SUPPLEMENTARY ENVIRONMENTAL IMPACT ... Report...2017/03/30 · SEIA Report Proposed Sand Extraction...

SUPPLEMENTARY ENVIRONMENTAL IMPACT ASSESSMENT (SEIA) FOR THE

OFF‐SHORE SAND EXTRACTION PROJECT AT KERAWALAPITIYA

Submitted by

Sri Lanka Land Reclamation and Development Corporation

To

Central Environmental Authority

December, 2016

SEIA Report– Proposed Sand Extraction Site 3 – December 2016 Page | i

TABLE OF CONTENTS

TABLE OF CONTENTS ...................................................................................................................................... i

LIST OF TABLES ............................................................................................................................................ vii

LIST OF FIGURES ............................................................................................................................................ x

Chapter 1 : INTRODUCTION ................................................................................................................. 1

1.1 Name of the Project: Offshore Sand Extraction Project at Kerawelapitiya .............................. 1

1.2 Name of the Developer: Sri Lanka Land Reclamation and Development Corporation ............. 1

1.3 Background information ........................................................................................................... 1

1.4 Objectives and Justification of the project ................................................................................ 3

1.5 Objectives of the SEIA study ...................................................................................................... 3

1.6 Brief outline of the methodologies adopted in SEIA preparation ............................................. 4

1.6.1 Geotechnical and Geophysical investigation ............................................................................ 4

1.6.1.1 Geotechnical investigation ........................................................................................................ 4

1.6.1.2 Geophysical Investigation ......................................................................................................... 5

1.6.2 Coastal Engineering aspects ...................................................................................................... 6

1.6.3 Biological studies ....................................................................................................................... 6

1.6.3.1 Desk Studies .............................................................................................................................. 6

1.6.3.2 Marine Biological Studies .......................................................................................................... 6

1.6.4 Description of the present condition of the water quality concerning nutrient dynamic, algae blooms and water turbidity ............................................................................................. 8

1.6.4.1 Phytoplankton analysis .............................................................................................................. 8

1.6.4.2 Determination of Chlorophyll‐a content in waters ................................................................... 8

1.6.4.3 Analysis of physico‐chemical parameters ................................................................................. 8

1.6.4.4 Nutrient analysis ........................................................................................................................ 9

1.6.5 Assessment of the socio‐economic environment ..................................................................... 9

1.7 Government policy regarding the project ............................................................................... 10

1.7.1 National Policy on “Sand as a Resource for the Construction Industry”‐ 2006 ...................... 10

1.8 Applicable laws and regulations .............................................................................................. 10

1.8.1 National Environmental Act No. 47 as amended by Act No. 56 of 1988 and Act No 53 of 2000 (NEA) ............................................................................................................................... 10

1.8.2 Coast Conservation Act No. 57 of 1981 ................................................................................... 11

1.8.3 Mines and Mineral Act No.33 of 1992 (MMA) ........................................................................ 11

1.8.4 Marine Pollution Prevention Act No. 59 of 1981 .................................................................... 11

1.8.5 The Antiquities Ordinance No. 9 of 1940 (now Act) and the subsequent amendments, in particular Antiquities (Amendment) Act No 24 of 1998 ......................................................... 12

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1.8.6 Colombo District (Low‐Lying areas) Reclamation and Development Board Act No 15 of 1968 and Law No. 27 of 1976, Act No. 52 of 1982 and Act No. 35 of 2006 ............................ 12

1.9 Preliminary approvals needed for the proposed project ........................................................ 12

1.10 Any conditions laid down by state agencies in granting preliminary clearance for the project ..................................................................................................................................... 13

1.11 Compliance with the existing conservation and development plans of the area ................... 13

Chapter 2 : DESCRIPTION OF THE PROJECT AND REASONABLE ALTERNATIVES .................................. 1

2.1 Description of the Project ......................................................................................................... 1

2.1.1. Proposed Mining Site ................................................................................................................ 1

2.1.1.1 Location of the Borrow Area (with grid co‐ordinates) in relation to the surrounding sea areas and adjacent coastlines ................................................................................................... 1

