environmental impact assessment of a proposed info-tech complex in east calcutta wetlands

The Environmentalist, 22, 241–260, 2002©2002 Kluwer Academic Publishers. Manufactured in The Netherlands.

Environmental impact assessment of a proposed info-tech complexin East Calcutta wetlands

P.K. SIKDAR,∗ S. MONDAL, L. SAHA, S.S. SARKAR and S. BANERJEEDepartment of Environment Management, Indian Institute of Social Welfare and Business Management,

Kolkata 700 073, India

Summary. An info-tech complex is proposed for 286 acres (116 ha) of land within the East Calcuttawetlands. The proposed site is 15 km east of Kolkata city and only 8 km south of Dum Dum airport.The site is vacant, with pockets of agricultural land and a few degrading water-logged areas. In order toassess the likely impact of the proposed development on the environment, a rapid environmental impactassessment of an area of 10 km radius from the centre of the project site was carried out. The presentstatus of the environment with respect to ambient air, surface water, groundwater, soil, landuse, noise, andsocio-economics of the core and buffer zone has been documented and correlated with 24 project activitiesduring construction, development and operational phases. The frequency of adverse impacts is greaterthan that of beneficial impacts. Out of the total adverse impacts 20 are short term, reversible and have alow magnitude. The total impact score for the proposed project is (−)468.75 and as per the AssessmentValue Index Scale the environmental impact of the proposed project activities is ‘no appreciable impact.’But there are certain sectors where the environment will be adversely impacted. Therefore, appropriatemeasures have been suggested to ameliorate the adverse impacts. It is envisaged that if these measuresare implemented then there will be an improvement in the quality of the environment, as well as life, by687.5 units.

Keywords: environmental impact assessment, info-tech complex, East Calcutta wetlands, environmentmanagement plan

Introduction

An info-tech complex is proposed for 286 acres(116 ha) of land within the East Calcutta wetlands(Fig. 1). The area is bound by latitudes 22�33′09′′Nand 22�34′06′′N and longitudes 88�27′03′′E and88�28′12′′E. The proposed site is 15 km east ofKolkata city and only 8 km south of Dum Dumairport. This project has been conceived so as to

∗Dr P.K. Sikdar is a Lecturer in the Department of Envi-ronment Management, Indian Institute of Social Welfare andBusiness Management, Kolkata. S. Mondal is based at theCenter for Study of Man and Environment, Kolkata 700 091.L. Saha and S.S. Sarkar at the Department of Geography, Dur-gapur Government College, Durgapur 713 214; and S. Baner-jee at Ghezri Eastern Limited, Kolkata 700 093.

attract leading national and international compa-nies to invest in West Bengal in the fields of soft-ware design, information technology, multi-mediaand telecommunication systems to assist India tobecome a large export base in the global elec-tronics market and to provide companies basedin India with access to the latest developments intechnology.The core zone is bound on the western and the

northern sides by two important canals in EastKolkata; the Takdari Canal and the KrishnapurCanal respectively (Fig. 1). The site is vacant withpockets of agricultural land and a few degrad-ing water-logged areas like the reclaimed MollarBheri, Patrabad Bheri II and III. The developerproposes to preserve Doctor’s Bheri and Patra-bad Bheri. The proposed site comprises 100 acres

242 Sikdar et al.

Figure 1. Diagrammatic sketch map of the proposed info-tech complex; East Kolkata, India. Key for abbreviations: R&D—Researchand Development; Stn—Station; P.O.—Post Office; Tel. Exch.—Telephone Exchange; Admn—Administration.

(40.5 ha) of water bodies including the canals.Some inhabitants of nearby villages use the areato raise paddy with rainwater without any licencefrom the government.There are no unusual birds inhabiting the area,

although local birds viz. sparrows, mayna, crows,etc. are present. No migratory birds visit the landduring any part of the year. The land is not knownto be a natural habitat for reptiles, amphibians,fish, flies or other insects, but fish are rearedin about 100 acres (40.5 ha) of fisheries, whichinclude tanks and canals. Garbage dumping is notcarried out on the proposed site and sewage waterdoes not pass through it.The proposed info-tech complex will be divided

into relatively large size plots (Fig. 1). Large sizeplots have been considered so as to keep the

density of population at a minimum. The airportbeing within 10 km, no high-rise buildings willbe constructed and the building coverage will be45–50 percent of the total area of each plot. Thecomplex will be ringed and interconnected by ahierarchy of roads, 30 m and 18 m wide. The 30m wide roads will be four-lane free-ways and willhave a green verge of non-deciduous trees alongthe road. The roads will also be lined with pave-ments on either side. The vehicles that will haveaccess to the complex will be battery-operated.Other vehicles will be parked outside the com-plex, preferably near to the zone determined asbus-terminal and taxi-stands.The existing canals (Takdari and Krishnapur

canals, Fig. 2), which are in environmentally badcondition, will be upgraded. Trees will also be

Environmental impact assessment 243

Figure 2. Study area with locations of environmental monitoring station.

planted along the sides of the canals and thisshould increase the aesthetic beauty of the areaand prevent caving of the sidewalls of the canals.The expected sewage generation from the pro-

posed project is 1.7 million litres per day (mld).Sewage will be transferred through an under-ground drainage system to the sewage treatmentplant. The treated water will be reused for green-ery development and management of the waterbodies within the complex. A garbage disposal ser-vice will also be provided for the complex.The total water requirement for the project will

be 2.1 mld. If the expected discharge of each tube-well to be created is 65,000 litres/hour, the numberof tubewells required for eight hours pumping perday will be four. The depth of each tubewell will

be 150 m. The water collected from the tubewellswill be stored in overhead reservoirs. From theoverhead reservoirs the water will be distributedthrough a network of underground pipes.The climate of the area is predominantly influ-

enced by the north-east and south-west monsoons,which control the temperature, wind direction andprecipitation. The climate of Kolkata and its sub-urbs enjoys mild winter, brief spring, hot summerand prolonged monsoon. The cold weather sets inby the middle of November and lasts till about themiddle of February. January is the coldest month,when the temperature rarely goes below 10�C.Due to the proximity of the sea the climate ofthe area becomes quite pleasant during the win-ter months. Temperature tends to rise from the

244 Sikdar et al.

middle of February and from the beginning ofMarch, days become appreciably warmer with arapid increase of temperature from the middleof March till May. During this period, the tem-perature varies from 20�C to 40�C and the maxi-mum temperature rises up to 43�C. Nearly 80 per-cent of the annual precipitation of 1600 mm fallsduring the months of June to September due tothe prevalence of the south-west monsoon, whichoperates in full force over the area due to itslocation near to the Bay of Bengal. During thisperiod the fluctuation between maximum and min-imum temperature as well as between maximumand minimum humidity ranges significantly.In order to assess the likely impact of the pro-

posed development on the environment, a rapidenvironmental impact assessment of an area of10 km radius from the centre of the project sitewas carried out.

