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The rapid growth of Chennai city with increasing trend in industrialization and economic development, demands the immediate augmentation of drinking water source for the long depleted water supply. Chennai Metropolitan Water Supply & Sewerage Board (CMWSSB) has planned to augment the water supply to Chennai city by setting up a 100 MLD Seawater Desalination Plant in Kattupalli village, near Minjur, north Chennai. The scheme has been proposed on Design, Build, Own, Operate and Transfer (DBOOT) basis under twenty five years license. The project location identified for development is shown in Fig. 1. The satellite imagery depicting the project region is shown in Fig. 2. The project has been awarded to Special Purpose Vehicle (SPV) named as Chennai Water Desalination Limited (CWDL) constituted of IVRCL Infrastructures & Projects Ltd., Chennai and BEFESA Construccion y Tecnologia Ambiental, S.A., Spain. The project envisages ultimate delivery of 100 MLD (million litre per day) of water with a TDS not exceeding 500 ppm. The scheme comprises of: i) drawl of 237 MLD of sea water from the Bay of Bengal through intake pipeline, ii) pre treatment of intake water, iii) desalting seawater through Reverse Osmosis, and iv) discharge of 137 MLD of brine reject into the sea through submarine pipeline and outfall diffuser. As the project is directly related to marine environment, a detailed Marine Environmental Impact Assessment report comprising of various proposed activities in the marine environment, base line environmental condition, impacts due to development, mitigation measures and Marine Environmental Management Plan has been prepared separately and submitted. The present report involves additional information on the environmental studies relating to the terrestrial aspects, viz., i) socio-economic aspects, ii) air environment, iii) water environment, iv) noise environment, v) flora & fauna, vi) risk analysis, and vii) environmental management. The objective are aimed: i) evaluate the existing environmental status of various environmental parameters, ii) identify the possible impacts due to the proposed desalination plant, iii) suggest proper mitigation measures to minimize the impact, and iv) devise a suitable environmental monitoring scheme and identify an Environmental Management Plan. For the purpose of this study, the area has been divided into two zones, namely, the core zone and the buffer zone. Core zone represents the entire project area of about 60 acres, while the buffer zone encompasses the surrounding area lying in 5 km radius from the center of the project area. The Ministry of Environment and Forests (MoEF), Government of India, has classified the coastal zone into four categories, namely, Coastal Regulation Zone (CRZ) I, II, III and IV. In strict consonance with above stipulation, all construction activities in the desalination plant are planned beyond 200 m from the HTL. The desalination plant is proposed to be located near Kattupalli village at Ponneri Taluk, Thiruvallur district, Tamil Nadu. The site falls part of the Survey of India Toposheet No 66 C/7, ant it is located approximately at Latitude 13019’06” N and Longitude 80020’17” E. It lies 4 km north of Ennore Port and 22 km north of Chennai. Athipattu is the nearest rail head and tThe area is approachable from the North Chennai Thermal Power Station (NCTPS) – Ennore Port road, through Chennai – Manali – Minjur road. The location plan is given in Fig 3. The project area is spread over 60 acres and it forms as coastal plain with sandy soil and sparse vegetation. The general slope of the area is from northwest to southeast. The area is bounded by Bay of Bengal on the east. Buckingham canal is flowing on the west. 1.4. CLIMATE
The proposed desalination plant envisages a product water of 100 MLD and the scheme comprises of: i) drawl of 237 MLD of sea water from the Bay of Bengal through intake pipeline, ii) pre treatment of intake water, iii) desalting seawater through Reverse Osmosis, and iv) discharge of 137 MLD of brine reject into the sea through submarine pipeline and outfall diffuser. The plant layout is shown in Fig. 4. The process flow sheet indicating the salient details and the plant layout is shown in Fig. 5. The intake is designed to draw seawater having the ambient salinity of around 35 PSU (Practical Salinity Unit equivalent to ppt - parts per thousand), at the rate of 237MLD through an intake system. The water will be drawn from the Bay Bengal to the Plant through a gravity flow. The intake head will be located at 