2.1.1.2 Extent of the site ....................................................................................................................... 2

2.1.1.3 Water depth to the sand deposit .............................................................................................. 2

2.1.1.4 Estimated reserves .................................................................................................................... 4

2.1.1.5 Amount of sand to be extracted: 70 million m3 ........................................................................ 4

2.1.1.6 Proposed mining depth from the surface of the deposit .......................................................... 4

2.1.1.7 Dredging plan ............................................................................................................................ 4

2.1.1.8 Method of dredging and time schedule .................................................................................... 6

2.1.1.9 Safe extraction / acceptable level of extraction ........................................................................ 6

2.1.1.10 Mining history of the site and its environs ................................................................................ 6

2.2 Methodology of operation ........................................................................................................ 9

2.2.1 Type of dredger/s to be used .................................................................................................... 9

2.2.2 Number of vessels to be used ................................................................................................... 9

2.2.3 Frequency of vessel movements, estimated time frame for mining ........................................ 9

2.2.4 Route of dredger/ barge operation during the project period ................................................. 9

2.2.5 Unloading of sand at the Port City Development site ............................................................. 10

2.3 Evaluation of Alternatives ....................................................................................................... 10

2.3.1 No action alternative ............................................................................................................... 10

2.3.1.1 Dune sand ................................................................................................................................ 10

2.3.1.2 Land based sand ...................................................................................................................... 10

2.3.1.3 River sand ................................................................................................................................ 11

2.3.2 Alternative sites ....................................................................................................................... 11

2.3.2.1 Extraction of sand from near shore ......................................................................................... 11

2.3.2.2 Extraction of sand in deeper areas beyond the proposed borrow area ................................. 11

2.3.2.3 Extraction from the navigation channel .................................................................................. 11

2.3.3 Alternative operational mechanism (quantities, mining depth, transportation routes etc.) . 12

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2.3.3.1 Quantity ................................................................................................................................... 12

Chapter 3 : DESCRIPTION OF THE EXISTING ENVIRONMENT .............................................................. 1

3.1 Physical Environment ........................................................................................................................ 1

3.1.1 Bathymetric data ....................................................................................................................... 1

3.1.2 Isopach map (Sand thickness map) ........................................................................................... 3

3.1.3 Description and assessment of hydrography of the area including tidal regime, wave conditions and directions. ......................................................................................................... 4

3.1.3.1 Tidal Data ................................................................................................................................... 4

3.1.3.2 Current Data .............................................................................................................................. 5

3.1.3.3 Wave Climate ............................................................................................................................ 8

3.1.3.4 Coastal Morphology ................................................................................................................ 10

3.1.3.5 Coastal Stability ....................................................................................................................... 13

3.1.4 Description of the present condition of the water quality concerning nutrient dynamic, algae blooms and water turbidity. .......................................................................................... 14

3.1.4.1 Phytoplankton abundance ...................................................................................................... 15

3.1.4.2 Chlorophyll‐a ........................................................................................................................... 19

3.1.4.2 TSS ........................................................................................................................................... 20

3.1.4.2 Nutrients .................................................................................................................................. 20

3.2 Biological Environment ............................................................................................................ 22

3.2.1 Description and assessment of present distribution, biodiversity and health of reef ecosystems .............................................................................................................................. 22

3.2.2 Description and assessment of present distribution and living state of sea grasses /sea weeds ...................................................................................................................................... 24

3.2.3 Description and assessment of present distribution, species composition and richness of sea bottom macrobenthos ...................................................................................................... 25

3.2.4 Description and assessment of occurrence of endangered, threatened and protected speciesincluding marine mammals ......................................................................................... 33

3.2.5 Description and assessment of hatchery/breeding grounds for commercial and ecologically important marine organisms. .............................................................................. 34

3.2.5.1 Spawning grounds ................................................................................................................... 34

3.2.5.2 Nursery grounds ...................................................................................................................... 37

3.2.6 Species diversity and quantity of fish captures (food fish) within the study area .................. 37

3.2.7 Ornamental fish catches (quantity and diversity) ................................................................... 41

