study of soil erosion/soil flow from the overburden area with the help of GIS in consultation of forest department.
So, CCL has requested CMPDI (HQ) to prepare the necessary scheme for fulfillment of the above condition vide their letter No. CGM (P&P) 09/815–18 dated 27.10.2009. Accordingly, CMPDI (HQ) has taken up job with job no.090309111.
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1.1 Consultation with forest officials A formal meeting between CCL and PCCF cum executive director of Forest Department, Jharkhand has been held on 7.12.09 in the office of later to discuss the compliance the condition laid down by Sr. Assistant Inspector General of Forest vide their letter no. F.No.8-114/2003 FC regarding the release of 237.300Ha. of forest land for Gidi ‘c’ Open- cast Project. On the basis of the above meeting forest department has given guidelines for the fulfillment of the conditions, set by Assistant Inspector General of Forest.
1.2 Scope of Work:-
The study of soil erosion from the leasehold area including overburden area with the help of GIS and preparation of a detailed scheme with sketches and drawings along with a cost estimate to minimize/prevent the water pollution, soil erosion arises due to surface runoff, and choking of streams in the mine lease area of the Gidi ‘C’ OCP project.
1.3. Objective of the scheme-
Prevention of Damodar river, Mangaradah nala and their tributaries from being choked along with protection of the leasehold areas from being eroded due to the high velocity of surface run-off, reduction of the fertility of the due to soil erosion owing to the ongoing Gidi ‘c’ OCP project for the benefit to the local habitants, animals and plants get good quality of land and clean water in sufficient quantity. It will also help to enhance the ecological balance of the area and will take care of the natural ecosystem.
1.4 Project History :-
The Project Report for New Gidi ‘c’ open-cast has been prepared by CMPDI RI-III in Oct. 1988 after being sanctioned by CCL board will superceeds the sanctioned Interim Report (Nov.1987) prepared by RI-3 in the Interim report (IPR 1987) it was stated that presently exploration is going on and therafter a P.R. will be prepared. So far, no capital expenditure has been against the I.P.R for Gidi ‘C’ 1987. Presently it is producing 0.6Mty Coal.
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CHAPTER - II
Project Profile
2.0 General A report for Gidi ‘C’ Open-cast Project has been prepared for a target capacity of 0.6 Mty BY RI-III,CMPDI, CCL, a subsidiary company of CIL, is proponent of the mine. It would excavate 13.15 Mt of coal of “F” long flame Grade from Seam VI to Seam VIII in 24 years of mining life span with the help of a shovel - dumper combination to feed North India thermal power projects. Maximum no. of manpower required is 720
2.1 Location:- a) Latitudes - 23041’48” and 23043’16”N b) Longitudes- 85022’42” and 85023’45”E c) Topo sheet No. – 73 E/6 on 1:63,360 scales. d) Company – Argada area,C.C.L e) Dist – Hazaribagh f) State – Jharkhand.
2.2 Surface Communication: - Gidi ‘C’ is connected with Ramgarh by motorable roads both via Sikra and Gidi ‘A” colleries. It is situated at a distance of 25 km from Ramgarh via Sikra colliery . The Patratu Saunda branch line of the Eastern railway extends to the middle of the property.
2.2.1 Airways- Nearest Air service is available from Ranchi, that is 70 Km. away from the project.
2.2.2 Distance of important place a) G.M.office, Kuju 15 km. b) Ranchi - -- 60 km. (Takes 1.5 hr. By road) c) Hazaribagh -- 90 km (1.5 hr. By road)
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2.3 Topography Drainage : - The area is gently undulating on the south east of Gidi ‘C’ (NE) Block runs the Bundu hill range trending roughly NW-SE. This a range with isolated hillocks rising to a maximum height of about 459m above M>S>L. The ground elevation of the explored area ranges from 393 m.( north west, of MKGC-30) to 336 m (South of MKGC-20). The Marmarha Nala constitute the main drainage system of the area and forms the eastern boundary of the block. 2.4 Climate As per the annual temperature map of India (National Atlas), the area falls within the daily mean temperature zone 22.50c to 25.00c. The summers as well as winters are extreme. According to the annual rainfall map of India (National Atlas), the area falls under the rainfall zone 1200mm to 1400mm. 2.5 Boundary of the mining block Two quarriable blocks have been identified for which two quarries, viz. quarry-1 and quarry-2, have been planned. 2.5.1 Quarry-1 Bounadary North eastern boundary The quarry top edge has been fixed in the incrop of naditoli seam (Argada L, M, N, o merged seam). South Western Boundary Quarry floor limit in the south west has been restricted to coal to OB thickness ratio of 1:3 South Eastern Boundary On the south east the quarry surface has been restricted to a distance of 60 m from marmarma Nala. A protective embankament is proposed against this nala. North Western Boundary Towards the north west the quarry would be extended only up to borehole no NDGD-10 on account of the following consideration. i) Reducing trend in the seam thickness ii) Deterioration in quality, iii) Increase in top cover and stripping ratio iv) Reduction in the width of the quarry.
2.5.2 Quarry-2 Bounadary Quarry 2 would be worked in three phases, viz phase-I, phase-IA and Phase –II. North eastern boundary
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In the north east quarry top edge has been fixed in the incorp of Argada I-seam, and in the north where Argada ‘T’ seam is less than 1 m, thick, in the incorp of Argada ‘H’ seam. South Western Boundary On the south west quarry floor would extend up to fault F1 (I), beyond which are the quarries and existing dumps of Gidi ‘C’ opencast mine. The area occupied by the existing railway siding and CHP complex has been kept in phase-II of quarry-2 South Eastern Boundary The quarry surface has been restricted to a distance of 60 m from Marma Nala. A protective embankment is proposed against this nala. North Western Boundary In the north west quarry bottom edge has been fixed in the incorp of seam argada ‘H’. The area covered by the existing workers colony has been in Phase-IA
2.5.3 Phase- I Bounadary North East – argada ‘I’ seam incorp South west - A 60 m barrier against existing railway siding South east- A 60 m barrier against Marmarma nala North west – a barrier against existing workers colony.
2.6 Geology 2.6.1 Geological Report The geological data given in the P.R is from the “Geological report on coal Exploration Gidi ‘c’ (NE) Block” prepared by MEC, Nagapur, April, 1988. The above G.R identified a potential quarriable block (Gidi ‘c’ (NE) Block) for quarrying seams Argada A, B, C, D, E, F, G, H & I only. 2.6.2 Structure of the block Strike and dip: Over the larger part of the block, the bedding strike is NNw-SSE except in the northwestern part, where it takes a swing becomes almost E-W. strata are having 150- 300 south westerly dip. Faults: The block is structurally less complicated. A total of 6 faults numbered F1 to F6 have been deciphered on the basis of intersections in boreholes and floor contour plans coupled with geological cross sections . the suffix I and II faults refer to the first and
New Gidi ‘C’ OCP 5 Job no. - 090310041 CMPDI Prevention of soil erosion second generation of faults respectively. Besides several minor faults having throw of 5 m or less may be present. The faults can be broadly grouped in two groups according to their trend :- (i) Faults trending NEW-SSW (ii) Faults trending NNW-SSW The first group of faults trending NNE-SSW is represented by 4 faults. All the faults of the first group head towards east except faults F5(II) which head towards the west. The maximum throw of this group of faults is about 20 m. The second group of faults trending NNW-SSE is represented by two faults F1(I) and F2 (I) which head towards east. The maximum throw of this group of faults is about 40 m. 2.6.3 Geological & Mining Characteristics Table shows the Geological & Mining Characteristics of the project Table – 2.6.1 Sl. No. Particulars Unit Value III QUARRY PARAMETERS Quarry-I Quarry- II Max Strike length of the quarry A a) At Surface m 1020 1560 b) At Floor m 960 1370 Max width of the quarry B c) At Surface m 310 470 d) At Floor m 220 320 C Maximum Depth of quarry m 80 120 Area of Excavation of the D. Sq.Km 0.2 0.6 quarry at surface
Product – Mix QUALITY The average product – mix quality of ROM is of grade ‘F – Long Flame’ with UHV of 2442-3049 Kcal/Kg.
