Final Dpr for Tallah Tank

1

Chapter 1: Executive Summary

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. Kolkata, one of the largest

metropolis of India have, since its founding more

than 300 years ago, undergone ribbon

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

2

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:

3

Table 1.1 Allocation of land and population in KMA

Particulars Total Area (Sq. Km.) Population* (In Million)

Non Municipal areas 964.61 2.35

Municipal areas

- Kolkata Municipal Corpn 197.54 4.57

- Chandannagore Municipal Corpn 22.22 0.16

- Howrah Municipal Corpn 49.99 1.00

- Other municipal bodies 614.67 6.64

Total 1851.41 14.72

* 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.

4

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.

5

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.

6

(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.

7

Chapter 2: Present Status

2.1 Kolkata Municipal Corporation: An Introduction

(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 South-

West part of the city.

8

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.

9

Palta Water Treatment Plant Source:

Headwork command

zones

Storage capacity WARD Ward

area

coverage

1 95%

2 80%

3 100%

4 100%

5 100%

6 90%

7 100%

8 100%

9 100%

10 100%

11 100%

12 100%

Direct supply from

Tallah Pumping

Station

44 MG

[4 semi-UGR and 1

overhead reservoir]

15 95%

16 90%

17 100%

18 90%

19 75%

20 75%

21 70%

22 60%

23 40%

24 60%

25 60%

26 100%

10

27 100%

28 100%

36 80%

37 80%

38 100%

39 100%

40 100%

47 100%

48 100%

49 100%

Direct supply from

Tallah Pumping

Station

44 MG

[4 semi-UGR and 1

overhead reservoir] 50 30%

64 20%

65 10%

68 100%

69 100%

70 50%

71 30%

72 30%

Direct supply from

Auckland Sq.

6.5 MG

73 30%

46 100%

50 70%

51 100%

52 100%

53 100%

54 100%

55 100%

61 100%

62 100%

R.S.M. Sq. 6 MG

63 100%

11

23 20%

41 90%

42 50%

43 90%

44 80%

Md. Ali Park

4 MG

45 30%

13 100%

14 100%

29 100%

30 100%

31 100%

32 100%

33 90%

34 80%

Bagmari 6 MG

35 100%

19 25%

20 25%

21 30%

22 40%

23 40%

24 40%

Jorabagan Park * 3.5 MG

&

8 MGD WTP

25 40%

42 50% Jorabagan Park 3.5 MG &

8 MGD WTP 45 70%

75 100%

76 100%

77 100%

78 100%

Watgunj 2.5 MG

&

5 MGD WTP

79 50%

Park Circus 4 MG 58 30%

12

59 50%

64 70%

65 40%

Headwork command

zones

Storage Capacity Ward Ward

area

coverage

65 10%

67 100%

91 70%

92 5%

106 5%

107 15%

Kasba 3.5 MG

108 5%

13

Garden Reach Water Works Source : Headwork command

zones

Storage Capacity WARD Ward area

coverage

74 50%

80 30%

81 90%

89 70%

91 10%

92 60%

93 80%

94 70%

116 30%

117 60%

118 40%

119 40%

127 20%

Direct supply from

GRWW

18 MG

129 10%

132 30%

133 80%

134 80%

135 80%

136 70%

137 70%

138 30%

139 25%

140 25%

Direct supply from

GRWW

18 MG

141 25%

Behala 4.5 MG 115 90%

14

116 20%

117 20%

118 40%

119 35%

120 75%

121 80%

122 70%

123 75%

124 5%

125 20%

126 70%

127 50%

128 100%

129 60%

130 100%

131 100%

132 50%

123 10%

124 70%

125 40%

Daspara BPS 3 MG

126 10%

115 50%

116 30%

117 15%

Sirity BPS 2 MG

122 15%

95 70%

96 100%

97 60%

98 100%

Ranikuthi 3.5 MG

99 100%

15

100 90%

101 40%

102 40%

110 10%

111 90%

112 90%

113 90%

Bansdroni

2 MG

114 75%

103 95%

104 90%

105 75%

106 60%

107 10%

Garfa

3 MG

92 20%

70 100%

71 80%

72 100%

73 90%

74 20%

82 60%

83 100%

84 100%

85 100%

86 100%

87 100%

88 100%

Kalighat 4 MG

90 80%

16

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 on-

going construction of Water Treatment Plant and Headwork.