Baseline environmental conditions

Geology and geomorphology

The area forms a part of the lower deltaic plainof the Ganga Delta and is generally flat in nature.The area has been formed by the continuousdeposition of alluvium carried by the Hugli River.The land surface with its elevation of 3–5 mabove the mean sea level slopes gradually towardssouth and south-east. This elevation differs locallybecause of palaeo-levees, palaeo-courses, channelbars, etc. The principal present day drainage is theHugli River, which flows through the west of thestudy area.The sub-surface geology of the area is com-

pletely blanketed by the Quaternary sediments.The subsurface distribution of lithological units

Table 1. Stratigraphy of the area of East Kolkata, India

System Series Lithology Depth (m)

Quaternary Holocene Clay and silt, with peaty intercalations at 12.5two depth ranges from the surface

(i) 2–5 m dated at 3990±70 years B.P.Pleistocene (ii) 12–12.6 m dated at 7030±70 years

B.P.Sand, fine to coarse with clay lenses, gravel 296and calcareous concretions.

Tertiary Pliocene Clay, bluish grey, soft and sticky to >614

occurring in the area has been ascertainedfrom lithologs from deeper exploratory boreholesdrilled by various agencies. These lithologs indi-cate the existence of an underlying Tertiary clay.This bed has been intersected at an average depthof 296 m. This clay bed continues up to a depth ofat least 614 m below land surface. The lithologsalso reveal the occurrence of a clay bed in theupper Quaternary part of the geological succes-sion. These two clay beds are dark grey in colour,sticky and plastic to semi-plastic in character. Theclay beds are often found to contain stringers ofsilt and fine sand. They are less plastic whereverthey are admixed with fine sand or silt (Sikdar,2000).A conspicuous feature of the Quaternary

sequence is the occurrence of fine to coarse sandhorizons mixed occasionally with gravel. The con-tinuity in the sequence of the sand, which formsthe aquifer material, is broken by the occasionaloccurrence of clay lenses of limited lateral extent.The sand is highly micaceous and often tends tobe silty. The sands are on average moderately wellsorted reflecting deposition in a fluvial environ-ment (Sikdar, 2000). The Quaternary stratigraphyof the area (Table 1) has been compiled on thebasis of lithological, floral, faunal and radiocarbondating (Chaterji et al., 1959; Banerjee et al., 1984;Sen and Banerjee, 1990; Barui and Chanda, 1992;Hait et al., 1996). The fining upward sequenceof the Quaternary sediments possibly indicates afluvio-deltaic environment of deposition. Towardsthe close of sedimentation, bog and marshy con-ditions prevailed as indicated by the occurrenceof peat in the upper horizons of the sediments.Occurrence of marsh or salt lakes to the east ofKolkata also lends additional evidence for a bogenvironment.


The yellow colour of the sands (at a depthrange of 24 m to 76 m) is thought to be dueto oxidation of the sediments generated from theArchaean terrain of the Chotonagpur Plateau andbrought down by the rivers flowing from the west.The colour of the sediments occurring above thishorizon ranges from grey to light grey and theywere deposited under reducing conditions andbrought down from the Himalayan domain duringthe late Quaternary period (Sikdar, 2000).

Land use

A study of land use was carried out for the BufferZone (BZ) of the proposed project. A circle of10 km radius defines the BZ with its centre at theproposed project site (Fig. 2). It covers an areaof 314 km2. The BZ lies between latitude 22�28′Nand 22�39′N and longitudes 88�21′E and 88�33′E.A land use map was prepared through visualinterpretation of satellite imagery (IRS-IA, 20thNovember 1998, FCC) on 1:50,000 scale alongwith ground checking. Other collateral data fromthe corresponding Survey of India toposheets(1:50,000) and the map of Calcutta published bythe NATMO (1:25,000) were also used in thisstudy. The land use classes, the area covered byeach land use class and the percentage of the totalarea are given in Table 2.

Ambient air quality

The background level of air pollution in respectof suspended particulate matter (SPM), therespirable particulate matter (RPM), nitrogen

Table 2. Land use pattern of the buffer zone, info-techcomplex East Calcutta wetlands

Land use class Area (km2) Percentage

Agriculture 120.6 38.4Built-up land with vegetation 64.2 20.5Wetlands 51.5 16.4Groveland 45.3 14.4Built-up land 17.1 5.4Rural settlement 10.0 3.2Park and open spaces 05.2 1.6Burial ground 00.1 0.1Total 314.0 100.0

oxides (NOx), sulphur dioxide (SO2), carbonmonoxide (CO) and lead (Pb) was monitored atfour fixed stations (Fig. 2, marked AQ) during themonths of December and January of 1997–1998.The monitoring was carried out for 24 hours dura-tion twice a week at all the four stations for sixweeks. The ambient air quality monitoring stationswere located at a height varying between 3 m and10 m.The sampling procedures for measurement of

SPM, RPM, NOx, SO2, CO and Pb were accord-ing to the internationally accepted standard tech-niques through use of a respirable dust sampler.Analytical methods of measurement were carriedout in accordance with the Bureau of Indian Stan-dards (BIS) 5182–Part II (1969), Part IV (1973),Part VI (1974) and Part X (1974). The results ofthe ambient air quality monitoring are given inTable 3 and are self-explanatory. The data havebeen compared with the National Ambient AirQuality Standard for 24-hour time weighted aver-age concentration values (CPCB, 1994) to providea quantitative estimate of the stress on the ambi-ent level air.