3.3 Social Environment .................................................................................................................. 43

3.3.1 Description and assessment of fisheries and aquaculture resources in the study area including type, catch and production, value etc. .................................................................... 43

3.3.1.1 Number of fishers (Fishing population) ................................................................................... 43

3.3.1.2 Number and types of fishing crafts and gears operated ......................................................... 44

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3.3.1.3 No. of dependents ................................................................................................................... 47

3.3.2 Identification offishing grounds and fishing routes (a map to be provided indicating such areas within the mining area and vessel / barge operational area) ....................................... 48

3.3.3. Description and assessment of present fishery and fishery related activities ........................ 52

3.3.3.1 Fish production of the area ..................................................................................................... 52

3.3.3.2 Value of fisheries (food fish) ................................................................................................... 54

3.3.3.3 Income of the fishing community........................................................................................... 55

3.3.3.4 Fishery related activities.......................................................................................................... 55

3.3.3.5 Demographic characteristics of fishery related community ................................................... 57

3.3.3.6 Education level of fishery related people ................................................................................ 58

3.3.3.7 Age structure of fishery related persons ................................................................................. 58

3.3.3.8 Income from fishery related activities .................................................................................... 59

3.3.4 Seasonal migration /movement of fishermen ........................................................................ 61

Chapter 4 : ANTICIPATED ENVIRONMENTAL IMPACTS ....................................................................... 1

4.1 Physical Environment ................................................................................................................ 1

4.1.1 Coastal morphology .................................................................................................................. 1

4.1.2 Water quality impacts due to sediments .................................................................................. 1

4.1.2.1 Possible Impacts ........................................................................................................................ 1

4.1.2.2 Dredging Process ....................................................................................................................... 5

4.1.3 Water quality impacts due to ship waste .................................................................................. 7

4.2 Biological Impacts ...................................................................................................................... 8

4.2.1 Impact on coral reefs and sea grass beds ................................................................................. 8

4.2.2 Impact on Soft Bottom Macrobenthos ..................................................................................... 8

4.2.3 Impact on Endangered species.................................................................................................. 9

4.2.4 Impact on breeding and spawning ground ............................................................................... 9

4.2.5 Impact on fishing ground and route .......................................................................................... 9

4.2.6. Impact on phytoplankton and other aquatic plants ................................................................. 9

4.3 Social Impacts ............................................................................................................................ 9

4.3.1 Curtailment of fisheries industry ............................................................................................... 9

4.3.2 Perceptions of fishery related persons on impact of sand dredging ...................................... 10

4.3.3. Impacts on food‐fish and ornamental fish catches (quantity and diversity), fishing seasons, economic gains to fisher communities ..................................................................... 10

4.3.4 Value of fishery and aquaculture impact by the project ......................................................... 10

4.3.5 Impacts on food fish and ornamental fish catch (Quantity and diversity) .............................. 10

4.3.6 Navigational hazards ............................................................................................................... 10

4.3.6.1 Marine Pollution and Oil Spillage arising from accidents........................................................ 10

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4.3.6.2 Collisions of vessels ................................................................................................................. 12

Chapter 5 : PROPOSED MITIGATORY MEASURES ................................................................................ 1

5.1 Mitigation Measures _ Physical Resources ............................................................................... 1

5.1.1 Near Shore Coastal Processes ................................................................................................... 1

5.1.2 Turbidity .................................................................................................................................... 1

5.2 Mitigation Measures _ Biological Resources ............................................................................. 2

5.2.1 Impact for the sensitive habitats (Reefs and Seagrass bed) ..................................................... 2

5.2.2 Impact of breading grounds / spawning grounds ..................................................................... 3

5.2.3 Impact to the soft bottom macrozoobenthos and endangered species. .................................. 3

5.2.4 Impact of fishing grounds .......................................................................................................... 3

5.2.5 Suspended sediment (turbidity) effect on phytoplankton and other aquatic plants ............... 4

5.3 Impact for Water quality ........................................................................................................... 4

5.4 Mitigation Measures _ Social Resources ................................................................................... 4