17

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 Sub-

Continent, 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.

18

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) Availability of perennial source for raw water, pollution and salinity free.

iii) 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

19

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 Clari-

flocculation, patented by the French Firm M/s. Ondeo Degremond which utilizes very

20

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 CAPACITY 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)

1868-

06 MGD

One 42dia C.I. Palta- Tallah Gravity Main.

One more Intake Jetty (presently known as Old Intake Jetty)

Boiler with steam engine driven Pump for Intake Pumping Station

Four Kutchha Settling Tanks

1888-1893

20.5 MGD

24 Slow Sand Filter Beds

21


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.

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.

1905-1911

37.5 MGD

Diesel engine supply pumps.

1920- 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.

1922-1936

72 MGD

Laying of a 60 riveted steel pipe, Palta-Tallah Main.

1951- One battery of 18 MGD capacity Rapid Gravity Sand Filter Bed was

22


commissioned (each of 1.5 MGD capacity of 12nos.R.G.F Beds).

1954- Conversion of Steam Turbine to Electrically Driven Motor.

1957-1961 84 MGD 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.

1961-1971

144 MGD

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)

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.

1997-2004 220 MGD

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.

23


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. Suction Pipes (under operation) Year of Construction

Jetty No-1

i) 48dia C.I. Pipe-01 no. ii) 54dia C.I. Pipe-03 nos.

1868-1936

Jetty No-2 i) 60 M.S. Pipes:-02 nos. 1961-1971

Jetty No-2 i) 72 M.S. Pipes:-03 nos. 2001-2004

3.6 PALTA- TALLAH TRANSMISSION MAIN:-

Sl.No. Type of Transmission Main Year of Laying

1. 42" C.I. Gravity Pipeline 1868-1870

2. 48" C.I. Gravity Pipeline

(Subsequently converted to pressure

Main)

1888-1922

3. 60" M.S. Riveted pipeline (Pressure

Main)

1922-1936

24

4. 72 M.S. Welded pipeline (Pressure

Main)

1957-1961

5. 62" M.S. welded pipeline and HDPE

pipeline (pressure main)

1971 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

Transmission Main

Laying of the pipeline has started construction from

February, 2008 onwards and successfully

commissioned on September12. Methodology

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.

3.7 CHRONOLOGICAL GROWTH OF FILTER BEDS AT I.G.W.T.P.

Type Year Qty. Capacity Remarks

1870 12 nos. 1 MGD each

1888-1893 24 nos. 1 MGD each

In the year 1972, 6 nos.

beds were demolished as

to built up the Clarifier

No.4, 5 & 6 of 100 MGD

Plant.

Slow Sand Filter Bed

1905-1911 05 nos. 2 MGD each

25

01 no. 2 MGD each 1920-1936

17 nos. 3 MGD each

Rapid Gravity Sand Filter

Bed (18 MGD Plant) 1952 12 nos. 1.5 MGD each

Rapid Gravity Sand Filter

Bed (60 MGD Plant) 1968 32 nos. 2 MGD each

1997 06 nos. 3.33 MGD

each

2002 06 nos. 3.33 MGD

each

Aquazur "V" type Filter Bed

(60 MGD)

2004 06 nos. 3.33 MGD

each

Nozzle type Rapid Gravity

Sand Filter Bed (40 MGD)

2006 12 nos. 3.33 MGD

each

3.8.0INDIRA GANDHI WATER TREATMENT PLANT (PALTA WATER WORKS) AT A GLANCE

3.8.1 ENVIRONMENT:

Year of commissioning 1870

Area of Palta Water Works 482 acres

Ground altitude advantage 3.1 Meter

Trees 50,000 nos. (approx)

Power Consumption Rs. 3.90 Crores per Month

26

3.8.2 RIVER WATER LIFTING STATION :

Name of the Station Suction Pipes Motor Rating Pump Rating

IntakeStationNo.1i) 36dia M.S.Pipe-01 no. ii) 48dia C.I. Pipe-01 no. iii) 54dia C.I. Pipe-03 nos.