9 m water depth at a distance of 589 m from the shore. The intake and outfall layout is shown in Fig. 6. Physical treatment Disinfection The untreated water will be chlorinated by applying a dose of sodium hypochlorite in the underwater intake channel and in the pump aspiration chamber. After the dose of chlorine has been applied, an ORPT gauge equipped with alarms will indicate the oxidation level obtained following chlorine injection. Coagulation & Flocculation In order to eliminate suspended matter and colloids present in the sea water, a dose of ferric chloride (coagulant) will be applied, enabling the formation of flakes. Flocculation will take place immediately in three chambers (428 m3 each unit), with the addition of polyelectrolyte. Suspended solids will be eliminated in three gravity settlers (1450 m3 each unit). Filtration The seawater is filtered in two stages in order
to eliminate remaining suspended solids and organic matter: the
first stage consists of filtration through the sand filters; and
the second stage consists of filtration through the anthracite
filters at a faster speed. The sand filters will be single-bed
filters, with two layers of silica sand, one with a sand height
measuring 300 mm and an effective dimension of 2 mm; and another
with a sand height measuring 1000 mm and an effective dimension
of 0.9 mm. A static mixer will be installed before the sand filters
in order to facilitate and complete the mixing of previously-metered
chemical products. The horizontal cylindrical filters will be
assembled in parallel formation, so that the discharge is distributed
between all of them, in the normal operation process. Chemical treatment Sulphuric acid Dosing Sulphuric acid dosing equipment is designed to
reduce the pH of sea water and prevent precipitation of carbonates
and bicarbonates, as well as to generate sufficient CO2 for post-treatment
with dolomite. The installations consist of storage tanks, transfer
pump and one metering pump per line, plus one reserve pump. The
reduction of pH makes the bactericide action of the chlorine more
effective. The injection points of these products may be located
at the outlet of the sea water pumps. Sodium bisulfite product is added in order to eliminate residual chlorine from the dose of sodium hypochlorite. The equipment consists of two preparation tanks and one metering pump per line, plus one reserve pump. The product is added on line in order to provide the longest contact time possible. Antiscalant dosing Since sea water is concentrated in the membranes, and in order to prevent the precipitation of ferric hydroxide, calcium fluoride, calcium sulphate and strontium sulphate salts, an antiscalant will be metered to prevent the formation of crystalline networks, by maintaining the dispersed ions and enabling the limit of the solubility product of these salts to be exceeded. The product is added on line and before the RO system. Ultrafiltration Due to the characteristics of raw water, and in order to prevent fouling in the reverse osmosis membrane, an ultra filtration unit will be installed. It consists of 26 modules containing 88 modules each. The working pressure is established at maximum 2 bar. Auxiliary equipment for backwash and chemical cleaning is also provided. High-pressure pumping As mentioned previously, the pumping and energy recovery equipment consists of high-pressure pumps, a unit for recovering energy from the brine with hyperbaric or compression chambers, and recirculation or booster pumps to increase the pressure of the rest of the water transferred in the direction of the membranes. The aim of the pressure groups is to provide the necessary pressure to overcome the osmotic pressure of the raw water and system pressure drops. The water discharged from the reverse osmosis modules is used to feed the hyperbaric/compression chambers, thus achieving maximum energy economy. The high-pressure pumping equipment consists of the same number of motor-pump groups as lines, each group provides the total discharge that must be treated by each line. One complete non-installed group will also be kept in reserve. This reserve group will be available to replace any of the other groups. This reserve group is connected to the collector which feeds the chassis of the R.O. modules, so that any one of the motor pump groups can be replaced in normal operating conditions. Reverse Osmosis Train Spiral wound membranes will be used. Seven (7) membranes of each type are placed in the pressure vessel. The proposed design consists of one pass and one stage. System recovery is established at 