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Desilting Varthur Lake Detailed Project Report | April, 2018

Report prepared by

sensinglocal


This is a DPR for taking up ‘Stage 1 Desilting at Varthur Lake’. It has been compiled by Sensing Local for Mineral Enterprises Ltd. (MEL) and submitted to Bengaluru Development Authority (BDA), the custodian of the Lake.

3rd April, 2018

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Table of Contents 1. Executive Summary

7

2. Introduction 2.1. Background and Context 2.2. Scope of Work 2.3. Methodology

9 10 11

3. Current Status of Varthur Lake 3.1. Bengaluru’s Network of Lakes 3.2. Varthur Lake

12 13 13 15 16 17 26

3.2.1. Location 3.2.2. Profile of the lake 3.2.3. Current use of the lake 3.2.4. Issues and their causality 3.2.5. Impact on the lake and its surroundings

4. An Action Plan for Revival 4.1. The Vision: A Vibrant Urban Lake 4.2. Strategic Action Plan 4.3. First Action: Desilting 4.3.1. Desilting and its relevance 4.3.2. Phasing of the desilting process

30 32 34 34 34

5. Stage I Desilting: Detailed Plan 5.1. Chosen Method: Dry Dredging 5.2. Quantity and extent of desilting 5.2.1. Factors determining the quantity and extent 5.2.2. Quantification of silt to be removed 5.2.3. Extent of silt removal

5.3. Details of the dredging process 5.3.1. Type of equipment 5.3.2. Identification of access points for equipment 5.3.3. Process

5.4. Silt management and potential use 5.5. Social Awareness & Education

6. Post-desilting Actions 6.1. 6.2. 6.3.

Prevention of Silt Accumulation (installation of silt traps) Design and Construction of wetlands Impact assessment and monitoring

35 36 36 37 38 38 38 39 40 43 44 45 45 46 47

7. Estimation and Costing

48

8. Timeline of activities

49

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9. Supporting actions and stakeholder accountability

50

Annexures

51

• Annexure I: Letter dt. 29.07.17, from BDA permitting MEL to take up Vathur Lake rejuvenation under its CSR Funds

51

NOC for proceeding with DPR Annexure IV: Schematic drawings of the sediment accumulation and proposed desilting Annexure V: Detailed drawings showing silt removal from the lake bed upto 2m Annexure VI: Stacking of sediments, Plan and sections Annexure VII: Comprehensive plan for desilting

55 57 63 69 77

• Annexure II: Stakeholder consultations summary 53 • Annexure III: Letter dt. 26.02.18, from BDA accepting the MEL report submitted and issuing • • • •

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List of Figures Figure 1: Issues faced at Varthur Lake - frothing, garbage dumping, etc.

9

Figure 2: Population growth predicted in wards around Varthur Lake

10

Figure 3: Bangalore’s valley system and network of lakes

12

Figure 4: Koramangala Challaghatta valley lake series

13

Figure 5: Varthur Lake series

14

Figure 6: Lake network directly feeding Varthur Lake

14

Figure 7: Main inlets and outlets of Varthur Lake

15

Figure 8: Harvesting of weeds by locals for livestock

16

Figure 9: Varthur lake water used for irrigation of farmlands

16

Figure 10: Lack of sewerage connection of the area around Varthur Lake

17

Figure 11: Water quality of lakes and location of STPs

18

Figure 12: Extent of weed growth in Vathur Lake - W

20

Figure 13: Weed growth at different points in the Lake

21

Figure 14: Schematic longitudinal section showing the sludge and sediment accumulation in Varthur Lake

22

Figure 15: Historic contours map of the Varthur Lake Bed

23

Figure 16: Contour map showing the current levels of the Varthur Lake Bed

23

Figure 17: Article dt: 31.05.17 about Solid waste burning at Varthur Lake

24

Figure 18: Frothing at the outlets seen at Varthur Lake

25

Figure 19: Mapping of the water level for borewells in 50 & 100m buffer

26

Figure 20: Borewell depth in Varthur Catchment

26

Figure 21: Weed harvesting at Varthur Lake, to be used for cattle feed

27

Figure 22: Number of patients treated per week for skin diseases, gastroenteritis, typhoid and

dengue, in 5 hospitals around Varthur Lake

27

Figure 23: Actions & Agencies responsible for an Integrated Action Plan

31

Figure 24: Dry/ Mechanical Dredging

35

Figure 25: Stacking Plots in and around Varthur Lake

36

Figure 26: Area demarcated for desilting

38

Figure 27: Hydraulic Excavator and Dumper being used to clean a water body

38

Figure 28: Access routes to the stacking plots

39

Figure 29: Construction of channels

40

Figure 30: Creation of compartments

41

Figure 31: Plan with 4 stacks

41

Figure 32: Location of Silt traps

45

Figure 33: Location of wetlands

46

Figure 34: Location of data collection

47

Figure 35: Timeline of activities

49

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List of Tables Table 1: List of lakes in Varthur Lake series and their areas

14

Table 2: Summary of issues at Varthur Lake and their causality

17

Table 3: Quality of water in Varthur Lake

19

Table 4: Quality of slush and sediment in Varthur and Bellandur Lake

19

Table 5: Algal species found in Varthur Lake

21

Table 6: Macrophytes in Varthur Lake

21

Table 7: Volume of Sludge & Sediment

23

Table 8: Actions & Agencies responsible for a Strategic Action Plan

33

Table 9: Details of land available for stacking

37

Table 10: Silt stacking quantity estimation

41

Table 11: Maximum permissible concentrations of potentially toxic elements in soils after

6

application of sewage sludge and maximum annual rates of addition (DoE, 1996)

43

Table 12: Details of the cost of the desilting process

48

Table 13: Supporting actions, status, agency accountable & timeline

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1

Executive Summary

The second largest lake in Bengaluru (180.4 Hectares) - Varthur Lake is today a highly polluted lake, contaminated with domestic sewage, wastewater and industrial effluents through decades of misuse. Experts suggest Varthur lake is in stasis for 2.5 years till interventions are finished at Bellandur. However, it has been established that the lake cannot continue to be ignored till all the external factors are favourable, and it requires immediate protection measures. Mineral Enterprises Ltd. (MEL) had approached Bengaluru Development Authority (BDA) with regard to the Varthur Lake issue and proposed to help out financially, utilising its CSR funds. The lake has not been desilted for the last 40 years, which has resulted in the total accumulation of 4.49 million m3 of both sludge and sediment. Therefore, the ‘First Action’ that is proposed to be taken up by MEL is Part Desilting of Varthur Lake using dredging as a process. This is to lay the base for developing a lake-front in the future through strengthening of the bund, construction of the wetland, lakefront design, etc. Given the high dependency of the lake revival process on the improvement of quality of source water entering the lake, the plan will be strategically divided into two stages, of which the first stage will be taken up immediately by MEL. The primary purpose of desilting in this stage is to prevent the lake from getting worse. Due to constant siltation over the years, the western end of the lake, near the inlet from Bellandur is extremely shallow and highly susceptible to drying out. This also poses issues to the sustenance of the natural wetland on this edge, which has been largely destroyed due to the speedy flow of water and raw sewage.

The total quantity proposed to be desilited is 0.85 million m3, covering almost 258.60 acres of the lake area and a maximum depth of 2m across. This is to take place in the shallow part of the lake (comprising almost 60% of the lake area) ensuring that it is desilted till the historic contour level and further be developed as the constructed wetland. The process for delisting will be through dry dredging, which will be undertaken using a combination of Hydraulic Excavators and High Capacity Dumpers. The process of execution will be as follows:

• • • • •

Construction of diversion channels Creation of compartments to initiate dry dredging, through building a temporary bund Stacking of the silt Treatment of the silt for odour control Managing the weed through distribution to farmers and/or composting

Once stocked, the excavated silt will be re-used or dumped based on its quality. The quality has been classified into the following three types:

• Type 1: High concentration of mixed waste material like plastics, laminates, glass etc. and high toxicity • •

(heavy metals). Will be required to be dumped in landfills. This is proposed to be picked up by BBMP and faciliated by BDA. Type 2: Removed from the top layer (sludge), within safe limits of heavy metal for agricultural use. Will be open for local farmers to collect and use after testing. Type 3: Hardened deeper sediment layer that has some presence of heavy metals. This will be used for the lake-front development, wetland, block making, etc. 25% of the sediment removed can potentially be used for pathway alone.

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As the desilting process will trigger a start of the rejuvenation process of the lake, the team will be engaging with the plethora of stakeholders (local farmers, resident groups, schools, etc.) around throughout the process. The intent is to build awareness among all stakeholders, with regard to on-going actions in the lake and keeping them involved throughout. This is to enable a larger community positively participate in the process and actively be a part of the Lake maintenance in the long run. The total project cost is estimated at INR 24.9 crores, to be taken up by MEL under its CSR Activities. The time to desilt 0.8 million m3 is estimated to span 6-8 months, subject to seasonal weather conditions. Looking back at the 4.49 million m3 of silt accumulated over 45 years, on an average, there has been siltation of approx. 0.1 million m3 per year. As part of Stage 1, the amount of silt being removed is 0.8 million m3, targetted towards construction of a wetland, that will ensure. Therefore, by this estimation, the lake will be back to its current state in just 8 years if the infrastructure to clean the source water and a mechanism to stop illegal dumping is not put in place. As this action sits among multiple actions within the Action Plan for Revival (Chapter 4), it is therefore key that the remaining be taken up in tandem, to ensure the success and sustainability of the ‘First Action’.

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2

Introduction

2.1 Background and Context The issue of Polluted Lakes in Bengaluru is not an unheard story. The rapid urbanization in the city that has outpaced the infrastructure development required to support it. This has led to the death of lakes through either encroachment and/or contamination (industrial effluents, waste and sewage). The second largest lake in Bengaluru - Varthur Lake is today a highly polluted lake contaminated with domestic sewage, wastewater and industrial effluents through decades of misuse (Figure 1). Experts suggest Varthur lake is in stasis for 2.5 years till interventions are finished at Bellandur; the lake upstream and the prime source of water for Varthur. Investigation of current government plans, however suggest it is likely to remain polluted for many more years still. To add to this, the population trends in Bengaluru show (Figure 2) that the Varthur catchment has witnessed a 45% decadal growth rate between 2001-11.

The problem we face today is not just a lack of scientific data to understand extent of the issue, but it is the absence of an integrated plan and the building of consensus among all stakeholders for actions moving forward.

Figure 1: Issues faced at Varthur Lake - Frothing, Garbage dumping, etc.