3 nos. 6KV, 630 BHP,

61A Slip Ring Induction

Motor (Make: Mather &

Platt Ltd) and 1no. 6KV,

582 / 448 KW, 110 / 92

A Squirrel Cage

Induction Motor (Make:

L.S. & Electro-motors

Ltd.)

3 nos. 50 head, 2MGH capacity Centrifugal Pump

(Make: Mather & Platt

Ltd.)

and 1 no.45 head,1.75 MGH capacity Centrifugal

Pump (Make: Worthington)

Intake Station No.2 i) 60M.S.Pipes:-02 nos. 3 nos. 6KV, 630BHP, 61A Slip Ring Induction

Motor (Make: Mather &

Platt Ltd.)

1no. 6KV, 390BHP,

35A Squirrel Cage


NGEF) yet to be

commissioned.

3 nos. 54 head, 2 MGH capacity Centrifugal Pump

(Make- Mather & Platt

Ltd.)

1no. 50 head, 1 MGH capacity Centrifugal pump

(Make: Jyoti Ltd.) yet to be

commissioned.

Intake Station No.3 i) 72 M.S.Pipes:-03 nos. 6 nos. 6KV, 460KW, 57A Squirrel Cage


BHEL)

6 nos. 50 head, 1.75 MGH capacity Centrifugal Pump

(Make- Mather & Platt

Ltd.)

27

3.8.3 NATURAL SEDIMENTATION:

SettlingTanks Area Capacity

Primary Settling Tank-1 628m79m = 49612 sq. m 18 MG Primary Settling Tank-2 600m79m = 47400 sq. m 18 MG Primary Settling Tank-3 573m108m = 61884 sq. m 24 MG Primary Settling Tank-4 546m108m = 58968 sq. m 24 MG Final Settling Tank 4,45,000 sq. m. 300 MG

3.8.4 SLOW SAND FILTER BEDS:

1 MGD capacity bed 30 nos



Total no. of beds 53 nos

Installed capacity: 93 MGD

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).

28

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:-

Name of the Station Motor Rating Pump Rating

Pressure Station no-1 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)

3 nos. 120 Head,1.75 MGH capacity Centrifugal Pump (Make-

Mather & Platt)

Pressure Station No-2 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)

3nos.120Head,2500GPM Capacity Centrifugal Pump (Make-Mather &

Platt)

1no.120Head,2 MGH capacity Centrifugal Pump (Make-K.S.B.

Shanghai)

Pressure Station No-3 6nos.6KV,875KW,120A Squirrel cage Induction Motor

(Make- L.S. &Electromotors Ltd )

6nos.120Head,1.5 MGH capacity Centrifugal Pump

Make:- KBL

29

3.9.10 TRANSFORMERS

Sl.

No.

Rating Quantity Location

1 15 MVA, 33 KV / 6.25 KV 2 nos. At 33/6 KV Sub-Station.

2 500 KVA, 6 KV / 400 Volt 1 no. Do

3 100 KVA, 6 KV / 400 Volt 1 no. At 6 KV Sub-Station.

4 750 KVA, 6 KV / 400 Volt 2 nos. At C.S.R.-II

5 250 KVA, 6 KV / 400 Volt 8 nos. At Pr-1: 3 nos., Int-2: 2 nos., Pr-2: 2 nos., Pr-3: 1 no.

6 50 KVA, 6 KV / 400 Volt 1 no. At Pr-2.

30

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

31

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.

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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).

33

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.

34

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.

35

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

36

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

Critical Engineering Assessment is under progress

37

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.

38

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 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 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.

39

5.4.0 Replacement vs. Restoration Replacement Restoration

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. How long it can survive and risk of failure in future. 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. Material (steel) is not produced through a modern process which follows high uncertainty of material properties.

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 is prone to water leakage and rivet of structure cannot be easily changeable. Uncertainty of permanent nature fastener like rivet is very high.

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.

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.

40

5.5.0 SUSTAINABILITY & DURABILITY OF STEEL STRUCTURE

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

41

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.

42

5.6.2 A Basic flow diagram of the Tallah Pumping Station is given below :

5.6.2.1 Present Status of The Structure

After more than 100 years of service rendered by this large elevated steel structure requires some special engineering 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.