45%. Number of trains is established at 5 units for 100 MLD output. A differential pressure gauge is placed between the feed water and the brine, with a high-pressure alarm and on-screen recording unit. The differential pressure indicates when and to which extent the membranes have been fouled. Each general produce water collection pipe will be connected to the product tank. A three-way valve will be installed at the product outlet of each pressure vessel for sampling purposes. A panel for each train will also be provided. Booster Pumps The hyperbaric/compression chambers supply part of the feed water to the membranes until a slightly lower pressure results to that achieved by the brine. These recirculation pumps are used to increase this pressure to the membrane feed. Energy recovery system As mentioned previously, brine energy is recovered at the outlet of the membranes by means of hyperbaric/compression chambers. This system is used instead of Pelton-type turbines because of its greater energy performance. These chambers comprise cylinders with internal pistons that enable brine to be separated from the sea water, whenever you want to increase pressure. Sea water enters on one side and when the cylinder is full, the brine enters from the other side and, due to its high pressure, exerts pressure on the sea water and displaces it; when the sea water is to be displaced, a valve opens on the brine side to be discharged, sea water enters on the other side, thus repeating the cycle. Since a piston separates the brine from the sea water, the mixing of the two is minimal, less than 1.5 %. The performance rate of the chambers is 95.4%.The cylinders will be made of stainless steel and wet surfaces will be covered with HDPE (High Density Polyethylene). The rest of the pipes and sets of valves will be made of AISI 904 L-class stainless steel. Due to the large number of chambers installed in parallel formation, there are no flow or pressure fluctuations. Treated water tank The produced water will be stored in a 20,000 m3 tank .The dolomite saturation towers will be installed on the tank. Since the water is treated before entering the tank of the unit, an auxiliary 200 m3 tank will be available for internal usage. Disinfection of produced water Before the produced water is transferred to the
network, it will be treated with dolomite in order to increase
its pH level to a value between 6.5 and 8.5 and to maintain the
LSI (Langelier Saturation Index) between 0 and 0.4. Sodium hypochlorite
will also be used in order to achieve residual chlorine around
0.5 ppm. The pH levels will be adjusted to between 6.5 and 8.5, as established in the Specifications, by means of treatment with dolomite. Dolomite reacts with the CO2 produced during treatment of make-up water with sulphuric acid, thus increasing water alkalinity and hardness. Two towers will be built for treating produced water with dolomite; like counter-flow filters, these towers will be placed on the produced water tank. Auxiliary services Besides various auxiliary services like membrane cleaning equipment, neutralisation and emptying system, flushing system, filter cleaning equipment, service water network, instrumentation, service air supply, fire prevention system, communication systems, laboratory services, workshops, control system, etc will also be provided in the plant. All necessary buildings will be constructed to house decanter and sea water cabins, process requirements, control room, laboratory, electrical services , work shop and store, offices and staff area, etc. State of art latest technological systems and equipments will be deployed in the project to achieve desired objectives. The brine rejects of the order of 137 MLD with a salinity of 70 PSU are released into the sea, using HDPE submarine pipelines of 1 x 1400mm dia and diffuser ports outfall system, which has been designed to have maximum mixing in order to attain ambient salinity within a short distance. The typical outfall diffuser is shown in Fig. 7. A detailed mathematical model study has been done and a separate report has been submitted on the design of diffuser and ports, initial dilution, and a secondary diffusion. As the latest technological inputs and state–of-art instrument and equipments are inbuilt into the process system, there will be practically no negative impacts on the environment due to the project. 