Final DPR For Tallah Tank
Final DPR For Tallah Tank
Final DPR For Tallah Tank
1.1 Kolkata Metropolitan Area : (i) The historic city of Kolkata is situated in the banks of River Hooghly having perennial source of surface water. than 300 years Kolkata, one of the largest ago, undergone ribbon metropolis of India have, since its founding more
development along the two banks of River Hooghly. It is the main port and has a vast hinterland covering the entire North Eastern region of India, and spreads westwards through Bihar, Orissa, parts of Uttar Pradesh and Madhya Pradesh. (ii) Kolkata is the capital of the state of West Bengal, located on the eastern shore of India. Kolkata metropolitan is also one of largest urban conglomeration of the country with a population of 14.72 million (2001 census) and a density of 7950 persons per Sq. Km. It has spread linearly along the bank of river Hooghly (Ganga). (iii) Kolkata metropolitan area is largely consisting of 3 Municipal Corporations and several urban local bodies within an area of 1851.41 Sq. Km. (iv) The economic growth in the city has evolved with the time with more service sector growth and reducing primary and secondary sector inputs. Primary Sector 1
which was contributing around 77% in 1985-86 has reduced to 56% in 2001-02 with tertiary sector (primarily IT, ITES and BPO industries) grown from 23% to 44% in the same period.
(v)
Kolkata at 88030 Eastern longitudes and 220 33 northern latitude is 120 km from Bay of Bengal and stands on the eastern bank of river Hooghly. The city could primarily be divided into two parts i.e. old historic city in northern portion which is heavily congested and the new city which is better planned in southern part. Slums and dilapidated structures also exist in many pockets of the city proper and house over 25% of the city's population (Census 2001).
(vi)
The weather in the city is quite humid with variation from 50% to 85% and typical temperature variation from 420C to 80C. The rainy season begins in the month of June and lasts up to October bringing in moderately severe rains with an average rainfall of 160.5 cm.
1.2 Water scenario in KolkataMetropolitan Area (KMA) (i) The Kolkata Metropolitan Area (KMA) is primarily been serviced by two sources i.e. (a) Surface water from the perennial river of Hooghly; and (b) Ground water sources. Out of these two sources, the water from river Hooghly is being treated and supplied to a very limited area of KMA through the treatment plants but majority of remaining KMA to depend on the Ground water source. (ii) For the purpose of analysis, the population in KMA could be divided into two parts i.e. municipal areas and non-municipal areas. (iii) The distribution of population and area in both these areas are as follows:
Allocation of land and population in KMA Total Area (Sq. Km.) 964.61 Population* (In Million) 2.35
Non Municipal areas Municipal areas - Kolkata Municipal Corpn - Chandannagore Municipal Corpn - Howrah Municipal Corpn - Other municipal bodies Total * As per census 2001
1.3 Water scenario in Kolkata Municipal Corporation (KMC) Area (iv) In 1848, importance of pure and wholesome water supply to the City was given a top priority through proper legislation : In 1865, work of construction of 6 MGD water works at Palta situated 24 Kms. away from the northern side of Kolkata. Between 1888 to 1893 filtration capacity of Palta was increased from 6 MGD to 20.5 MGD. In 1905 supply was increased to 26.5 MGD by introducing pressure in 42" & 48" dia. C. I. gravity transmission pipe from Palta to Tallah. Between the year 1907 and 1911, capacity of the plant was increased from 26.5 MGD to 37.5 MGD with addition of 4 nos. primary settling tank and construction of few more slow sand filter bed. Between the year 1922 and 1936, generation capacity was increased gradually from 37.5 MGD to 100 MGD. But, in the 1961 it came down to 80 MGD.
From 1870 to 1933, per capita supply increased gradually from 15 gallons to 64 gallons and this was again decreased to 31 gallons in 1951 and only 27 gallons in the year 1961. Again in 1962, expansion scheme of 60 MGD. Was taken up to increase the capacity to 160 MGD. Calcutta Metropolitan Water And Sanitation Authority (CMW&SA) presently known as KMW&SA was formed through enactment on 2.10.1966. It was created with the purpose of maintenance, development and regulation of water supply, sewerage and drainage services etc. for the CMA with a view to promotion of public health and for matters connected therewith. In the field of water supply, KMW&SA has constructed and was operating and maintaining 60 MGD (272 MLD) at Garden Reach Water Works situated at the southern side of Kolkata from where KMC was getting water of 40 MGD. Kolkata Municipal Corporation further taken augmentation of 100 MGD at Palta Water Works in three phases. First phase was commissioned in the year 1997 with 20 MGD capacity and total capacity had gone up to 180 MGD. KMW&SA has further augmented their production capacity at Garden Reach Water Works of 60 MGD in May 2001. Presently KMC is receiving 82 MGD of water from Garden Reach Water Works. In 2nd phase 40 MGD was commissioned in the year 2004 and total capacity gone to 220 MGD. Construction of 40 MGD Plant was completed in the year 2006 and the plant capacity of Palta was further augmented to 260 MGD. KMC has taken over the Garden Reach Water Works from KMWS&SA w.e.f. July, 2011 and presently its operation and maintenance is being carried by KMC. KMC has further strengthen its transmission capacity for carrying treated surface water from Palta to Tallah Reservoir through a project under JnNURM intervention by laying a Dedicated Transmission Main having 64diameter from Palta to Tallah and the same was commissioned on September, 2012. 4
The main is now effective transmitting treated surface water from the Treatment Plant at Palta. Further KMC has planned to refurbish its old 18 MGD Rapid Gravity Filtration Plant, which is lying at dilapidated; in phased manner through ADB financing. KMC augmented two water treatment plants with Headwork at Watgaunj Square having capacity 5 MGD. and at Jorabagan Park having capacity 8 MGD respectivelyand these plants are in operation since Jan, 2006. Due to age-old system of water treatment plant we are not able to achieve 100% efficiency of plant capacity. At present we are getting water at 80 % efficiency. There is also problem in age old transmission mains, which are not capable of carrying required quantity of water, require thorough refurbishment. As water is coming from treatment plant to storage reservoir continuously (24 hours a day), there is no scope to close down the transmission main for refurbishment. K.M.C. is thinking an alternative route for laying a transmission main so that refurbishment can be done by closing the existing transmission mains one by one. After this refurbishment, K.M.C. will develop the water treatment plant for carrying more water in future. 1.4 Need for development of surface water source: (i) Kolkata City is North-South bound. Its water supply arrangement has been provided, by this time, from two sources one at Palta (within Barrackpur district), supplying water to KMC storage station at Tallah which is at the extreme North of Kolkata City. The other filter water supply source was maintained and operated earlier by KMW&SA, a sister organization of KMDA and the same was taken over by KMC since July, 2011, which is at the extreme South end of Kolkata City. North-South City area has already been developed and growth is being observed at the eastern part of Kolkata along E.M. Bye-pass. The eastern portion of Kolkata City is first developing and huge multi-storied buildings are coming up as the prospective growth set back. This area is naturally supplied with individual ground water sources and in a small way by KMC also through deep tubewells.