RESERVES The total geological reserve in the Gidi ‘c’ NE Block (for which Quarry-2 has been envisaged including phase-II) is estimated at 25.37 M.tss in Argada B to Argada-I seams. In this case the dip side boundary has been fixed upto vertical line of railway siding. For the final stage quarry plan for phase –II of quarry -2, total minable reserves from seam Argada-A to Aragada-I are estimated as 25.97 M.Tes In this case, the dip side
New Gidi ‘C’ OCP 6 Job no. - 090310041 CMPDI Prevention of soil erosion boundary is fixed along the fault F1(1) at the quarry bottom, so the reserves beyond fault F1(1) are also included in the batter of the quarry-2 Hence, the comparison of minable reserve with geological reserve is not on like to like basis In the PR made in 1988 minable reserves & obr of quarry-1 and only phase-I of quarry-2 were considered OVERBURDEN A total of 5.20 million Cum of overburden was estimated in the project for quarry-1 and a total of 19.8. Million Cum of overburden in the project for phase-I of quarry -2. STRIPPING RATIO Based on the above figures, the overall stripping ratio for the Coal reserves of 3.75 million tons for quarry -1 against the total OB 5.20 MM3 is 1.39 Cum/t, and for the Coal reserves of 9.40 million tones of phase-I of quarry -2 against total OB 19.8 Million Cum is 2.11 Cum/t Mining System Considering geomining conditions of the deposit namely (i) steep gradient and (ii) multiple seams, shovel dumper mining system is proposed. Coal seams and OB are proposed to be extracted in horizontal slices. The height of benches for the proposed 4.6 cum rope shovel is 12m with a width of 40 m working benches. The slope for both coal & OB benches is adopted as 700. Dragline system of mining has been ruled out on account of steep seams. Life of the mine At a rated output of 0.6 Mt of ROM coal per annum and mineable reserves of 13.15 Mt, the life of project is estimated as 24 years.
Summarized Data New Gidi ‘c’ OCP (0.6Mty) Value S.no Particulars Unit Quarry-1 Quarry-2(Phase-I) 1 Minable reserve M.tes 3.75 9.40 2 Volume of OB M.m3 5.2 19.80 3 Stripping ratio (Av.) M3/te 1.39 2.11 Seams considered Naditoli seam Argada-B, C, D,F, 4 for mining (Argada-LMNO) G, H& I seams 5 Life of the mine 1st to 8th 6th to 24th
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2.7 MICRO-METEOROLOGICAL STATUS (i) Wind Speed/Direction during Summer Season Generally, light to moderate winds prevail throughout the season. Winds were light and moderate particularly during the morning hours. During the afternoon hours, the winds were stronger. Wind speed readings are ranging from <1 km/hr to 14.8 km/hr. The seasonal average wind speed is observed to be 5.4 km/hr. The wind patterns of the season are presented below: The analysis of wind pattern during the season shows that the predominant wind direction is from North-West with a wind frequency of 14.32%. It is followed by South- West with 10.15% frequency. The other observed directions are South-East (5.95%), South (5.89%), North (4.99%), West (4.68%), others 32.76 %, etc. The calm conditions prevails 21.30%. The wind speeds of 1-5 km/hr and 5-11 km/hr are recorded for 41.53 % and 34.68% of the total time respectively. In a complete year average 2 to 3 storm/gale strike the region with average speed of 50 to 60 Km/hr. That causes the uprooting of trees, blow out the CGI sheet’s roof and erosion and transportation of soil dust. Seasonal Wind Distribution Location- Core Zone Period : - April-June 2006 Wind Wind Velocity (Km/hr) & % Duration Direction < 1 1 - 5 5 - 11 11 - 19 N 2.71 2.10 0.18 NNE 1.92 1.23 0.09 NE 2.39 2.25 0.05 ENE 1.46 1.19 0.09 E 1.57 1.89 0.05 ESE 1.78 1.39 - SE 2.75 3.02 0.18 SSE 1.78 1.69 0.05
S 2.60 3.06 0.23 SSW 1.78 1.19 0.14 SW 4.82 4.78 0.55 WSW 1.42 1.56 0.14 W 2.85 1.60 0.23 WNW 1.83 0.82 0.09 NW 8.09 5.86 0.37 NNW 1.78 0.65 0.05 CALM 21.30 41.53 34.68 2.49
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Seasonal Wind Distribution, Graphical Presentation
(ii) Temperature Temperature values are ranging from297.0 to 319.1 OK. The seasonal average temperature value during this period is found to be 305.7 OK. (iii) Relative Humidity The daily average relative humidity values are in the range of 37.2 to 69.7 %. The seasonal average humidity value is found to be 53.3%. (iv) Cloud Cover Mostly clear sky is predominant during the study period. (v) Atmospheric Pressure The ave. atmospheric pressure value has been found to be around 750 mm Hg. (vi) Rainfall Normal average rainfall of the region is about 1826 mm. Nearly 80% of total rainfall occurs in rainy season (15 June to 15 September). Maximum rainfall recorded in 24 hr. 192.5mm in monsoon period and 58.0mm in non monsoon period. Average rainy days occurred in a year is about 75 days and out of those, 60 days occurred in rainy season. The daily average rainfall during the rainy season is 9.33 mm.
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Table showing the percentage distribution of rainfall in 21 years Sl. Annual Rainfall in mm Number of Percentage of No. From To Years Distribution 1 0 200 Nil Nil 2 201 400 Nil Nil 3 401 600 Nil Nil 4 601 800 Nil Nil 5 801 1000 7 33 6 1001 1200 5 24 7 1201 1400 4 19 8 1401 1600 2 10 9 1601 1800 1 5 10 1801 2000 2 10
Chances of rainfall in 24 hr. during rainy season Sl no. Rainfall in 24 hr Chances of rainy days Percentage 1 100 mm and above 1 1.67 2 50mm to 100 mm 7 11.7 3 25mm to 50 mm 10 16.7 4 2.5 mm to 25mm 42 70.0
2.8 Land Cover Following table shows the present land cover of Gidi ‘C’ OCP as per satellite imaginary photograph taken from IRS-P6 Liss-III satellite. Table Table : Area of Land use/cover class in core zone of Gidi ‘c’ OCP of CCL Land Use/cover Class Area Level -I Level -II Area in Km2 (1) Settlement (i) Industrial 0.15 Sub-total: 0.15 (2) Vegetation Cover (i) Scrub 0.56 (ii) Plantation on OB dump 0.80 Sub-total: 1.13 (4) Wasteland (i) Waste Upland 0.57 Sub-total: 0.57 (5) Mining area (i) Coal Quarry 0.08 (ii) OB dump 0.10 Sub-total: 0.38 Total: 2.06
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Satellite data imaginary taken from IRS-P6/LISS-III; Band# 2,3,4,5; Path#106, Row#55 and used as primary data source for the study.
