Vashi Creek Water Quality NaviMumbai

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gnmXH$ _S>bEDITORIAL BOARD

lr {ed Hw$_ma {ZXoeH$/B[agoZ A`jShri Shiv Kumar Director/IRICEN Chairman

lr EZ. gr. emaXm d[a> m`mnH$/B[agoZ gX`Shri N. C. Sharda Sr. Professor/IRICEN Member

lr gwYmewe_m m`mnH$/B[agoZ gX`Shri Sundhanshu Sharma Sr. Professor/IRICEN Member

lr drU Hw$_ma m`mnH$/B[agoZ gX`Shri Praveen Kumar Sr. Professor/IRICEN Member

lr. E. Ho$. mXd d[a> m`mnH$/B[agoZ H$m`H$as gnmXH$Shri A. K. Yadav Sr. Professor/IRICEN Executive Editor

( i )

FROM THE DESK OF THE EXECUTIVE EDITOR

This issue of Construction Bulletin features two interesting articles. In the first paper, the

authors have described instrumentation carried out to measure settlement and pore pressure on a

trial embankment to decide the suitability of the proposed methodology for construction of theembankment of a new double line project between Belapur/Nerul to Uran. Here the alignment

passes through coastal zone consisting of compressible marine clay sub-soil with ground water at

a depth of 0.45 to 2.00 m. from existing ground level where large scale sub-soil settlement is

expected.

The second paper highlights the methodology for transplantation of matured trees which

come in the way of developmental works. The transplantation of trees will not only conserve the

environment but also enable early availability of site to accelerate progress of the work.

The best way to disseminate knowledge is through publication of articles on the specialised

works carried out by you. I, therefore, request the readers to actively participate by sending ar-

ticles on various issues related to construction, which you feel important to be shared with others

through this forum. The articles may be sent on a CD or through e-mail.

This bulletin is also available on the website at www.iricen.gov.in

With best wishes,

- EXECUTIVE EDITOR


4/27

New Website of IRICENAn appeal to all users

IRICEN has recently revamped its website www.iricen.gov.in. Various new

features have been provided such as, discussion forum, classified list of engineering

officers, world railway division, links to various Indian Railways and other railway

related websites, downloading facilities for various IRICEN publications.

A facility has been created for members login after entering the user ID and

password. Once you login with the valid user ID & password, you can edit your

profile along with your photo and the same will be reflected in the classified list ofengineering officers. Therefore by availing this facility, you can make the list dynamic

by updating your profile. You can e-mail to us at [email protected] getting

your user ID & Password.

IRICEN's Websitewww. iricen.gov.in

Informs you About IRICEN

Tells you Its vision, mission & quality policy

Explains Its services & training facilities

Gives you The vast pool of knowledge by way of

discussion forum

Provides Links to Indian Railways & World Railways

Supplies IRICEN publications in PDF format

Please do visit our website & be a part of it.

( ii )


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C O N T E N T S

VH$ZrH$s nong/ TECHNICAL PAPERS

1. CONSTRUCTION OF RAILWAY TRIAL EMBANKMENT WITH 1

INSTRUMENTATION FOR MEASURING SETTLEMENTS AND

PORE PRESSURE OF COMPRESSIBLE MARINE CLAY SUB-SOIL

S.K.Gupta and A.V. Kulkarni

2. TRANSPLANTATION OF TREES FOR EARLY EXECUTION OF 15

DEVELOPMENTAL WORKS

By A. K. Rai

VH$ZrH$s nongHo$ boIH$m|mam `V {H$E JE {dMma A{Zdm n goB[agoZ Ho$ {dMma Zht h&The views expressed by the authors of technical papers are not necessarily theviews of IRICEN

{d f ` d Vw

mam H$m{eVPublished by

{ZXoeH$

The Director

^maVr` aob {g{db B{O{Z`ar gWmZIndian Railways

Institute of Civil Engineering

nwUo - 411 001.Pune - 411 001.