(ii)
Ground water contents high dissolved solids and salinity. There have some possibility of arsenic contamination in ground water, which is now within desirable limit as per CPHEEO manual. Some tubewells have already been closed in which arsenic content is beyond desirable limit. It is reported that eastern zone of Kolkata city is adjacent to arsenic threatened area like Sonarpur, Baruipur etc. Development of surface water source is urgently required particularly in eastern zone of Kolkata City to avoid extraction of ground water to provide potable surface water and to achieve the objective of sustainable development of quality of life (QOL). The approach should be comprehensive one and development action should be incremental over space and time with a scope of producing proportionate benefits. Therefore, the objective is to provide safe water and adequate sanitation services to specific target population within a specified time frame. With this objective, KMC has taken up construction of Raw Water Intake Jetty at Ma-er Ghat, Bagbazar, Raw Water pipeline and 30 MGD Water Treatment Plant at Dhapa alongwith its distribution system to cater the need of Flittered Water demand of the Eastern fringe of the city.
1.5 Strategic Plan for Water Supply: The objective of development in the sector of water supply is to ensure availability of safe potable water to all. To achieve this basic objective, norms & standard for water supply has been marginally adjusted to utilize the existing facilities to the maximum extent. As a part of this effort KMC is now planned to strengthen its existing installation as well. Notwithstanding to speak that Retrofitting programme of Century old Tallah Elevated Steel Reservoir will enrich KMC to serve the Citizen in a better way. Efforts are to be made to reduce wastage. Special attention need to pay to ensure that quality of water remains within stipulated standards. Due considerations have been given for the economically weaker section and their social habits.
(i)
Kolkata Municipal Corporation (KMC) is the largest Municipal Corporation in West Bengal having an area of 187.54 square kilometers with population of 4.57 million as per 2001 Census.
(ii)
Kolkata City is North-South bound. Its water supply arrangement has been provided, by this time, from two sources one at Palta (within Barrackpore District), supplying water to KMC storage station at Tallah, which is at the extreme North of Kolkata City. The other filter water supply source was earlier maintained and operated by Kolkata Municipal Water & Sanitation Authority (KMW&SA), which is at the extreme South end of Kolkata City. Since, July 2011 this plant is being operated by KMC. The area is naturally supplied with individual ground water sources and in a small way by KMC also through deep tubewells.
(iii)
Beside these two major plants, KMC is also operating two other minor WTPs at Jorabagan on the North-West Part of the city and Wattgaunje on the SouthWest part of the city.
2.2 -BASELINE SURVEY Existing Facilities: (i) Kolkata was earlier covering the City Proper and Jadavpur Unit, South Suburban Unit and Garden Reach Unit spread over 141 Wards and 15 Borough. Recently three (3) wards Joka area has been added to KMC area and now KMC area covers total 144 Wards within the limitation of 15 Boroughs. Tallah-Palta water service district provides filtered water to city proper particularly north, central and part of south Kolkata. Garden Reach water service district covers some parts of City Proper, Jadavpur Unit, S. S. Unit and Garden Reach Unit. The facilities are supplemented by ground water. Presently KMC has 444 nos. big dia. tubewells for providing ground water where surface water source is inadequate. Further Joka area is under developing stage and now mainly feed with ground water source. (ii) Initially filter water was coming from Palta Water Works and Stored at Tallah Pumping Station from where water pumped out for distribution in the city. Due to growth of the city, facility of pumping became inadequate for even distribution of water pressure to the consumer point. KMC has constructed several Headworksto boost up the water pressure in the locality during supply hours. (iii) KMC has successfully commissioned Palta Tallah Dedicated 64 Transmission Main under JnNURM on 22nd September, 2012. (iv) KMC has taken up construction of 30 MGD Water Treatment Plant at Dhapa to provide water to the adjoining area of E.M. Bypass as well as to cover scarcity of Zone of Eastern Fringe of Kolkata City, where potable water is now being provide through Big Dia. Tube Well. Construction work of this project is nearing completion stage. (v) Following Headworks are operated with various zones.
Headwork command Storage capacity zones Direct supply from 44 MG Tallah Station overhead reservoir]
WARD
1 3 4 5 6 7 8 9 10 11 12 15 16 17 18 19 20 21 22 23 24 25 26
95% 80% 100% 100% 100% 90% 100% 100% 100% 100% 100% 100% 95% 90% 100% 90% 75% 75% 70% 60% 40% 60% 60% 100%
27 28 36 37 38 39 40 47 Direct supply from 44 MG Tallah Station overhead reservoir] 48 50 64 65 68 69 70 71 72 73 R.S.M. Sq. 6 MG 46 50 51 52 53 54 55 61 62 63 Pumping [4 semi-UGR and 1 49
100% 100% 80% 80% 100% 100% 100% 100% 100% 100% 30% 20% 10% 100% 100% 50% 30% 30% 30% 100% 70% 100% 100% 100% 100% 100% 100% 100% 100%
10
4 MG
23 41 42 43 44 45
20% 90% 50% 90% 80% 30% 100% 100% 100% 100% 100% 100% 90% 80% 100% 25% 25% 30% 40% 40% 40% 40% 50% 70% 100% 100% 100% 100% 50% 30%
Bagmari
6 MG
13 14 29 30 31 32 33 34 35
Jorabagan Park *
19 20 21 22 23 24 25
42 45 75 76 77 78 79
Park Circus
4 MG 11
58
59 64 65
Ward Ward area coverage 65 67 91 92 106 107 108 10% 100% 70% 5% 5% 15% 5%
12
Garden Reach Water Works Source : Headwork command Storage Capacity zones Direct supply from 18 MG GRWW 74 80 81 89 91 92 93 94 116 117 118 119 127 129 Direct supply from 18 MG GRWW 132 133 134 135 136 137 138 139 140 141 WARD Ward area coverage 50% 30% 90% 70% 10% 60% 80% 70% 30% 60% 40% 40% 20% 10% 30% 80% 80% 80% 70% 70% 30% 25% 25% 25%
Behala
4.5 MG 13
115
90%
116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 Daspara BPS 3 MG 123 124 125 126 Sirity BPS 2 MG 115 116 117 122 Ranikuthi 3.5 MG 95 96 97 98 99 14
20% 20% 40% 35% 75% 80% 70% 75% 5% 20% 70% 50% 100% 60% 100% 100% 50% 10% 70% 40% 10% 50% 30% 15% 15% 70% 100% 60% 100% 100%
100 101 102 110 Bansdroni 2 MG 111 112 113 114 Garfa 3 MG 103 104 105 106 107 92 Kalighat 4 MG 70 71 72 73 74 82 83 84 85 86 87 88 90
90% 40% 40% 10% 90% 90% 90% 75% 95% 90% 75% 60% 10% 20% 100% 80% 100% 90% 20% 60% 100% 100% 100% 100% 100% 100% 80%
15
Some other pockets of scarcity in surface source in different wards are presently supplemented by tube wells and will be covered by surface water either by ongoing construction of Water Treatment Plant and Headwork.