Groundwater condition

Groundwater in the Quaternary upper clay, silty-clay zone (aquiclude) occurs under unconfinedconditions while in the deeper granular zones itis under confined conditions. The mean diameterof the sediments of the upper horizon (<90 mbelow ground level (bgl)) ranges between 1.5�with a mean of 2.1� (fine sand) while those of thelower horizon varies between 1.13� to 2.07� witha mean of 1.6� (medium sand) (Sikdar, 2000).Field pumping test results (Chaterji et al., 1964;

Niyogi et al., 1966; Banerjee and Khan, 1982)in and around the study area indicate that inthe north (around Salt Lake) the transmissiv-ity values range between 3500 and 4700 m2/daywhich decreases to 1560–2070 m2/day in the south(around Santoshpur). The hydraulic conductivityvalues within the area vary both vertically andhorizontally (Sikdar, 2000). Well-sorted sands ofmedium to coarse textures are characterised byhigher values of hydraulic conductivity than theless sorted fine clastics (Sikdar, 2000).

246 Sikdar et al.

Table 3. Concentration of different air pollutants, East Calcutta wetlands

National AmbientNo. of Min. Max. Mean Air Quality % of deviation

Station observations �gm−3 �gm−3 �gm−3 Standard �gm−3 from standard % of compliance

SPMAQ1 12 75�9 272�5 185�6 100.0 +85.6 8.3AQ2 12 135�8 474�1 254�8 200.0 +27.4 25.0AQ3 12 110�8 438�3 225�4 200.0 +12.7 50.0AQ4 12 121�7 503�4 325�1 100.0 +225.0 0.0Overall 48 75�9 503�4 247�7 — — —

RPMAQ1 12 50�7 212�6 147�3 75.0 +96.4 8.3AQ2 12 74�0 270�2 184�4 100.0 +84.4 16.6AQ3 12 70�5 301�4 163�0 100.0 +63.0 41.6AQ4 12 47�4 369�3 217�2 75.0 +189.6 8.3Overall 48 47�4 369�3 178�0 — — —

NOxAQ1 12 18�5 144�1 51�2 30.0 +70.6 16.6AQ2 12 33�2 152�9 98�3 80.0 +22.8 25.0AQ3 12 17�8 115�5 59�4 80.0 −25.7 83.3AQ4 12 19�7 97�1 48�7 30.0 +62.3 16.6Overall 48 17�8 152�9 64�4 — — —

SO2AQ1 12 5�2 25�9 11�3 30.0 −62.3 100AQ2 12 5�4 43�5 19�7 80.0 −34.3 100AQ3 12 1�4 39�3 17�8 80.0 −40.6 100AQ4 12 4�2 41�6 17�9 30.0 −40.3 100Overall 48 1�4 43�5 16�7 — — —

COAQ1 12 2�42 4�0 3�13 1.0 +213.0 0.0AQ2 12 3�00 6�0 4�39 2.0 +114.5 0.0AQ3 12 3�08 4�5 3�48 2.0 +74.0 0.0AQ4 12 3�01 5�5 4�23 1.0 +323.0 0.0Overall 48 2�42 6�0 3�80 — — —

PbAQ1 12 1�44 0�07 0�50 0.75 −33.4 91.7AQ2 12 1�03 0�07 0�45 1.0 −55.0 83.4AQ3 12 2�22 0�02 0�50 1.0 −50.0 83.4AQ4 12 1�04 0�03 0�30 0.75 −46.7 83.3Overall 48 2�22 0�02 0�44 — — —

The fresh water aquifer in the study areais under confined conditions where the produc-tive aquifer occurs under a thick blanket ofclay, thereby precluding the possibility of directrecharge. Due to large scale withdrawal of ground-water from the confined aquifer there has beena noticeable change in the hydrological regimeas indicated by the contour maps prepared withthe reduced levels of piezometric surface data(Fig. 3). The earliest piezometric surface dataavailable in and around Kolkata were from 1956.The piezometric surface at that time was undu-latory and gently sloping southward (Fig. 3A).

The groundwater flow system was an ‘open’ one.In 1985 (Fig. 3B and C) the piezometric sur-face showed a drop of 6 to 8 m and a ground-water trough developed in south-central Kolkataresulting in a ‘closed’ groundwater flow system. In1993 (Fig. 3D) there was a two-fold increase inthe area of the groundwater trough compared tothat of 1985 (Sikdar, 1999, 2000). The groundwa-ter trough extended mainly towards the north andeast. The obliteration in the natural groundwa-ter flow pattern is clearly a result of uncontrolledgroundwater withdrawal. With this informationin mind the depth to piezometric surface was


Figure 3. Long-term change in the status of piezometric surface and groundwater flow direction. Arrows indicate groundwaterflow direction. A. Contour map showing the elevation of the piezometric surface with reference to the mean sea level during post-monsoon, 1956. B. Degree four trend surface map of the elevation of the piezometric surface with reference to the mean sea levelduring pre-monsoon, 1985. C. Degree four trend surface map of the elevation of the piezometric surface with reference to the meansea level during pre-monsoon, 1985. D. Degree four trend surface map of the elevation of the piezometric surface with reference tothe mean sea level during pre-monsoon, 1985.

248 Sikdar et al.

Figure 4. Spatial distribution of depth to piezometric surface, December, 1997; East Kolkata, India.

measured at two depth levels from thirty-threehydrograph stations within the study area duringthe month of December, 1997. During that timethe piezometric surface in the shallow zones (18to 60 m bgl) was close to the surface. The depthof the piezometric surface ranged between 4 and7 m bgl. During the same period the piezometricsurface in the deeper aquifer zones (>90 m bgl)rested at a deeper level generally ranging between6 and 15 m bgl at the NW, W, SW, N, S and cen-tral part of the study area. The deepest piezomet-ric surface (15.2 m bgl) was recorded in the west-ern part of the study area. At the project site thedepth to the piezometric surface ranged from 6to 8 m bgl for the deeper aquifer whereas for the

shallower aquifer it rested between 4 and 6 m bgl(Fig 4.).The maximum recession of the piezometric

surface as a result of groundwater developmentover the last 41 years (1956–1997) has occurredin the Beleghata-Sealdah-Tangra region located inthe western part of the study area. In this area theaverage depth to piezometric surface during thepost monsoon of 1956 was 4.87 m bgl and wasaround 14.11 m bgl during the same period of1997, thus indicating a general drop of piezomet-ric surface to the tune of 9.24 m (Table 4). Fromthis region, north and southward, there is a gen-eral decrease in the amount of recession of thepiezometric surface.