Other major city distribution network

STILL IN FULL SERVICE CONDITION AFTER 104 YEARS OF PERFORMANCE

9 NO MAJOR DEFORMATION 9 NO LEAKAGE FROM WALL 9 RUNNING IN FULL LOAD CONDITION

43

LEAKAGE OBSERVED FROM BOTTOM OF THE

TANK WHICH CONSEQUENTLY

CORRODING THE MAIN SUPPORTING

STRUCTURAL MEMBERS

NO LEAKAGE OBSERVED FROM THE RIVETTED

STEEL PLATE WALL

44

FULL PERFORMING RIVETTED

COLUMN SPLICE

TANK SUPPORTING PURLIN BEAM WITH TIMBER SLIPPER IN GOOD CONDITION COMPRESSION FLANGE OF PURLIN

IS UNRESTRAINED

COMPRESSION FLANGE

WEAK SUPPORT NO TORSIONAL RESTRAINPROVIDED CONNECTION AT BOTTOM FLANGE ONLY

45

TIMBER SLIPPER DISPLACEMENT DEVELOPED IN MANY AREAS PRODUCING LARGER SPAN OF BOTTOM PLATES AND THUS SOMETIMES LOCALLY UNSAFE WHICH BECOME A SOURCE OF LEAKAGE

IN ABSENCE OF TIMBER SLIPPER THE TANK BOTTOM DEFORMED AND CORRODED HEAVILY AND BECOME STRUCTURALLY UNSAFE AREA

46

RAIN WATER ACCUMULATION AT BASE LEVEL POSING A THREAT OF HIGH CORROSION AT COLUMN BASE.

COLUMN BASES ARE ENCASED BY ORDINARY PLAIN CONCRETE AND PRODUCED MULTIPLE CRACKS ON THE ENCASED CONCRETE

STAGING STRUCTURE IS ROBUST TYPE AND HIGHLY STABLE AND NO SIGNIFICANT DEFORMATION IS FOUND

47

FOUNDATION INSPECTION IS IN PROGRESS AND CORROSION AREA DETECTION & STUDY

48

HIGH LOCAL DEFORMATION AND CORROSION LEADS TO LOCAL FAILURE OF ROOF IN SOME AREA REQIURED IMMIDIATE INTERVENTION

50

TANK WALL & RIVET INSPECTION IS IN PROGRESS

51

IN-SITU METALOGRAPH ON COLUMN

ULTRASONIC TEST ON RIVET IS IN PROGRESS

52

5.7.1 Scope

Structural assessment will be carried out here, as this structure is aging and there might

be a change in resistance due to structural deterioration which is a time-depending

processes like corrosion fatigue etc. Though here in Tallah tank load actions has not

been changed significantly since its inception.

100 years back when modern engineering codes and standard were just about to begin

its journey towards a modern era of engineering, this robust steel structure was design

and constructed by British engineers at that time It is obvious that the original design ,

drawing specification and other document of this structure is rarely available after

passing 100 years or more. So, a high uncertainty is one of the main problem areas of

this assessment work. It is imperative that to get knowledge of this old historic structure

a detailed critical engineering assessment on the basis of the guideline of modern

international standards has to be carried out.

5.7.2 Standards used in assessment work :

Engineering critical assessment of this structure and its reliability analysis has been

carried out by the following international standards and literatures:

(i) ISO:13822

(ii) ISO:2394

(iii) Historical Structural Steel Work Handbook British Constructional Steelwork

Association Ltd.

(iv) Pocket companion useful information tables use of steel manufactured by DORMAN