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Figure 2: Population growth predicted in wards around Varthur Lake (Source: BBMP Restructuring Committee Report, 2015)

Considering the above factors, Mineral Enterprises Ltd. had approached Bengaluru Development Authority (BDA) with regard to the Varthur Lake issue and proposed to help out financially, utilising its CSR funds. A letter permitting the same was issued by BDA on the 29.07.2017 (Annexure I). However post the issue of the letter, there seemed to be a lack of clarity with respect to the actions for rejuvenation and a lack of usable data to assess the same. The latest DPR dates back to 2009, hence not applicable for current assessments. As a result, MEL began its own process of understanding the first action it could take up in the lake. Through several stakeholder meetings with scientists, government officials, community members, other citizen groups (Annexure II), and using the Expert Committee report as a guideline document, the team evaluated and put together a series of ‘First Actions’ as a part of a larger suggestive Action Plan (refer Chapter 4). A report dt:15.02.18 was submitted by MEL to BDA listing the suggestive first actions, in response to which BDA issued an NOC (Annexure III) to take up the same.

2.2 Scope of Work The ‘First Action’ that is proposed to be taken up by MEL is Part Desilting of the Lake using dredging. This is to lay the base for developing a lakefront in the future through strengthening of the bund, construction of the wetland, lakefront design, etc. This report puts together the parameters to determine the scope for desilting the lake and the extent of the work that will be undertaken by MEL through its CSR funds, as listed below:

• • • • •

The current purpose of desilting the lake (considering that raw sewage will continue to enter the lake) Area available for stocking of material (permanent and temporary) Process to be adopted (wet/dry dredging) Extent of funds available from MEL Supporting actions by other stakeholders (funded by govt. bodies, citizen association and other CSR funds) ensuring that the desilting sustains The plan for Stage I desilting of the lake is detailed out in this report. This includes plans and sections showing the extent of dredging, stocking plans, silt usage and disposal, estimation and timeline.

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2.3 Methodology As there already exists a plethora of studies that assess the status of Varthur Lake, the intent was to gather relevant data and build on the same through primary data collection methods, for developing the desilting plan. The methodology followed is as listed below:

• • • • • • •

Secondary research and collation of relevant reports on Varthur Lake by IISc, BDA, BBMP and KLCDA Preliminary site visits and assessments to capture status of the lake Stakeholder interviews to understand the impact of pollution, relevance of actions and past failures Development of an Integrated Action Plan through assessment of the current status and external factors influencing the lake Collation of usable data from the above mentioned reports and govt. agencies to determine silt accumulation. These data sets include water and sediment quality, bathymetric map, current lake bed contours, lake boundary, etc. Creation of a Desilting Plan and subsequent discussion with BDA and KLCDA DPR preparation for the extent of desilting to be taken up by MEL

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3

Current Status of Varthur Lake

3.1 Bengaluru’s Network of Lakes The naturally undulating terrain of Bengaluru city, with its hills and valleys, lends itself perfectly to the development of tanks that impound rainwater, store it for future use and ensure groundwater recharge. To respond to the land locked nature of Bengaluru, most of the water bodies were man made tanks to harvest water for use. These tanks since then have become live ecological systems. The tanks in Bengaluru were designed in cascades from higher to lower elevations; as one tank overflowed, the excess water would flow into the next tank in the cascade. The flow of water is from North to South-east as well North to South-west along the natural gradient of the land. Bengaluru has three main valley systems: Hebbal, Koramangala-Challaghatta and Vrishabhavathi (Figure 3). Varthur Lake lies in the KoramangalaChallaghatta valley, part of one of the three lake series, namely Puttenahalli, Hulimavu and Varthur lake series (Figure 5).

¯

¯

Hebbal Valley

Vrishbhavathi Valley Koramangala Challaghatta Valley

LEGEND LEGEND

LEGEND

BBMP Boundary Boundary BBMP

BBMP Boundary

Lakes & Tanks

Lakes & Tanks

Drains Drains

Drains

Lakes && Tanks Tanks Lakes

Lakes & Tanks

Parks/Green Spaces/Play Spaces/Play Parks/Green Grounds Grounds

Parks/Green Space Grounds

Valley-1 Valley-1

Valley-1

Valley-2 Valley-2

Valley-2

Lakes & Tanks Varthur Lake

Bellandur Lake

Valley-3 Valley-3 Scale Scale 1.5 00 1.5

33

Kilometers Kilometers

Figure 3: Bangalore’s valley system and network of lakes

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Valley-3 Scale 66

0

1.5

3

Kilometers

6


3.2 Varthur Lake 3.2.1. Location Varthur Lake, the second largest lake (Table 1) after Bellandur is part of the Varthur Lake series and the last lake in the Koramangala-Challaghatta valley. The total catchment area of the lake is 279 sq.km with a population of 39.5 lakhs (surveyed in 2011) accounting for a third of Bengaluru (Figure 4).

¯ ¯

¯

Varthur Lake series

Varthur Lake Bellandur Lake

LEGEND

LEGEND

Lakes & Tanks LEGEND Subtype

Puttenahalli Lake Series

Subtype

Lakes & Tanks Subtype

Lakes & Tanks Lakes & Tank

Lakes & Tank

Drains_Valley Lakes & Tank KC VAlley Polygon Drains_Valley

KC VAlley Polygon

KCValley_DEM

KCValley_DEM

Value

Value

KC VAlley Polygon

880.0 KCValley_DEM

Hullimavu Lake Series

Drains_Valley

Value

880.0

823.2

823.2

880.0 766.5

766.5

823.2

Scale 0 Scale 0

Scale

766.5

1

2

Kilometers 1 2

4 4

0

1

2

4

Kilometers

Kilometers

Figure 4: Koramangala Challaghatta valley lake series

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ÂŻ Byappanahalli Lake Doddanekundi Lake Kundalahalli Vibhuthipura Lake Lake Chinnappanahalli Lake Challaghatta Lake Varthur Lake Bellandur Lake

Area (hectares)

Byappanahalli Lake

3.23

Haralur Lake

5.16

Kasavanahalli Lake

8.91

Kaikondahalli Lake

27.09

Doddanakundi Lake

47.08

Vibhuthipura Lake LEGEND Kundalahalli Lake

Kaikondahalli Lake

Agara Lake

Name of the lakes

Lakes & Tanks

Chinnappanahalli Lake

Kasavannahalli Lake

Subtype

Lakes & Tank

10.48 56.8

Agara Lake

24

Bellandur Lake KC VAlley Polygon

361

Drains_Valley

Haralur Lake

30.2

KCValley_DEM

Varthur Lake

Value

180.4

880.0 823.2

Figure 5: Varthur Lake series

Table766.51: List of lakes in Varthur Lake series and their areas Scale 0

1

2

4

Kilometers

Doddanekundi Lake

Munekolala Lake

Sheelavantha kere Thubarahalli Lake

Varthur Lake

Bellandur Lake

Bhoganahalli Lake

Legend Devarabisana Halli Lake

Lakes & Tanks

Tank

Drains

Gunjur Lake

Elevation(m) Value

860.7 810.9

Figure 6: : Lake network directly feeding Varthur Lake

761.3

Scale

0

0.5

1

Kilometers

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3.2.2. Profile of the Lake Varthur extends from Thubarahalli on the east upto Varthur Main road on the west covering an area of 180.4 Hectares (445 Acres). The lake has 3 main inlets, along with 28 minor inlets (Figure 7). The lake receives more than 90% of its water from the Bellandur inlet (Figure 6) and the rest from the other minor inlets. The lake overflows into two major outlets to the west, which then join the Dakshina Pinnakini flowing into Tamil Nadu.

North-west wier

From Thubarahalli

Varthur Lake

South-east wier

From Bellandur Lake From Gunjur village

LEGEND

Figure 7: Main inlets and outlets of Varthur Lake (Source: BDA Revised Masterplan 2031)

Roads Buildings Drains Classification

Other Drain

ÂŻ

Main Drains

Scale

1 cm = 250 m

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3.2.3. Current uses of the Lake The dependence on the lake as a source of water has also undergone tremendous change. Once used extensively for irrigation, fishing, recreation and domestic purposes, today the lake’s value as a community resource has reduced significantly. The few remaining farm lands near the lake depend on the lake directly for irrigation purposes (Figure 9), while the weeds at the periphery are also harvested as fodder for the livestock (Figure 8).

Figure 8: Harvesting of weeds by locals for livestock

Figure 9: Varthur lake water used for irrigation of farmlands

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3.2.4. Issues and their causality As a consequence of unregulated planning and rapid urbanisation of the city, coupled with incomplete sewage infrastructure; the overall lack of maintenance (Figure 10), has led to multiple problems at varthur Lake. These issues include aspects like water pollution, eutrophication, frothing, illegal dumping of waste and industrial effluents as well as flooding in surrounding areas. These continue to have an impact on the natural environment and public health of the citizens around. The main issues and their casualties are detailed out below and a summary of the same is listed in Table 2.

Figure 10: Lack of sewerage connection of the area around Varthur Lake (Source: BBMP Restructuring Committee Report, 2015)

Issue

Causality

Lake water highly polluted, designated as Class E

Source water contamination from untreated sewage and industrial effluents

(Industrial cooling, irrigation and controlled waste disposal)

Reduced Dissolved oxygen

Nutrient rich water in the lake from sewage is a cause for algal and plant growth

Frothing of the Lake & frequent fires

Cause by chemicals and pathogens from the sewage and effluents

Diminishing Lake profile and Settlement of sediments and silt in the lake has reduced it’s depth and lake capacity hence it’s water holding capacity. This coupled with illegal dumping of debris and filling in the lake bed has made it open to encroachments. Lack of fences to regulate use of lake and poor solid waste management Illegal domestic & construction waste dumping at the lake altering the topography and water flow Table 2: Summary of issues at Varthur Lake and their causality

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[A] Poor quality of lake water due to contaminated source water Varthur lake receives over 90% (480-560 MLD) of its water from Bellandur Lake, which also suffers high levels of pollution from the entrance of raw sewage and industrial effluents.1 The lake also receives 60-70 MLD of raw sewage from local drains around Varthur lake. The cause of this is the lack of an complete underground drainage (UGD) systems and Sewage Treatment Plants (STPs) in its catchment, and sporadic instances of industrial effluents being dumped illegally (Figure 11).