Satellite Imagery
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CHAPTER – III Soil Erosion
3.0 - General
When the top layer of soil wears away and worn part of it is transported from one place to another by certain agency, this phenomena is called soil erosion.
And at the same time, due to action of some rain and wind, disintegration of rocks goes on naturally to form the soil. This process is continuous so the there is natural balance between the erosion and formation of soil.
Due to action of rain and wind, some portion of soil gets eroded and transported naturally. Soil erosion has affected land all over the world from small residential landscaped properties to large forests and deserts. Soil erosion is described as soil particles being shifted around due to the devastating impact of
Rainfall, Wind and Ice melts. It is a natural process but in most cases, human activity speeds up the process. Following are the description of Soil Erosion caused by above agencies:-
3.0.1 Rain Fall Erosion
Our ancestors used to believe that water erodes the soil when it flows over the surface in the form of surface runoff. But today this idea has been proved to be almost wrong. Because the investigation has shown that most of the erosion done by water is due to the impact of the falling rain-drops. The erosion capacity of surface run-off is very small and it acts only as a partner.
The water erosion process starts as soon as the rain starts. The two principal erosive agents that become active during the rain storm are:
(a) Falling rain drops; (b) Flowing runoff;
a) Falling rain drops - When a rain drop strikes the soil surface, it breaks down the clods and the aggregates of the soil and thus, the soil particles are torn loose from their moorings in the soil mass. The energy of the falling water is applied from the above and is utilized in detaching the soil particles, while the energy of the surface runoff is applied parallel to the surface and is utilized in transporting the dislodged soil particles.
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CMPDI Prevention of soil erosion
The erosion caused by rain storms is also known as Splash-Erosion-Process. Another important fact which we must mention here is that, the amount of erosion from hilly catchments is always more than that from flat catchments (provided all other conditions remain the same). This is, because, when a rain falls
Splash-Erosion
over the flat area, the incoming splash balances the outgoing splash; while when the rain drops strike the sloping land surfaces, a major proportion of the splash moves down. Hence, relatively larger quantities of soil is transported when catchments is sloping than the catchments is flatter. b) Flowing run-off - The fraction of the rainfall which does not infiltrate (soak into) the soil will flow downhill under the action of gravity; it is then known as run-off or overland flow. If rain continues, the increasing depth of water will eventually increase. Overland flow that is released in this way is likely to flow downhill more quickly and in greater quantities (i.e. possess more flow power as a result of its kinetic energy), and so may be able to begin transporting and even detaching soil particles. Where it does so, the soil surface will be lowered slightly. Lowered areas form preferential flow paths for subsequent flow, and these flow paths are in turn eroded further.
Following chart shows infiltration capacity under different type of management.
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CMPDI Prevention of soil erosion
Table – 3.0.1(b) Water infiltration under different types of management
3.0.2 Wind Erosion -
Soil erosion by wind may occur wherever dry, sandy or dusty surfaces, inadequately protected by vegetation, are exposed to strong winds. Erosion involves the picking up and blowing away of loose fine grained material within the soil. Damage from wind erosion is of numerous types. The most serious and significant by far, however, is the change in soil texture caused by wind erosion. Finer soil fractions (silt, clay, and organic matter) are removed and carried away by the wind, leaving the coarser fractions behind. This sorting action not only removes the most important material from the standpoint of productivity and water retention, but leaves a more sandy, and thus a more erodable soil than the original.
Wind erosion mainly depends upon the type, speed and duration of storm.
3.0.3 Ice erosion
Snow and glacier melt occur only in areas cold enough. Typically snowmelt will peak in the spring and glacier melt in the summer, leading to pronounced flow in rivers affected by them. The determining factor of the rate of melting of snow or glaciers is both air temperature and the duration of sunlight. In high mountain regions, streams frequently rise on sunny days and fall on cloudy days.
Soil erosion due to ice melting is not applicable in this region because it is a tropical region and temperatures do not go down to freezing point.
3.1 Consequences of Soil erosion
Damage from the soil erosion is of numerous types however the most serious and significant consequences are mentioned below-
1) Water Pollution;
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CMPDI Prevention of soil erosion
2) Unbalanced water availability; 3) Chocking of Streams; 4) Change in soil texture; 3.1.1 Water pollution- Water is the most essential requirement after air for survival of any kind of life and needs more or less some fixed quantity of water. It holds the pivotal position in the total environment, so that its availability is in optimum quantity, it can protect all aspects of the environments and if availability is less or more than requirement then quality of all aspects of environments gets endangered. Water is made available by the nature in good quantity and quality in the form of rain water, under ground water and through river, Nala, ponds etc. This water gets affected due to disturbance in the nature by means of man’s activities associated with construction, mining activities, etc.
Mainly two types of actions cause water pollution.
a) Mixing of foreign substance with natural water causing physical and chemical changes.
b) Interception or diversion of full or part of water from any source.
The operation of mining and allied activities of this project would have impact on water quality through generation of waste water in the surrounding area in the ways discussed below. The source of such a polluted liquid effluent has their impact on water quality and these are discussed elaborately in EMP report.
3.1.2 Inappropriate water availability- Less the soil is covered with vegetation, mulches, crop residues, etc., more the soil is exposed to the impact of raindrops. When a raindrop hits bare soil, the energy of the velocity detaches individual soil particles from soil clods. These particles can clog surface pores and form many thin, rather impermeable layers of sediment at the surface, referred to as surface crusts. They can range from a few millimetres to one cm or more; and they are usually made up of sandy or silty particles. These surface crusts hinder the passage of rainwater into the ground reservoir and reduce the water holding capacity of the earth with the consequence that runoff increases. Soil erosion reduces the capacity of the local ponds, wet land, stream/nala,etc. This increased the speed of the surface runoff and creates the flood like situation any where in downstream side. Due to low infiltration rate, ground water reservoir does not get fully recharged resulting in the shortage of quality water at this place. Thus create inappropriate water availability in the region.
3.1.3 Chocking of Streams - Rainfall water which does not infiltrate into the soil starts to flow downhill under the action of gravity. Initially, run-off moves down the slope as a thin diffused film of water which has lost virtually all the kinetic energy which it possessed as falling rain. Thus, it moves only slowly, has a low flow power, and is generally incapable of detaching or transporting soil particles.