IS> 15, H$.1,

Volume 15, Number 1

OyZ 2005

June 2005

( iii )

INDIAN RAILWAYS CONSTRUCTION BULLETIN

^maVr` aob {Z_mU H$m`n{H$m


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^maVr` aob {Z_mU H$m`n{H$mIS> 15, H$. 1, OyZ 2005

Indian Railways Construction Bulletin

Vol. 15, No. 1, June 2005

CONSTRUCTION OF RAILWAY TRIAL EMBANKMENT WITH

INSTRUMENTATION FOR MEASURING SETTLEMENTS AND

PORE PRESSURE OF COMPRESSIBLE MARINE CLAY SUB-SOIL

ByS.K.Gupta * and A.V. Kulkarni **

1. Introduction

The new double line project between Belapur/Nerul-Seawood to Uran comprising of

23.70 Km of route length in Navi Mumbai has been sanctioned by Railway Board vide

letter No. 97/Proj./BB/5/1 dated 10-7-1997 at an estimated cost of Rs. 495.44 Crores.

This project connects the Uran and Jawaharlal Port Trust in Navi Mumbai to Mumbai via

Central Business District of Navi Mumbai through Harbour lines of Central Railway (Fig.1).

Fig. 1 Project alignment

* Dy.CE (C), Juinagar, Central Railway

** Astt. Executive Engineer, Juinagar, Central Railway

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Vol. 15, No. 1, June 2005

2. Geology

This region falls under tropical belt with monsoon rainfall conditions. Major part of the

alignment passing through coastal zone is affected by tidal water everyday. Most of the

coastal zone consists of soft marine clay having depth of 2 m to 16 m. The ground water

is at a depth 0.45 m to 2.00 m from the existing ground level. The whole stretch can beclassified in to following zones based on bore hole details:

Chainage (meter) Depth of clay Maximum height of bank

(meter) from ground level

(meter)

0595 to 2720 6.00 14.00

4005 to 5500 2.00 8.03

11473 to 13500 4.00 11.63

13500 to 21760 7.00 to 16.00 4.65

The following different types of marine clays were met with in sub - strata

.

Sr. No. Type of clay N value Un-drained cohesion

value (C)

1 Yellow stiff clay 5 0.49 kg/cm2

2 Grey soft marine clay 1 to 4 0.13 to 0.24 kg/cm2

3 Yellow stiff to hard silty clay with gravel 20 to 28 NA

4 Completely weathered rock 29 to 52

(moorum)

5 Moderately weathered RQD=0 to 77

amygdaloidal Basalt

Sub-soil strata along the chainage is shown in Fig. 2 below.

Fig. 2 Sub - soil strata

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Vol. 15, No. 1, June 2005

The properties of the subsoil indicate that these layers would undergo large settle-ments under the extra load of embankment.

3. Background

1. Being the construction of formation on compressible marine clay, RDSO/GE direc-torate was consulted. After carrying out the detailed investigation, RDSO has pre-pared the consultancy report No. GE-19 of December 1998. Main recommendationsof this report were as under:

a) 1m top clay was to be excavated and thrown away outside the alignment. It was tobe replaced by selected specified compacted soil up to 150 mm below groundlevel, over which a refilled compacted coarse grained sand filter of thickness 600mmwas to be laid where depth of marine clay is up to 4.00 m

b) Where the depth of the clay was more than 4 m, use of sand piles of 500 mm dia,at 2000 mm in square pattern, up to the depth of hard strata along with a base layer

of 1200 mm thick coarse sand layer with deep cross drains and longitudinal drainson both sides of the embankment was to be adopted.

2. The excess expenditure due to this recommendation was to the tune of Rs. 60crores. The requirement of the sand would have been approximately 6,00,000 cum. Inview of this, the matter was referred back to RDSO to review their recommendationsand to suggest another alternative economical method.

3. RDSO, in the revised recommendation, advised not to use sand piles and lay only300 mm thick sand layer on existing ground. However, in this recommendation RDSOhas desired that monitoring of the settlement of the bank as well as development of thepore water pressure in the clay strata below should be done to assess the condition ofthe incipient failures of the bank so that the construction of the bank can be carried out

in stages, keeping necessary interval of time between stages.