LEGEND LEGEND Status of of Lake Lake Status

Status of treatment infrastructure

Healthy Lake Lake Healthy Dry Lake Lake Bed Bed Dry

Partially treated sewage Proposed STPs

Polluted, Drying Drying Polluted,

¯

5 MLD

100 MLD

120 MLD

Heavily Polluted Polluted Heavily

Existing STPs

Drains Drains

Proposed STPs

11

Healthy Lake Dry Lake Bed Polluted, Drying

¯

22

Kilometers Kilometers

10 MLD

Status of Lake

Heavily Polluted Drains Scale 0

0.5

1

2

Kilometers

Varthure Lake

560 MLD

Existing STP 246 MLD

Bellandur Lake

Scale Scale 0.5 00 0.5

LEGEND

Untreated sewage

Bellandur Amanikere STP (proposed)

LEGEND

4.5 MLD

Agara STP (proposed)

LEG

Status of Lake

Status

Healthy Lake Dry Lake Bed Polluted, Drying Heavily Polluted

¯ Figure 11: Water quality of lakes and location of STPs (Source: Status of Lakes – ATREE, 2012; STP – Expert Committee Report, 2016)

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Drains Scale 0

0.5

1

Kilometers

2

¯

Scale 0

0.


The current quality of water has dropped and consistently remains at Class E. The physico-chemical analysis revealed the nutrients, organic and ionic components Varthur Lake receives, that make up the contamination of the lake water (Table 3) and sediment (Table 4). The tests suggest concentrations of heavy metals in both the water and sediment, along with the presence of E-Coli. The contamination of the sediment demonstrates the pollution that has been allowed to enter the lake over the last many years. Parameter

Optimum Range

Varthur Lake S1

S2

S3

Temperature

-

28.1

28.4

28.4

pH

6.5 -8.5

8.9

8.64

8.77

E. Coli (MPN/ 100 ml

<100

887

967

764

Total Plate Count (CFU/ 100 ml)

<5000

12456

14325

10237

Dissolved oxygen (mg/L)

>4

3.01

3.37

3.11

BOD (5-day 20 deg C) (mg/L)

<3

14.25

9.64

10.24

Carbon dioxide (mg/L)

-

52

39

36

Nitrate Nitrogen (mg/L)

0.1

0.2614

0.1964

0.2021

Phosphate Phosphorous (mg/L)

0.2

0.5221

0.3221

0.2966

Lead (mg/L)

0.1

0.7884

0.6541

0.6334

Mercury (mg/L)

0.01

0.325

0.396

0.2301

Table 3: Quality of water in Varthur Lake (Source: KLCDA Report July, 2017) Description

Units

Slush

Sediment

Bulk Density

kg/cum

500

1700

Organic Carbon

%

18

8

Nitrogen

%

3

0.35

Phosphorous

%

2.5

0.28

Cadmium

mg/kg

7

2.4

Cobalt

mg/kg

8

5

Copper

mg/kg

68

30

Iron

mg/kg

20395

13580

Manganese

mg//kg

140

98

Nickel

mg/kg

26

20

Lead

mg/kg

7

6.5

Zinc

mg/kg

106

45

Sodium

mg/kg

2175

2075

Potassium

mg/kg

7750

6025

Calcium

mg/kg

581

608

Magnesium

mg/kg

433

1452

Table 4: : Quality of slush and sediment in Varthur and Bellandur Lake (Source: Bellandur & Varthur Lakes Rejuvenation Blueprint, 2017) Desilting Varthur Lake | Detailed Project Report

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Status of Varthur Lake â&#x20AC;&#x2DC;Varthur lake is the second biggest lake, after Bellandur lake, in Bengaluru city where water quality parameters were monitored during July, 2017. Among the various water quality parameters monitored, at 3 different locations, only the water temperature and pH were within the limits. On the other hand, all the remaining water quality parameters like dissolved oxygen, BOD, CO2 , Nitrate nitrogen, phosphate, phosphorous, Mercury, E coli and TPC were exorbitantly high. Dissolved oxygen was too low, BOD was 5 times higher, carbon-dioxide was extremely high, nitrate concentration was 26 times high, phosphate was 2 times high and heavy metal concentrations were too high. The E. Coli and TPC was also found to be on higher side. It is clear from the above observations that most of the water quality parameters in Varthur lake are not in desirable level. Very low DO coupled with high BOD, CO2 , Nitrate nitrogen, phosphate phosphorus indicate the eutrophic condition of the lake. High E-coli and TPC count strongly indicate that this lake receives large quantities of domestic sewage all along. The concerned authorities are requested to take stringent measures to save the lake from dying.â&#x20AC;&#x2122; Source: LDA Report July 2017

[B] Depleted oxygen levels in the lake due to widespread eutrophication The unregulated flow of both sewage and industrial effluents has lead to nutrient rich water. As a result, there is very widespread eutrophication of the lake, manifesting in the form of extensive algal and macrophyte growth (Figure 5 & 6). Thus, causing oxygen depletion of the lake leading to instances of fish kills and diminished biodiversity.

Figure 12: Extent of weed growth in Vathur Lake - January (Source: Google Earth, 2018)

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Figure 13: Weed growth at different points in the Lake Chlorophyceae

Cyanophyceae

Bacillariophyceae

Euglenophyceae

Chlamydomonas sp. Chlorogonium sp. Scenedesmus sp. Ankistrodermus sp. Chlorella sp

Cylindrospermopsis sp. Arthrospira sp. Microcystis sp. Oscillatoria sp. Anabaena sp. Merismopedia sp. Lyngbya sp.

Gomphonema sp. Cymbella sp. Navicula sp. Pinnularia sp. Nitzschia sp. Synedra sp. Fragillaria sp. Cocconeis sp. Melosira sp.

Phacus sp. Euglena sp. Trachelomonas sp. Lepocinclis sp.

Table 5: Algal species found in Varthur Lake (Source: Assessment of treatment capabilities of Varthur Lake, 2011)

Plant species

Common Name

Typha augustifolia

Cat tail

Colocasia essculanta

Taro

Cyperus haspans

Dwarf papyrus sedge

Alternanthera phyloxiriodes

Alligator weed

Eichhorniacrassipes

Water hyacinth

Lemna gibba

Duckweed

Lemna minor

Lesser duckweed

Pistia stratiotes

Water lettuce

Table 6: Macrophytes at Varthur Lake (Source: Assessment of treatment capabilities of Varthur Lake, 2011)

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[C] Recurring waste dumping and siltation, resulting in diminishing Lake profile and lake capacity Open access to the lake bed and its surroundings has resulted in rampant dumping B of solid waste and construction debris by citizens, BBMP workers and contractors alike. The absence of a proper Solid Waste Management Collection System in the area coupled with incomplete fencing and lack of monitoring of the lake, has led to recurring dumping.1 While shallow areas of the lake being exposed has made it vulnerable to encroachments, the inflow of raw sewage from the inlets is also bringing with it sludge, sediment, solid waste and construction debris. The absence of silt traps has resulted in this getting accumulated in the lake bed, thereby altering its depth and water holding capacity. A The morphometric survey conducted by CES (IISc.) in 2016 (Figure 15 & 16) overlaid over the historic depth, shows that over the past 20 years, the capacity of the lake has dropped from 6.1 Million m3 to a mere 1.6 Million m3 . This has been a result of the constant siltation process, which has reduced the depth from 6m to 2m at the deepest end (Figure 14). Table 7 shows the current sediment accumulation in the lake which totals upto 4.49 Million m3 . LEGEND

ÂŻ 0

0 [A] 200

400

600

800

1,000

Running Lenght (m)

1,200

1,400

1,600

1,800

2,000

2,200

Section A-B

Scale 1 cm = 250 m

2,400

2,600

2,800 [B]

Water Level

-0.5 -1

Existing Existing depth Depth

-1.5 -2

Sludge

Depth (m)

-2.5 -3 -3.5 -4 -4.5 -5

Historic depth Sediment Historic depth

-5.5 -6

Figure 14: Schematic longitudinal section showing the sludge and sediment accumulation in Varthur Lake (Source: Bellandur & Varthur Lake Rejuvenation Blueprint,2017)

1. http://www.newindianexpress.com/cities/bengaluru/2017/may/31/after-froth-its-now-fire-at-bengalurus-varthur-lake-1611109.html)

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Mineral Enterprises Limited


5.5

m

3m m 3.5 4m m 4.5 5m

2.5 2m

1.5m

1m

0.5m

6m

m

5m

0.

1m 0.5m

N

Figure 15: Historic contours of Varthur Lake Bed

0 100 200

(Source: Bellandur & Varthur Lake Rejuvenation Blueprint,2017)

400

2.2

mm .0.0 21 5m 1.2 m 1.55m 2.2 .75m 1

0.7

0m 1.0 .55m m 1.2 m 5 . 1 5m 1.7

5m 0.7

m 0.5

0.0m

0.25m

0.0m

0.25m

5m

2.0

m

5m

Scale is in meters

N 0 100 200

400

Scale is in meters

Figure 16: Current contours of Varthur Lake Bed

N 0 100 200

(Source: Bellandur & Varthur Lake Rejuvenation Blueprint,2017)

400

Scale is in meters

Sl.no.

Description

Quantity

1

Surface area of Lake (hectares)

190.75

2

Current Storage volume (Million Cu.m)

6.1

3

Volume of Slush deposit (Million Cu.m)

0.62

4

Volume of Sediment deposits (Million Cu.m)

3.87

5

Bulk density of sediment (kgs per cu.m)

1700

6

Weight of sediment present in the lake (Million tonne)

6.58

Table 7: Volume of Sludge & Sediment (Source: Bellandur & Varthur Lake Rejuvenation Blueprint,2017) Desilting Varthur Lake | Detailed Project Report

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Figure 17: Article dt: 31.05.17 about Solid waste burning at Varthur Lake (Source: http://www.newindianexpress.com/cities/bengaluru/2017/may/31/after-froth-its-now-fire-atbengalurus-varthurlake-1611109.html) 24

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[D] Frothing in the lake Extensive and toxic frothing in the lake can be predominantly seen at the weirs of the lake (Figure 18). The cause of frothing is attributed by experts to the pollutants in the water and turbance in its flow as it drops from a higher level to a lower one.