LONG & CO. Middlesbrough, England 1906

(v) IS:883 1994 : Design of Structural Timber in Building

(vi) IS:805 Code of Practice for use of steel in gravity water tank

(vii) BS:5950 1 Structural Steel Code

(viii) BS:7910 2005 : Flaw detection of structural steel

53

5.7.3 Objective

Structural assessment is a process to determine, how reliable the existing structure is

able to carry current and future load and fulfil its task for a given time period. The first

step of the assessment process is to identify the most significant limit states. Associated

with the limit states are the structural variables to be investigated and with those the

assessment procedure to be applied. Engineering Critical assessment - is a designation

for methods used for the assessment of the acceptability of imperfections. These ECA

methods are also recommended for the assessment of steel railway bridges. Application

of ECA for assessment of crack growth, corrosion, wear and tear and other deterioration

detected during in-service inspection is a well-established practice. In service inspection

is facilitated by the fact that deterioration usually results in well-defined imperfections of

a single type and often localised (e.g. fatigue cracks). This permits application of special

procedures for non-destructive testing, able to give quantitative information on the size

of the imperfections. The deterioration may be monitored during a number of

inspections in order to follow the growth of cracks, the progress of corrosion, etc.

There are two main objectives to conduct assessment of existing structures, the

assurance of structural safety and serviceability and the minimisation of costs

5.7.4 General Procedure of Assessment

Assessment procedure is composed of so many distinct steps to evaluate the actual

condition of the structure. The evaluation and condition assessment of Tallah Tank has

been carried out as per international standard ISO:13822 the basic recommendation of

this code in the form of flow chart is given below :

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7.5 Methodology of Assessment work :

Main task of this assessment is to ensure that the structure and the part of the structure

do not fall under loading. The assessment of this structure is carried out from a very

preliminary level to a higher sophisticated level using modern limit state principles with

characteristic value and partial safety factor. A schematic flow chart for this work has

been given below:

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5.7.6 Preliminary Qualitative Assessment

5.7.6.1 General

Qualitative assessment is an intuitive activity which have been carried out based on experience.

This is a subjective assessment of the deterioration effect and other damage through visual

inspection.

5.7.6.2 The structure :

(a) Configuration : The structure of Tallah tank is a robust nature with a overall tank dimension is

321ft.x 321ft. (96m.x96m) 18ft. (6m.) Height. The staging structure has 49nos. 4-legged trestles,

14nos. 6-legged trestles, 1no. 9-legged trestle and 1no. 7-legged trestle supporting riser pipe. The

height of the staging structure upto the under side of the tank bottom plate is 94ft. (28.67 M.). All

the trestles are braced in between the columns.

(b) Sections : All the section used in this structure are rolled sections like I-section, Channel, angles

and plates.

(c) Connections : original connection in this structure are mostly riveted and in some connections it

is bolted.

(d) Tank : Tank wall and base are built by plates and connected through rivets.

(e) Tank support : Tank is supported directly on wooden planks, rested on the top of joists which is

consequently supported by twin joist.

(f) Tank Roof : Roof of tank is made of precast concrete slab and supported on horizontal beam

framing. The horizontal beam frames supported by internal columns in 6m.x6m grid.

(g) Column Base : The base is gusseted base riveted with column and rested on a grillage

foundation.

(h) Foundation : As per the available drawing and document the foundation is a grillage type

arrangement with encasing by concrete and finally supported on soil, stabilized by sal ballah

piles.

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5.7.6.3 Material :

To ascertain the quality and origin of the material of the whole structure require a in-depth study.

The history of this tank as indicated above depict that this structure came up in a historical

juncture when the world industry just entering into the era of low carbon steel. From visual

inspection it may be concluded that the steel of this structure is neither cast iron nor wrought

iron. However, a detailed on-site and laboratory testing is absolute necessary to ascertain the

exact quality of the steel.

5.7.6.4 Document search :

(a) Original Drawings & Design

(b) Original Schedule and Specification

(c) History of maintenance

(d) History of any accidental or extreme event

(e) Original Construction detail

5.7.6.5 Structural Performance Assessment

Generally this structure is performing satisfactorily till today. It is observed through a

preliminary observation which are as follows :

(i) Assessment of Safety : This structure designed and constructed based on earlier codes, or

designed and constructed in accordance with good construction practice when no codes applied,

may be considered safe to resist actions other than accidental actions (including earthquakes,

survived in 1934 Bihar Earthquake). Following observation have been made through inspection :

Inspection does not reveal any evidence of serious and significant overall damage, distress or deterioration.

The structural system is reviewed, including investigation of critical details and checking them for stress transfer.

The structure has demonstrated satisfactory performance for a sufficiently long period of time for extreme actins due to use and environmental effects to have occurred.