4. Therefore, it has been decided to construct the trial embankment with instrumenta-tion to measure the actual settlement and pore water pressure in sub-soil during theconstruction as well as after completion of the work.

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Vol. 15, No. 1, June 2005

4. Instruments and their installation

4.1 Vibrating wire type piezometer

A vibrating wire piezometer (VWP) (Fig.3) is designedfor taking pore pressure readings electrically in sub-soil.Itconsists of magnetic, high tensile strength stretched wire,one end of which is anchored and the other end fixed to

a diaphragm that deflects in some position to the appliedpressure. Any variation in pore pressure causes thediaphragm of the sensor to deflect. This changes thetension in the wire, thus affecting the frequency of vibra-tion. Thus, any change in pore pressure directly affectsthetension in the wire. The pore pressure is proportionalto the square of the frequency and the read out unit (Fig.4)

is able to display this directly in engineering units. Thecable iscarried from the piezometer tip to the terminal boxand is protected against any possible damage duringconstruction.

Fig. 3 Vibrating wire piezometer

Fig. 4 Read out unit

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These instruments have been installed at site as per RDSOs pre determined locationsand depths, and as per manufacturers installation procedures. Total fourteen numbers ofvibrating wire type piezometer (VWP) to measure the water pore pressure in sub-soil has

been provided. One VWP has been provided on either side of the embankment at groundwater level, and 12 m at the center line of the embankment at the longitudinal interval of 2 m

and at vertical interval of 1m depth from ground level i.e. 3 at every 1 m, 2 m, 3 m and4 m depth from ground level.

Installation of piezometer

i. Make a 100 mm diameter bore hole up to a depth of 200 mm below the proposedtip level of piezometer and clean the bore.

ii. Keep the borehole full with water.

iii. Pour measured quantity of saturated clean and well graded sand up to 150 mmdepth from the bottom of the hole.

iv. Tamp the sand in the hole with a tamping rod.

v. Record the reduced level of the top of the sand layer in bore hole.

vi. Lower the piezometer tip assembly along with cable, withdrawing the casingpipe if provided, into the hole as shown in Fig.5.

vii. Fill the bore hole with saturated sand, around the piezometer tip about 300 mmabove piezometer and gently tamp the sand with a tamping rod.

viii. Bentonite seal should be provided over it and fill the remaining bore up to groundlevel with local clay slurry.

ix. Laying of leads: Excavate main and offset trenches for laying the piezometercables from the hole to the instrument house.

x. Each cable should be properly separated.

xi. Cables should not be stretched out prior to backfill and slack of about 10%should be uniformly distributed in each cable, in order to compensate fordifferential settlement along the length of the cable.

xii. After placing the cables, trench should be back filled. A min. 450 mm compactedtypical embankment material must cover before allowing movement of anymachinery over the trench.

xiii. Initial readings of all Piezometers are recorded at the time of installation.

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Fig. 5 Typical sketch showing installation of the piezometer

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4.2 Magnetic extensometer

It is a device used for monitoring vertical movement/settlement in embankments/ sub soil. It consists of a

magnet, signal receiver, and a probe as a read switchencapsulated inside it.

The spider magnets positioned out side a centralaccess tube grip the surrounding soil at locationswhere displacement is to be monitored. A probe in-corporating read switch is lowered within the accesstube to sense the position of magnets. The read switch

closes on entering a magnetic field and activates abuzzer in the signal receiving instruments.

There are 2 types of magnets, the spider magnet tobe provided in sub-soil; and the plate type magnetused in embankment above ground (Fig.6).

PLATE

TYPE

SPIDER

MAGNET

Fig. 6 Plate and spider magnets

The signal receiver consists of a reel with battery pack and buzzer. A 30 m long hightensile, virtually non-stretchable, nylon coated steel flat cable, marked at every 1 cm, con-nects probe into the signal receiver ( Fig.7).

PROBE

SIGNAL RECEIVER

Fig. 7 Probe and signal receiver

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Installation of magnetic extensometer

i. Make a vertical uniform 100 mm dia. borehole upto the hard strata depth.

i. Take PVC pipe of adequate length and plug bottom end.

ii. Lower pipe vertically at center of the hole.

iii. Insert magnet holder over PVC tube into the hole with the help of graduated GI

pipe/ access pipe pushing slowly downwards to place the magnet holder at

desired depth as shown in Fig. 8.