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If rain continues, the increasing depth of water will eventually increase. Overland flow that is released in this way is likely to flow downhill more quickly and in greater quantities (i.e. possess more flow power as a result of its kinetic energy), and so may be able to begin transporting and even detaching soil particles and pick up soil contaminants from such as:- a)Runoff from OB Dump – 28.90 mm3 of O.B. materials would be dumped externally in this project. OB material would consist of broken stones, shales, coal and finer particles. The surface run-off from the embankment would be polluted with suspended and dissolved solids. These polluted run–off would ultimately drain into Damodar River through small channel and will pollute its water and choke the stream if allowed to discharge in the streams untreated b) Run-off from Construction Site- During the construction phase of the project, large area of land would be devegetated and degraded on account of site preparation for construction of roads, buildings etc. The runoff from these areas would carry large quantity of suspended solids, which can pollute and choke the natural drains, flowing through the area such as Magardah nala, Damodar River only in the initial phase of construction. c) Run-off from Coal Dump- The project has been so planned that coal dumps will not be created. But, if there may be situation when coal dumps would be unavoidable. So surface run – off from these dumps would be polluted with coal particles and other suspended particles which will finally pollute the Damodar river if unattended.
d) Runoff from built up Areas - Surface runoff from built up areas i.e. building, roads, roof tops etc. may not be highly polluted, but even then run–off may have high concentration of suspended solid i.e. sand, silt and coal particles. Above run-off, besides the soil particles, also carries the municipal garbage, petroleum, pesticides, fertilizers, pebbles, etc and discharge it in the next order stream, river and is transported well away from the point of origin and finally merge in sea. However, sediment may also be deposited within the rill or gully, or beyond the rill or gully’s and confines in a depositional fan, at locations where the gradient slackens. Thus, it chokes the water ways. Here it may be stored for a variable period of time, possibly being reworked by tillage activity, until a subsequent erosion event of sufficient size to re-erode the stored sediment. It may then be re-deposited further downstream.
3.1.4 Change in Soil Texture - The most serious and significant affect of the soil erosion by far is the change in soil texture caused by wind/water erosion. Finer soil fractions (silt, clay, and organic matter) are removed and carried away by the wind, leaving the coarser
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CMPDI Prevention of soil erosion fractions behind. This sorting action not only removes the most important material from the standpoint of productivity and water retention, but leaves a more sandy soil and thus a more erodible soil than the original. Successive removals eventually create such a soil condition wherein plant growth is minimized and erodibility is greatly increased. Damage results both from the erosion and the consequent dust storms. Control becomes more and more difficult. In the extreme, the sands begin to drift and form unstable dunes which encroach on better surrounding lands. Throughout recorded history, huge agricultural areas have been ruined for further agricultural use in this manner
3.2 Estimation of Soil Erosion
Erosion is a natural geomorphic process occurring continually over the earth’s surface and it largely depends on topography, vegetation, soil and climatic variables and, therefore, exhibits pronounced spatial variability due to catchments heterogeneity and climatic variation Soil erosion is a three stage process: (1) Detachment, (2) Transport, and (3) Deposition of soil. Different energy source agents determine different types of erosion. There are four principal sources of energy: physical such as wind, water, gravity, chemical reactions and anthropogenic, such as tillage. Soil erosion begins with detachment, which is caused by break down of aggregates by raindrop impact, sheering or drag force of water and wind. Detached soil particles are transported by flowing water (over-land flow and inter-flow) and wind, and deposited when the velocity of water or wind decreases by the effect of slope or ground cover. Three processes viz. dispersion, compaction and crusting, accelerate the natural rate of soil erosion. These processes decrease structural stability, reduce soil strength, exacerbate erodibility and accentuate susceptibility to transported by overland flow, interflow, wind or gravity. These processes are accentuated by soil disturbance (by tillage, vehicular traffic), lack of ground cover (bare fallow, residue removal or burning) and harsh climate (high rainfall intensity and wind velocity). Above problems can be circumvented by describing the catchments into approximately homogeneous sub-areas using Geographic Information System (GIS). In this study, the remote sensing and GIS techniques (through Satellites Imagine and interrelated software) were used for derivation of spatial information, catchments describing, data processing, etc. Various factors of Universal Soil Loss Equation (USLE) were generated
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and overlaid to compute spatially distributed gross soil erosion for the area using 11-year rainfall data. The concept of transport accumulation of soil was formulated by using the GIS for generating the transport capacity. Using these formulae, the amount of sediment rate from a particular sub-area is indicated. Following three formulae have been used for estimation of soil erosion in this project. This formula uses the USLE, WET and SMCP equations. 1). USLE (Universal Soil Loss Erosion) 2). WET (Watershed Erosion Tool) 3). SMCP (Soil Management & Conservation Practice) Factors included in these equations are collected, studied and reviewed using the Geomatic information system (GIS) and data, plan and information gathered from the field and others sources. Following are the data source required in the above equations.
3.2.1 Data Source The following data are used in the present study:
Primary Data Satellite data [IRS-P6/LISS-III; Band# 2,3,4,5; Path#106, Row#55] was used as primary data source for the study. The raw satellite data was obtained from NRSA, Hyderabad, on CD-ROM media.
Secondary Data Secondary (ancillary) and ground data constitute important baseline information in remote sensing, as they improve the interpretation accuracy and reliability of remotely sensed data by enabling verification of the interpreted details and by supplementing it with the information that cannot be obtained directly from the remotely sensed data. The following secondary data were used in the study: (i) Survey of India topographical map –73E/9 &10, and 73E/5&6 (ii) Vicinity map supplied by CCL showing village, road and drainage etc. (iii) Present and proposed Landuse Plan.
(iv) Cross section of nala and OB dumps.
3.2.2 Area under consideration for soil erosion calculation
Gidi ‘C’ OCP is running project and producing coal from small patch. A Project report of Gidi ‘C’ OCP 1.0Mty prepared and has been sanctioned. Soil erosion for present condition and proposed condition will different. So assessment for soil erosion will be done for both the existing and proposed condition.
a) Following table shows the present land use status of the Gidi ‘c’ OCP which is being used for the different activities.
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Table-3.5.2(A) Sl no Land use Area in ha 1 Present Mining area 40 2 Proposed Mining Area 30 3 Colony and infrastructures 45 4 Abandoned Quarry 110 5 Abandoned OB Dump 95 6 Reclaimed area 70 7 Green Belt & Safety Zone 160 Total 550
3.5.3 Division of the Area In above land use plan, whole has been differentiated in following three zone for the purpose of calculation of soil erosion.
1) Infrastructure and Colony area 2) External & internal OB Dump and Active OB dump area 3) Green Land, safety zone and
Soil erosion of the above zone would be calculated with the appropriate methods which are described below. Chart shows the % land area of the different zone considered for soil erosion.
Area Selected for Calculation of Soil Erosion
Infra. Stu.Colony 23%
OB Dump 47%
Green land 30%
Infra. Stu.Colony OB Dump Green land
Chart 3.5.3 The general formula of USLE is given below The USLE equation is: A = R * K * LS * C * P Where, A = Predicted soil loss (tons per acre per year) R = Rainfall and runoff factor K = soil erodibility factor
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LS = slope factor (length and steepness) C = Crop and cover factor P = Preservation practice factor A - The tons of soil lost per acre per year. The value "A" is usually compared to a value "T". T is the amount of soil loss that is considered "tolerable". Each soil series has a value T listed in the soil survey.
R - Rainfall and runoff factor. R is based on the total erosive power of storms during an average year and depends on local weather conditions. Calculation of R factor is the summation of daily erosive factor (y). Where in (y) = 3.2353+1.7890 In (x)
K - Soil erodibility factor. Depends on texture, structure, and organic matter. The k-factor was generated from detailed-reconnaissance soil map (1:100,000) and assigned values according to soil texture as studied by GIS.