Figure 18: Frothing at the outlets seen at Varthur Lake

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3.2.5 Impact on the lake and its surroundings [A] Drop in levels of groundwater The silt accumulation at the lake has led in its reduced capacity and porosity to allow for groundwater recharge. This has further resulted in the fall in water levels in the surrounding borewells and drying up in some cases (Figure 19 & 20). Additionally, the increasing extraction of water from borewells has also affected the same. The Bellandur & Varthur Lake Rejuvenation Blueprint Report (2017) states, â&#x20AC;&#x2DC;Water table has declined to 300 m from 28 m and 400 to 500 m in intensely urbanised area such as Whitefield, etc. over a period of 20 years with the decline in wetlands and green spaces.â&#x20AC;&#x2122;

Figure 19: Mapping of the water level for borewells in 50 & 100m buffer

NUMBER OF BOREWELLS

(Source: Presentation of study by KK English School, 2014)

DEPTH OF BOREWELL

Figure 20: Borewell depth in Varthur Catchment (Source: Presentation of study by KK English School, 2014)

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[B] Threat to public health Impact of toxic water in the lake has had a reach far beyond its boundaries. The groundwater samples from various borewells within a radius of 1km of the lake has been measured to have higher levels of nitrate, traces of heavy metal and biological contamination. Since this water continues to be used for domestic purposes, it has been found to have health impacts like gastroenteritis, typhoid and skin diseases among residents living nearby (Figure 22).1 Weeds growing in the lake (that tend to behave as nutrient absorbers), harvested as fodder for cattle (Figure 21), are also likely contaminating the dairy products produced from these cows. In addition, as suggested in the Expert Committee Report (2016) â&#x20AC;&#x2DC;The high concentration of heavy metals in the lake water translates into very high concentrations of heavy metals in the fish from the lake and also in the crops that are cultivated downstream and consumed in and around Bengaluru.â&#x20AC;&#x2122;

Figure 21: Weed harvesting at Varthur Lake

Figure 22: Number of patients treated per week for skin diseases, gastroenteritis, typhoid and dengue, in 5 hospitals around Varthur Lake (Source: Presentation of study by KK English School, 2014) 1. Varthur Lake Catchment - Borewell mapping & water quality analysis presentaiton on by KK English School student

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[C] Threat to lake ecology The extensive weed growth in the lake due to eutrophication has resulted in the decrease in oxygen levels. This has impacted the ecology of the lake, with multiple instances of fish kills. A newspaper report from 2016 points to how there used to be 30 fish species in the lake and now there are merely two that are struggling to survive.1 This has also further impacted the appearance of a wide variety of bird species and reduced the biodiversity of the lake, adversely affecting the lakeâ&#x20AC;&#x2122;s ecosystem. Ornithologist Ullas Anand says that Varthur Lake had paddy fields all around it, and that this was the lake that recorded the most number of Eurasian Coots here. â&#x20AC;&#x2DC;Our waterbird census from between 1988-1999 indicated 800-900 Eurasian Coots at Varthur Lake - the most number in the city. However, when we surveyed the lake again starting from 2015, these numbers had fallen by 98%.â&#x20AC;&#x2122;2

1. https://timesofindia.indiatimes.com/city/bengaluru/POLLUTION-THREAT-Once-home-to-30-fish-species-Varthur-Lake-has-onlytwo-left/articleshow/54204823.cms 2. http://www.newindianexpress.com/cities/bengaluru/2018/feb/02/is-varthur-lake-a-lost-cause-1767356.html 28

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4

Action Plan for Revival

4.1 The Vision: A Vibrant Urban Lake Delivering a Vibrant Urban Lake is a long term aspiration for Varthur Lake. It is highly dependant on actions that are facilitated by multiple agencies in the city and other external factors. Some of the external factors include the following:

• Catchment area of Varthur is 1/3rd of Bengaluru (i.e. 297 sq.km.), hence it is at the receiving end of all pollution from the Koramangala-Challaghatta Valley

• Varthur lake is reported by experts to be in stasis for 2.5 years till interventions at Bellandur Lake, (source of over 90% of Varthur’s source water) are finished

• Limited UGD coverage & STPs in a rapidly urbanizing area, resulting in raw sewage being let into the •

lake, which is estimated to increase over time Illegal dumping of construction waste and industrial effluents into the lake continue

The addressing of all these aspects in the form of an integrated Action Plan, will ensure the timely revival of the lake. The key actions, data source and the agencies responsible for the same are indicated in Figure 23.

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Mineral Enterprises Limited


Figure 23: Actions & Agencies responsible for an Integrated Action Plan

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D1

Usability of the sediment/Disposal protocol

R1

Expert Committee Report

KK School

BDA - Master Plan

KSPCB

D3

D4

D5

measures for public health)

D2

D3

Borewell water testing (Control

Water quality (for monitoring progress & lake rejuvenation plan)

Sediment quality

D1

D2

2 Treatment/Removal of contaminated water

BDA-KLCDA

1 Dredging: Removal of contaminated sediment

BDA-KLCDA

R2

3

R3

• Who will set this up? • Where would they need to be set up? (time) • Land size requried? (space) • Technology needed to be set up

6

D4

Restructuring drains

Identifying drains legal & illegal

Regulating no. of inlets

BBMP - BWSSB

Fencing & bunding of the lake

Design of the Boundary (access)

BDA-KLCDA

5 Setting up of cleaning infrastructure (STPs, wetlands, UGDs, garbage & silt, traps)

BWSSB - KSPCB

Pollution load assimilation capacity Effectiveness of weeds

Removal of Weeds

4

Effectiveness of lake cleaning efforts to be dependent on quality of source water over time

BDA-KLCDA

Cleaning of Lake

CLEAN LAKE

7

R4

D5

Protocols for polluters permissible limits

Identifying polluters and what is the nature of pollution

Stopping pollution (Industrial and domestic sources)

KSPCB

Cleaning Source Water

8

Monitoring water quality (Sensors)

KSPCB

R

D

Research

Data sources

Live monitoring (Sensors)

KSPCB

9

Maintaining Clean Lake

Pubic Space enhancement (bund creation, jogging track, park, etc) Economic-Ecological Ecosystem: Farmers, Fisheries, Pottery

VIBRANT URBAN LAKE


4.2 Strategic Action Plan Based on several consultations with experts, government officials, citizen bodies and locals, an action plan was developed. From these actions, one of them has been selected as a ‘First Action’ to be taken up by MEL based on the relevance and importance of the same. The 3 Phases of the Action Plan are described below and the respective actions are listed in Table 8. While the subsequent ‘First Action’ has been detailed out in this report. PHASE I - PROTECTION Defining the Lake boundary, increasing the depth and controlling the no. of access points. Protection of the Lake so that external factors like encroachment, dumping of waste, etc. do not occur. This phase will ensure a safe zone to initiate the revival effort. PHASE II - STRATEGY Detailed Action Plans & Vehicle for Implementation The over dependence on external factors and multiple agencies, apart from the high financial burden, demands a ‘Tactical and Integrated Strategy’ for its revival. PHASE III - REVIVAL & REJUVENATION Making Varthur Lake a thriving ecosystem & community resource. This process can start only after the source water is clean.

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Mineral Enterprises Limited


Sl.No. Action

Status

Phase I: Protecting the lake in order to then initiate its unhindered revival 1

Removal of Encroachments

Ongoing, BDA

2

Completion of Fencing and Entrance Gates

Ongoing, BDA

3

Restoration of damaged waste weir & sluice gates

Ongoing, BDA

4

Assessment & reporting of non-compliant Apartments & STPs

To be taken up, KSPCB

5

Desilting (Stage I)

Action by MEL

6

Installation of Silt Traps

Ongoing, Whitefield Rising (CSR funds)

7

Bund strengthening & lake bed edge (incl. stone pitching)

To be taken up

8

Wetland design & construction

To be taken up

9

Water quality monitoring

To be taken up, KSPCB

10

Security (Homeguards & Prahari Vigilance Vehicles) to monitor illegal dumping

To be taken up, BBMP

11

Maintenance (Cleaning of Silt Traps)

To be taken up, BBMP

Phase II: Developing a Tactical & Integrated Strategy 12

Setting up of SPV

13

Assessment studies & reports

Commissioned via SPV

Social integration (weed harvesting as cattle feed, water for irrigation, recreation etc.) Environment & Health Impact Integrated Water Management 14

KC Valley Action Plan

To be taken up, KLCDA

15

Detailed Project Report for Revival and Rejuvenation of Varthur Lake

Commissioned via SPV

Phase III: Revival and Rejuvenation of Varthur Lake 16

Completion of UGD and setting up of STPs to treat water coming into the lake

17

Desilting (Stage II)

18

Lakefront and Island development

19

Activating the Lakefront

20

Setting up a Water Treatment Plant

To be taken up, BWSSB

Table 8: Actions & Agencies responsible for a Strategic Action Plan

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4.3 First Action: Desilting 4.3.1. Desilting and its relevance Desilting is a process of digging or excavation of the lake bed to remove accumulated silt. While normally desilting in lakes is undertaken to increase their storage capacity, in the case of varthur, the necessity for desilting arises from the need to address the following issues:

• Groundwater recharge

Recharging of groundwater resources in the vicinity, which has fallen from 28m to 300-500m 1 • Augmenting storage Increase the storage capacity • Removal of toxic sediments Due to sustained inflow of sewage and effluents, lake sediments are contaminated • Potential to create finance for lake rejuvenation ‘Value of the accumulated silt ranges from INR 658 crores (sand) to INR 822 crore moulded to bricks)’ 1

4.3.2. Phasing of the desilting process Given the high dependency of the lake desilting process on the external factor of source water quality (a key determinant of silt deposition in the lake) and further, the reliance of improvement of source water itself on coordinated actions between multiple agencies for infrastructure development expected to take up to 2.5 years. To make the desilting process effective and sustainable, the desilting plan has been strategically divided into two stages, of which the first stage will be taken up by MEL.

• Stage 1 - Immediate (Phase 1 - Protecting the lake in order to then initiate its unhindered revival)

The first stage is to be taken up immediately. The primary purpose of desilting in this stage is to prevent the lake from getting worse. Due to constant siltation over the years, the eastern end of the lake, near the Bellandur inlet is extremely shallow and highly susceptible to drying out. This also poses issues to the sustenance of the natural wetland on this edge, which has been largely destroyed due to the speedy flow of water and raw sewage. Therefore, this stage is to focus on desilting a majority of the shallow end, in an attempt to redefine the lake bed boundary and revive the wetland. The available land near the lake for stacking has been used to calculate the quantum of desilting that can take place in the first phase.

• Stage 2 - After STP construction (Phase 3 - Revival and Rejuvenation of Varthur Lake)

The second stage will be taken up only after the quality of water entering the lake will improve, ensuring a considerable reduction in siltation. The objective of this phase is to remove all the silt (sediment and sludge) in the lake and prepare it to receive clean water and increase its holding capacity.

The next section details out Stage 1 of the desilting plan, as the activity to be taken up under MEL’s CSR funds.