Fig. 8 Installation of magnetic extensometer

After installation of magnet holder, fill the hole with local soil gently, so that positionof magnet holder is not disturbed.

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v4.3 Toe movement prints (TMP)

Toe movement points (Fig.9) are provided torecord/measure the horizontal movement of the toedue to horizontal displacement of sub-soil.

TMP, 25 mm dia., 1.3 m long MS rod withfinished top and central punch mark at top, are tobe installed in 150mm bore holes in cementconcrete about 1.0 m below the ground level and30 cm above the ground level, at a distance of 10

m intervals on either side of embankment. Itenables to record toe movement due tosettlement of embankment.

Total 24 numbers of TMPs have been provided,12 on either side of embankment. Fig. 9 Toe movement point

4.4 Surface settlement points(SSP)

It is provided to record the settlement of ground surface as well as top of the finished

earthwork. These are to be installed at pre-determined locations to record surfacesettlementduring and after construction of embankment.

Surface settlement platform/points (SSP) with M.S. rod of 25 mm dia with noncorrosive and machine finished top, fixed at the bottom and grouted in cementconcrete. The M.S. rod encased in G.I. casing pipe in concrete platform having 400 mm dia.as per the drawing.

Total 8 numbers of SSPs were provided, 6 on the top of the embankment and 1 eachon either side of the embankment.

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5. Scheme and sequence of construction

5.1 Location

Construction of rail embankment with instrumentation were done where the depth of

marine soft strata is more than 4 m and height of the embankment is more than 10 m. theScheme of instrumentation is shown in Fig. 10 to 12.

Fig. 10 Scheme of instrumentation

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Fig . 11 Scheme of instrumentation (contd.)

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Fig. 12 Scheme of instrumentation ( contd.)

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5.2 Construction of embankment

a) Removing the vegetation and leveling the ground

b) Laying of 30 cm thick well graded granular soil duly compacted

c) Making the bore at predetermine location for installation of piezometers and

magnet extensometers in sub soil

d) Installations of piezometers and magnet extensometers in bore holes as shownin sketch

e) Laying of 30 cm thick sand layers

f) Then the construction of bank is started with side slopes of 2.5:1

g) The bank is laid in layers of 30 cm. thickness duly compacted to 98% maximumdry density (MDD)

h) Taking the readings of VWP & magnetic extensometer regularly

i) The work of embankment is to be stopped when the pore pressure reading

exceeds the 0.7 kg/cm2 till it drops down below this reading

6. Frequency of observations

In observational method of construction, the embankment is designed with marginalfactor of safety. The strength will increase with dissipation of pore water pressure. Thus, it isnecessary to keep a close and vigilant watch over pore pressures, settlements and toemovements during construction. In the initial stages, normally up to 2-3 m height ofembankment, the observations may be recorded once a week, but as the height of construc-tion increases, frequency of observations required is as under:

i. During construction Daily

ii. After completion Fortnightly upto 6 months.

iii. After completion Monthly after 6 months.

6.1 Readings of piezometers

Height of

embankment

from GL

(m)

Pore pressure in piezometer (Kg/cm2)

At depth of

At ground

water level1m 2m 3m 4m

At the time of

installation0.08 0.12 0.22 0.32 0.37

0.05 0.12 0.23 0.32 0.38

0.14 0.31 0.41 0.53 0.59

0.14 0.34 0.45 0.58 0.63

0.13 0.38 0.50 0.6 0.68

Earth work up to

1 m Ht

2 m Ht

3 m Ht

4 m Ht

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Vol. 15, No. 1, June 2005

6.2 Readings of magnetic extensometer

Reduced levels of magnetic extensometer

Work is still in progress and earthwork is to be done up to the height of 10m fromground level.