16
Chapter-3 INDIRA GANDHI WATER TREATMENT PLANT (FORMERLY KNOWN AS PALTA WATER WORKS)
3.1 Introduction After a 33 KM drive from Raj Bhavan, Kolkata through Barrackpore Trunk Road, Barrackpore Lat Bagan erstwhile Governors Place and Military area, one will be arriving at lush green Water Treatment Complex of Kolkata Municipal Corporation. A unique of its kind and largest in Asian SubContinent, it covers an area of 482 acres of land with nearly 50,000 trees & vast water bodies, situated along east bank of Hooghly River. Indira Gandhi Water Treatment Plant Complex is pride of Kolkata Municipal Corporation and the excellence of past and present employees involved. Based on hydraulic study, this stretch of Hooghly River course at Palta was selected to have minimum effect of salinity and siltation problems with a ground altitude advantage of 3.1m in respect of Tallah Pumping Station. This water works was started functioning way back in 1868 with a meager 6 MGD capacity. A number of notable British and Indian Engineers and Experts extended strenuous effort and technical expertise for its inception, commissioning and subsequent development to meet increasing demand of potable water. At present this prestigious treatment plant grown up to 260 MGD capacity of filter water. Produced filtered water is conveyed through 6 (Six) trunk mains each of 72,000 ft. long and of different diameter pipes (42, 48, 60, 72, 62"& 64") for the present. KMC has recently commissioned its sixth transmission main by the state of the art technology of Micro tunneling methodology with a view to bridge the gap of treatment facilities at Palta and the existing transmission capacity of the Palta Tallah pipelines.
17
3.2 History of Water Treatment facilities for the City of Joy Kolkata gets its drinking water supply from two major water treatment plants, one in the North, located at Barrackpore, known as Palta Water Works (renamed Indira Gandhi Water Treatment Plant), having installed capacity 260 MGD and one in the South, located at Garden Reach, having installed capacity 120 MGD and two others minor WTP located at Jorabagan having capacity 8MGD &Wattgaunj having capacity 5MGD. Total treatment capacity of all the WTPs combined together is 393 MGD. The British constructed Palta Water Works during the years 1868 to 1870. This was to arrange a reliable and quality water supply system for Kolkata, which was the then Capital of British India. The following were the main reasons behind the selection of the site at Barrackpore, about 27.0 Kilometers up the river Hooghly from the Esplanade, for the establishment of the Water Works : i) Availability of vast land area, gifted by the Barrackpore Cantonment Authority, on the East Bank of the River. ii) iii) Availability of perennial source for raw water, pollution and salinity free. Level advantage, as the Water Works Site was about 3.05 meters above the ground level in Kolkata, particularly at Tallah which allowed filtered water to flow from the Water Works to Kolkata by gravity alone, thus saving energy by avoiding pumping. iv) Security, provided by the Military Cantonment Authority as well as State Police Authority at Barrackpore. 1. Accordingly, during the Vice-Royalty of Lord Mayo, in 1870, Palta Water Works commenced supplying filtered water to Calcutta City with an initial capacity of 6.0 MGD (27,273.0 M3/day). For this a 42"dia Cast Iron Water Main was laid from Palta Water Works to Tallah Pumping Station, along Barrackpore Trunk Road, over a distance of about 69,000 ft. This pipe, still in
18
use, transports about 8.0 MGD (36,364.0 M3/day) of drinking water from Palta to Tallah by gravity alone, utilizing about ten feet fall in level from Barrackpore to Kolkata. 2. Over the years, as the population of Kolkata increased, new Water Treatment Plants were constructed with additional pumping stations and water supply to the city gradually increased. New water conveying pipelines were also laid from Palta to Tallah. 3. The British left the Country leaving 482 Acres (approx.) of land at Palta for water manufacturing purpose. By utilizing this vast land area, Kolkata Municipal Corporation went on increasing the water production capacity as and when it became necessary.
3.3 Treatment Philosophy As things stand at present, four separate water treatment plants, using four different technologies are operating at Palta. These are i) Pre and Final Settling Tanks with a total detention of about 80 hours. Inflow into these settling tanks is from a 100 MGD capacity Clari-flocculators. Settled water to the extent of 93MGD is fed into a series of Slow-Sand-Filter-Beds, while about 18 MGD of clarified water is fed directly into a battery of Rapid Gravity Sand Filter Beds, before the same enters the Settling Tanks. The Settling Tank and Slow Sand Filter System is of Nineteenth Century Vintage. This is No.1 Water Treatment Plant. ii) The conventional Clari-flocculation and Rapid Sand Filtration Process used in the 60 MGD capacity No.2 Water Treatment Plant. iii) The No.3 Water Treatment Plant using the modern Pulsator Technology for Clariflocculation, patented by the French Firm M/s. Ondeo Degremond which utilizes very
19
rapid gravity sand filters of Aquazur V-Filter type. There are three modules having capacity of 20MGD each & hence present capacity of this plant is 60 MGD. iv) The No-4 Water Treatment Plant using the modern Plate settler for Clari-flocculation and the sedimented & clarified water is then passed to false bottom nozzle Filter Beds for next stage of treatment i.e. Filtration. Suspended impurities present in the incoming clarified water are filtered out as the water passes down the layer of sand of Nozzle Filter Beds. The present capacity of this plant is 40 MGD The filtered water produced in each of these four water treatment plants is fed into a long and large underground suction manifold system from which the three nos. large clear water pumping stations draw water and pump the same into five nos. high pressure trunk water mains transporting filtered water from Palta Water Works to Tallah Pumping Station. Each of these three water treatment plants has chlorination arrangement for maintaining a residual chlorine level of 0.5 mg/litre in the filtered water pumped to the city. 3.4 CHRONOLOGICAL PICTURE OF GROWTH:
YEAR 1868-
CAPACITY 06 MGD
PLANT STATUS One Intake Jetty. 02 Nos.24dia C.I. suction pipes to lift the River water. Boiler & Engine House. 06 Nos.Pucca Settling Tanks. 12 Nos. Slow Sand Filter Beds (01 MGD capacity each) One 42dia C.I. Palta- Tallah Gravity Main.