Chapter 6 : ENVIRONMENTAL MANAGEMENT PROGRAMME ............................................................ 1

7.1 Purpose of an Environmental Management Plan ..................................................................... 1

7.2 Implementation of Mitigatory Measures .................................................................................. 1

6.3 ImplementationofMonitoringProcedures ................................................................................. 1

6.4 Institutional Arrangements for Compliance Monitoring and Impact Confirmation Monitoring ................................................................................................................................. 1

6.5 Environmental Monitoring Programme (EMoP) ....................................................................... 2

Chapter 7 : CONCLUSION AND RECOMMENDATION ........................................................................... 1

SEIA Report– Proposed Sand Extraction Site 3 – December 2016 Page | vi

ANNEXURES:

Annex I : Terms of Reference (ToR)

Annex II : References

Annex III : Sources of data and Information

Annex IV : List of preparers including their work allocation

Annex V : Geophysical Survey Report

Annex VI : Exploration Licenses

Annex VII : Waste Management Plan

Annex VIII : Oil Spill Contingency Plan

Annex IX : Sea water and sea sediment analysis reports

Annex X : National Policy on “Sand as a Resource for the Construction Industry”‐ 2006

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LIST OF TABLES

Table 2.1: Metric Grid Coordinates of Mining Site ...................................................................... 2

Table 2.2: Sand reserves calculation .......................................................................................... 4

Table 2.3: Sand thickness (based on Borehole investigation) ...................................................... 8

Table 3.1: Measured Current Velocity and Direction .................................................................. 6

Table 3.2: Relative composition of phytoplankton species (dominant;>4.99%, moderate;1.00‐4.99%, rare, <1.00%) ............................................................................................... 17

Table 3.3: Default trigger values of chemical and biological stressors for Australian marine waters. ................................................................................................................... 20

Table 3.4: Hard coral species identified (up to the genus) within the sand mining site or adjacent areas during the survey ............................................................................. 23

Table 3.5: Soft coral species identified within the sand mining site during the survey ............... 24

Table 3.6: Sea weed species possibly available within the sand mining area or surrounding areas ...................................................................................................................... 25

Table 3.7: Relative abundance of macro‐benthic organisms found in different sampling locations/ substrates in theproposed sand dredging area (individuals/ m2) .............. 27

Table 3.8: Turtle nesting beaches around proposed sand extracting area ................................. 34

Table 3.9: The presence of ichthyoplankton (fish eggs/ larvae) at the sand mining site ............. 35

Table 3.10: List of food fish species recorded within sand mining area and surrounding areas .... 38

Table 3.11: List of ornamental fish species collected by the divers engaged in ornamental fish collection at the sand mining site and surrounding areas ......................................... 42

Table 3.12: Distribution of coastal fishing population in the Negombo Fisheries District, 2015 .... 43

Table 3.13: Age structure of active fishers ................................................................................. 44

Table 3.14: Educational level of active fishers ............................................................................ 44

Table 3.15: Types and number of craft operated in the proposed project area ........................... 45

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Table 3.16: Fishing gears according craft category ..................................................................... 47

Table 3.17: Number of family members according to craft category ........................................... 47

Table 3.18: Gears operate mostly at sand dredging site, their seasonality and target species ...... 52

Table 3.19: Annual fish production of Negombo Fisheries District by FI Division ......................... 53

Table 3.20: Annual fish production of Negombo fisheries district by type of fishing crafts in Mt .. 53

Table 3.21: Fishing trip details by boat type ............................................................................... 54

Table 3.22: Fish catch, average farm rate value and fish value in Negombo fisheries district in 2014 by major commercial groups ........................................................................... 54

Table 3.23: Net income calculation for OFRP boats .................................................................... 55

Table 3.24: Net income calculation for NTRB boats .................................................................... 55

Table 3.25: Fishery related activities of Negombo fisheries district by FI divisions ....................... 56

Table 3.26: Ice plants and production capacities in the Negombo fisheries district ...................... 57

Table 3.27: Total number of members in a household of fishery related family ........................... 57

Table 3.28: Education level of fishery related persons ................................................................ 58