7. Conclusion

Wherever high embankment is required to be constructed on compressible strata or

on weak sub-soil, it is better to go for instrumentation by constructing the trial embankment on

short stretch. It will help in deciding the

B Methodology for construction

B Stages of construction

B Anticipated settlement of subsoil

B Designs of side slopes

Height of

embankment

from GL (m)

Earth work up to

0 m ht

1 m Ht

2 m Ht

3 m Ht

4 m Ht

Location of extensometerat depth from ground level (m)

1stat -4.00 2ndat -2.00 3rdat 0.00 4that 3.00

Net Settlement till

date in m

-2.545 -0.545 1.455 -

-2.545 -0.545 1.455 -

-2.545 -0.560 1.445 -

-2.605 -0.615 1.380 -

-2.560 -0.585 1.400 4.715

0.015 0.040 0.055

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TRANSPLANTATION OF TREES FOR EARLY EXECUTION OF

DEVELOPMENTAL WORKS

By A. K. Rai*

1. Introduction

Developmental works, often, necessitate cutting of trees. At times, valuable, grownup trees have to be felled. Besides, sometimes the construction activity has to wait forpermission for felling of trees. This results in overall delay in completion of the project. Similarsituation arises when individual trees lying close to existing structures cause unsafe conditionsfor the structure and have to be removed.

Transplantation of grown-up trees is a procedure through which this loss of trees canbe avoided. The first attempts towards such transplantation were made in U.S.A. in 1970s.Over the years transplantation has been accepted as an alternative to cutting of trees tofacilitate developmental activities.

In India, isolated relocation of trees were undertaken during 1980s and 1990s tofacilitate construction of buildings, widening of roads and other similar projects. In the late1990s, large-scale transplantation of trees was undertaken in Delhi first to facilitate

construction of flyovers and widening of roads, and then for construction of Delhi Metro.Railways have also adopted this practice in several cases. Tiruchirapalli Division of SouthernRailway has successfully transplanted grown-up trees at few stations including a century old

Peepal tree at Tiruppadiripuliyar station. Recently, in April 2005, fourteen Ashoka trees, lyingat the proposed site for new bungalow for Director/IRICEN at Pune, have been shifted toalternate locations.

The survival rate of transplanted trees is claimed to be around 70% to 90%. Of course,the survival rate depends on site conditions, size of trees, season and care taken during andafter transplantation. This survival rate is considered to be fairly good.

In this article the procedure for transplantation and other related issues have been

discussed in detail.

2. Best time for transplant

Some species of trees can be transplanted in any moderate season i.e. other thanextreme summer and winter. However many delicate species may not survive transplantationin unfavorable conditions. It is preferable to undertake transplantation in autumn or earlyspring.

* Professor (Works), IRICEN, Pune.

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3. Preparing the tree

Transplantation of tree is a shock to it. The tree has, therefore, to be prepared towithstand this shock. This is done in two steps, namely preparation of shoot system and

preparation of root system.

To reduce the requirement of food for the tree, its branches are trimmed. In case oflarge trees, pruning also becomes necessary from handling considerations. Normally onlysecondary branches are pruned. At the time of pruning, the tree should be well watered.Saw should be preferred to axe for pruning. The cut ends should be applied with clay or cowdung to prevent drying and growth of fungus.

As part of preparing the root system, the roots of the tree are also pruned. This isdone by digging a trench around the tree (Fig.1). The location of trenching depends on typeand size of the tree (Fig.2). After cutting the trench, overall 50% of the roots are cut with a

sharp object. The soil should be kept wet during this activity. After cutting the roots, fungicideis spread on the cut area. Afterwards, root hormone is applied at cut surfaces. Then thetrench is filled up with loose soil. At this stage the tree is left for a few days. If considered

necessary, the tree should be supported. This activity prepares the tree for transplantation intwo ways. Firstly, the trenching facilitates final digging out of the root ball. And secondly, theroots in the cut portion start growing up and are in position to fulfill the requirements of thetree for water and nutrition just after replanting. After the trenching the tree is to be wateredregularly. In about three or four weeks the roots start sprouting and the plant is ready forreplanting.