LS – L factor and S factor are combined into one factor. The LS- factor is generated from the following equation: LS = (L/22.1)m (0.065 + 0.045 S + 0.0065 S2), Wischmeir and Smith (1978)
n m LS = (Ls / 22.1) x (Sinβ / 0.0896) by Moore & Wilson (1992): L - Length is the distance between the beginning of water runoff on the land and location of sediment deposition on the land or runoff enters a well-defined channel. The slope length factor computes the effect of slope length on erosion. Slope length longer than 1000 ft are not used in this interactive calculator because the calculation may not be reliable.
S - Slope steepness. The slope steepness factor S computes the effect of slope steepness on erosion. C - Cover factor. Compares cropping practices, residue management, and soil cover to the standard clean fallow plot. C-factors for different management practices are developed based on their observed deviation from the standard, which is clean till with continuous-fallow conditions. P - Preservation practices implemented into the management system. It is the soil loss with contouring and /or strip cropping, or terracing to that with straight row cropping / planting up-and-down slope (i.e., parallel to the slope).
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This method is most suitable for moderate slope and slope length but for large area. It may be used in both barren and covered land. So this formula is used for determination of soil erosion for natural ground which has low slope and having low cover. So, soil erosion from infrastructures sites, which has low slope and low cover have been done by using the USLE formula.
a) Following table gives the assessment of soil erosion from the infrastructures sites and township of the existing running mines of New Giddi ‘C’ OCP. Table-3.5.3(A) Land Runoff Soil slope Cover Ave. soil Sl consider for factor erodibility factor factor erosion Method no erosion R factor K LS C t/a/y All Infra USLE 1 564.9 0.259 0.470 0.050 3.44 t/a/y structures 2 Colony 564.9 0.3 0.402 0.056 3.811t/a/y USLE
3.5.4 SMCP (Soil Management & Conservation Practice) This SMCP calculator determines erosion or detached sediment by considering following factors. i) The first factor is the size or area of the site of interest. ii) The second factor involves the idea of raindrop impact energy. When a raindrop falls from the sky and hits the ground, the surface soil adsorbs the energy. Erosion occurs when the energy is powerful enough to detach soil. The amount of energy the rainfall of a particular storm depends upon the frequency of the storm and the location. Certain areas of the country frequently have higher energy storms than other areas. iii) A third factor is the soil texture. Just as soil texture influence water infiltration, it also impacts how easily soil can be detached. iv) A fourth factor is the influence of the arrangement of the land surface or the topography of the site of interest. The steepness and the length of distance down the slope both will affect erosion. v) The final factor is land cover. Erosion level depends on how much of the bare soil is vulnerable to raindrop impact. The erosion calculator will show how each of these factors affect the erosion.
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This method is most suitable for steep slope but small length. So this formula is used for determination of soil erosion from external dump and embankment which has steep slope and small length. a) Following table gives the assessment of soil erosion from external dump and embankment which has steep slope but small length of the existing running mines. Presently all dumping is being dump in abandoned mines and it will trap all soil erosion arises due to surface run-off during rain.
Table-3.5.4(A) Length of Width of Ave. soil Sl Ave. Slope Infrastructure slope in Slope in erosion Method no angle % ft ft t/a/y Abandoned SMCP 1 200 2500 40 8.0 dump
Results Output from SMCP calculator:- Based on the previously inputted of parameters and a 20 year simulation, soil loss was determined. The results in the above table and the following figures represent the output of the Water Erosion Prediction project (WEPP) calculation. The following table and graph presents the result output, slope profile and soil loss & deposition location.
WEPPCAT Simulation Results Scenario: Baseline State: Jharkhand Climate Station: Hazaribagh Management: Bluegrass Soil: SUCARNOOCHEE(SICL) Slope Shape S-shaped(45%) Slope Length (ft): 200 Slope Width (ft): 2500 Average Annual Precipitation (in/yr) 54.3 Average Annual Runoff (in/yr) 13 Average Annual Soil Loss (ton/A/yr) 8.2 Average Annual Sediment Yield (ton/A/yr) 8.0
Version Run on: September 8, 2012, 10.27 am
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A. AREA OF NET SOIL LOSS
** Soil Loss (Avg. of Net Detachment Areas) = 8.2 t/a ** ** Maximum Soil Loss = 14.7 t/a at 81.6 ft. **
Area of Soil Loss Soil Loss MAX MAX Loss MIN MIN Loss Net Loss MEAN STDEV Loss Point Loss Point ft. t/a t/a t/a ft. t/a ft. ------
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0.0- 156.8 8.2 4.7 14.7 81.6 1.3 1.6
B. AREA OF SOIL DEPOSITION
** Soil Deposition (Avg. of Net Deposition Areas) = -13.3 t/a ** ** Maximum Soil Deposition = -24.4 t/a at 160.0 ft. **
Area of Soil Dep Soil Dep MAX MAX Dep MIN MIN Dep Net Dep MEAN STDEV Dep Point Dep Point ft. t/a t/a t/a ft. t/a ft. ------156.8- 160.0 -13.3 15.8 -24.4 160.0 -2.1 158.4
Results Interpretation: Based on the previously inputted of parameters and a 20 year simulation, soil loss was determined. The results in the above table and the following figures represent the output of the WEPP calculation. The top figure presents the slope profile, while the bottom figure indicates were on the slope soil is eroded or deposited.
3.5.5 WET (Watershed Erosion Tool) The erosion calculations are based on the WEPP model, developed by a group of scientists at the National Soil Erosion Research Laboratory. The WEPP erosion model is a continuous simulation computer program which predicts soil loss and sediment deposition from overland flow on hill slopes, soil loss and sediment deposition from concentrated flow in small channels, and sediment deposition in impoundments. In addition to the erosion components, it also includes a climate component which uses a stochastic generator to provide daily weather information, a hydrology component which is based on a modified Green-Ampt infiltration equation and solutions of the kinematic wave equations, a daily water balance component, a plant growth and residue decomposition component, and an irrigation component. The WEPP model computes spatial land temporal distributions of soil loss and deposition, and provides explicit estimates of when and where an watershed or on a hill slope that erosion is occurring so that conservation measures can be selected to most effectively control soil loss and sediment yield.
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In this model, following parameters are required as input data in the WET computer programming calculator for soil erosion.
1) Field length 2) Field width 3) Slope size 4) Steepness of slope 5) Type of soil 6) Region as per rainfall 7) Management system
This method is most suitable for both steep & flat slope of short or long length but should have some type of land cover it may be wooded, residential and agricultural. So this formula is used for determination of soil erosion from the green land, green belt / safety zones.
a) Following table gives the assessment of soil erosion from green land & safety zone which has large area with some covers of the existing running mines.