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Predicted deterioration taking into account the present condition and planned maintenance ensures sufficient durability, and

There have been no changes for a sufficiently long period of time that could significantly increases the actions on the structure or affect its durability, and no such changes are

anticipated.

(ii) Assessment of Serviceability :

Structure has performed its intended services since last 104 years without any breakdown even for a single day.

The structure has undergone some deformation in the plate structure of the tank. Leakage in different areas of the tank observed specially in the bottom and corner region. Rivets flaws in the form of distorted head, loosen head and in some cases rivets are

missing.

Some deformations in supporting beam. No major vibration observed.

5.7.6.6 Structural System Evaluation

This structure was built in a time that no proper standards for loads were available, specially the

concept of wind load was generally absent. In this above perspective the following observation

was made regarding the structural system.

i. The whole tank with heavy load of water (4.8m height) is directly supported on the timber

slippers just rested on the supporting steel I-beams/purlins. It reveals that the structure was

designed and conceptualised for transfer of vertical loads only.

ii. In staging structure the trestles were also designed for vertical loads only and the bracing system

provided for reduce the slenderness of the column (I-sections) rather than to take the horizontal

wind and earthquake load. In many cases the bracing members were provided with inadmissible

slenderness ratio.

iii. Due to the above system of bracing response of this member against horizontal load is very

weak.

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iv. In the process the trestles could not perform as a latticed support system and made the column

partially independent to take the high vertical load of water.

v. All the trestles are independently supporting the tank and tank bottom frame structure without

proper portal effect in orthogonal vertical planes.

vi. The tank roof and bottom structure is weak under the huge horizontal wind and seismic load due

to its inherent weakness along the plane.

5.7.6.7 Water Distribution System Assessment

Each of the distribution pipelines, feed from Tallah Pumping Station, have their unique demand

pattern throughout the 24-hr day cycle. The only flywheel of the Tallah water supply

distribution, whose gross quantum varries from 2 MG/Hr. to 16 MG/Hr. throughout the day,

complements the paralleling of the installed pumps. The water discharge through the only

inlet/outlet pipeline ( 60 dia.) of ESR reverses its direction eight to ten times a day, serving its

very purpose of coupling in the network. Rating of the Pumps are purposely synchronised with

the Height of ESR as it remain with distribution network. At present, no major change/upgrading

of the system is urgently required.

5.7.7.1 Qualitative Assessment

Subjective evaluation of corrosion level. The published booklet can be purchased by contacting the Director. National Metallurgical

Laboratory, Jamshedpur-831007 (The Map of India makes the News).

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Corrosion is another word for rust, the breakdown of metal. In a water tank, corrosion is due to

an electrochemical reaction. An electrical current flows through

the water from one point on the water tank's inner surface to

another. The flow of the current results in corrosion of the

tank's surface as some of the metal dissolves into the water. An

ampere of current flow in a water tank over a year's time can

result in 20 to 24 pounds of steel being taken into solution.

A corroding water tank works in the same way as a battery. A battery has an anode and a

cathode. The anode is an area which gives off electrons (negatively charged particles which

make up a current.) The electrons flow from the negatively charged anode (-) to the positively

charged cathode (+). In order to flow from the anode to the cathode, electrons must pass through

what is called a closure circuit or an electrolyte, a substance which forms a bridge between the

anode and cathode.

Visual investigation of rivet, flaws: Inspection and repairs of hot rivets have been done in the following way:

The number of rivets inspected overall in a structure shall be at least of 5%. Heads of driven

rivets shall be visually inspected and shall satisfy the following acceptance criteria:

& The rivet heads shall be centred. The head eccentricity relative to the shank axis shall not exceed 0.15 d0 where d0 is the hole diameter.

& The rivet heads shall be well formed and shall not show cracks or pits,

& The rivets shall be in satisfactory contact with the assembled parts both at the outer surface of the plies and in the hole. No movement or vibration shall be detected when the rivet head is lightly

tapped with a hammer.

& A small well-formed and centred lip may be accepted if only a small number of rivets in the group is concerned.

& Inspection of satisfactory contact shall de done by lightly ringing the rivet head with a hammer of 0.5 kg. The inspection is carried out in a sequential fashion.