1. Bellandur & Varthur Lake Rejuvenation Blueprint, 2017

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Mineral Enterprises Limited


5

Stage I Desilting: Detailed Plan

5.1. Chosen Method: Dry Dredging As the lake bed is relatively shallow due to over 45 years of silt accumulation, making it unsuitable for deployment of wet Dredgers, dry/mechanical dredging process has been considered as the preferred method. In addition, it has also been evaluated that wet dredging would substantially stir up the waters, thereby muddying the lake waters with the sediment below. Dry dredging would thereby be a better, economical, and efficient option for desilting of Varthur Lake. Dry/mechanical dredging is the use of heavy (often stationary) equipment to extract debris and materials from the bottom of a body of water (Figure 24). Mechanical dredging sometimes, but not always, involves the draining of the water body. The advantages of mechanical dredging are listed below:

• • • • • •

Used at the shoreline or working off of a barge Uses any construction excavator or bucket dredger Better for larger objects, can remove debris Rugged and capable of removing hard packed materials Efficient for disposal at long haul distances. More economical than wet dredging

Dry dredging being the preferred method in the process of desilting, the optimum time for the same is in the summer months, when the water in the lake is relatively less, thus exposing extremely shallow portions of the lake bed. As a result, the pumping out of water is estimated to be much lesser. If it were to be carried out post monsoon, these areas will be submerged and would restrict the desilting activity.

Figure 24: Dry/ Mechanical dredging

Image source: http://wdbach.com/wp-content/uploads/2011/06/dredging-bigpic.jpg http://www.focusondrainage.com/index.cfm?pge=prod&prod_id=4267&glb_id=1&contest_id=1 Desilting Varthur Lake | Detailed Project Report

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5.2. Quantity and extent of desilting 5.2.1.Factors determining the quantity and extent The quantity and extent of desilting in Stage I is determined by the following factors:

â&#x20AC;˘ Finances available (INR 22-25 crores)

The financial resources required for this activity will play a role in the extent of silt to be removed, as it is determined by the CSR amount that MEL is ready to put into desilting.

â&#x20AC;˘ Availability of land for stacking in the vicinity (34.69 Acres)

The silt that is extracted from the lake needs to be temporarily stocked before it is transported to the potential user or to the landfill. The availability of land for the purpose of stacking, governs the quantity that can be removed from the lake.

The land for stacking has been made available after negotiation with the landowners in the vicinity of Varthur Lake. There are 4 land clusters made available on the south side of the lake, alongside and within the boundary (Figure 25). The ownership of land varies from private developers, farmers and government for the land within the lake bed. The details of the land parcels for stacking are listed in Table 9.

Stacking Plots

Minor Irrigation Pipeline

Minor Irrigation Pipeline Stacking Plot 2

Sy no. 299

Sy no.16 Sy no.15 (part)

Sy no. 300

Sy no. 301

Stack 1

Sy no.13

Sy no.22 Sy no.21 Sy no.20 Sy no.18

Stocking Plot 1

Stack 2

Stack 3

Stack 4 N

0 100 200

400

Scale is in meters

Figure 25: Stacking Plots in and around Varthur Lake

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Mineral Enterprises Limited


Stack number

Survey number

Stack 1

299

Land area (sq.m)

Land owner

12,277 Farmers

Facilitating Agency Whitefield Rising

301

9,066 Farmers

Whitefield Rising

303

8,538 Farmers

Whitefield Rising

Stack 2

Stacking plot 1

Stack 3

13

6,842 Farmers

Whitefield Rising

15 (part)

7,785 Farmers

Whitefield Rising

7,699 Farmers

Whitefield Rising

16 Stack 4

BDA

18

17,306 Mantri developers

Whitefield Rising

20

5,716 Mantri developers

Whitefield Rising

21

4,861 Mantri developers

Whitefield Rising

22 (part) Stacking plot 2 TOTAL AREA

43,681 BDA

10,807 Mantri developers 5,839 BDA

Whitefield Rising BDA

140,417 sq.m (34.69 Acres)

Table 9: Details of land parcels available for stacking

5.2.2. Quantification of silt to be removed The stacking of silt on the land available is proposed to be between 20m-30m high (height determined by the land shape), to ensure it is within safe limits (refer Annexure VI). Based on this, the total quantity of silt that can be stored and therefore extracted from the lake is calculated as shown below: Area of land available for stacking = 34.69 Acres Volume of sediment that can be stocked on this land as per safe limits (i.e. 20m to 30m) = 1.1 million m3 Therefore, Volume of sediment that can be removed from the lake (assuming a reduction of 25%) = 0.85 million m3

Desilting Varthur Lake | Detailed Project Report

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5.2.3. Extent of silt removal Based on the above volume, the area available for silt removal was taken starting from the shallow end towards the deep end. The maximum depth to be dredged is taken to be 2m below the current levels of the lake bed such that at least 50% of the lake area is being desilted. It is to be noted that the boundary from the shallow end (western side) has been taken from the pipeline road currently been put by the Minor Irrigation Department, instead of the lake boundary. The identified area of 258.6 Acres is demarcated in Figure 26, and detailed plan and sections of the same are given in Annexure IV & V.

Outlets

Minor Irrigation Pipeline

Inlets nt of Exte

ging

Dred

Lake boundary LEGEND Lake Boundary De-Silting Boundary

N

Irrigation Pipeline 0

Figure 26 : Area demarcated for desilting

100

200

400

Scale is in meters

5.3. Details of the dredging process

LEGEND

5.3.1. Type of equipment

Actual_Lake Main Drains

Dry Dredging is proposed to be undertaken using combination of Hydraulic Excavators and High capacity Other Drains dumpers capable of working in waterlogged conditions (Figure 27).

ÂŻ

Figure 27 : Hydraulic Excavator and Dumper being used to clean a water body

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Mineral Enterprises Limited

Scale 1 cm = 250 m


Two-sets of machines as a combination of Hydraulic Excavator and Dumpers will be deployed for the simultaneous construction of the northern and southern channels and subsequently to undertake dredging in compartments. The number of machines to be deployed has been determined on the basis of several parameters including availability of working area, quantity of silt to be excavated, pace of handling desired, lead distance for disposal, and availability of dumping areas.

5.3.2. Identification of access points for equipment Two main roads have been identified to access the lake and the parcels of land available for stacking and silt disposal. Additionally, an access road will be created using the lake sediment along the southern edge of the lake bed. This will subsequently be converted to the lake front. These are shown in Figure 28.

LEGEND

Access netw

Access poin

HAL Old Airport Road

Stacking plo

N 0

100

200

Scale is in meters

ad in Ro

r Ma

u Varth

Minor Irrigation Pipeline

Temporary access road

Idgha Road

Balagere Road

LEGEND Access network Access point

Figure 28 : Access routes to the stacking plots

Stacking plots

N 0

100

200

400

Scale is in meters

Desilting Varthur Lake | Detailed Project Report

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5.3.3. Process The process of desilting is given below and the Comprehensive plan is enclosed in Annexure VII.

[A] Construction of channels Varthur Lake currently has a continuous flow of non-potable contaminated water from Bellandur lake at its west end along with effluents and sewage waters flowing in through multiple inlet drains on the northern and southern sides. This inflow cannot be blocked and needs to be channelised during the course of desilting operations as it is necessary to consider the needs of local farmers who utilize the waters of the lake for farming, horticulture, and floriculture activities in areas adjacent to Varthur Lake. Keeping this in mind, in the desilting process new channels are proposed to be excavated alongside the northern and southern banks of the lake to divert the inflows towards the deeper holding area of the lake towards the east (Figure 29). It is planned that this exercise is to be carried out after assessing the maximum estimated quantum of flow of the water from Bellandur lake and from the inlet drains on the northern and southern sides of the lake. The depth of each channel shall be determined based on the estimated volume of these inflows.

Minor Irrigation Pipeline

Outlets

Inlets

ting

Desil

Diversion channels

Lake boundary LEGEND Lake Boundary De-Silting Boundary

N

Irrigation Pipeline 0

100

200

400

Scale is in meters

Figure 29 : Construction of channels

LEGEND Actual_Lake Main Drains

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Mineral Enterprises Limited

ÂŻ

Other Drains

Scale 1 cm = 250 m


[B] Creation of compartments Silt excavated from the lake shall be used to erect a temporary bund running across the width of the lake to demarcate a part or whole of the area proposed to be desilted in each phase (Figure 30). Lake waters lying upstream of such temporary bund shall then be drained out by being guided or pumped into the channels or into the holding area of the lake.

Outlets

Minor Irrigation Pipeline

Inlets

orary Temp bund

g

dgin

f Dre

nt o Exte

Lake boundary

Compartments

LEGEND Lake Boundary De-Silting Boundary

N

Irrigation Pipeline 0

100

200

400

Scale is in meters

Figure 30 : Creation of compartments

Once majority of the lake water is drained out of the area proposed to be dredged, this area would become LEGEND suitable for undertaking dry dredging operations. Actual_Lake

[C] Stacking of the silt

Main Drains

ÂŻ

Other Drains The excavated silt is proposed to be dumped in the identified areas surrounding the lake in 4 stacks (Figure 31). Each stack will go up to a maximum of 30m height, which is within the safe limits. The volume of silt Scale that can be stacked in each of these piles is done as 3D calculations using1 Datamine. Details of the same cm = 250 m are shown in Table 10.

Stacks number

Area of the stacking Maximum height plot (m2) of stack (m)

Volume of the stack (m3)

Tonnage * (tonnes)

Stack no. 1

29881

20 185,426

333,766.80

Stack no. 2

43681

30 596,286

1,073,314.80

Stack no. 3

22326

20 111,882

201,387.60

44529

20 290,248

Stack no. 4 TOTAL

140417

1,183,842

522,446.40 2,130,915.60

*assuming bulk density @ 1.8 tonnes/m3 Table 10: Silt stacking quantity estimation

Desilting Varthur Lake | Detailed Project Report

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Minor Irrigation Pipeline

0m

20m

10m

Stack 1

0m 10m

30m

20m 10m 0m

20m 10m 0m

LEGEND

20m

Stack 2

Lake Boundary

Stack 3

Stack 4

Irrigation Pipeline

0

100

200

Dimensions are in meters

Figure 31: Plan showing 4 Stacks Figure 31: Plan showing 4 Stacks

in 4 stacks (Figure 31). Each stack will go up to a maximum of 30m height, which is within the limits. volume silt that be stocked in each ofare these is done The safe plan and viewsThe of each stack of is attached in can Annexure VI. All parcels of land to bepiles used only for as 3D calculations using Datamine. Details of the same are shown in Table 10. temporary stacking. The plan and views of each stack is attached in Annexure VI. All parcels of land are to be [D] Odour control used only for temporary stacking. In order to tackle the odour (if any), an odour control solution mist will be sprayed on the surface of the silt pile as soon as it is stacked by the dumper. The quantity and frequency will be evaluated once a testing is [D] control doneOdour on the silt from the lake bed, prior to initiation of the dredging process.