1888-1893
20.5 MGD
One more Intake Jetty (presently known as Old Intake Jetty) Boiler with steam engine driven Pump for Intake Pumping Station Four Kutchha Settling Tanks 24 Slow Sand Filter Beds
20
YEAR
CAPACITY
PLANT STATUS One 48 dia. C.I. Main laid from Palta to Tallah (Gravity Main).
1895-
26.6 MGD
One filtered water pumping station was commissioned & started to pump the filter water under pressure.
1905-1911
37.5 MGD
Chief Engineer Mc. Cabes Scheme: Expansion of Old Intake Jetty. Installation of Pumping Machineries to lift water. 05 nos. (2 MGD capacity each) Slow Sand Filter Beds. Diesel engine supply pumps.
19201922-1936 72 MGD
Augmentation plan to provide continuous supply of 100 MGD has been adopted. Further expansion of Old Intake Jetty. 03 Nos.54 dia. rivetted suction pipes to lift the river water. Steam Turbine driven centrifugal pumps at Raw Water Intake Station (presently known as Intake Station No-1). 17 Nos. 03 MGDcapacity each Slow Sand Filter Beds added. One 02 MGD capacity Slow Sand Filter Bed added. 200 MG capacity storage Final Settling Tank. Steam Turbine driven centrifugal pump at Pressure Station (presently known as Pressure Station No.-1). Extension and connection of 48 Palta-Tallah C.I. main with 84 Manifold at Pressure Station. Re-conversion of 42 C.I. main from pressure to Gravity Main. Laying of a 60 riveted steel pipe, Palta-Tallah Main.
1951-
One battery of 18 MGD capacity Rapid Gravity Sand Filter Bed was 21
CAPACITY
PLANT STATUS commissioned (each of 1.5 MGD capacity of 12nos.R.G.F Beds). Conversion of Steam Turbine to Electrically Driven Motor.
One 72 M.S. Electrically protected Palta-Tallah main laid. A new Jetty was installed with two nos. 60 Steel Suction main. An Intake Station (presently known as Intake Station No-2) with Centrifugal Pump & Electrically Driven Motor. 06 nos.Clari-flocculators (10 MGD capacity each) installed. A battery of 60 MGD Rapid Gravity Sand Filters (02 MGD capacity each) was commissioned. A Pressure Station (presently known as Pressure Station No.-2) with Centrifugal Pump & Electrically Driven Motor.
1975-1984
160 MGD
Filter water was augmented from 144 MGD to 160 MGD by introducing 100 MGD new Clarifier plant by eliminating partially the functions of Kutchha Settling Tanks.
1994-1997
180 MGD
New 20 MGD Pulsating Clarifier Plant with Aquazur V type Rapid Gravity Sand Filter Beds were commissioned in April1997 (i.e. Module No.1)
1997-2004
220 MGD
Module No.2, capacity of 20 MGD, Pulsator type Clarifier Plant with Aquazur-V type Rapid Gravity Sand Filter Bed was commissioned in November 2002. Approx. 1.0 KM inner lining works of the 62 M.S. Palta-Tallah Main along B.T. Road near Panihati has completed in the year 2003 by HDPE pipe. The Intake Station No-3 & Pressure Station No-3 equipped with all equipments & machineries including pipeline connections etc. commissioned in July 2004. Module No.5, capacity of 20 MGD, Pulsator type Clarifier Plant with Aquazur-V type Rapid Gravity Sand Filter Bed was commissioned in July 2004.
22
YEAR
CAPACITY
PLANT STATUS Laying of the remaining portion of the 62M.S. Palta-Tallah Main (with HDPE pipe) has been completed and the entire pipeline is commissioned in July, 2004. Construction of a 33 KV Sub-Station with all its accessories for additional power supply at IGWTP is completed and commissioned in July 2004.
2004-2006
260 MGD
Module No.3 & 4, capacity of 40 MGD, Plate settler type Clarifier Plant with false bottom nozzle type Rapid Gravity Sand Filter Bed was commissioned in Feb 2006.
3.5 RAW WATER INTAKE JETTYS :Sl. Jetty No-1 Suction Pipes (under operation) i) 48dia C.I. Pipe-01 no. ii) 54dia C.I. Pipe-03 nos. Jetty No-2 Jetty No-2 i) 60 M.S. Pipes:-02 nos. i) 72 M.S. Pipes:-03 nos. 1961-1971 2001-2004 Year of Construction 1868-1936
3.6 PALTA- TALLAH TRANSMISSION MAIN:Sl.No. 1. 2. Type of Transmission Main 42" C.I. Gravity Pipeline 48" Main) 3. 60" M.S. Riveted pipeline (Pressure 1922-1936 Main) C.I. Gravity (Subsequently converted to pressure Year of Laying 1868-1870 Pipeline 1888-1922
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4. 5.
72 M.S. Welded pipeline (Pressure 1957-1961 Main) 62" M.S. welded pipeline and HDPE 1971 pipeline (pressure main) Laid from Dunlop to Barrackpore Chiriamore 1997 Laid from Dunlop to Tallah Pumping Station 2004 Barrackpore Chiriamore to I.G.W.T.P. by using 1400mm. HDPE Pipe.
6.
64 MS Tallah Palta Dedicated Laying of the pipeline has started construction from Transmission Main February, 2008 on onwards and successfully Methodology commissioned September12.
involved in laying is Conventional cut & cover, Elevated on pedestal &in majority of alignment by modern Micro-Tunneling at 8 m beneath the finished Road surfaces of congested and ever busy B.T. Road. Raw pipes are directly procured from SAIL, a Govt. of India Undertaking & are being processed by State of the Art Pipe processing Unit built up at the IGWTP Campus.
Year 1870
Qty. 12 nos.