Table 3.29: Age Structure of fishery related persons .................................................................. 58

Table 3.30: Mean Income by fishery related activity .................................................................. 59

Table 3.31: Factors affecting fishery related activity ................................................................... 60

Table 3.32: Seasonal calendar of fishing operations for OFRP craft ............................................. 61

Table 3.33: Seasonal calendar of fishing operations for NTRB crafts ........................................... 61

Table 3.34: Seasonal calendar of fishing operations for NBSB crafts ........................................... 61

Table 4.1: Details of Sediment Source for Dredging Operations .................................................. 6

Table 6.1: Environmental Monitoring Programme adopted during sand dredging period by SLLRDC ..................................................................................................................... 3

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Table 6.2: Environmental Management Plan .............................................................................. 4

Table 6.3: EnvironmentalMonitoringPlan (EMoP) ....................................................................... 7

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LIST OF FIGURES

Figure 1.1: Original borrow Area of 100km2 (Reserved from 1994‐2012) ...................................... 1

Figure 1.2: Borrow area of 56 km2 (Reserved in 2012) ................................................................. 2

Figure 1.3: Present borrow area of 83km2 (Reserved in 2015) ..................................................... 2

Figure 2.1: Present borrow area of 83km2 (Reserved in 2015) ..................................................... 1

Figure 2.2: Depth Variation within Sand Extraction Area ............................................................. 3

Figure 2.3: Schematic diagram of dredging operation .................................................................. 6

Figure 2.4: Borehole Locations ................................................................................................... 7

Figure 2.5: Proposed Navigation Plan ......................................................................................... 9

Figure 3.1: Location of the Proposed Site 3 ................................................................................. 1

Figure 3.2: Bathymetry of the Proposed Site 3 ............................................................................ 2

Figure 3.3: Cross Section across the Extraction Site ..................................................................... 2

Figure 3.4: Model Bathymetry from Negombo to Mt. Lavinia ...................................................... 3

Figure 3.5: Isopach Map of the Sand Extraction Area ................................................................... 4

Figure 3.6: Measured Water Level Data with Locations ............................................................... 5

Figure 3.7: Current Velocity and Current Direction in SW Monsoon ............................................. 6

Figure 3.8: Current Velocity and Current Direction in NE Monsoon .............................................. 7

Figure 3.9: Current Field around study area (towards North Direction) ........................................ 7

Figure 3.10: Current Field around study area (towards South Direction) ........................................ 8

Figure 3.11: Wave Roses of Measured Wave Data (1998 – 2014) _ Seasonal Overall Waves ........... 9

Figure 3.12: Wave Roses of Measured Wave Data (1998 – 2014) _Annual Swell, Sea and Overall Waves ...................................................................................................................... 9

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Figure 3.13: Histogram Plots of Percentage of Occurrence for Hs of Measured Wave Data (1998 – 2014) _ Annual Swell, Sea and Overall Waves .......................................................... 10

Figure 3.14: Depth Variation across the Extraction Site ............................................................... 11

Figure 3.15: Different Strata below the Sea Bed .......................................................................... 12

Figure 3.16: Contour Map of Surface Sand Thickness .................................................................. 12

Figure 3.17: Map of the study area showing sampling sites ......................................................... 15

Figure 3.18: Phytoplankton density in the area ........................................................................... 16

Figure 3.19: Relative composition of diatoms and dinoflagellates in the area ............................... 16

Figure 3.20: Variation of species richness ................................................................................... 19

Figure 3.21: Chlorophyll‐a contents in the area ........................................................................... 19

Figure 3.22: TSS variation in the area .......................................................................................... 20

Figure 3.23: Variation of nitrite concentration in the area ........................................................... 21

Figure 3.24: Variation of nitrate concentration in the area .......................................................... 21

Figure 3.25: Variation phosphate concentration in the area ........................................................ 22

Figure 3.26: Variation of silicate concentration in the area .......................................................... 22

Figure 3.27: Distribution of reefs within the proposed sand extraction area ................................ 24

Figure 3.28: Macrobenthos found at the sand extracting site with their abundance (individuals/ per square meter). .................................................................................................. 26