Fig. 1 Trenching scheme

Root Pruning Trench

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Vol. 15, No. 1, June 2005

Fig. 2 Trenching around the tree

4. Site selection

The transplantation site should be chosen close to the original location so that thedamage caused to the tree in transportation is minimal. The site chosen for planting shouldbe suitable to the particular species in terms of soil type, moisture, drainage, light and wind.

The selected site should match with the original location. In case suitable conditions are notavailable naturally, the site conditions will have to be suitably modified.

5. Digging out

Unlike the fully mechanized digging out in U.S.A. and other developed countries, thedigging out is done manually in India. The tree should be well watered for two-three days

before the digging. It should be ensured that the plant roots do not get dried during thetransplantation process. The tree is dug out with its soil ball. The root system together withsoil ball is called root ball. The size of root ball should cover major roots. A root-ball diameterequal to 6 inches for each inch of trunk diameter can be taken as rough norm. In case ofshrubs the root ball diameter should be about half of the branch spread. The root ball depthshould cover all major roots. The cutting of roots should be done with sharp tools. For

digging out, the trench dug earlier should be extended all around the tree and should be dugdeep enough to get below the major roots. All the roots should be completely cut beforetaking out the root ball.

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6. Plantation pits

Proper planting pits are must for survival of transplanted trees. The pits should be

approximately two times wider than the root ball of the tree (Fig.3). The sides of the pit shouldbe roughened. The depth of the pit should be at least equal to the depth of root ball. The pit

should be treated with fungicide.

2 times the root ball width

Fig. 3 Planting pit

7. Uprooting and transportation

The branches of the tree may have to be tied up to prevent injury during digging or

transportation. It is also advisable to mark one side of the trunk so that the tree can beplanted in the same orientation. In the entire process the tree should be protected from directsunlight and winds. It is preferable to carryout the exercise in evening or night. The timetaken in transportation and replanting should be kept minimal.

The area around the tree is watered taking care that the area doesnt become muddy

and difficult to work in. Then the trenching around the tree is completed. As 50% roots hadalready been cut at the time of preparing root system, the remaining 50% roots are cut clean

with sharp tools, treated with fungicide and applied with root hormone. The root ball is thencovered with jute cloth or any similar material and kept damp during the transplantation. It isdesirable to treat the jute cloth with fungicide and insecticide. It is a good practice to carrysufficient soil from the original place.

Once the root ball is completely cut and covered, the tree is held with the help of chain.Then the tree is lifted by a hydraulic crane of sufficient capacity ( Fig.4). The tree is then takento the new site either directly by the crane (Fig.5) or by using a trailer. While transporting, thetree should be adequately supported and protected. Tall trees would particularly requiresupports.

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Fig. 4 Uprooting of tree

Fig. 5 Shifting of uprooted tree

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Vol. 15, No. 1, June 2005

8. Planning

The bottom of the planting pit should be filled with sand. Then the pit should be sprayed

with fungicide and adequately watered before planting. The tree is lowered in the pit with thekeep of crane. The tree is planted at the same depth as in the previous location. While

planting it is preferable to retain the orientation of the plant relative to sun. Then the pit is filledwith good soil.

9. Post plantation care

Subsequent to the re-plantation, the tree should be provided with sufficient water andnutrition. After the transplantation, the trees shed leaves but sprouting takes place after thetree adjusts to the new site. Complete acclimatisation may take three to four months andduring this period the tree should be taken good care of. To match the food habit of the tree,it is always advisable to use the same soil in the immediate vicinity. Supply of water and

nutrients should be controlled.

10. Expenditure of transplantation

In Indian conditions the expenditure of transplantation of mature trees is reported tobe between Rs. 3000 to Rs. 8000 per tree. Obviously the expenditure will depend on size oftree and distance of new site. However, this expenditure is small as compared to the value ofthe grown up trees and benefits that accrue to the society.

11. Conclusion

The process of transplantation has now been accepted as a viable option to cutting oftrees to facilitate new construction. It would also help preserve grown-up trees of rare varietyand trees having historical significance. Adoption of transplantation techniques is also likely

to expedite commencement of projects, as it would be easier to obtain necessary clearancesfor transplantation than for cutting of trees.

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