Load assessment :

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Main load on the structure is water load lumped at the top which will not undergo any changes in

future. This load is in permanent in nature, but changes with the water level of the tank. Dead

load of the structure consists of the structural members like joists, channels, angles, planks and

roof cladding, this also a permanent load and will change with implementation of retrofitting

measurement recommended in this report.

5.7.7.2 Quantitative Assessment

Checking Of Rivets By Hammer Sounding: It is found from the visual and hammer sounding testing of rivets, flaw detection is very

high more than 40%. This requires more detail testing to ascertain the acceptability limit.

[Refer Annexure 1A]

Ultrasonic Testing Of Rivets: Nearly 10% of the rivets shows defective to Ultrasonic testing by random sampling.

[Refer Annexure 1B]

Ultrasonic Thickness Measurement : Ultrasonic thickness measurement of plate was carried out and found that severe loss of

material in some locations of the plate and members.

[Refer Annexure 2B]

Hardness Test: Hardness of the structural steel is not generally specified in any code. But to attain the

required ductility, the hardness is generally kept below HRb80(150 BHN). We found higher

hardness in many members, which is not obviously the original hardness of the members.

Hardening effect of columns due to cyclic loading for more than 100 years is evident. For firm

conclusion, destructive test on column sample is a must. A correlation can be drawn with the

case of plate where HRb 63 shows lesser elongation. Higher the hardness, lower the ductility.

[Refer Annexure 3A].

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In-situ Metallography: From this test it is observed Microstructure if column indicates initial stage of fatigue

decay, quite natural after working life of more than 100 years.

[Refer Annexure 4].

Physical and Chemical Property Test on Sample in Laboratory: Laboratory test on two samples was carried out which shows the steel is low carbon steel with

acceptable mechanical properties.

[Refer Annexure 5A& 5B].

5.8.0 STRUCTURAL VALIDATION

5.8.1 Simulation of Model

5.8.1.1 ORIGINAL MODEL :

Original model of the Tallah tank structure was made by STAAD Pro V8i with available

dimension from the drawings and site measurement.

[Refer Annexure-6A].

The original model of the steel tank is developed on the basis of following parameters.

A. UNCERTAIN PARAMETER

i. Geometric properties of section

ii. Physical property of steel

iii. No reference of original design calculation

iv. Type of wood and its physical property

v. Foundation system including base detail and exact support condition

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B. DATA AVAILABLE AND SIMULATION

i. Partial details of columns and bracings are available from one number available original

drawing (Drg. No.2, Date:13.08.1907) out of total 9 drawing. Though the drawing information is

not matching with all the member sizes and arrangement found at original structure at site.

ii. Further geometric details are available from as built drawing developed after site survey.

iii. Some section data is available from steel handbook. (Ref: HISTORICAL STEELWORK

HANDBOOK & DORMAN LONG 1906 HANDBOOK)

iv. Physical properties like fy/E/mu-of steel are taken from recent code considering steel

conforming to IS 2062 & IS 800 : 2007.

v. Properties of wood are taken from IS 883 : 1994. (Consider Sal wood)

C. ANALYSIS AND DESIGN

i. For analysis and design of the structure standard software STAAD Pro V8i is followed. The

whole structure is analyzed and designed in two parts i.e. Staging of and Main Tank . The Main

Tank is developed by Finite Element Method. 12m x 12m panel length is taken for representative

corner of the tank.

ii. The Dead Load is calculated for vertical plate and bottom plate as per above data. [Ref: Load

Calculation]

iii. The Live Load (Load duo to Water) is taken for 4.7m (max.) water depth.

iv. In staging model the diagonal bracings are designed as truss member.

v. The support of staging model is taken as pinned support.

vi. The support condition of Main Tank model is taken as spring support system in FE model

with specified Kfy value and Released Mz condition.

vii. The grade modulus(Kfy) of wooden plank is calculated. (Ref. Calculation sheet of Grade

modulus)

viii. The supporting beam (purlin) of tank model is failed.

ix. The diagonal bracing is failed duo to high slenderness.

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5.8.1.2 DETERIORATION MODEL :

The Deterioration Model has been simulated based on the detail investigation and original

model. The basic features of this model are shown in Annexure 6B.