3.1. EXISTING SOCIO-ECONOMIC ENVIRONMENT The proposed desalination plant and the related project activities would entice more positive impact as well as marginal adverse impacts on the socio economic front. Keeping this in view, the existing socio-economic setup of the area has been studied in order to predict the likely impacts and to suggest a mitigation measures for minimizing adverse impact, if any. The socio economic study covers the project area the core zone (project area) and the buffer zone (5 km radius). Base line data and relevant information on socio- economic environment has been collected from 2001 census record and substantiated with field surveys. Core zone The total project area of the desalination plant comprises of 60 acres. It is a barren land and it belongs to TIDCO, Government of Tamilnadu. The land has been leased for construction by TIDCO. There are no habitations in this designated area and no rehabilitation is involved. Buffer zone The buffer zone of the proposed project, encompassing 5 km radius from the center of the core zone, consists of 6 rural villages namely Kattur, Karugali, Kalanji, Kattupalli, Voyalur and Puzhidivakkam of Ponneri Taluk from Tiruvallur district. The details of villages falling in the study area are given in the Index plan in Fig. 8. Based on the 2001 census, the following details
are gathered. Of the total population, there are 6046 (55.07%) literates of which 3495 (31.83%) are male and 2551 (23.24%) are female. About 29.77% of the total population are Main workers , 11.40% are Marginal workers and the remaining 58.83 % are non-workers. Cultivators and the agricultural laborers contribute
about 62.18% of the total Main workers. The project area, upto Ennore port is connected by good metal road and there after for a reach of 4 km till the site is connected by Kutcha road. Surrounding villages are well connected by metal road. Most of the villages depend on the ground water
sources like open wells and bore wells. The salt pans , fishing, collection of fire
wood, collection of dead sea shells etc. provide employment for
the local population. The socio-economic impact due to the project during construction and operational phases are enlisted below. Construction stage During the peak construction phase, about 100 unskilled and 20 skilled workers are expected to be employed. Since it is expected that the project developer will employ local people during construction, the people from nearby villages are expected to migrate close to project site for the job opportunity. But such migration will be purely temporary and will prevail only during construction phase. These temporary workers have to be provided with basic necessary facilities like temporary shelters, drinking water, fuel, sanitation and garbage disposal, food supply, fire fighting etc. Accordingly, the need for felling fire woods for cooking purpose will not arise. Hence, the hygienic status of the area will not be disturbed. During the construction activities, preference will be given for the local population only. Hence, there will be less migration and there will not be any adverse impact on the host community. As all the safety and health protection measures will be strictly followed during construction phase, no occupational health or safety problems are envisaged. The existing Kutcha road will be laid as metal road and lighting facilities will be erected along the roadside during the construction stage itself. Hence, better access facilities to the area will be created for the surrounding population of the project site, particularly for the people at Kattupalli and Kalanji villages. Looking to the above factors, the project will provide employment potential temporarily for 125 persons. Besides, improvement of access roads with connected civil works, will give indirect benefit to many local people. Overall, the construction phase will bestow a positive impact on the area. Operational phase During the operational phase, the project will provide permanent employment for about 30 people. Further it will provide direct and indirect employment for about 200 persons on account of contractual job as well as auxiliary services like maintenance of pipes, equipments etc. Besides, the project will provide about 100 MLD of potable water to Chennai city, catering to the needs of nearly 2.5 million people. The project operations are limited to production of clean water directly involving about 30 persons only. The staff will be housed mostly at developed locations like Chennai, Minjur etc. Looking to the sparse personnel absorption in the project, there will be no adverse impact on surrounding population on factors like culture, religion, etc. 3.3. IMPACT ON MARINE COASTAL COMMUNITY Along the eastern side of the project area lies the sea and adjoining beaches, which are free from habitation and any dwellings. There are no boat beaching locations. No mechanized fishing boats are anchored in this region. The Kattupalli kuppam, which is the nearest small fisherman hamlet is situated more than one kilometer away from the project site and thus will not be affected by the project operations. The main occupation of the people in this hamlet is fishing in deep sea only. As mentioned earlier, there will be sea water