Table 4. Comparative study of the depth to piezometric surface with time, East Kolkata area

Depth to piezometric surface(metres) below ground level

Area Year Pre-monsoon Post-monsoon Net recession (metres)

Bagbazar-Shyambazar 1958 — 7.921980 12.44 11.011985 13.96 12.35 6.281993 — 12.531994 14.49 —1997 — 14.20

Ultadanga-Maniktola 1956 11.26 4.821980 12.51 10.29 7.501985 — 10.871993 13.00 11.101997 — 12.32

Beliaghata-Sealdah-Tangra 1956 — 4.871958 7.06 —1980 12.43 10.891985 12.69 11.23 9.241993 — 12.201994 13.85 —1997 — 14.11

Kasba-Gariahat-Dhakuria 1958 6.33 —1980 11.86 10.401985 12.91 11.221993 — 11.31 3.981994 13.15 —1997 — 14.38

Sikdar (1999) has estimated that the totalquantity of groundwater flowing in the Kolkata’saquifer is 218.5 million litre per day (mld) whilethe total quantity of groundwater withdrawalis 292 mld. Thus, groundwater is being overexploited to the tune of 73.5 mld. This overexploitation will lead to a further recession of thepiezometric surface and as a result there will bea further expansion of the area under depressionin future. It can be concluded that the aquifer inthe buffer zone is under high stress and furtherexploitation for any new developmental projectmay cause permanent damage to the aquifer sys-tem in the form of land subsidence and ground-water quality deterioration.

Groundwater quality

In order to assess the groundwater quality, foursamples were collected from hand tubewells atdifferent depths (Fig. 2, marked GW) during the

month of December 1997 and analysis was car-ried out following the procedure of BIS 1488 andAPHA (1985). Results of analyses of the ground-water samples from these sites and their com-parison with the Indian Drinking Water Standard(BIS: 10500, 1991) are presented in Table 5 andare self-explanatory. Sikdar and Dasgupta (1997)and Sikdar et al. (2001) had shown that cop-per, nickel, cadmium, chromium and arsenic arepresent in the groundwater of Kolkata in pocketsand it is likely that the concentration will increasespatially and in quantity with increase in ground-water development in and around Kolkata.

Surface water quality

The present study area is characterised by manyman-made canals, ponds and channels, which arethe main surface water bodies in this region. Inorder to understand the quality of the inland sur-face water, five samples were collected (Fig. 2,marked SW) and were analysed for a few selected

250 Sikdar et al.

Table 5. Comparison of groundwater samples with BIS: 10500, 1991, for East Kolkata

Location (Fig. 2) BIS: 10500

Parameter GW1 GW2 GW3 GW4 DL PL

Colour (Hazen) 0 0 0 0 5 25Odour Odourless Odourless Odourless Odourless Unobjecti- Unobjecti-

onable onableTaste Unobjecti- Unobjecti- Unobjecti- Unobjecti- Agreeable Agreeable

onable onable onable onableTurbidity (NTU) 20�5 9�0 11�0 16�0 5�0 10�0pH 7�28 7�02 7�04 7�15 6.5–8.5 NRTotal hardness as CaCO3 (mg l−) 564 432 640 360 300 600Iron (mg l−) 1�0 0�25 0�6 5�6 0�3 1�0Chloride(mg l−) 1100 247�08 404 376 250 1000Residual, free chlorine (mg l−) <0�15 <0�15 <0�15 <0�15 0�2 —Dissolved solids (mg l−) 2009 670 989 837 500 2000Calcium (mg l−) 48 70 64 66 75 200Magnesium (mg l−) 106�56 61�68 58�56 46�8 30 100Copper (mg l−) 0�008 0�006 0�01 0�007 0�05 1�5Manganese (mg l−) 3�25 0�25 0�45 0�30 0�1 0�3Sulphate (mg l−) 105 1�0 28 2�0 200 400Nitrate (mg l−) <0�002 0�004 0�04 <0�002 45 100Fluoride (mg l−) <0�03 <0�03 <0�03 0�5 1�0 1�5Phenolic compounds (mg l−) <0�0005 <0�0005 <0�0005 <0�0005 0�001 0�002Mercury (mg l−) <0�0005 <0�0005 <0�0005 <0�0005 0�001 NRCadmium (mg l−) <0�001 <0�001 <0�001 <0�001 0�01 NRSelenium (mg l−) <0�01 <0�01 <0�01 <0�01 0�01 NRArsenic (mg l−) <0�003 <0�003 <0�003 <0�003 0�05 NRCyanide (mg l−) <0�005 <0�005 <0�005 <0�005 0�05 NRLead (mg l−) <0�01 <0�01 <0�01 <0�01 0�05 NRZinc (mg l−) 0�03 0�02 1�4 0�03 5�0 15�0Chromium, total (mg l−) <0�008 <0�008 <0�008 <0�008 0�05 NRAlkalinity (mg l−) 425 325 290 290 200 600Aluminum (mg l−) 2�6 1�2 1�5 1�9 0�03 0�2Boron (mg l−) <0�05 <0�05 <0�05 <0�05 1�0 5�0Total coliform (MPN/100 ml) 45 Nil 15 10 10 10Faecal coliform (MPN/100 ml) 15 Nil Nil Nil 0�0 0�0

DL—desirable limit, PL—permissible limit in absence of alternate source; NR—no relaxation.

parameters. Among the five surface water sam-ples two were collected from ponds and the othersfrom canals/channels. Pond water is used for pis-ciculture, and therefore, can be comparable withInland Surface Water (IS 2296) of Class D; twowater samples were collected from canals whichare presently used for disposal of industrial anddomestic effluents, and therefore, can be com-pared with IS 2296 Class E; and the remainingsample was collected from the Dry Weather Flow(DWF) Channel of Kolkata Municipal Corpora-tion (KMC) which carries Kolkata’s sewage waterand industrial waste water and disposes to theKulti-Ganga River. This water sample was com-

pared with industrial effluent disposed into inlandsurface water [Environment (Protection) SecondAmendment Rules, 1993, Government of India].The results of the analysis of the water samplesand their comparison with their respective stan-dards are presented in Tables 6–8 and are self-explanatory.