Figure 3.29: Macro benthos organisms identified in the proposed sand extracting areas ............. 33

Figure 3.30: Ichthyoplankton (fish eggs/ larvae) density distribution ........................................... 36

Figure 3.31: Fish larvae and different developing stages of eggs found at sand mining site during the ichthyoplankton survey ..................................................................................... 36

Figure 3.32: A map of the fishing grounds plotted based on the information and GPS positions provided by fishermen and through direct observations .......................................... 49

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Figure 3.33: The map of the operated fishing gears inside and around the proposed sand dredging site ........................................................................................................... 50

Figure 3.34: The map of the fishing operations directed to respective target species present inside or around the proposed dredging site ............................................................ 51

Figure 4.1: Bathymetry of the Study Area with Computational Mesh ........................................... 3

Figure 4.2: Selected Areas in Dredging Site for Modelling ............................................................ 5

Figure 4.3: Two Dimensional Plots for Spreading Sediment (Suspended Floaters) Concentration at Dredging Location D2 and D5 ................................................................................ 6

Figure 4.4: Two Dimensional Plots for Spreading Sediment (Suspended Floaters) Concentration at Dredging Location D3 and D4 ................................................................................ 7

Figure 5.1: Recommended Dredging Area ................................................................................... 2

Figure 7.1: Proposed Areas for Sand Extraction ........................................................................... 2

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Executive Summary

Preamble:

Environmental Approval under part IV C of the National Environmental Act and the Development Permit under the Coast Conservation and Coastal Resources Management Act was received for the proposed Colombo Port City Development Project in March 2016based on the Supplementary EIA submitted in December 2016. In complying with the permit conditions, the Ministry of Megapolis and Western Development requested the Sri Lanka Land Reclamation and Development Corporation (SLLRDC) to supply a quantity of 30‐40 million m3 of sand as an alternative source for the reclamation works.

The SLLRDC has the approval (under the EIA of November 2007) to dredge 4 million cubic meters of sand per annum every 3 years for a period of 15 years from a borrow area of 100km2 situated off Kerawalapitiya to meet the needs of the construction industry. Therefore, under the approved EIA, a total of 20 million m3 of sand could be extracted over the 15 year period from the reserved burrow area.

Approvals to dredge a quantum of 70 million m3 of sand from the same sand borrow area is requested from the Central Environmental Authority (CEA) by SLLRDC to be used on the following basis:

(a) Approximately 30‐40 million m3 of sand to be extracted over a maximum 3 year period to meet a portion of the total requirement of 65 million m3 needed to complete the Colombo Port City project.

(b) Approximately 30 million m3 to be extracted over a period of 10‐15 years for the purpose of meeting the increasing demand for sand for the construction industry and to mitigate the adverse environmental impacts of river sand mining.

This Supplementary Environmental Impact Assessment study (SEIA) is carried out for the extraction of 70 million m3 of sand for the above purpose. This SEIA should read along with the original EIA Report (2007) titled “Off Shore Sand Extraction for the Construction Industry – Kerawalapitiya”.

The results of the Geophysical Investigations carried out in 2016 shows that a total of 187 million m3 of sand is available in the proposed site. After keeping a safety margin of 0.5m thick sediment, a total of 144 million m3 is available for extraction. The average thickness of the sand deposit varies from 1.95m to 2.45m. According to the borehole investigations the minimum and maximum thickness of sand deposit within the site is 0.4m and 4.9m respectively.

The average water depth from the water surface to the deposit at the proposed site is about 30m. The minimum and maximum water depths of the area vary between 19m to 35m respectively.

Physical Environment:

Numerical modelling was carried out in order to formulate the existing marine environment of the proposed extraction area based on the site specific wave, current and water level data. Hydrodynamic nature of the environment was established and near shore coastal processes were assessed. The state‐of‐art modelling technique was carried out to assess the fine sediment dispersion due to dredging operation. High levels of fine suspended sediment over long periods may have some adverse environmental impacts. Therefore, a dredge dispersion study was commissioned to investigate these potential impacts in detail.