In order to tackle the odour (if any), an odour control solution mist will be sprayed on the surface of the silt pile as soon as it is stacked by the dumper. The quantity and frequency [E] Weed management will be evaluated once a testing is done on the silt from the lakebed, prior to initiation of the dredging process. Removal of the weeds is to take place during the silt excavation. All the weeds once extracted are to be stacked on one single available site. While some weeds may be taken by the farmers as fodder for livestock, the remaining are to be cut and composted on site for 40 days, after which this will be available to be used as manure by local farmers.

[E] Weed management

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Mineral Enterprises Limited

400


5.4. Silt management and potential use The excavated silt is proposed to be dumped temporarily in the designated areas (as identified previously) and is proposed to be re-used based on its quality. The quality of the silt is estimated to vary over the lake bed based on the following conditions • solid waste mixed with it • if its highly toxic at points close to inlets or contaminated by high amounts of industrial effluents • the top surface being more sludge • bottom part, perhaps being harder with varying degree of contamination. Therefore, it is proposed that once removed, representative samples will be tested area-wise to assess the use of the sediment. The usage based on the quality is listed below: Type 1: High concentration of mixed waste material like plastics, laminates, glass etc. and high toxicity (heavy metals) To be mostly found around the lake periphery; highly toxic and therefore cannot be put to any use. This material will have to be dumped in the closest BBMP landfill. Therefore, permissions for the same need to be facilitated by BDA and KLCDA. Type 2: Removed from the top layer (sludge), within safe limits of heavy metal for agricultural use The top loose layer (sludge) is known to be high in nutrients and can potentially be used for farming. However, this will be considered only if the heavy metal content is within the limits (refer table 11). Post testing and clearance from the Agriculture department (to be facilitated by BDA and KLCDA), this silt will be open for local farmers to take it to their respective farmlands, using their own transportation. Type 3: Hardened deeper sediment layer that has some presence of heavy metals The silt in the lower layers (below the sludge) is estimated to be much harder sediment that is more compact and can be used for construction. It is therefore proposed that this be used for the following purposes:

• Permanent filling of 10.79 acres at Stack-1, which could be potentially developed as a tree park. This area can be stacked up to an average height of 1.5m and therefore can take in almost 0.065 million m3 of sediment.

Table 11: Maximum permissible concentrations of potentially toxic elements in soils after application of sewage sludge and maximum annual rates of addition (DoE, 1996)1 Desilting Varthur Lake | Detailed Project Report

43


â&#x20AC;˘ For bund construction along 6560m of the shoreline. For this, considering a trapezoidal fill in with the top â&#x20AC;˘ â&#x20AC;˘

width of 20m, depth of 1m, slope of 370 and bottom width 21.3m; a total quantity of 0.135 million m3 of sediment can be used. Wetland construction based on the design that will be proposed. On site block making using mining dust and fly ash as a composition based on the material strength of the sediment.

5.5. Social Awareness & Education The lake has historically been a very important resource for the local farming communities and was maintained by the same. However, in recent times, with urbanization in the region, this inter-dependency has drastically reduced. The remaining farming communities still continue to rely on the lake for water supply, harvesting weeds for cattle fodder. The schools nearby too have been engaging with the lake in some instances to educate children around water quality. However, the poor water quality and public space around has discouraged engagement by the larger residents. The desilting process now triggers a start of the rejuvenation process of the lake. Therefore, engaging with the plethora of stakeholders around to educate them with regard to the on-going actions in the lake. While, keeping them involved throughout, also opens up the opportunity to have this larger community positively participate in the process and actively be a part of its maintenance in the long run.

1. Sources and Impacts of Past, Current and Future

44

Mineral Enterprises Limited


6

Post-desilting Actions

The lake was desilted last in 19701, so 45 years or so hence, the current silt accumulation in the lake is 4 Million m3. This means on an average, there has been siltation of approx. 88,900 m3 per year. As part of Stage 1, the amount of silt being removed is 800,000 m3. Therefore, by this estimation, the lake will be back to its current state in just 9 years if the infrastructure to clean the source water and a mechanism to stop illegal dumping is not put in place. While STPs are built upstream and around the lake to remove sewage by the next 2.5 years, and fencing is complete, the immediate measures to be put in place include silt traps at the inlets, a wetland at the lake along with frequent and vigilant monitoring of the lake to stop illegal dumping.

6.1. Prevention of Silt Accumulation (installation of silt traps) During and post-dredging, there are control measures required to prevent further siltation of the lake to make the desilting process effective. To address this, silt traps at major inlets should be constructed. A silt trap is like a shallow trench, where runoff from drains/inlets/channels is allowed to accumulate. When runoff reaches the silt trap, it is slowed down which enables 1) settlement of sediment (silt) so it doesnâ&#x20AC;&#x2122;t accumulate in the lake 2) trap pollutants attached to the sediment and not get discharged into the lake.2 The sediment that accumulates in the silt trap is to be dug out frequently for efficient functioning of the silt traps. This helps maintain the lake capacity and reduce the long term cost of maintenance of the lake. Moreover, if the quality of silt is desirable, it can be regularly harvested for different purposes. The lifespan of a sediment trap depends on the frequency of sediment removal. Currently three silt traps have been proposed at Varthur Lake, by Whitefield rising. One of which is already installed and two locations are to be decided. Based on inlets bringing in the maximum inflow, two more locations have been identified for installation of silt traps and are indicated in Figure 32.

Installed silt traps Proposed silt traps

Figure 32 : Location of silt traps 1. https://timesofindia.indiatimes.com/city/bengaluru/no-desilting-after-1970-varthur-lake-bears-the-brunt-of-solid-waste/articleshow/56033212.cms 2. http://www.fwagsw.org.uk/files/7814/5346/3682/Silt_Trap_Information_Sheet.pdf

LEGEND DesiltingActual_Lake Varthur Lake | Detailed Project Report Main Drains

45


6.2. Design and Construction of wetlands Since the source water entering the lake will be untreated for the next few years, there is a need to take measures within the lake, to improve the quality of water. As the current wetland of the lake has been destroyed due to various factors like the turbulent flow of water, high concentration of sewage, etc., the desilting process lays an opportunity to re-construct the wetland to augment the water quality. A wetland is a complex assemblage of water, substrate, plant litter, invertebrates and an array of microorganisms. The mechanisms that are available to improve water quality are therefore numerous and often interrelated. Therefore, the size and design of the wetland needs to be evaluated in accordance with the quality of water entering the lake, the desired quality of lake water and the area available in the lake for wetland construction. This can be assessed post the dredging process and therefore designed according to the above mentioned factors. The suggested area indicated in Figure 33.

Minor Irrigation Pipeline

Inlets

Outlets

ng

i redg

D nt of Exte Bund

Lake boundary

LEGEND Lake Boundary De-Silting Boundary

N

Irrigation Pipeline 0

100

200

400

Scale is in meters

Figure 33 : Location of wetland

LEGEND Actual_Lake Main Drains

ÂŻ 46

Mineral Enterprises Limited

Other Drains

Scale 1 cm = 250 m


6.3 Impact assessment and monitoring Prior to initiating the dredging process, the following aspects will be measured:

• Water quality of the lake, irrigation and ground water (Figure 34) • Bathymetric map of identified lake bed area, which is to be dredged

"

!

On completion of the work, another testing at the same locations and a map of the dredged area will be developed for comparison and impact assessment. Additionally post the installation of silt traps and the wetland construction, testing of the water quality will be required on a monthly basis. Other aspects of monitoring include the provision of security guards and Praharis to ensure that there are no occurrences of illegal dumping in the lake. !"

"

^

"

"

"

! " ^

^ " # ^ !"

"

^ ^ "

!

"

" ^

^"

"

!!

" " ^

^"

"

LEGEND

^ " # ^

!

!!

^

Sediment Collection Points (6)

!

Ground Water Collection Points (5)

#

Irrigation Water Collection Points (1)

"

¯

Lake Water Collection Points (11) Actual_Lake

Scale

1 cm = 250 m

LEGEND Figure 34 : Locations for data collection

^

Sediment Collection Points (6)

!

Ground Water Collection Points (5)

#

Irrigation Water Collection Points (1)

"

¯

Lake Water Collection Points (11) Actual_Lake

Desilting Varthur Lake | Detailed Project Report

Scale

1 cm = 250 m

47


7

Estimation and Costing

The total project cost for Stage I Desilting is estimated at INR 249,793,172.00 and will be taken up by Mineral Enterprises Ltd. under its CSR funds. The details of the cost of desiliting is in Table 12.

Sl. No. Item of work

Quantity

Unit

1

Site surveying

2

Water quality testing

3

Sediment testing

4

Flow measurements

5

5

Dredging

6

Odour control

7

Site rental for stocking

Acres 2,200.00

569,800.00

34

Samples 4,000.00

136,000.00

7

Samples 3,000.00

21,000.00

858,799 1,545,838 90,897

Table 12: Details of the cost of the desilting process

Mineral Enterprises Limited

Cost

259

TOTAL

48

Unit rate

inlets 40,000.00 cubic m 200.00 tonne 44.00 square m 100.00

200,000.00 171,759,800.00 68,016,872.00 9,089,700.00 249,793,172.00


2017

Dec

Jan ‘18

Apr

Submission of Concept Report - 'First Action(s)' by MEL

2/18

Permission to initiate desilting

M2

DPR submission to BDA

4/18

M1

M3

Wetland Þlling as per design

Lake bund strengthening and Þlling as per design

Installation of Silt Traps

2/18 Meeting with KLCDA & other stakeholders

Mar

2/18 Meeting with BDA

Feb

De-silting Lake bund and wetland design

Site preparation (access road, channel & bund construction)

Site Survey

Water and sediment quality assessment

Review and permissions

DPR preparation & internal review

Base Data collection for creation of DPR

Preliminary Site Survey

Secondary Research & Meetings

M4

M5

2018 Completion of Work

M6

Crucial meetings & Sumissions

Post-desilting Actions

Desilting process

8 Timeline of activities

Figure 34 : Timeline of activities

Desilting Varthur Lake | Detailed Project Report

49


9

Supporting actions and stakeholder accountability

The effectiveness of the â&#x20AC;&#x2DC;first actionâ&#x20AC;&#x2122; of de-silting in the lake, is conditional upon the fulfillment of the following complementary actions. Listed in table below (Table 13) are the actionable items, agencies incharge and estimated timeline for their completion. Sl.No. Action

Status

Agency Accountable

Timeline

Activities related to Desilting 1

Signing of MoU (BDA, KLCDA, MEL, Revenue Dept.)