intake pipe lines for the drawl of sea water and an outfall pipeline
for discharging the brine rejects into the sea. Installation of
sub marine pipelines, intake head and outfall diffuser in the
sea will not have any adverse impact on the marine organisms,
fishing, boating operations due to inbuilt design factors as shown
below: b) Marker buoys placed close to intake and outfall can help the boats to divert and avoid collision. c) The pipeline will be buried or allowed for
natural burial in sea floor so that it will not cause any hindrance
to fishing and navigation. e) The outfall diffuser are designed with appropriate
number of ports which can increase the mixing of brine discharge
so that it attains the ambient salinity within a short distance
and time. On the otherhand, the local fishermen community and others are bound to get the following positive socio economic benefits: a) Direct employment opportunities during construction stage, during laying of inlet and outfall pipelines, by the way of hiring of boats etc. b) Direct and indirect employment opportunity during the operation stage of the plant. c) Improvements of the local amenities like better approach roads, communication, electricity, water supply, educational & recreational facilities, hospitals/ dispensaries, etc. which will bring the basic comfort to the local society. d) Improvement in the general living standards
and knowledge sharing. g) Improvement in the economic growth in the region. Besides, the project implementation will augment
the water supply capacity to In view of the above facts, it can be concluded
that the advent of this project will result in a net positive
impact on the socio economic front of the local population due
to improvement in the social status of the area and the economic
benefits derived from this project. 4.1. EXISTING AMBIENT AIR QUALITY Air pollution is emanated basically due to the presence of foreign substances in air. The principal objective of the Ambient Air Quality Monitoring (AAQM) is to assess the existing levels of air pollution as well as the regional background concentration surrounding the site. The ambient air quality depends upon the emission scenario, meteorological conditions and the background concentration of specific contaminants. The study of the baseline ambient air quality data in the area is an essential. It is a primary requirement for assessing the impact on air quality due to the proposed activity and also to enumerate the potential environmental changes likely to occur when the project is commissioned. The following parameters were analysed at the sampling locations established in the study area. Suspended Particulate Matter Design criteria for ambient air quality monitoring study network As previously described, the morphological formation of the site is a plain coastal area with sandy soil and sparse vegetation. Due to proximity of sea, the soil is saline and no agricultural activities are possible in the area. The Ennore port is about 4 km south of the site and the North Chennai Thermal Power plant is about 6.5 km south of the plant. Two ambient air quality-monitoring stations were selected based on the proximity of the habituated villages to the plant, wind directions and other logistics of setting up the necessary monitoring instruments at the required locations. The relative directions and distances of these stations with respect to the project site and details of these stations are described below.
Method of sampling Standard Monitoring and Analysis procedures were
adopted for determining the Air quality parameters. The methodology
adopted is briefly described here under:
The SPM, RPM, SO2 and NOx are monitored on 24 hourly basis as per CPCB (Central Pollution Control Board) guidelines. Data Analysis The Ambient Air Quality data for SO2, NOx , SPM
and RPM are presented in Fig. 12. It is seen that , the SO2 levels
in the studied locations ranged from 6.0 mcg/m3 to 9.0 mcg/m3.
The NOx concentrations varied from 8.0 mcg/m3 to13.0 mcg/m3. In
case of SPM, the values varied from 58.0 mcg/m3 to 76.0 mcg/m3
, while the RPM values varied from 19.0 mcg/m3 to 22.0 mcg/m3.