Soil

The soils are typically deltaic alluvial soils rich incalcium. Free CaCO3 occurs in the surface soiland within the soil profiles. The soils have low to


Table 6. Comparison of pond water with IS 2296 Class D water, East Calcutta wetlands

Characteristics ofwater (Fig. 2)

Tolerance limit as Sensitivity toParameter per class D SW2 SW3 pollution

pH 6.5—8.5 8.1 8.3 LowDissolved oxygen (mg l−) 4 (Min.) 7.4 7.8 Good for piscicultureElectrical conductance at 1000×10−6 (Max.) 773×10−6 1026×10−6 Medium to high25�C (m hos)

Oil and grease (mg l−) 0.1 (Max.) 3.7 5.8 High

Table 7. Comparison of canal water with IS 2296 Class E water, East Calcutta wetlands

Characteristics ofcanal water (Fig. 2)

Tolerance limit as Sensitivity toParameter per class E SW1 SW5 pollution

pH 6.0—8.5 8.2 7.8 LowElectrical conductance at 2250×10−6 (Max.) 592×10−6 2175×10−6 SW1—Low,25�C (m hos) SW5—Medium

Sodium absorption ratio 26 (Max.) 1.54 6.38 LowBoron (mg l−) 2 (Max.) <0.05 <0.05 LowTotal dissolved solids (mg l−) 2100 (Max.) 314 1125 SW1—Low,

SW5—MediumSulphates (mg l−) 1000 (Max.) 30 102 LowChlorides (mg l−) 600 (Max.) 91 443 SW1—Low,

SW5—Medium

Table 8. Comparison of dry weather flow (DWF) channel water with effluent standard, East Calcuttawetlands

Characteristics of Sensitivity toParameter Effluent standard DWF water (SW4, Fig. 2) pollution

Suspended solids, (mg l−) 100 (Max.) 958 HighpH value 5.5 to 9.0 7.4 LowOil and grease, (mg l−) 10 (Max.) 11.42 HighTotal Kjeldal nitrogen (mg l−) 100 (Max.) 1.6 LowBOD (mg l−) 30 (Max.) 110 HighCOD (mg l−) 250 (Max.) 135 MediumArsenic (mg l−) 0.2 (Max.) 0.014 LowHexavalent chromium (mg l−) 0.1 (Max.) 1.2 HighTotal chromium (mg l−) 2.0 (Max.) 1.3 MediumZinc (mg l−) 5.0 (Max.) 1.35 LowManganese (mg l−) 2.0 (Max.) 0.5 LowIron (mg l−) 3.0 (Max.) 11.8 High

Sensitivity: High—Higher than standard; Medium—More than half the standard but lower than standard(max.); Low—Less than half the standard.

252 Sikdar et al.

Table 9. Physical and chemical characteristics of soils, East Calcutta wetlands

Location (Fig. 2)

Parameter S1 S2 S3 S4

Colour in Munsell Nos. 5Y 5/1 5Y 5/1 10YR 4/3 2.5Y 6/2(Grey) (Grey) (Brown) (Light brownish

grey)Texture up to 1 m depth Silty clay loam Clay Loam Silty clay loamHydraulic conductivity (cm sec−1) 4�0×10−8 4�4×10−8 3�0×10−8 4�7×10−8Bulk density (mg m−3) 0�99 1�24 0�98 1�10Moisture holding capacity (%) 70�54 59�05 63�92 56�28pH (1:2.5) 8�01 7�18 7�61 7�91Available N2 (mg kg−1) 87�5 77�0 173�2 61�2Available P2O5 (mg kg−1) 41�2 82�4 654�9 274�8Available K2O (mg kg−1) 406�5 446 556 262Organic carbon (gm kg−1) 22�6 12�5 25�9 8�6Sand (%) 10 15�4 49�5 14�5Silt (%) 57 21�6 27�5 55Clay (%) 33 63 23 30�5Iron (mg kg−1) 5860 6330 5850 5900Copper (mg kg−1) 35�6 60�2 212�3 31�6Manganese (mg kg−1) 421�7 290�1 603�5 448�7Zinc (mg kg−1) 48 61�8 68�5 42�6Lead (mg kg−1) 45�4 45�4 604�5 36�4Cadmium (mg kg−1) <0�01 <0�01 <0�01 <0�01Chromium (mg kg−1) 73�2 97�6 434�1 63�4Nickel (mg kg−1) 40 60 48 28Cobalt (mg kg−1) <0�05 <0�05 <0�05 <0�05

medium levels of organic matter and a mediumlevel of available phosphate and potash. Kolkataand the neighbouring areas are represented byclayey soils. The soil contains 30 to 50 percent clayand 20 percent sand and becomes sticky when wet,and hard when dry.Soil samples were collected from four sites

within the study area (Fig. 2, marked S). Aftercollection the samples were dried in sunlightand then analysed for some selected parametersincluding heavy metals. The samples were anal-ysed according to the methods described by Jack-son (1973) and Black (1982). The results of thechemical analyses are given in Table 9.In general the soils are mildly alkaline to alka-

line, with pH varying from 7.18 to 8.01. Siltand clay are the dominant mechanical compo-nents in most of the samples except for the sam-ple at S3 site. In this site sand particles areadded to the soil as a result of garbage farm-ing. Bulk density of the soil is low at sites S1(0.99 mg m−3) and S3 (0.98 mg m−3) possiblydue to addition of high organic carbon or organic

matter. Organic carbon ranges between 8.6 and25.9 mg g−1. Hydraulic conductivity values of thesoil are similar, with value of hydraulic conductiv-ity (K) in the order of 10−8 cm sec−1. Results ofsoil infiltration tests indicate that steady infiltra-tion rate is minimum (0.4 cm hr−1) at S2 site andmaximum (1.4 cm hr−1) at S3 site. High compact-ness of soil at S2 site and high porosity at S3 sitecould be the reason for low and high infiltrationrates. Among the sites infiltration rate graduallydecreases at S3 location. Percolation rate rangesbetween 1.3 to 4 cm hr−1. Percolation rate followsa similar trend as that of infiltration. The con-centration of the available N2, available P2O5 andavailable K2O are very high at site S3. This is dueto mixing of garbage with the soil for cultivation.The concentrations of heavy metals in the soil

at sites S1, S2 and S4 are within the range of nor-mal agricultural soil. At site S3, the concentrationof Cu and Pb are above the range of normal agri-cultural soil, but the concentration of other heavymetals such as Fe, Mn, Zn, Cr and Ni are withinthe normal range. It is interesting to note that the