Remarks
In the year 1972, 6 nos. beds were demolished as 1888-1893 24 nos. 1 MGD each to built up the Clarifier No.4, 5 & 6 of 100 MGD Plant. 1905-1911 05 nos. 2 MGD each
24
1920-1936 Rapid Gravity Sand Filter Bed (18 MGD Plant) Rapid Gravity Sand Filter Bed (60 MGD Plant)
1952
1968 1997
2 MGD each 3.33 each 3.33 each 3.33 each 3.33 each MGD MGD MGD MGD
Aquazur "V" type Filter Bed 2002 (60 MGD) 2004 Nozzle type Rapid Gravity 2006 Sand Filter Bed (40 MGD)
3.8.1 ENVIRONMENT: Year of commissioning Area of Palta Water Works Ground altitude advantage Trees Power Consumption 1870 482 acres 3.1 Meter 50,000 nos. (approx) Rs. 3.90 Crores per Month
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Motor Rating
Pump Rating
i) 36dia M.S.Pipe-01 no. 3 nos. 6KV, 630 BHP, 3 nos. 50 head, 2MGH 61A Slip Ring Induction capacity Centrifugal Pump iii) 54dia C.I. Pipe-03 Motor (Make: Mather & (Make: Mather & Platt Platt Ltd) and 1no. 6KV, Ltd.) nos. 582 / 448 KW, 110 / 92 and A Squirrel 1 no.45 head,1.75 Cage MGH capacity Centrifugal Induction Motor (Make: Pump (Make: Worthington) L.S. & Electro-motors Ltd.) i) 60M.S.Pipes:-02 nos. 3 nos. 6KV, 630BHP, 3 nos. 54 head, 2 MGH 61A Slip Ring Induction capacity Centrifugal Pump Motor (Make: Mather & Platt Ltd.) 1no. 35A NGEF) 6KV, 390BHP, Cage to be 1no. 50 head, 1 MGH capacity Centrifugal pump (Make: Jyoti Ltd.) yet to be commissioned. Squirrel yet (Make- Mather & Platt Ltd.)
6 nos. 6KV, 460KW, 6 nos. 50 head, 1.75 MGH 57A BHEL) Squirrel Cage capacity Centrifugal Pump Ltd.) Induction Motor (Make: (Make- Mather & Platt
26
SettlingTanks Primary Settling Tank-1 Primary Settling Tank-2 Primary Settling Tank-3 Primary Settling Tank-4 Final Settling Tank
3.8.4 SLOW SAND FILTER BEDS: 1 MGD capacity bed 2 MGD capacity bed 3 MGD capacity bed Total no. of beds 30 nos 06 nos 17 nos 53 nos
3.8.5 100 MGD PLANT:Clariflocculator: 06 nos. Capacity: 16.66 MGD each. 3.8.6 18 MGD PLANT:12 nos. Rapid Gravity Sand Filter Bed (1.5 MGD capacity each) Average Output:12 MGD (4 nos. of bed are out of operation, major repairing & overhauling work is essential KMC has planned to demolish the entire plant and construct a new 20 MGD Plant utilizing the area).
27
3.8.7 60 MGD WATER TREATMENT PLANT: Clariflocculators: 06 nos. (Capacity-10 MGD each) Rapid Gravity Sand Filter Bed: 32 nos. (2 MGD capacity each) Average Output: 65 MGD 3.8.8 100 MGD MODERN WATER TREATMENT PLANT:Pulsator Clarifiers: - 9 nos. (Capacity 6.6 MGD each) Acquazur-V type Rapid Gravity Sand Filter Bed: - 18 nos. (Capacity -6.6 MGD each) Average Output: - 60MGD (3 nos. of Module are operating with capacity of 20 MGD each) Another 40 MGD capacity Water Treatment Plant (with Plate Settler type Clarifiers- 03 nos. and Rapid Gravity Sand Filter Beds- 12 nos.) is commissioned on 06/02/2006. 3.8.9 FILTER WATER PUMPING STATION:-
Motor Rating 2nos. 6KV, 1120KW, 146A Squirrel cage Induction Motor (Make-L.S. & Electromotors Ltd.) 1no.6KV,1500BHP,138.5A Squirrel cage Induction Motor(Make-Mather & Platt)
Pump Rating 3 nos. 120 Head,1.75 MGH capacity Centrifugal Pump (MakeMather & Platt) 3nos.120Head,2500GPM Capacity Centrifugal Pump (Make-Mather & Platt) 1no.120Head,2 MGH capacity
2nos.6KV,1150BHP,102 A Squirrel cage Induction Motor (Make-Mather & Platt) 1no.6KV,1300BHP,117A Squirrel cage Induction Motor (Make-Mather & Platt) 1no. 6KV, 1343KW,170A Squirrel Cage Induction Motor (Make-Helmke Orbis)
Centrifugal Shanghai)
Pump
(Make-K.S.B.
28
3.9.10 TRANSFORMERS
Sl. No. 1 2 3 4 5 6
Rating 15 MVA, 33 KV / 6.25 KV 500 KVA, 6 KV / 400 Volt 100 KVA, 6 KV / 400 Volt 750 KVA, 6 KV / 400 Volt 250 KVA, 6 KV / 400 Volt 50 KVA, 6 KV / 400 Volt
Location At 33/6 KV Sub-Station. Do At 6 KV Sub-Station. At C.S.R.-II At Pr-1: 3 nos., Int-2: 2 nos., Pr-2: 2 nos., Pr-3: 1 no. At Pr-2.