To be taken up

KLCDA

2

Facilitation of land for stacking

To be taken up

Whitefield Rising / Varthur Rising

Land usage rights to be confirmed prior to dredging

3

Community engagement

To be taken up

Whitefield Rising / Varthur Rising

Continuous through the process of the project

4

Disposal of toxic silt (mixed with waste) at landfill

To be taken up

BBMP

To be picked up same day that it is dumped

Other supporting actions 5

Completion of Fencing and Entrance Gates

Ongoing

BDA

To be carried out by before initiating desilting

6

Restoration of damaged waste weir & sluice gates

Ongoing

BDA

To be carried out by before initiating desilting

7

Assessment & reporting of To be taken up, KSPCB non-compliant KSPCB Apartments & STPs

Pior to completion of de-silting

8

Installation of Silt Traps

Ongoing

Whitefield Rising / Varthur Rising

Parallel to de-silting activity

9

Water quality monitoring

To be taken up

KSPCB

Post desilting

10

Security (Homeguards & To be taken up Prahari Vigilance Vehicles) to monitor illegal dumping

BBMP

Prior to de-silting

11

Maintenance (Cleaning of Silt Traps)

BBMP

Post de-silting

Ongoing

Table 13: Supporting actions, status, agency accountable & timeline

50

Mineral Enterprises Limited


Annexures REVIVAL OF VARTHUR LAKE: PROPOSED FIRST ACTIONS

Annexure I - Letter dt. 29.07.17, from BDA permitting MEL to take up Vathur

Annexure I: Permission letter from BDA to MEL to initiate work at Lake rejuvenation under its CSR Funds Varthur Lake

NIKITA BALIGA

12

Desilting Varthur Lake | Detailed Project Report

51


REVIVAL OF VARTHUR LAKE: PROPOSED FIRST ACTIONS

NIKITA BALIGA

52

Mineral Enterprises Limited

13


REVIVAL OF VARTHUR LAKE: PROPOSED FIRST ACTIONS

Annexure II: List of stakeholder meetings and key outcomes

Annexure II - Stakeholder consultations summary Stakeholders

Issue & Causality

Government authorities BDA

Mr. Veda Murthy, Only by 2020 Total Mr. Nagaraj sewage of 480 MLD will be cleaned, till then no action will solve the pollution problem at Varthur Lake KCLDA Seema Garg Finances for this treatment process is the biggest hurdle

Actions taken

Actions suggested

11/20 STPs have been set up, 3 are being step up

Deweeding to be carried out.

on-going satellite mapping with ISRO EMPRI helped in preparing an atlas of all lakes in the city

Consult a Limnologist before do the deweeding Meet Dr. Bela Zutshi, head of Zoology wing Integrated water management plan is required Building underground sewage pipelines for all buildings in the catchment area

Ramprasad Primary sources of pollutants is Domestic sewage Dangerous gases are trapped in the lake bed STPs isnâ&#x20AC;&#x2122;t suitable for immediate consumption Transfer of water to Kolar leave only seasonal rainwater and the 50 MLD of untreated sewage to flow Lack of finances for UGD BWSSB B.V. Satish Lack of finances for Bellandur-Amanikere STP construction of STPs. completed by Jan 2018 STPs are not a profitable venture.

Experts

ATREE Sharachandra STP technology has not Hydrological data for Lele changed in 70 years and Bellandur lake the standards don't look for many of the chemicals

Carry out an investigation about concentration of heavy metals at Varthur lake and tracing it in the food chain Flow analysis for Varthur Lake and a complete hydrological understanding RO plants for better water quality Start Small, Start upstream NIKITA 14 Report Desilting Varthur LakeBALIGA | Detailed Project

53


REVIVAL OF VARTHUR LAKE: PROPOSED FIRST ACTIONS

Stakeholders

Issue & Causality

Julong (De-weeding machine) Mr.Hans Machine extracts only floating water hyacinth, not to remove the grass. De Scalene (research institute) Raja Vijaykumar Primary reason identified for the foaming was that the natural balance of lake is off Due to pesticides going in the food and medicines we eat, there are many chemicals that enter into sewage Phosphine trapped in the bottom of the lake is also the cause of fire in the lakes. FEM (Water testing) Samuel Heavy metals like Rajkumar Chromium found in the lake.

Local Community

Whitefield Rising Ambika Sen Varthur used to be 30-35 ft deep but now it is 6-8ft

Jagadish Reddy Lake has deteriorated in the past 8-12 years Natural methods of Weeding were adopted earlier, where the weeds were allowed to flow out of the lake.

54

Mineral Enterprises Limited

Actions taken

Actions suggested

4 month research work, Bellandur needs to run like simulated the lake a company, in order for it to environment in the lab be sustained and discovered that this foam in Varthur is a stabilised foam. Seegehalli lake was cleaned up by De scalene

Research conducted in the lakes of Hebbal, Vathur, Bellandur & Peenya for Chromium

Inventure School has set up a water lab, which was initially guided by Ecoparadigm

Whitefield Rising has initiated the installation of silt traps at the inlets Engineered wetlands at inlets, preferable to STPs Aqua Pure has developed a micro system for cleaning water Meshing needs to be done after de-weeding to contain the macrophytes growth

NIKITA BALIGA

15


Annexure III - Letter dt. 26.02.18, from BDA accepting the MEL report submitted and issuing NOC for proceeding with DPR

Desilting Varthur Lake | Detailed Project Report

55


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Mineral Enterprises Limited


Annexure IV - Schematic drawings of the sediment accumulation and proposed desilting

The historic and existing contour map and 4 key schematic sections across the lake showing the proposed desilting level are provided here:

• • • •

Drawing no. 1 - Schematic Longitudinal Cross Section AA’ Drawing no. 2 - Schematic Transverse Cross Section BB’ Drawing no. 3 - Schematic Transverse Cross Section CC’ Drawing no. 4 - Schematic Transverse Cross Section DD’

Desilting Varthur Lake | Detailed Project Report

57


4m m 4.5 5m

3.5

1.5m

0.5m

1m

Desilting Level

Water level

Depth (m)

-6.5

-6

-5.5

-5

-4.5

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

0

200

400

600

800

1,000

1,200

5.5

m

N

Silt to be removed

A’

400

2,000

Scale is in meters

0 100 200

6m

Running lenght (m) 1,400 1,600 1,800

Schematic Longitudinal Cross Section at AA’

A

2.5

m

m 3m

5m

0.

2,200

2,400

A

0.0m

2,600

2,800

3,000

Lake Boundary

Historic depth

Existing depth

0.25m

Lake Boundary

m

Plan-Existing Contours (2016)

0.5

Plan-Historic Contours

2m

1m

Mineral Enterprises Limited

0.5m

58 2.0

m

400 Scale is in meters

0 100 200

5m m 1.0 5m 1.2 m 1.5 m 5 1.7

0.7

A’

Drawn by: Naveen Kumar GT

Title: Schematic Longitudinal Cross Section at AA’

Date: 21-03-2018

Drawing No: 01

Project name: Desilting Varthur Lake - Detailed Project Report

Client: Bengaluru Development Authority (BDA)

N

2.2

5m


B 4m m 4.5 5m

3.5

1.5m

1m

Desilting Level

Water level

-6

-5.5

-5

-4.5

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

0

100

200

300

5.5

m

N

6m

400

600

Scale is in meters

0 100 200

B’ Runing Length (m) 400 500

Schematic Transverse Cross Section at BB’

0.5m

5m

0.

2.5

m

m 3m

700

800

Lake Boundary

Plan-Existing Contours (2016)

Historic depth

Silt to be removed

Existing depth

0.25m

Lake Boundary

Depth (m)

2.0

m

400 Scale is in meters

0 100 200

5m

B m 1.0 5m 1.2 m 1.5 m 5 1.7

0.7

Drawn by: Naveen Kumar GT

Title: Schematic Transverse Cross Section at BB’

Date: 21-03-2018

Drawing No: 02

Project name: Desilting Varthur Lake - Detailed Project Report

Client: Bengaluru Development Authority (BDA)

N

2.2

B’

0.5

m 0.0m

Plan-Historic Contours

2m

1m

0.5m

Desilting Varthur Lake | Detailed Project Report

59

5m


3.5

1.5m

1m

Desilting Level

Water level

-6

-5.5

-5

-4.5

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

0

50

100

150

200

5.5

m

N

450

500

400

Scale is in meters

0 100 200

6m

Running Length (m) 300 350 400

Silt to be removed

250

Schematic Transverse Cross Section at CC’

0.5m

C

2.5

m

m 3m

5m

0. 4m m 4.5 5m

C’

550

600

650

Lake Boundary

Historic depth

Existing depth

C

2.0

m

N

5m

400 Scale is in meters

0 100 200

2.2

Drawn by: Naveen Kumar GT

Title: Schematic Transverse Cross Section at CC’

Date: 21-03-2018

Drawing No: 03

Project name: Desilting Varthur Lake - Detailed Project Report

Client: Bengaluru Development Authority (BDA)

0.7

5m

Plan-Existing Contours (2016)

0.25m

Lake Boundary

Depth (m)

m 1.0 m 5 1.2 m 1.5 m 5 1.7

C’

0.5

m 0.0m

Plan-Historic Contours

2m

1m

Mineral Enterprises Limited

0.5m

60


m

4m m 4.5 5m

3.5

2.5

m

1m

D

0.5m

Desilting Level

Water level

-6

-5.5

-5

-4.5

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

0

50

100

150

200

250

5.5

m

N 400

Silt to be removed

450

Scale is in meters

0 100 200

6m

Running Lenght (m) 300 350 400

Schematic Transverse Cross Section at DD’

3m

5m

0.