Table 10. Noise level monitoring results, East Kolkata

Day time Night time(6 am to 10 pm) (10 pm to 6 am)dB (A) dB (A)

Location(Fig. 2) Location Area/Class Max. Min. Avg. Max. Min. Avg.

N1 Salt Lake Residential 60.1 50.0 55�9∗ 58.1 44.0 48�1∗

N2 Lake Town Residential 64.4 50.0 54�4 52.0 44.0 47�9∗

N3 Gopalpur Residential 61.2 42.2 48�5 52.8 43.1 46�5∗

N4 Rajarhat Market Commercial 70.4 50.4 57�9 63.5 52.1 57�1∗

N5 Lauhati Residential 58.6 40.0 51�8 54.8 38.7 43�9N6 Dum Dum Air Port Commercial 78.2 65.8 70�5∗ 78.2 62.4 68�9∗

N7 Dum Dum Industrial 70.0 52.4 59�8 61.6 47.2 52�0N8 Shyambazar Commercial 84.2 60.5 70�0∗ 76.7 58.5 68�0∗

N9 Sealdah Commercial 74.0 60.2 69�0∗ 69.5 57.1 64�6∗

N10 Tangra Industrial 83.0 64.0 70�9 63.7 47.3 54�5N11 Bantola Silence 63.7 38.4 46�7 49.2 40.1 44�7∗

N12 Anandapur Residential 55.4 45.2 49�5 53.2 43.2 48�1∗

N13 Kasba Residential 80.8 51.7 62�0∗ 62.0 50.0 56�1∗

N14 Makaltola Silence 68.4 39.5 50�5∗ 58.6 43.5 50�4∗

N15 Bagmari Industrial 67.2 47.6 53�1 53.2 39.8 48�4N16 Project Site Silence 50.1 40.2 44�8 49.9 38.1 42�1∗

∗Noise level above Indian Standard.In each case number of observations are 20.

concentration of Cd and Co are below the rangeof normal agricultural soil in all samples.

Ambient noise

Noise was measured at sixteen locations (Fig. 2,marked N) during day and night time, for average,maximum and minimum levels in dB(A). Thedetails of the noise monitoring results and thecomparison of noise level with the Indian Stan-dards are given in Tables 10 and 11 respec-tively. The average noise level in commercial areas(Table 11) was slightly higher than the limits forboth day and night. Night time average values for

Table 11. Comparison of noise level results with Indian standard, East Kolkata

Day time Night time(6 am to 10 pm) (10 pm to 6 am)dB (A) dB (A)

Area/Class Range Avg. Std. Range Avg. Std.

Industrial 53.1–70.9 61.3 75 48.4–54.6 51.6 70Commercial 57.9–70.5 66.8 65 57.1–68.9 64.6 55Residential 48.5–62.7 53.8 55 43.9–56.1 48.4 45Silence 44.8–50.5 47.3 50 42.1–50.4 45.7 40

residential areas and the ‘silence’ zone were abovethe limit, whereas for the other class the noiselevel was within the prescribed limits. The ‘silence’zone noise level was above the standard at nighttime due to the use of diesel pumps within theproject area at night.

Socio-economy

The socio-economic study within the buffer zonehas been based on the demographic data of thearea according to the 1991 Census. The totalpopulation of the study area is 173,535 with apopulation density of 2778 persons per km2. The

254 Sikdar et al.

population density is higher than that of the stateof West Bengal (767 persons per km2). The per-centages of the Schedules ‘Caste’ and ‘Tribe’ tothat of total population within the study area are38.7 percent and 0.8 percent respectively. The per-centages of Schedules ‘Caste’ and ‘Tribe’ to thetotal population of West Bengal are 23.6 percentand 5.6 percent respectively. Literacy rate withinthe study area is 46.5 percent against 57.7 per-cent for West Bengal. The employment opportu-nity is very poor. There are 25.8 percent mainworkers and 0.9 percent marginal workers withinthe study area as compared to 30.2 percent and2 percent in West Bengal. It is important to notethat there are no permanent residents within theproject area except for some temporary residenceof migrant skilled and unskilled workers in andaround the project site. Medical facilities are verypoor. There are fourteen subsidiary health cen-ters and only one primary health center. Post andtelegraph facilities are not adequately providedexcept to a few sub-post offices. Very few villageshave markets within reach and most of the peoplehave to travel a long distance (about 5 km) formarketing.