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Chapter 4 Historical Background of Tallah Tank Tallah tank a common name of the Tallah Overhead 110 ft. high steel tank containing 9 million gallons of water, it is an engineering feat unrivalled in the whole of the world. Designed by Mr. W.B. MacCabe, the then Chief Engineer of the Calcutta Corporation, 1901, the work was done mostly by Indian engineering firms. The massive elevated reservoir next to the Tallah Pumping Station, which is a virtual lake, ushered Calcutta into the world as the biggest metropolis of the East. The images of that reservoir presents are often quite striking. Just the size of it is memorable great unfinished-looking matte-black thing that it is. Motoring by on the Barrackpore Trunk Road, one is apt to see the strobe-like effect produced by the passing column and girder arrangement, and the great rows of symmetry which appear are almost haunting in their impact. The support structure seems very slender and lofty to carry such tremendous weight. The water alone weighs 40,800 metric tons, and the structure itself is 8670 metric tons. The construction of this modern engineering fact was undertaken by, mostly Indian firms. T.C. Mukherjee and Co. was the contractor for the preparation of the foundation. Sir Rajendranath Mukherjees Martin &Co.were the contractor for the concrete foundation. The roof was erected by Arracon& Co. and Babu Kali SunkerMitter. The tank itself was fabricated by Clayton, Son & Co., Leeds. T.C. Mukherjee & Co., the contractors for the preparation of the foundation, did a wonderful job. The site contained several old tanks (hence Tallah or Talao) these were first dewatered, then piled with Sal bullah piles 20 to 25 feet long, and filled in with jhama khoa well rammed, a retaining wall of piling and concrete being constructed to prevent any lateral displacement of the soil beneath the foundations. The whole area was then consolidated by heavy steam-rollers, after which a 9-inch khoa bed was laid down and rolled in, as if a road were being constructed. Upon this bed the foundation proper was laid, consisting of a bed of cement concrete 2 feet 6 inches in thickness, reinforced near its base by flat steel ties, and near its surface by a system of rolled steel joists, upon which the bases of the main columns rest. The water contained in the tank weighs some 40,000 tons and the structure about 8500 tons; including the ferro-concrete foundation, the load on the soil is about 12 cwt. per square foot, which leaves a large margin of safety even in the treacherous soil of Calcutta. The construction work of the majestic overhead reservoir was inaugurated on 18th November, 1909 by the then Lieutenant Governor of Bengal, Sir Edward Baker, when the first column was anchored by him. The overhead tank was commissioned on 16th May, 1911, though completed earlier on 12th January. The steel tank, at the height of 110 feet, is 16 feet deep, 321 feet square and is divided into four compartments, which can be used independently of each other, so that one or more compartments can at any time be thrown out of work for cleaning or repairs, without any interruption to the town supply. The Calcutta Metropolitan Development Authority undertook extensive repairs to this overhead reservoir in 1978-79 by cleaning the bottom, changing the tiles numbering 200, and by welding new
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sheets to the corroded metal sides. The total expenditure on the elevated reservoir at Tallah amounted to about Rs.5 lakhs. The essential function of the overhead reservoir is to enable the pumps at Tallah to be worked at one constant head and speed, instead of being pressed or retarded to conform to the fluctuating demands of the consumer, which varied in 1910 from about 7.5 gallons per head at height to perhaps 75 gallons per head during each hour of maximum demand. The obvious means of overcoming the difficulty was to create a reserve during the hours of minimum demand for use during the period of maximum demand. The necessary degree of elasticity in the method of supply, so as to render it capable of varying automatically with the demand, could only be secured by the force of gravitation which, provided that the system is designed to meet the maximum demand, must automatically adjust to my demand short of the maximum. The overhead tank furnished the solution to the problem. The Tallah Overhead Tank has silenced the critics of Mac Cabe of the fear of earthquakes, cyclones and other disasters that afflict Calcutta. The 1934 earthquake of Bihar and Bengal dispelled the gloomy prophecies of Mac Cabe. The overhead tank and the steel structures have now completed more than 100 years without stopping water supply even for a day to depend upon this single source in these days of aerial attacks and terrorist activities calls for rethinking on the part of the City Fathers. Being a conspicuous object, commanding a very extensive area on account of the open Chitpur Railway yard and absence of skyscrapers in the outskirts of the metropolis, constant vigil is called for. 4.1 TALLAH PUMPING STATION There are four pumping stations at Tallah, having a total installed capacity of more than 25 million gallons per hour. Station No.1 is served by a 8 million gallons capacity underground reservoir receiving water from Palta and is equipped with two 0.625 MGH, one each of 1.50MGH,0.8 MGH & 1.01 MGH capacity pumps driven by electric motors. Station No.2 is served by a 10 million gallons capacity semi-underground reservoir receiving water from Palta and is equipped with three 1.75 MGH and one 1.0 MGH capacity pumps driven by electric motor. Station No.3 is served by a 7 million gallons capacity semi-underground reservoir receiving water from Palta and is equipped with four 1.75 MGH capacity pumps driven by electric motors. Station No.4 is served by a 10 million gallons capacity semi-underground reservoir receiving water from Palta and is equipped with four 1.75 MGH capacity pumps driven by electric motors The 9 million gallons capacity overhead reservoir acts as a hydraulic balancer and helps in maintaining requisite pressure in the mains supplying water to the city. The Tallah Pumping Station has four chlorinators each of 40 lb. per hour capacity. Both Palta Water Works and Tallah Pumping Station have the facilities of alternate power feeder lines to counteract power failure. 31
Tallah elevated reservoir and pumping station were designed to cater to the needs of Calcutta within Shyambazar and Rashbehari Avenue to the exclusion of localities outside Mahratta Ditch or present Upper and Lower Circular Roads, i.e., Cossipur, Chitpur, Maniktala, Tollygunge, Jadavpur, Behala, Garden Reach &Entally. The suburban municipalities of Tollygunge, Jadavpur, Behala and Garden Reach are not served by Tallah Overhead Tank. Even within the Mahratta Ditch itself there are three Booster Stations (with their capacity in brackets in million gallons): 1. Mohammed Ali Park or former Halliday Park (4.0), 2. Raja SubodhMullick Square or former Wellington Square (6.0), 3.Auckland Square (6.0). Recently KMC has constructed one new MS transmission main having 64 inch dia which carries water from its generation point to main storage point at Tallah through micro-tunneling, the latest trenchless technology under the financial assistance of JnNURM. The existing Palta-Tallah 42 cast iron gravity main functioning since 1870, 48 cast iron main carrying 20 million gallons per day, 60 inch steel main under pressure to carry 50 million gallons daily functioning since 1928-29 and 72 inch Main carrying 60 million gallons a day completed in 1964 will not be disturbed. The area in the Tallah Pumping Station was augmented by adding 44 bighas of land in 1964 or so. The 72 Palta-Tallah Main was commissioned by the Late AtulyaGhosh, M.P. and Congress President on 25th April, 1964. This cathodically protected pipeline is the first of its kind in the world (B.K. Dey at the International Conference on Corrosion at Moscow in 1964). The Palta Water Works alone supply Calcutta with 260 million gallons of water a day (add for Municipal Calcutta: - Garden Reach 120 mgd; Watgunge 5 mgd; Jorabagan Park 8 mgd; Garden Reach second unit 15 mgd; and Dhapa Filter Water Source 30 mgd).