4.2. IMPACT ON AIR QUALITY 4.3. MANAGEMENT PLAN – AIR ENVIRONMENT 4.4. MONITORING a) High Volume Air sampler with RPM attachment, Photo colorimeter/ Spectro photometer, Electronic Weighing balance, Desiccators, Glass wares, etc. b) Wind anemometer, Wind direction finder, Wet
and dry bulb thermometer, Pressure gauge and Rainfall gauge for
meteorological studies. 5.1. EXISTING WATER ENVIRONMENT Buckingham canal flowing west of the site is the nearest surface water body in the region. This is a drainage channel and water of Buckingham canal is not used for potable purpose. The general ground water quality in the project area at shallow depth of say 20 to 30 feet is comparatively good. However, the quality deteriorates and becomes saline at greater depth. Sampling locations The following water sampling locations were selected for water analysis. W1- Open well at Kalanji village Five different samples were drawn from the bore
well within the plant premises (W2) namely, Data Analysis & Interpretation The water quality of 5 samples collected from location W2 is given in Table 3. From the Table , it is seen that the Total dissolved solids, total hardness, chlorides, sulphates, are generally higher than the limits. It is also observed that these values increase with the depth of water as pumping time increases. 5.2. IMPACT ON WATER ENVIRONMENT & MANAGEMENT PLAN Construction stage During the project construction stage, water will be required only for construction activities and for potable use of the manpower. This requirement will be met by procuring water from the outside source and as such there will not be any pumping of ground water from the area and hence there will not be any impact on the ground water regime in the area. There will not be any effluent generation due to construction activity. During construction, no waste will be dumped on land in the site. With these measures and due to the short term nature of construction phase, there will be no impact on this parameter. Operation phase The total water requirement for this plant is as follows: a) About 237 MLD of sea water to produce 100
MLD potable water. The water required for cleaning of membranes and the potable need will be met from service tank in the plant. The sea water required for sand and anthracite filters will be met from the sea water inlet source. As such, there will be no requirement of any surface or ground water sources for meeting the water needs of the plant. The effluents generated from this unit are: i) About 137 MLD of brine reject. iii) Domestic effluent. Since the salinity of the brine reject will be high around 70 PSU, the discharge of brine must be selected in a manner that it has a minimum impact on the marine environment. This is achieved by releasing the brine reject into the sea through diffuser ports outfall system which will be designed to have mixing in order to attain ambient salinity within a short distance. A mathematical model will determine the form, name, distribution and attack angle, as well as the expulsion speed of the brine in the diffusers at the end of the underwater discharge/outlet pipe in order not to harm marine life. The washing waters from the filters and the membranes will be neutralised and will be emptied into the sea through an independent pipe, separate from the brine discharge pipe. The domestic effluent comprising mainly sewerage water will be collected in Septic tank of adequate size with soak pit arrangements. From the above, it is seen that the plant process envisages zero discharge of water on the land and as such there will not be any adverse impact on the terrestrial water environment. By adopting mitigation measures as described earlier, the impact on the marine water environment will be negligible. 5.3. MONITORING 6.1. EXISTING NOISE ENVIRONMENT: Noise may be defined as unwanted sound, which interferes with the normal hearing of a human. Noise levels near the roads depend on the type of vehicles plying (light vehicles, heavy vehicles) etc., the intensity of traffic, maintenance of vehicles and also on the human / industrial activity in the vicinity. Noise is sound that is composed of many frequency components of different sounds distributed over the wide audible frequency range. Exposure to noise levels beyond prescribed limits may lead to several effects such as: a) Noise induced hearing loss Sampling Locations The noise measurements were carried out at the following stations where the ambient air quality was measured : N1 - Kattupalli Village In order to assess the pattern and intensity of noise levels with reference to time, the following methodology was adopted. i) Measurement of ‘A-weighted’ sound
level continuously both during day & night levels using noise