Table- 3.5.5(A) Length Ave. soil Sl. Area Soil Land Steepness Item Region along erosion Method no in Acre Texture Cover of soil slope t/a/y Green land & Rocky Light 1 471 Silty Moderate Long 0.83 WET safety zone Mts Wooded
Input Data and Result Of WET Calculator
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Location
Desert (SW) Land Use and Land Input: Cover Land Area Rocky Mts. Soil Texture 560 (NW) Wooded acres If Agriculture, Sand Crop Appalachain Residential Storm Frequency Mts.(NE) Sandy Agriculture Row Crops Loam Frequent Storm If Wooded, Central Pasture Lowlands (Upper Silty Clay Tillage Implement Infrequent Heavily Wooded Midwest) Loam Storm Conventiona Lightly Wooded Great Plains Clay l Plow Very Infrequent (Lower Midwest) Storm If Residential, No-Till Plow Atlantic & Tillage Direction Scraped Bare Gulf Coasts (SE) during Construction Up & Down Results: Slope Slope Erosion Length along slope Mulched during Steep Construction (Detached Very Long With Sediment) Mod. Contours Long Steep Young Grass 471.299701293 Moderate Moderate Established tons Grass Short FlatBotto m of Form
3.6 Final assessment for soil erosion a) Following table shows the predicted soil erosion of different land use before and after prevention measures of the existing New Giddi ‘C’ OCP. Table- 3.6(A) Area Characteristic of Ave. soil erosion No Method Under use land t/a/y without PP 1 All Infra structures Low slope & low 3.44 USLE 2 Colony cover 3.81 Very steep slope 3 Abandoned dump 8.0 SMCP & small length Green land & Large area and 6 0.83 WET safety zone with some cover Chart showing the comparison of soil erosion of existing and proposed land use plan
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Existing Calculated Soil Erosion
9 8 8 7 6 5 3.81 4 3.44 3
Soil Erosion t/Ha/Yr Erosion Soil 2 0.83 1 0 Inf. Stu Colony Aband Dump Green land
Existing Proposed
Result Interpretation
Prediction for soil erosion form the New Giddi ‘C’ OCP is done by using the USLE equation SMCP and WET model. All model were used on most suitable land use conditions such as;-
USLE equation was used for soil erosion calculation for the land patches of infrastructures sites.
SMCP model was used for soil erosion calculation for the dumps and embankments
WET model was used for soil erosion calculation for the Greenbelt and safety zone.
Result come out for different landuse area of existing condition is between 0.83 to 8.0 t/a/y which is between in the normal range of soil erosion in this type of soil.
It is observed that only 10 to 25% of total eroded soil gets lost (carried away out side the leasehold area) and remaining eroded soil deposited where the slope is easy. Soil loss graph substantiate the observation.
This soil erosion can be minimized around 90% by providing optimum cover and suitable arrangement such that baffle wall, guiding channel, gully plug, etc.
In our case about 95% of soil loss can be prevented by providing the proper treatment such that sedimentation pond/tank, gully plug weir, etc.
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CHAPTER – IV Control measures
4.0 General
Surface runoff causes the water pollution as well as the soil erosion problem. The principal environmental issues associated with runoff are the impacts to surface water, groundwater and soil erosion through transport of water pollutants to these systems. Ultimately these consequences translate into human health risk, ecosystem disturbance and aesthetic impact to water resources. Some of the contaminants that create the greatest impact to surface waters arising from runoff are petroleum substances, coal particles, inorganic substances, soil, etc. These surface runoff translated into overland flow and surface water flow and deposited the soil and others pollutant there. These depositions badly affect land quality and capacity of the river/nala.
4.1 General Concept of Control measures for:-
1) Water Pollution 2) Soil Erosion (A) Soil erosion due to surface runoff
(B) Soil erosion due to blowing wind
4.1.1 General Concept of Control measures for Water Pollution - Opencast mining has various type of water pollution source which degrade the quality of water of nearby river/nala and under ground water reserve.
a) Basic approach to control the surface runoff water is to differentiate the mine into "clean" area and "dirty" area zone for the purpose of surface run-of. "Dirty" area run-off is water coming from stockpile, reclamation area, open cut mining areas etc. and therefore normally it requires treatment prior to discharge. "Clean" areas run-off is water, which passes through the undisturbed areas & green belt areas and it is prevented from entry to "dirty" areas through the use of diversions, drains and allowed to discharge the
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water into nearest natural drain directly because it does not need treatment. Regular monitoring is done to check the pollution level.
b) The liquid effluent generated at washing stations and workshop would be polluted with high concentration of suspended solid, oil & grease. These effluents are treated in treatment plants inside the workshop. No effluent is allowed to go outside because whole system is designed on the basis of zero discharge system. c) Municipal effluents are not allowed to discharge on either land or inland water sources without proper treatment because it can pollute land & other stream. Every housing unit or in group will be provided with septic tank and the outflow is led to soak pit. Other municipal effluent will be routed through sedimentation tank. The quality of effluents should conform to standards laid down in IS 4764 (Tolerance limit for sewage effluents discharged into inland surface water & IS 2490 – tolerance limit for industrial effluents discharged into inland surface water). All effluent shall be tested on quarterly basis. Action
4.1.2 General Concept of Control measures for Soil Erosion
Soil erosion occurs when wind or water washes away the topsoil from an area of land. Soil erosion is natural, but it quickly becomes problematic when people begin construction works and cutting down the vegetation cover. So it is very important to prevent soil erosion. Erosion of soil is basically depending upon the speed of surface flow / wind speed and vegetation and others type of covers.
Appropriate soil erosion control measures of different sources are recommended below to limit the soil erosion to a minimum extent.
(A) Soil erosion due to surface runoff
List of sources that are responsible for soil erosion, their characteristic and volume have been discussed above. Overland flow that is released is likely to flow downhill more quickly and in greater quantities (i.e. possess more flow power as a result of its kinetic energy), and so this flow of water become able to begin transporting and even detaching soil particles. Where it does so, the soil surface will be lowered slightly. Lowered areas
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form preferential flow paths for subsequent flow, and these flow paths are in turn eroded further and transported up to a location where the speed of flow down to carrying capacity. These depositions creates the obstacle in the way of spontaneous water flow causing large area submergence, cutting of sides of channel besides the degradation of water quality in Mangardah Nala and Damodar river.
In view of the above, basic approach in deciding the appropriate soil erosion control measures, are as follows –
The amount of soil erosion that occurs in an area depends upon two factors: the speed with which water and wind travel across it, and the abundance of plant life that is growing there. Since we have no control over the speed of the wind, how heavily it rains, or the currents of the nala / river, so we need to concentrate on the factor we can control are
(i) Surface cover (vegetation cover and other) and
(ii) Breaking the speed of surface flow.
Plant life protects topsoil in many ways. It prevents heavy rains from beating down on land and knocking the topsoil loose. It prevents the soil from drying out as quickly, thereby protecting it from being blown away by strong winds. The roots of the plants hold the soil in place, so it is not washed away as easily. Soil erosion is inversely proporsnate to soil cover and the speed of the runoff. A 60 % of land cover would result in 85% reduction in soil erosion and further breaking the speed of surface runoff up to scouring speed by baffle wall and any other means would result in further reduction of soil erosion by 45%. So in this combination 94% reduction in soil erosion can be achieved. i) Soil Erosion from Construction site Presently no major civil or any other type of construction works is going on in the project. In future, if any construction work would start, the following preventive measures would be taken up to reduce the opportunity of soil erosion/water contamination at construction site. Site to be taken for construction at different time horizon should be clearly marked.