500

550

600

Lake Boundary

650

D 0.25m

Historic depth

Existing depth

m

Plan-Existing Contours (2016)

0.0m

Lake Boundary

Depth (m)

0.5

D’

Plan-Historic Contours

1.5m

D’

2m

1m

0.5m

Desilting Varthur Lake | Detailed Project Report

61

2.0

m

400 Scale is in meters

0 100 200

5m m 1.0 m 5 1.2 m 1.5 m 5 1.7

0.7

Drawn by: Naveen Kumar GT

Title: Schematic Transverse Section at DD’

Date: 21-03-2018

Drawing No: 04

Project name: Desilting Varthur Lake - Detailed Project Report

Client: Bengaluru Development Authority (BDA)

N

2.2

5m


62

Mineral Enterprises Limited


Annexure V - Detailed drawings showing silt removal from the lake bed upto 2m

Annexure V contains the following list of drawings: • Drawing no. 1 - Desilting Plan With Historic Contours • Drawing no. 2 - Desilting Plan With Existing Contours • Drawing no. 3 - Transverse Cross Section AA’ • Drawing no. 4 - Transverse Cross Section BB’

Desilting Varthur Lake | Detailed Project Report

63


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Mineral Enterprises Limited


Desilting area

258.60 Acres

Volume of silt to be removed

0.85 million m3

Maximum depth of desiltig

2 meter

N

B

5m

A 4.5

4m

5m

m 3.5

3m

m 1.5m

1m

2m

0.5m

0.5m

B'

A'

1m

Desinting boundary

00 -11 ' CH -AA tion Sec

2.5

'

m

00

-BB

tion

-17

CH

Sec

Irrigation pipeline

5.5

m

0.

6m

Lake Boundary

Client: Bengaluru Development Authority (BDA) Project name: Desilting Varthur Lake - Detailed Project Report Title: Desilting Plan with Historic Contours Scale: 0

100

Date: 22/03/2018

300 All dimensions are in meters Drawing No: 01

Surveyor & Drawn By: Keshavamurthy. R & Naveen Kumar G T

Desilting Varthur Lake | Detailed Project Report

65


Desilting area

258.60 Acres

Volume of silt to be removed

0.85 million m3

Maximum depth of desiltig

2 meter

N

B 2.0

m

2.2

5m

Lake Boundary

1.7

5m 1.2

m

1.0

5m m 0.5

0.7

B'

0.25m

'

-BB

0.0m

00

-17

tion

Sec

00 -11 ' CH -AA tion Sec

Desinting boundary

CH

5m

A

Irrigation pipeline

A'

Client: Bengaluru Development Authority (BDA) Project name: Desilting Varthur Lake - Detailed Project Report Title: Desilting Plan with Existing Contours Scale: 0

100

Date: 22/03/2018

300 All dimensions are in meters Drawing No: 01

Surveyor & Drawn By: Keshavamurthy. R & Naveen Kumar G T

Desilting Varthur Lake | Detailed Project Report

66


Section AA' 0 -1 -2 -3 -4 -5 -6

0 -1 -2 -3 -4 -5 -6

Section A3-A3' 0 -1 -2 -3 -4 -5 -6

Depth (m)

0 -1 -2 -3 -4 -5 -6

Depth (m)

0 -1 -2 -3 -4 -5 -6

Section A2 - A2' Depth (m)

Section A1 -A1' 270.00 m

601.25 m

0 -1 -2 -3 -4 -5 -6

Depth (m)

0 -1 -2 -3 -4 -5 -6

0 -1 -2 -3 -4 -5 -6

Depth (m)

Section A1-A1'

50.0 m

Section A2-A2' 0 -1 -2 -3 -4 -5 -6 50.0 m

Client: Bengaluru Development Authority (BDA)

Section A3-A3' 0 -1 -2 -3 -4 -5 -6 50.0 m

Project name: Desilting Varthur Lake - Detailed Project Report

Depth (m)

0 -1 -2 -3 -4 -5 -6

Title: Transverse Section at AA' Scale:

0 1

3

Date: 22/03/2018

6

All dimensions are in meters

Drawing No: 03

Surveyor & Drawn By: Keshavamurthy. R & Naveen Kumar G T

Desilting Varthur Lake | Detailed Project Report

67


Section BB' 0 -1 -2 -3 -4 -5 -6

0 -1 -2 -3 -4 -5 -6

Section B3-B3' 0 -1 -2 -3 -4 -5 -6

0 -1 -2 -3 -4 -5 -6

Depth (m)

0 -1 -2 -3 -4 -5 -6

Depth (m)

0 -1 -2 -3 -4 -5 -6

Section-B2-B2' Depth (m)

Section-B1-B1' 270.00 m

780.8 m

0 -1 -2 -3 -4 -5 -6

0 -1 -2 -3 -4 -5 -6

Depth (m)

Section-B1-B1'

50.0 m

0 -1 -2 -3 -4 -5 -6

0 -1 -2 -3 -4 -5 -6

Depth (m)

Section-B2-B2'

50.0 m

Section B3-B3' 0 -1 -2 -3 -4 -5 -6 50.0 m

Client: Bengaluru Development Authority (BDA)

Depth (m)

0 -1 -2 -3 -4 -5 -6

Project name: Desilting Varthur Lake - Detailed Project Report Title: Transverse Section at BB' Scale:

0 1

Date: 22/03/2018

3

6

All dimensions are in meters

Drawing No: 04

Surveyor & Drawn By: Keshavamurthy. R & Naveen Kumar G T

Desilting Varthur Lake | Detailed Project Report

68


Annexure VI - Stacking of sediments, Plan and sections Annexure VI contains the following list of drawings:• Drawing no. 1 - Stacking of Sediments - Plan • Drawing no. 2 - Detailed Stacking Plan and Sections of Stack-2 • Drawing no. 3 - Isometric view of stack-1 • Drawing no. 4 - Isometric view of stack-2 • Drawing no. 3 - Isometric view of stack-3 • Drawing no. 4 - Isometric view of stack-4

Desilting Varthur Lake | Detailed Project Report

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70

Mineral Enterprises Limited


N

Lake Boundary

Irrigation pipeline

20m

0m 20m

10m

Client: Bengaluru Development Authority (BDA) Project name: Desilting Varthur Lake - Detailed Project Report Title: Stacking of Sediments - Plan

20m

Stack-1

0m

0m 10m

0m 10m

10m

20m

Scale: 0

30m

Stack-2

Stack-3

Stack-4

100

Date: 22/03/2018

300 All dimensions are in meters Drawing No: 01

Surveyor & Drawn By: Keshavamurthy. R & Naveen Kumar G T

Desilting Varthur Lake | Detailed Project Report

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CH-125

CH-100

CH-75

CH-50

CH-25

CH-0

10m

CH-0

CH-100

CH-75

150

CH-200

CH-175

CH-150

CH-125

CH-50

CH-25

30m 20m 10m 0m

30m 20m 10m 0m

30m 20m 10m 0m

30m 20m 10m 0m

20m 10m 0m

10m 0m

10m 0m

Sections at 25m intervals

CH-250

CH-225

CH-200

All dimensions are in meters

10m 0m

10m 0m

CH-175

CH-225

20m 10m 0m

CH-250

30m 20m 10m 0m

Desilting Varthur Lake | Detailed Project Report

CH-150

Scale: 0 50

20m 30m

Plan with Stack-2

0m

72

CH-250

CH-225

CH-200

CH-175

CH-150

CH-125

CH-100

CH-75

CH-50

CH-25

CH-0

Drawn by: Keshavamurthy. R Naveen Kumar G T

Title: Detailed Plan 0 Stacking 50 and Sections of Stack-2

Date: 21-03-2018

Drawing No: 02 150

Project name: Desilting Varthur Lake - Detailed Project Report

Client: Bengaluru Development Authority (BDA)

596286 m3

30m

Maximum height of stacking Volume of stacking

43681m2

Area of stack-2


Plan with Stack-1

LEGEND

Stack-1

Lake Boundary Irrigation Pipeline

0

100

200

400

Dimensions are in meters

Isometric view of Stack-1

Client: Bengaluru Development Authority (BDA) Project name: Desilting Varthur Lake - Detailed Project Report Title: Isometric View of Stack-1 Drawn by: Keshavamurthy. R Naveen Kumar G T

Drawing No: 03

Date: 21-03-2018

Desilting Varthur Lake | Detailed Project Report

73


Plan with Stack-2

LEGEND Lake Boundary

Stack-2

Irrigation Pipeline

0

100

200

400

Dimensions are in meters

Isometric view of Stack-2

Client: Bengaluru Development Authority (BDA) Project name: Desilting Varthur Lake - Detailed Project Report Title: Isometric View of Stack-2 Drawn by: Keshavamurthy. R Naveen Kumar G T

74

Mineral Enterprises Limited

Drawing No: 04

Date: 21-03-2018


Plan with Stack-3

Stack-3

LEGEND Lake Boundary Irrigation Pipeline

0

100

200

400

Dimensions are in meters

Isometric view of Stack-3

Client: Bengaluru Development Authority (BDA) Project name: Desilting Varthur Lake - Detailed Project Report Title: Isometric View of Stack-3 Drawn by: Keshavamurthy. R Naveen Kumar G T

Drawing No: 05

Date: 21-03-2018

Desilting Varthur Lake | Detailed Project Report

75


Plan with Stack-4

Stack-4 LEGEND Lake Boundary Irrigation Pipeline

0

100

200

400

Dimensions are in meters

Isometric view of Stack-4

Client: Bengaluru Development Authority (BDA) Project name: Desilting Varthur Lake - Detailed Project Report Title: Isometric View of Stack-4 Drawn by: Keshavamurthy. R Naveen Kumar G T

76

Mineral Enterprises Limited

Drawing No: 06

Date: 21-03-2018


Annexure VII - Comprehensive plan for desilting Annexure VII contains the drawing of comprehensive plan for desilting.


N North-west wier Varthur Road

From Thubarahalli

5m 1.7

1.5

5m 1.2

0.5

Desilting Area 0.25m

0.0m

m

0.7

5m

Irrigation pipeline

1.0

m

0m

2.0

m

2.2

5m

Lake Boundary

und

20 m B

Area: 1046524.7 m2

20m

South-east wier

From Bellandur Lake

20m

Stack-1

(Area: 22,881 m2)

0m 10m

0m 10m

0m

20m

0m

Stack-4

(Area: 44.529 m2)

Idgha Road (5.5m)

Stack-3

20m Balagere Road (5.5m)

10m

SH-35

20 m Bund

10m

(Area: 22,326 m2)

30m

Access Roads

Stack-2

(Area: 43,681 m2) 5.5m

Balagere

Road (5

.5m)

From Gunjur Village Client: Bengaluru Development Authority (BDA) Project name: Desilting Varthur Lake - Detailed Project Report Title: Comprehensive Plan Date: 26/03/2018

Scale:

0

100

300

700

Drawing No: 01

Surveyor & Drawn By: Keshavamurthy R & Naveen Kumar G T

All dimensions are in meters

Desilting Varthur Lake | Detailed Project Report

78

Varthur Lake Rejuvenation  

Detailed Project Report for first actions

Varthur Lake Rejuvenation  

Detailed Project Report for first actions

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