DATA AVAILABLE :

(i) More accurate sectional property is taken.

(Refer Annexure 2A)

(ii) Metal Loss of the structure due to corrosion is taken from statistical analysis of test

results. (UPV Test).

(Refer Annexure 2B)

(iii) Physical properties including actual grade of steel was determined by In-Situ Metallography

Study & laboratory tests on sample. (Refer Annexure 4)

(iii)The thickness of tank plate is taken from UPV test result.

(Refer Annexure 2A)

ANALYSIS AND DESIGN :

For analysis and design of the structure standard software STAAD.Pro V8i is followed. The

whole structure is analyzed and designed in two parts i.e. staging of tank and main tank. The tank

part is developed by Finite Element Method. 12m x 12m panel length is taken for representative

corner of the tank.

The Dead Load is calculated for vertical plate and bottom plate as per above data. (Refer Load

Calculation Sheet)

The Live Load (Load duo to Water) is taken for 4.7m (max.) water depth. (Refer Load

Calculation Sheet)

Wind load is calculated as per IS 875 (Part 3) -1987. (Refer Wind Load Calculation Sheet)

In staging model the diagonal bracings are designed as truss member.

The support of staging model is taken as pinned support.

Support condition for supporting beam (Purlin) is taken as pinned & offset above 487.5mm.

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The support condition of tank model is taken as spring support system with specified Kfy value

and Released Mz condition.

The grade modulus (Kfy) of wooden plank is calculated. (Refer Calculation sheet of Grade

modulus)

The supporting beam (Purlin) of tank is failed .

The diagonal bracing have failed due to high slenderness.

The columns have failed due to loss of metal (Corrosion).

5.8.1.3 RETROFITTING MODEL :

[Refer Annexure 6C]

Based on the deteriorated model and original model, the following observations were made :-

STAGING

Diagonal bracing is not safe due to slenderness of the member

Column is not safe under dead and live load condition

MAIN BEAM

The batten plate joining the two consecutive main girders has ruptured and deformed mainly.

PURLIN

a) Unrestrained condition

The compression flange of purlin beams have been observed to be unrestrained which might

cause lateral buckling. Hence the beams are unsafe.

b) Support condition

The tank is resting on the wooden planks on top of purlin beams. The wooden planks have been

observed to be in severely distressed condition. They have also been displaced from their

original position at many places thereby creating a void in between tank-bottom and purlin

which is highly vulnerable.

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c) Cantilever walkway

The walkway around the tank is a cantilever structure. Visual identification suggests that it had

undergone noticeable deflection at the free end. Apart from that the rivets that connect the

cantilever beam with the main girder are unsafe.

TANK

The members inside the tank are in highly distressed condition and demands immediate

replacement.

The members inside the tank has undergone local failure, and are in serious distress condition

due to high corrosion resulting into loss of metal.

The roof slab has deteriorated considerably along with prominent deflection.

The roof slab which is of R.C.C. has deteriorated considerably. At many portions there is

noticeable vertical deflection.

RETROFITTING TO BE DONE

1.Girder at eaves level for portal action of the tank

Eaves girders are added connecting the trestle top in both the directions for introduction of portal

effect between the trestles to enhance the response of the staging frame system against horizontal

load due to wind and seismic.

2.Stiffened the columns by connecting plates on flanges and web throughout the entire height.

The columns original sections reduced due to loss of metal for corrosion. The columns are

stiffened by adding 10mm thick plates on every face on web and flanges by welding. Thus the

depth of the column increases to 445mm. The thickness of the web and flange increases to 26mm

and 25 mm respectively

3. New members are added in the roof frame.

The existing roof frame has joist 200 as vertical posts. ISMC 200 shall be added on both the

flanges. The roof beams shall have to be removed and ISMB 300 and ISMB 250 to be placed as

main beams and cross beams respectively. ISMC 200 to be placed at 2m C/C to restrain the

compression flange of the main girders

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4. Addition of channel beams between 2 consecutive purlins to restrain the latters compression

flange.

The purlin beams 94m long without any lateral restraint eventually support the wooden planks on

which the tank rests. Unsupported length of compression flange of purlin reduce

Final Dpr for Tallah Tank

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