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Vegetation removal and breaking of earth would be controlled and confined to site which is immediately required for construction. Catch Drain will be provided around the township/construction sites during construction period to intercept water flowing out. Surface Run off from construction site would be channelised to sedimentation lagoon. The clear overflow water from lagoon will flow into near by natural streams Site for storage of rubbish, excavated earth etc. would be identified and drainage arrangements will be provided around these and connected to sedimentation lagoon to avoid pollution of natural streams. vi) As soon as construction is over, all sites would be vegetated & planted with trees. ii) Soil erosion from OB Dumps – Newly formed and barren OB dumps are the main culprit for the soil erosion particularly active and new OB dumps. Soil of the OB dump is easily eroded by both wind and water because it is in un-vegetated and in loose conditions. Following preventive measures would be taken up to reduce the opportunity of soil erosion/water contamination from overburden sites. First of all a Gabion wall of 1.25m to 1.75m height, depending upon the prevailing condition, of stone boulders all around the OB dump of would be constructed. This measure will check the OB dump from the spreading beyond the Gabion wall. Garland Drains will be provided around the retaining wall of size 1.5m (width) x 0.1.0m (depth) to check the surface run -off flowing out or into the OB dump. This drain is to convey the intercepted run-off water into sedimentation lagoon. This measure will prevent the surface run-off from spreading to any where. A sedimentation tank of sufficient size (5% of total runoff or 10th highest rainfall in 24 hr which ever is more) will be constructed so as having the one hour detention period most of the time. This act will arrest at least 90% of suspended soil particles that flow out with surface run-off.
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Over flow effluent from the sedimentation tank would be allowed to discharge in the nearby natural stream. A series of gully plug will be provided if speed of discharge water is above the scouring speed of soil. This will protect the stream bed and side from being scoured. Thus, there would be reduction in soil erosion.
Photo showing the toe wall Quick growing grass and vegetation cover would be done on the part of This will provide extra space for inactive dump all along the inclined flowing of water and thus will prevent and top portion of the dump. This will spreading of water. protect the soil particle from being Trees will be planted in three rows all detached due to action of rain fall around the OB dump. First row trees and hard wind blowing. Thus, there will be of short height, second row would be reduction in soil erosion. trees will be of medium height while Quick growing grass and vegetation third row trees will be of long height. would be planted on the route of These measures will break the water ways. velocity of wind and will prevent the soil erosion and spreading of dust. Garland drain and all flow channels should be cleaned regularly specially before the onset of the monsoon.
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iii) Run off from Coal Dumps – The project has been so planned that coal dumps would not be created. If unavoidable, baffle walls and garland drains would be provided around the coal dump to intercept the surface runoff flowing out from it and also to collect runoff from the surrounding of dump site. This drain will convey the intercepted water into sedimentation lagoon. Over flow from the sedimentation lagoon will be discharged into the natural drainage system. A series of gully plug will be provided if speed of discharge water is above the scouring speed (>1.5km/hr in this condition) of soil.
iv) Run off from built up areas Open drains would be provided along the roads, workshop, township and other service buildings. These drains will collect the water from built up area which is not much polluted except the normal suspended particles, garbage, silt and sand. This water would be diverted into sedimentation tank and from there to natural drains to convey into Damodar River. A series of gully plug will be provided if speed of discharge water is above the scouring speed of soil. v) Mitigation Measures for the Remaining Area Area would be divided in two zone, clean area zone and dirty area zone. Clean area zone comprises the un-broken zone where is not any type of activities are earmarked and having green land. In the dirty area zone, all infrastructures and activities are located. Both the area would be separated by storm drain or water guide channel so that water flowing out from each zone could not mixed-up. If speed of water, passes through these areas is more than scouring speed (0.5m to1.5m per second) than series of small baffle wall would be constructed. Height of baffle wall will be 3.0 to 5.0 cm more than the depth of the overland flow and width should be equal or more than the width of surface run-off. So, surface run-off will passes through over these baffle walls which will
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Dirty area zone is further divided into aggressive and non-aggressive area. Aggressive zone contains completely broken area such as quarry area, coal Photo shows the bund/waffle wall arrangement stockyard area, CHP area and other industrial area. Non-aggressive zone comprises of all administrative buildings, industrial buildings, road, etc.
Water flowing out from the non-aggressive zone will be guided to sedimentation tank. Effluent from here will be allowed to meet the natural local streams after breaking down the speed of the scouring speed of soil with the help of series of gully plugs.
Surface run-off coming out form the aggressive zone would be treated individually as mentioned in the para of “Mitigation Measures”. Over flow effluent from these sedimentation tanks would be sent into the large sedimentation pond. Effluent from here will be allowed to meet the natural local streams after reducing the speed below scouring speed with the help of series of gully plugs.
Final effluent will be checked regularly as per monitoring programme. If any deficiency is found then suitable rectification will be done.
All the vacant land would be vegetated with quick growing grass, bushes and small and medium size trees. Medium size trees would be planted All around the all administrative buildings, infrastructures buildings, coal storage site. Avenue plantation and strip plantation will be done all along the roads and in the colony area. Finally all the drainage system will be cleaned regularly and more frequently in monsoon season. All sedimentation tanks must be cleaned before the onset of rainy season
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(B) Control Measures for Soil Erosion by wind Damage from wind erosion is of numerous types. The dust storms resulting there are very disagreeable and the land is robbed of its long term productivity. Crop damage, particularly in the seedling stage, by blowing soil is often a major concern. Subsequent yield and quality losses are incurred and, in the extreme, tender seedlings may be completely killed. Often sufficient soil is removed to expose the plant roots or un- germinated seeds, and these results in complete crop failure. Sands begin to drift and form unstable dunes which encroach on better surrounding lands
Wind erosion depends upon the type of storm, speed, duration and type vegetation covers. It is studied that wind speed less than 20km/h has not much impact on soil erosion.
In above attributes, we can only control the speed of wind and vegetation cover. Wind speed can be reduced by erecting the some obstacles in the path of wind.
Planting of trees would be most suitable obstacle for breaking the wind speed and it also enhance the vegetation cover upon the soil. These plantations also reduce the evapotranspiration by 20% and help to maintain the soil moisture contents. Bonding affect between the soil particles increased due to increase in moisture contents and it resist the erosion force.
So the best arrangement would be two rows of tall trees surrounded by two rows of low trees, making up a 10-metre strip. Vegetation cover, grass or crop would be increased. It is particularly important to repair breaches in a hedge to keep the wind from pouring through at these points (the Venturi effect) and considerably reducing effectiveness.
Soil erosion by wind becomes significant when speed of wind increases to 20km/h means 6m/sec. In our region, wind speed hardily (3 or 4 times per year) increases to above limit. So there is no major problem of soil erosion caused by wind blow.
4.1.2 Mitigation Measures for River/Nala
First of all only treated water would be allowed to enter the river/nala. Initially one weir of height 1.5m would be constructed on the Mangardah nala between the existing bridge
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and dump. This weir would serve our dual purpose; firstly it will stop further transportation of soil, secondly it will facilitate the rain water
Systemic drawing of weir Photo showing the temporary weir
harvesting store the water for long period after rainy season and most important it will facilitate the local habitants to utilize the water. The detail design and specification of the weir would be provided separately after the clearance of this report, if CCL desire so.
4.1.3 Project Specifics flowing I) OB Dump;- In the given lease hold area there is no external active dump at present. All external dumps are old which got setteled and vegeted, so there is only soil erosion. More over these dumps are well within the leased hold area so chances is very less to soil erosion get transported outside the leased hold area. However some control measures have been suggested to prevent the flowing the soil out side the leased hold area.