level meter at each site on hourly basis continuously for 24 hours. The noise was measured in ‘A-weighted’ decibels [dB(A)]. The human ear can detect sound within a particular frequency range from approximately 20 to 20,000 Hertz. However, the ear is more sensitive to mid-frequencies between 1000 to 6000 Hz where most speech information is carried out, than low or high frequencies. This characteristic is taken into account in sound measurements by adjusting the spectrum of the measured sound pressure level for the sensitivity of human hearing. In the standardized sound measuring instruments, this is implemented with selectable ‘A-B and C-weighted networks’. The term ‘weighting’ is used because some frequencies are given higher or lower importance or weightage than other frequencies. The weighting functions employed correspond approximately to the response of human ear to low, medium and high sound levels. By far, the most common rating scale is the ‘A-weighted’ sound level and is expressed in dB(A). This noise rating was developed by the Environmental Protection Agency (EPA) specifically for community noise from all sources in the day and night. It was in this manner, the Sound Pressure Level (SPL) was measured at the sites. SPL= (20 Log10 P)/Po Where ‘P’ is the root-mean square sound pressure and ‘Po‘ is the reference sound pressure (20 ? Pa).. Data Processing The data collected from the field on an hourly basis were analyzed to determine the following statistical evaluation. The following statistical data for the noise levels measured were determined. i) L10 or Ten percentile exceeding level is
the level of sound which is exceeding 10% of the total time of
measurement. The simplest and most popular method for rating intermittent or fluctuating noise intrusions is to rely upon some measure of the average sound magnitude over time. The common average is the equivalent sound level, Leq. It is the energy average of the level (usually A-weighted) of a varying sound over the measurement period. It can be considered as the continuous steady noise level which would have the same total A-weighted acoustic energy as the real fluctuating noise measured over the same period of time. v) Lday - Day average sound level: Lday is defined as the equivalent noise level measured over a period of time during day (6 am to 10 pm). The Leq value measured for each individual hour and then averaged for 6.00 a.m. to 10 p.m. and is known as Lday. vi) Lnight - night average sound level : Lnight is defined as the equivalent noise level measured over a period of time during night (10 p.m to 6 a.m). The Leq value measured for each individual hour and then average for 10.00 p.m. to 6.00 a.m. and is known as Lnight. vii) Lmax - maximum noise level : This is the maximum level recorded at a particular site during the monitoring period. viii) Lmin - minimum noise level : This is the minimum level recorded at a particular site during the monitoring period. Data Analysis & Interpretation The results of the background noise level measured
are given in Tables 4 & 5 . A comparative chart showing noise
for both the locations is given in Fig 13. It is seen that the
ambient noise level in Kattupalli village varied from 36.40 to
53.40 dB(A) & in Kalanji village from 35 .90 to 50.10 dB(A)
. The present noise levels in all the observed locations are within
the limits prescribed by Ministry Of Environment & Forests
Notification given vide Appendix 2.. Construction phase Construction equipment like Shovels/loaders, mixer machines, vibrators etc and vehicular movement will cause minor rise in noise levels on site during construction. This will be limited and localised to the area of operation only. The study area is sparsely populated and as already motioned the nearest habituated village Kattupalli is situated about 1.5km away from the project site. As such the impact of noise on community is not significant. Also , appropriate mitigation measurers as given in para 6.3, will be taken to keep the noise level to the minimum. Operation phase: During the operation of the desalination plant, there may be noise level emanation from the following places: a) In the reverse osmosis process unit, high pressure pumps as well as booster/recirculation pumps may produce some noise. b) The blower provided in the filter cleaning unit for effective cleaning. These blowers in the filter cleaning unit have been provided with its own noise silencers. Hence the noise generation from this unit will be negligible. The expected noise level from the unit are:
Prolonged exposure to a high noise level is harmful to the human auditory system and can create mental fatigue, rebellious attitude, annoyance and carelessness which may lead to neglect of work and also result in accidents. The impact of noise level as per World Health Organisation’s 1986 notification is given below:
OSHA (Occupational Safety and Health Administration), USA and other similar organisations stipulate that noise level up to 90 dBA is acceptable for eight hours exposure Leq (Equivalent sound level) (8hrs) per day. But for the active working area of high pressure pumps, blowers, the noise level in the other areas say at a distance of 20m or so will come down and will be within the tolerance limits. In the active working areas earplugs will be used for personal protection of the staff. As already mentioned, the habituated villages