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Chapter 5 Need of the Project 5.1 Project Definition, Concept & Scope
Sustainable distribution of received treated surface water from Tallah Pumping Station is essentially required for the survival of the City of Kolkata.In order to transmit water upto the furthest point at a distance of more or less 10 Km, the consistent pressure potential at sending point (Tallah Pumping Station) is achieved by the performance of the Steel Overhead Tank. Out of total 190 MGD water, the four numbers of individual underground reservoirs having total volume 35.0 Million Gallon get the additional buffer of 9.0 Million Gallon by the interconnectivity between pressurized common manifold and the ESR. In the event of sudden & unforeseen power interruption, this ESR provides the breathing time by maintaining a backup supply till the entire system comes under control. Although initially the ESR was in operation to handle the water supply through only one pumping station but in course of time three more pumping stations were incorporated within the system by the help of the solitary ESR. All the individual pumps (16 in total) are also designed in consideration with the static height of the ESR. The entire distribution system may be affected at any sudden failure of the interconnection between the ESR and manifold. Notwithstanding the historic steel ESR has performed and add fragrance to the city distribution system since its inception and over a period of 100 years, consequently its structural stability has deteriorated over the course of time during its service. It is worthwhile to mention that it is an integral component of Tallah Pumping Station. Its essential performance is thus obvious for sustainable water distribution system of the City. In line with the same KMC has planned to strengthen it adopting a retrofitting measure. The estimated cost of the proposed retrofitting project comes in the tune of Rs. 5861.17 Lac. The maintenance of the asset as will be created upon completion will be borne by KMC from its own resource.
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5.2 Feasibility Report on Engineering Critical Assessment of more than 100 Years Old 9.0 MG Overhead Balancing Steel Tank at Tallah, Kolkata 5.2.1 Introduction 5.2.1.1 Tallah Tank A 9.0Million gallon capacities elevated steel tank built in 1907 and commissioned in 1909 in British India water for supply to Kolkata City. This robust tank is situated at northern fringe of Kolkata in the area called Tallah. This tank has already provided uninterrupted service for 104 years and still performing its design intended service. 5.2.1.2 Historical Perspective 5.2.1.2.1 Genesis of Kolkata Water supply Palta Water Treatment Plant 1860 Calcutta, nearly thirty-six people out of every thousand died of Cholera, Kalazar and Malaria. In the ChowringheeArea, where most Europeans lived, there were plenty of reserved ponds and freshwater lakes. The rest of the population, however, lived on stagnant pond water or wells. During the years after the Mutiny, the English started to seriously plan clean drinking water for the city. By 1870, a water treatment plant at Palta and two pumping stations in Tallah and Wellington Square were established, supplying water to predominantly European areas coveringfour hundred odd taps, iron columns with lion heads, supplied water to the rest. 5.3.0 An Engineering Mile Stone 5.3.1 First Biggest Modern Steel Structure in the world The structure of Tallah Tank perhaps is the first biggest on shore modern steel (Low carbon steel) structure constructed on the Earth just at the beginning of the modern steel era. The Titanic steel has similarity with this steel.
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5.3.2 A news for world press The construction and commissioning of large water tank made of modern steel was international news at that time, specially in the American press which described this tank as a great reservoir. Historically, first steel framing structure was built in the city of Chicago in America in 1884. Though many parts of the structure was made of cast and wrought iron and supported partly on granite piers. This structure was a ten storied building with steel frame of 138ft. (42m.) height and the name of the building was Home Insurance Building. Americans were advancing in skeleton steel framing technology at that time and may be for that reason American press highlighted this big Tallah tank structure. 5.3.3 Brief History of Modern Steel & Tallah Tank : Iron has been known since very early days. It was probably first discovered by chance by heating iron ore in charcoal fire. So much was the value of the metal was appreciated that in the middle age most of the forest in Britain was destroyed to make charcoal to smelt iron ore. It was found that the fire burned
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more efficiently when the wind was blowing. This let to the use of a force draft by means of bellows to increase the air supply and produce the iron more rapidly. Such primitive furnaces are the forerunner of the modern blast furnace, the charcoal being replaced by coke, a product of the coal not wood. Iron produced by early primitive methods did not actually become molten and could be forged and shaped by simple hammering. On the other hand molten iron produced by furnaces was hard and brittle since it absorbed 3% to 5% of carbon from the firing medium like coke. These are the fact, which is the part of history and classification of iron product became obvious. On this basis three basic iron product have been classified (i) Cast iron; (ii) Wrought iron (iii) Steel The basic difference chemically of the three is a amount of carbon and other impurities included with the iron, but the mechanical properties are the appreciably different. Steel has been produced for structural purpose since mid 19th century. Although it took 50 to 60 years for it to entirely replace cast and wrought iron. Structural steel quickly replaced wrought iron by the year 1900. Further development of structural steel (low carbon) in manufacturing was made by standard specification developed on the basis of BS-15, 1906 (early British Code) for Standard Specification of Structural Steel for bridges and general building construction. Tallah tank structure was designed in the year 1907 which shows that the structure was made with a steel of Standard Specification BS-15 and may be one of the earliest steel framing construction in the world. In other words, this structure was made one of the earliest standards in the world, and may be regarded as one of the greatest innovation in steel and structural engineering. 5.3.4 Quality of Steel A Historical Evaluation : This steel as explained earlier was manufactured based on BS-15, steel process open earth and the chemical composition are as follows: Carbon (C) = nearly 0.2% Sulphar (S) = 0.06% Phosphorus (P) = upto 0.07% Ultimate tensile strength = 28 to 33 Tons /Sq. inch
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5.3.5 Structural Design A Historical Evaluation 5.3.5.1 Resistance From the above it is revealed that the concept of yield stress was not properly developed. So the designed was made on the basis of fracture strength (ultimate strength) with high factor of safety. In modern working stress design, factor of safety used on the yield stress and in that way high factor of safety on ultimate strength reduced considerably. 5.3.5.2 Load In absence of proper regulation, codes and standards loading cannot be assumed with the fair degree of accuracy and which finally depends upon the engineers involved in design. In early 20th century there are three authorities for engineering guidance in Britain. (i)London County Council (ii)Institute of Structural Engineers (iii)British Standard Institution The first major steps towards controlling the design of steel structure in London area came in 1909. The London County Council Act 1909 says Buildings wherein the load and tresses are transmitted through each storey to the foundation by a skeleton frame work of metal --- required to be considered in design. Before the publication of London Council Act 1909 there were no standard specification for any type of loads specially wind load. Tallah tank drawing and design was completed atleast two years before the date of above LCC Act. On the basis of this historic fact this structure can be declared as a master piece of historic technological innovation in the world.