1) Catch drain foot drain will be provided at beam & inclined face on every layer of the dump at every 100m as shown in the drawing.
2).Top surface of OB dump will have transverse and longitudinal slope of 1:50 spreading outward so as rain water can be evacuated easily.
3) Curb of 15 to 20 cm will be provided all round the OB dump at each layer.
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This arrangement would intercept all surface run-off and prevent the water form spillage on inclined face of dump. Catch drain & foot drain will discharge the load in the garland drain.
4) A garland drain of size 1.5mx1.0m will be constructed all around the dumps and it will be connected to nearest abandoned mine. It would intercept the surface water coming out from dump as well as will take care of water coming from catch drai and foot drain. Garland will discharge the all load in the abandoned mine.
This type of arrangement have several advantages-
1). Water will be stored in to the mine void which can be utilized during the non- monsoon period. 2). Soil eroded by surface run-off will be dumped in to abandoned void. 3). This would completely prevent the eroded soil to be transported out the leased hold area. 4). Depth of mine would reduce gradually.
iii) Industrial Area:- Garland drain of size 1.0mx0.75m will be constructed all round of the industrial area i.s CHP, Coal stock, etc. This drain will intercept all the runoff coming out from the area and lead to sedimentation tank/ lagoon. Overflow from this lagoon would be allowed to meet the local stream after providing three or four gully-plugs.
iv). Remaining Area:- Total lease area of the project is 550 Ha. Marangara Nala is flowing along the Eastern side of the project and meets the southerly flowing Damodar river.at south-west corner of the project. 160 ha. land is falls in safety & green land while 70 ha. land is reclaimened and planted.
Surface runoff generated from the clean zone would be allowed to pass in the river/nala through local stream after providing three or four Gully plug in the stream.
All major mining activities will take place in this lower part of lease area. Mining area is amounting about 30ha. land which is completely broken, 45 Ha. of land will be partially broken.
Surface run-off from dirty zone will be guided to sedimentation lagoons/near by abandoned mine. Two sedimentation tanks/ponds of 8.0m x 6.0m x 1.6m (5% of total
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runoff or 10th highest rainfall in 24 hr which ever is more) size will be constructed, first at north-east corner and second between the haul road and guiding channel as shown in the plan. Over flow from this tank would be allowed to meet the nearby natural streams. Two or three Gully plugs would be provided in the stream.
v) Nala:- A weir/ check dam of 1.5 m height would be constructed in the up stream of the existing bridge across the Marangara nala. This weir/ check dam will serve many purposes: firstly, it will prevent the flowing out the sedimentation further, secondly it will serve as rainwater harvesting lagoon and finally it will serve as the storage of water for the villagers during the lean season. A typical cross-section has been given but actual size can be determined only after the detailed survey.
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CHAPTER – V Cost Estimate & Conclusion
5.1 Construction
The permanent Garland drain will be constructed with brick masonry all along OB dumps and coal stock yard. The temporary garland drain would be constructed along the quarry. All the storm drain along the road or colony will be of permanent type. The sedimentation lagoon near the OB dumps and in the dirty zone will be constructed of temporary type because the shape of the OB dump and the quarry will be changing with the time. Sedimentation tank near the CHP and workshop may be of permanent type if the location is final. Baffle wall may be of earthen or masonry construction depending upon the prevailing conditions at that time. All the gully plugs would be of permanent type construction.
5.1.1 Maintenance Sedimentation tank /lagoon should be cleaned every year before the on set of monsoon.Fishery work should be started in the sedimentation tank / recharged pits to keep the water clean and it will also make a way for income. Water analysis of recharging pit and nearby well should be done periodically, so that quality of water can be assessed.Vegetation should be done regularly at open spaces, on the way of surface run off, nearby area and other suitable places
5.2 Cost- 5.3 Total cost for the scheme comes to 198.4 Lakhs. This amount may changes at the time of construction due to prevailing condition and situations.
New Gidi ‘C’ OCP 39 Job no. --090310041 CMPDI Prevention of soil erosion
Table Rs. In lakh Sl.no Particular Unit Quantity Cost Remarks It will be constructed Cost of garland drain along 1 m 2100 16.8 departmentally dumps and quarry. using the HEMM Cost of storm drain along 2 m 1000 5 roads and buildings. Weir/Check dam of length 3 Nos 1 75 50m & 75m 4 Gabion/toe/retaining wall m 0.0 0 It will be constricted Sedimentation 5 Nos 3 1.5 departmentally tank/lagoon(Temp.) using the HEMM Guiding channel / baffle 6 m 3200 9.6 wall(Temp.) 7 Cost of gully plug Nos 100 0.5 Cost of plantation over OB 8 dump, embankment and m 50 50 development of green belt Cost of grassing over 9 Ha 50 30 embankment, OB dump Cost of arboriculture/ Road 10 LS 10 vegetation side TOTAL 198.4 * indicates this cost has been considered in EIA-EMP of Gidi ‘c’ OCP
5.1 Conclusion- a) Soil erodibility is an estimate of the ability of soil to resist erosion, based on the physical characteristics of each soil b) Soil erodibility is directly proportional to intensity of rainfall, speed and quantum of surface flow and inversely proportional to residue cover. c) All formulae used for calculation of soil erosion are based on the research done in foreign countries and it is still in nascent stage. So result may diverge in our prevailing conditions. d) Prevention of soil erosion scheme is prepared on the assumption that breaking the speed of surface run-off and higher the vegetation cover will prevent the erosion. e) Lease hold area is differentiated into ‘Clean & Dirty” zone
New Gidi ‘C’ OCP 40 Job no. --090310041 CMPDI Prevention of soil erosion
f) Generally, soil with faster infiltration rates, higher levels of organic matter and improved soil structure have a greater resistance to erosion. f) Sand, sandy loam and loam textured soils tend to be less erodible than silt, very fine sand, and certain clay textured soils.
g) Tillage and cropping practices which lower soil organic matter levels, cause poor soil structure, and result to increases in soil erodibility a) Past erosion has an effect on a soils' erodibility for a number of reasons. Many exposed subsurface soils on eroded sites tend to be more erodible than the original soils because of their poorer structure and lower organic matter. b) Maximum soil erosion occurs from newly dumped overburden waste and it reduced to 50% in each subsequent year.
5.2 LIMITATIONS The above formula and model used for predicting soil erosion by flowing water resulting from rainfall. These formula and model are based on the research done in foreign countries and it is still in nascent stage. The model may not be valid under extreme values of the parameters considered in the equation. So result may diverge in our prevailing conditions All the data and information used in the model is either supplied by project administration or the planning department of CMPDI. Shape & size of the mine has been changing continuously so the result may changing accordingly. The amount of water received during the monsoon season (15, June to 15, September) is important since this is the period of maximum rainfall. Conversely, rainfall received during the winter season is less significant because it does not cause soil erosion due to the small amounts and low intensity. There may be several other factors, in addition to those considered above, that could play a significant role in soil erosion. These factors, such as land configuration and management practices, can cause a deviation in estimated soil erosion values under certain conditions.
New Gidi ‘C’ OCP 41 Job no. --090310041