Environmental impact assessment

Twenty-four anticipated project activities havebeen identified during construction, developmentand operational phases, which may affect a num-ber of environmental parameters such as ambi-ent air, surface water, groundwater, soil, landuse,noise, and socio-economics. The impacts havebeen categorised as direct or indirect; short termor long term; reversible or irreversible; site spe-cific, local or regional; and adverse or benefi-cial. A detailed checklist of project activities, envi-ronmental parameters likely to be affected dueto such activities and the specific impact areas,nature, intensity and extent of such impacts aregiven in Table 12. Table 13 reveals that the fre-quency of adverse impacts is greater than that ofbeneficial impacts. But out of the total adverseimpacts twenty are short term and reversible andhave low magnitude.A semi-quantitative assessment of the impacts

of the major activities of the proposed projecton the different environmental parameters has

been attempted through a standard graded matrixsystem. Taking into consideration the degree ofstress that the various activities will impose cumu-latively, the seven environmental attributes havebeen ranked on a scale of 1 to 5 (Table 14). Thescore of each parameter has been converted toa probability value and then recalculated by mul-tiplying each value by a factor of 1000 to arriveat the parameter importance value (PIV), so thatthe values conform to the units of AssessmentValue Index Scale generally used for evaluatingthe degree of impact of a set of activities on envi-ronment.The degree of anticipated impact of each activ-

ity on each of the environmental parameters hasbeen graded as per the Index Scale below:

Degree of impact Impact value

Low = 0.5Appreciable = 1.0Moderate = 2.0Significant = 3.0High/Major = 4.0Permanent = 5.0

A (+)ve (−)ve sign has been assigned to eachimpact depending on its beneficial or adverseeffect respectively.The environmental impact matrix has been

set up with the three major project activitiesas columns and environmental parameters(attributes) as rows (Table 15). The PIV for eachenvironmental parameter has been placed asfirst column. An impact value has been assignedto each major activity-environmental parameterimpact area on the basis of the summation ofthe nature and intensity of impact and the IndexScale.The impact score for each environmental

parameter (SCi) has been calculated from the fol-lowing formula modified after Rau and Wooten(1980)

SCi = �PIV�in∑

j=1Iij

where ‘I’ is the impact value (on the scale of 1 to5, + or −) due to the effect of the project activity‘j’ on an environmental parameter ‘i’ and ‘n’ is thetotal number of project activities.


Table12.Environmentalimpactnatureandassessmentofinfo-techcomplex,EastKolkata,India

Environmental

parameters

Impact

Projectactivities

Impact

affected

Natureofimpact

intensity

Con

structiona

lph

ase

Sitepreparation

Generationofnoise

Noise

Direct,shortterm,reversible,adverse,local.

Low

Generationofdust

Air


Low

Generationofemployment

Socio-economic

Direct,shortterm,reversible,beneficial,local.

Low

Lossofgreenarea

Landuse

Direct,shortterm,irreversible,adverse,local.

Low

Excavationand

Depletionofsoil

Soil

Direct,longterm,irreversible,adverse,local.

Low

backfilling

Generationofdust

Air

Direct,shortterm,reversible,adverse,sitespecific

Low

Generationofnoise

Noise


Low

Stressonsurfacewater

Surfacewater

Indirect,shortterm,reversible,adverse,local

Low


Socio-economic

Direct,shortterm,reversible,beneficial,local

Low

Haulingofearth

Generationofdust

Air


Low

materialand

wastes

Generationofnoise

Noise


Low


Socio-economic


Low

Piling,cutting

Generationofdust

Air


Low

anddrilling

Generationofnoise

Noise


Low


Socio-economic


Low

Mixingof

Generationofdust

Air


Low

concreteand

mortar

Generationofnoise

Noise


Low


Surfacewater


Low


Socio-economic


Low

Concrete

Generationofnoise

Noise


Low

construction


Socio-economic


Low

Erectionofsteel

Generationofnoise

Noise


Low

structure


Socio-economic


Low

Road

Generationofdust

Air


Low

construction

Generationofnoise

Noise


Low


Surfacewater

Direct,shortterm,reversible,adverse,local

Low


Socio-economic


Low

Continued

256 Sikdar et al.

Table12.Continued

Environmental

parameters

Impact

Projectactivities

Impact

affected

Natureofimpact

intensity

Painting

Generationofpotentially

Soil


Low

toxicleachates

Surfacewater


Low

Employmentgeneration

Socio-economic


Low

Cleanup

Generationofdust

Air


Low

operation

Generationofnoise

Noise


Low


Socio-economic


Low

Landscaping

Generationofdust

Air


Low

andplantation

Changeinlandform

Landuse

Direct,longterm,reversible,beneficial,sitespecific

Low

Vision

Aesthetics

Direct,longterm,reversible,beneficial,sitespecific

Low


Socio-economic

Direct,longterm,reversible,beneficial,local

Low

Developmentof

infrastructuralfacilities

Establishmentof

Depletionofgroundwater

Groundwater

Direct,longterm,irreversible,adverse,local

Low

watersupply

Depletionofsurfacewater

Surfacewater

Direct,longterm,reversible,adverse,local

Appreciable

Easyavailabilityofsurface

Socio-economic

Direct,longterm,irreversible,benefical,sitespecific

Low

water

Establishmentof

Improvementofhealthof

Socio-economic

Direct,longterm,irreversible,beneficial,local

Significant

healthcentre

people

Disposalofhospitalwaste

Soil


Moderate

Surfacewater


High

Groundwater


Low

Establishmentof

Opportunitiesfortrade

Socio-economic


Significant

market,bank,

andcommerce

telephoneexchange,

postoffice

Establishmentof

Theftandfire

Socio-economic


Significant

policestationand

firestation

Establishmentof

Generationofairpollutants

Air


Low

busterminaland

taxistand

Generationofnoise

Noise

Direct,longterm,reversible,adverse,sitespecific

Low

Easycommunication

Socio-economic

Direct,longterm,irreversible,beneficial,regional

Significant

Continued


Table12.Continued

Environmental

parameters

Impact

Projectactivities

Impact

affected

Natureofimpact

intensity

Establishmentof

Opportunitiesforrecreation

Socio-economic


High

recreational

facilities

Constructionof

Preventionofpollutionof

Surfacewater


Appreciable

sewagetreatment

surfacewaterbodies

facilities

Establishmentof

Easyavailabilityofpower

Socio-economic


High

electricsupply

Operation

alph

ase

Generationof

Stressonsoil

Soil

Direct,longterm,reversible,adverse,sitespecific

Low

sewage


Surfacewater


Low

Generationof


Surfacewater


Low

stormwater

Dischargeof

Stressongroundwater

Groundwater

Direct,longterm,irreversible,adverse,regional

High

groundwater

Generationof

Employmentofskilled/

Socio-economic


Moderate

employment

unskilledworkers

Preservationof

Improvementoflanduse

Landuse

Direct,longterm,reversible,beneficial,regional

High

waterbodies

pattern

258 Sikdar et al.

Table 13. Nature and frequency of impact on environmental parameters, for info-tech complex, East Kolkata, India