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5.3.6 History of Construction : This massive elevated water reservoir designed by Mr. W. B. MacCabe, the then Chief Engineer of the Calcutta Corporation, 1901, the work was done mostly by Indian engineering firms. The construction of this modern engineering fact was undertaken by, mostly Indian firms. T. C. Mukherjee and Co. was the contractor for the preparation of the foundation. Sir Rajendranath Mukherjees Martin & Co. was the contractors for the concrete foundation. The roof was erected by Arracon& Co. and Babu Kali SunkerMitter. The tank itself was fabricated by Clayton Son & Co., Leeds. T. C. Mukherjee & Co., the contractors for the preparation of the foundation, did a wonderful job. The site contained several old tanks (hence Tallah or Talao) these were first dewatered, then piled with Sal bullah piles 20 to 25 feet long, and filled in with jhamakhoa well rammed, a retaining wall of piling and concrete being constructed to prevent any lateral displacement of the soil beneath the foundations. The whole area was then consolidated by heavy steamrollers, after which a 9-inch khoa bed was laid down and rolled in, as if a road were being constructed. Upon this bed the foundation proper was laid, consisting of a bed of cement concrete 2feet 6inches in thickness, reinforced near its base by flat steel ties, and near its surface by a system of rolled steel joists, upon which the bases of the main columns rest. The water contained in the tank weighs some 40,000 tons and the structure about 8500 tons; including the ferro-concrete foundation, the load on the soil is about 12 cwt. per sq.ft., which leaves a large margin of safety even in the treacherous soil of Kolkata.
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1. Structure already rendered more than 100years of performance. Its the time for going to a new one by replacing this.
1.
Structure is still performing, its design intended services uninterruptedly since 104 years and still today it is in full service condition. Tallah pumping station today handling filtered water of 200 MG/day for distribution to a vast part of Kolkata by this tank and pumping from other UG reservoir. Any changeof this system require renewal/change of the major part of existing distribution system philosophy and this will be a major task without interrupting the distribution system.
2. Apparent cost of a new balancing OH reservoir (RCC) nearly 2-times in respect to a all out repair-retrofitting cost of this existing structure.
2. Life cycle cost shall be considered and sustainability / durability of steel over concrete structure is always high provided this structure and its material is fit for retrofitting.
3. Steel structure of this type is vulnerable against corrosion if corrosion aspect can be properly addressed, remaining life of the structure can be adequately increased by proper retrofitting design with minimization of risk. 4. Evaluation of material property by NDT (on-site) and DT (Lab) can be done easily with the aid of modern test methodology and technique through which uncertainty can be minimized to a large extent. Material behavior and its property can be evaluated to a great extent. 5. Riveted structure can be made stronger by introduction of advance structural system with advantage of weldability of this steel. Leakage can be mitigated by modern epoxy or polymer base coating technology inside tank. Rivets in critically stressed area can be made redundant by introducing new local structural system with welding to original member.
4. Material (steel) is not produced through a modern process which follows high uncertainty of material properties.
5. Riveted structure is prone to water leakage and rivet of structure cannot be easily changeable. Uncertainty of permanent nature fastener like rivet is very high.
6. In early days the Structural design was done when wind and earthquake load was not properly considered due to lack of proper codes and standard. Can it be made safe under any extreme consequence due to wind and earthquake.
6. If the weldability of the structure can be established, there are wide scope of repair and retrofitting the same by strengthening the structural system as a whole and individual members as well in accordance with present codes and standards.
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5.5.1 Material efficiency Steels high strength-to-weight ratio is exploited in building structures, giving low overall environmental impacts. The other efficient use aspect contains low waste due to accurate design specifications combined with high-quality and durable steel products. 5.5.2 Energy efficiency The usage of operational energy is heavily influenced by the design of the steel structure. By specifying high-quality and property stable products, combined with efficient structural solutions enabled by different steel-based systems, the life-cycle energy consumption can be reduced. Using less energy will result in many sustainability credits. 5.5.3 Recyclability Steel construction enables controlled life-cycle design, including the possibility to design for recycling. The ease of installing a steel structure also shows the ease of designing for simple dismounting, reuse and recycling of the components. Steel is unique as construction material because it can be fully recycled over and over again into new first-rate steel. 5.5.4 Flexibility Steels long-span and high-rise capabilities create flexible spaces that facilitate changes in use during the life of the building. The steel structures long life and remountability enables repeated design for use optimization, saving money and winning sustainability. 5.5.5 Green Repair-Construction No waste generation Waste Minimizing waste is a priority for the construction industry. In steel construction Computer Aided Design (CAD) systems are efficiently integrated with the manufacture, producing high quality steel products to correct and stable
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dimensions, generating almost no wastage on site. Any steel waste is recovered and recycled into new steel.
5.5.6 Durability In general, aging effect of steel is much less than RCC due to its inherent quality to resist environmental action. It is true the steel under exposed condition developed corrosion, but in modern days mitigation of corrosion by proper coating or with electrolytic process (cathodic protection) is easily achievable. Constructional steel can last much longer than any other building material. Thereby, steel products often can be reused as new products. Steel system durability and strength brings safety and long lasting functionality for the intended service, which is an important part of sustainable use of constructions.
5.5.7 Maintenance Maintenance of buildings is vital to achieve longevity. A properly designed steel framing and exposed steel construction products might require regular maintenance, often for aesthetic reasons also. A wide range of advanced and sustainable coatings is available for steel. When used in accordance with recommended maintenance programmes these coatings offer long-term protection, resulting in reduced environmental impact and enhance life. 5.6.0 PRESENT STAUS OF TALLAH TANK 5.6.1 Significance in Water Distribution System Tallah tank is a pivotal part of the whole distribution system of water supply operated from Tallah Pumping Station serving the major portion of Water Supply of Kolkata. The overhead tank not only ensures the continuous static (38m.) head of common manifold of the designed hydraulic network but the huge size (9MG) of it also helps to stabilize the pressure potential of common manifold by acting as a balancing reservoir which regulates the bidirectional hydraulic discharge through its single connective pipeline of 60 inches diameter.
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5.6.2 A Basic flow diagram of the Tallah Pumping Station is given below :
After more than 100 years of service rendered by this distribution large elevated steel structure requires some special engineeringnetwork attention. It is obvious that the structure deteriorated with passing of time which can be identified through a simple overview. The structure is still performing its design intended service till today, but 100 years of exploitation of this huge structure under heavy load of water and high wind load (Kolkata is high wind zone area) shows some deformation, corrosion, vibration etc. The task of today is to verify the present status of the structure to avoid any catastrophes in future. The past and present performance of this structure categorically proved that the structure withstand each and every load action in last 100years and more without reaching any undesirable state of local or global failure.