are located far away from the unit and there will not be any impact
of noise on the community due to this plant operation. The following measures are suggested for minimizing the noise levels during the construction as well as operation stage: Construction & Operation Stage i) Choosing construction equipment generating
minimum noise and vibration only. 6.4. MONITORING 7.1. EXISTING BIOLOGICAL ENVIRONMENT Flora & Fauna Flora Core Zone Bufferzone a) Area facing the open sea The land use of the study area is shown in Fig. 14. The sea front area is typically of sandy type and from Puzhidivakkam in the south of the buffer zone up to the proposed desalination plant is developed for North Chennai TPS and Ennore Port. The Buckingham canal occupies major part of the area. Numerous salt pans are located in the Swampy area near Buckingham canal. The inlands in the buffer zone comprises of sparsely populated villages namely kattupally, kalanji, Uranamedu, Sanganimedu, sand hills, scattered trees. The area is sparsely vegetated (Refer Photo). Casurina and cashew are predominantly seen at many places. Besides, Ain (Terminalia tomentosa) , Bibla (Semicarpus anacardi), Karanji (Pongamia glabra) etc, are also seen. Grasses like Eragrostic sp. Dieanthium anulakum are commonly present. Agricultural activities are totally absent due
to poor soil condition In the study area, fauna common to rural India such as hare, jackals, monkeys, langoors, pigs, etc and several species of birds and reptiles are present. No rare or endemic species are generally observed. Pulicat Bird Sanctuary This sanctuary is situated about 15kms north of the project area. Egrets, herons, kites, waterside birds, grey pelicans, ducks, etc are found visiting the lake. Species like crabs, clams, mussels, oysters, snails, sponges, prawn, etc are found in the lake. 7.2 IMPACT ON BIOLOGICAL ENVIRONMENT 7.3 MANAGEMENT PLAN By this way about 22.5 ha of the land can be
covered under plantation. Thus the area covered under plantation
works out to 37.5%, which is more than the norms prescribed by
the pollution control boards. Name of Plant Species 8. RISK ANALYSIS AND DISASTER MANAGEMENT PLAN Detailed risk analysis for the project has already been separately studied. The objective of risk analysis comprises of following aspects: Identifying the worst chemical and general plant hazards and the corresponding plant section and assessing their consequences in terms of asphyxiation, thermal radiation, explosion and toxicity effects. Assessing the overall damage potential of the identified hazardous events on the internal and external installation and on the population in the vicinity. Identification of accident sequences and consequences and Providing guidelines for the containment and mitigation of any incident and plan on-site or off-site emergencies based on the identified scenarios on the proposed plant. The risk analysis study has been carried out in two phases, viz. Preliminary Hazard Analysis (PHA) followed by Consequence analysis. Finally the vulnerable zones are plotted from which risk reducing measures are deduced and recommended. The salient findings of the risk analysis study are as follows: The proposed plant consists of units mainly
for treatment of sea water and uses the common chemicals being
used in water treatment. It can be observed that the risk at the desalination plant is comparable to criteria as used in some developed countries. When compared to a risk to an average motorist, the risk at this unit would appear to be ten to hundred times lower. Based on the risk analysis carried out for the project, a broad Disaster Management Plan (DMP) has been prepared, to incorporate both “On-site” and “Off – site” emergency plans, taking into consideration all technical reviews and suggestions as per acceptable norms. An organization structure is also devised to combat the emergencies. Roles and responsibilities of the emergency team are also fixed and the details are given in the main report. In view of aforesaid details, like incorporation of latest technological inputs with sophisticated equipments and control systems into the process design, pre project environmental status, predicted impacts due to the project operations and timely implementation of various environmental control measures to reduce the adverse effects due to the project operations, it will be seen that the advent of the project will give a big boost to this economically and socially backward region by way of creation of better employment potential, better educational and medical facilities, better aesthetical outlook of the area due to elaborate green belt development and better communicational facilities. Besides, the project implementation well augment potable water supply to Chennai city by 100 MLD which can cater to the demand of about 2.5 million population. This achievement will far out way any possible minor impact if any due to the project operations in the area.
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