Nature of impact Frequency

Adverse Low Appreciable Moderate Significant High Permanent Total

Direct Long term Reversible 4 — — — — — 4Irreversible 3 1 1 — 2 — 7

Short term Reversible 20 — — — — — 20Irreversible 1 — — — — — 1

Indirect Long term Reversible — — — — — — —Irreversible 1 — — — — — 1

Short term Reversible 2 — — — — — 2Irreversible — — — — — — —

Total adverse 31 1 1 — 2 — 35

Beneficial Low Appreciable Moderate Significant High Permanent Total

Direct Long term Reversible 2 — — — 1 — 3Irreversible 1 1 1 4 2 — 9

Short term Reversible 11 — — — — — 11Irreversible — — — — — — —

Indirect Long term Reversible — — — — — — —Irreversible — — — — — — —

Short term Reversible — — — — — — —Irreversible — — — — — — —

Total beneficial 14 1 1 4 3 — 23

Table 14. Parameter importance value (PIV) for different environmentalattributes, info-tech complex, East Kolkata, India

Environmental attributes Rank (1–5) Weighted PIV

Ambient air 4 4×1000/16 250�00Surface water 3 3×1000/16 187�50Groundwater 4 4×1000/16 250�00Soil 1 1×1000/16 62�50Landuse 1 1×1000/16 62�50Noise 1 1×1000/16 62�50Socio-economics 2 2×1000/16 125�00

Total 16 1000�00

Table 15. Environmental impact matrix before implementation of environmental management plan,info-tech complex, East Kolkata, India

Environmental Constructional Developmental Operational Impactattributes PIV phase phase phase score

Ambient air 250 −4 −0�5 0 −1125�0Surface water 187�5 −2 −4�0 −1�0 −1312�5Groundwater 250 0 −1�0 −4�0 −1250�0Soil 62�5 −1 −2�0 −0�5 −218�75Land use 62�5 0 0 +4�0 +250�0Noise 62�5 −4�5 −0�5 0 −312�5Socio-economics 125 +5�5 +20�5 +2�0 +3500�0Total impact scope (TIS) −468�75


Table 16. Assessment value index scale

Score value Extent of impact

>�−�1000 No appreciable impact�−�1000 to �−�2000 Appreciable impact but not injurious,

mitigation measure important�−�2000 to �−�3000 Significant impact, major control

measures necessary�−�3000 to �−�5000 Injurious impact, site selection to be

reconsidered<�−�5000 Irreversible damage, alternate site

to be considered.

The total impact score (TIS) is arrived atthrough the formula:

TIS=m∑

i=1SCi

where m= total number of environmental param-eters.The total impact score for the info-tech com-

plex is (−)468.75 and as per the Assessment ValueIndex Scale (Table 16) the environmental impactof the proposed project activities is ‘no apprecia-ble impact.’ The score does not takes into accountthe impacts of the proposed project on the eco-logical parameters but it portrays the impacts(adverse or beneficial) of the info-tech complexon the physical and socio-economic environmentin a synoptic manner. To ameliorate the adverseimpacts on the environment certain appropriatecontrol measures have been suggested below.

Environment management plan

To ameliorate the adverse impacts and increasethe beneficial impacts on some environmentalattributes the following environment managementplan might be adopted.

Construction and development phase

— Surface-treating of access road.— Sprinkling of water on the access road at reg-ular intervals.

— Developing a dense green belt around theproject area and the access road.

— Treating the wastewater by passing it throughsedimentation tanks before discharging intothe surface water bodies.

— Tapping of groundwater should be avoided.— Topsoil that will be removed should be usedfor green belt development.

— Workers working near high noise producingmachines should be provided with ear protec-tion equipment.

— Silencer, noise seals and vibration proofmountings should be provided to stationeryequipment producing high noise.

Operational phase

— The green belt should be well maintained.— Regular air quality monitoring should be car-ried out at least at one station within the corearea.

— The sewage generated should be treated andused for maintaining the green belt and themanagement of the water bodies.

— Monitoring of the treated water and surfacewater bodies should be strictly carried out andthe analytical results should be reported to thecompetent authority every month.

— The 2.1 mld of water that is to be extractedfrom the aquifer should not be tapped exceptfor emergency. Therefore, the project pro-ponent should make arrangements with theMunicipal authority to bring treated surfacewater to the area.

— Hospital wastes should be disposed as per therules. An incinerator should be installed forthis purpose.

— Medical and recreational facilities should beextended to the poorer section of the peoplewithin the buffer zone.

— An Environment Cell, headed by an Environ-mental Manager, should be created to lookafter all aspects of pollution control and envi-ronmental protection and upgradation.

Conclusions

It is envisaged that with the implementation ofthe suggested management plan there will be a

260 Sikdar et al.

Table 17. Environmental impact matrix after implementation of environmental management plan,info-tech complex, East Kolkata, India

Environmental Constructional Developmental Operational Impactattributes PIV phase phase phase score

Ambient air 250 −3�5 −0�5 0 −1000Surface water 187�5 −1�5 −3�0 −1�0 −1031�25Groundwater 250 0 −1�0 −3�5 −1125Soil 62�5 −1 −1�5 −0�5 −187�5Land use 62�5 0 0 +4�0 +250Noise 62�5 −3�5 −0�5 0 −250Socio-economics 125 +5�5 +20�5 −2�5 +3562�5Total impact score (TIS) +218�75

distinct improvement in the quality of the envi-ronment as well as of life. The total geoenviron-mental impact score in the changed condition isexpected to be (+)218.75 (Table 17). Hence thetotal improvement of the geoenvironmental qual-ity will be over the order of 687.5 units.

Acknowledgments

P.K. Sikdar thanks the Director, Indian Institute ofSocial Welfare and Business Management for giv-ing permission to publish the paper. The authorsacknowledge the help rendered by the HonorarySecretary, Center for Study of Man and Environ-ment. The President and Chief Executive Officerof Ghezri Eastern Limited is also acknowledgedfor sponsoring the work.

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environmental impact assessment of a proposed info-tech complex in east calcutta wetlands

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