Proposed sand extraction area is located approximately 6km away from the shoreline and beyond 20m depth offshore. In general, all the coastal processes are happening in near shore region within 2‐3km and depth up to 8‐9m. Since, sand extraction area is located in less dynamic area it will not create any disturbance to the hydrodynamic nature of the existing environment and thereby no


impact to the near shore process. Further, it is proposed to limit the sand extraction to 3m (Maximum) at a location to avoid creation of deep holes in the area. Impact on coastal morphology and coastal hydrodynamics of the area due to sand extraction is not significant.

From the comprehensive modelling investigations it was proved that the sediment dispersion due to dredging is localized and it will limited to a maximum of 100m from the dredging location. Further recorded maximum Total Suspended Solids (TSS) concentration is 10mg/lat the dredging site which is far below the recorded maximum ambient TSS levels during flood event of Kelani River. Therefore, increase in suspended sediment level during dredging operations is negligible and therefore no significant impact occurs during dredging operations.

Ecological and socio‐economic aspects:

The National Aquatic Resources Research and Development Agency (NARA) studied the ecological status and socio‐economic value of the proposed sand dredging site. The study recognized the ecological importance of the reef habitats lying in the shallow depths of the proposed dredging site for their intrinsic ability to support biological communities of ecological and economic importance. In association with sand dredging loss of benthic communities, increasing turbidity, elevating suspended sediment concentrations and thereby reducing light penetration, reducing primary production and reducing feeding opportunities and disturbances to migration routes of fish and other species are anticipated. Neither endangered species inhabiting nor extensive distribution of sensitive habitats reef reported in the dredging area, the impact from dredging on the marine ecology be highlight local, and temporary. The main impacts anticipated in the socioeconomic study was obstruction to fishing activities during sand dredging. No significant impact will anticipate on existing fisheries as the sand dredging area is not a prime fishing ground. Dredging will take place far off from trawling ground. Fishing will not be restricted and also the dredging site will not be declared as a no fishing zone. There are a number of technical and strategic mitigation measures which can be implemented in order to reduce the potential impact are proposed in this SEIA.

Proposed method of Sand Dredging:

Trailer Suction Hopper Dredger (TSHD) will be used for sand extraction work. The dredger will be equipped with a Global Positioning system (GPS) to ensure accurate position fixing to restrict the dredging within the designated area. The TSHD is basically scratching the seabed horizontally and not digging into it. It is a self‐propelled seagoing vessel fitted with a suction pipe dragged across the bottom which moves slowly through the water and scrape sand off the sea bed using a drag head connected to a suction tube and in to the hopper. The spill residual is generally small and although water is added during the suction stage of the operation, nowadays this too is limited and monitored.

Conclusion:

In order to minimize the potential impacts on the coastal area, ecology and income from fisheries it is proposed to apply the following guidelines for sand extraction:

1. Sand extraction to be limited only to the recommended areas given in Figure 7.1.

2. Use modern dredging methods.

3. Dredging to occur 3km beyond the shoreline and at water depths of 8m or more. The dredging at 8m depths will ensure that there will be no impact on coastal erosion based on near shore activity and the 3km distances will minimize impacts on fishing routes and fishing activities. Moreover, the 3 km minimum distance will ensure no impact on “ma dal” fishing too.

4. Dredging depth to be limited to 3m from the surface of sediment provided 0.5 m of sediment is preserved after extraction.


5. As much as possible, dredging has to be avoided in areas having fish spawning and unique habitats.

6. Allow fishermen to engage in fishing within the allocated dredging sites by giving proper notice in advance and after dredging work is done to re‐commence fishing. (This will be done in accordance with COLREG regulations issued by the International Maritime Organization)

7. Implement a livelihood support and benefits program for fishing community ensuring long‐term benefit in uplifting their livelihoods.

SEIA Report– Proposed Sand Extraction Site 3 – December 2016 Chapter 1 - Page | 1

CHAPTER 1 : INTRODUCTION

1.1 Name of the Project: Offshore Sand Extraction Project at Kerawelapitiya

1.2 Name of the Developer: Sri Lanka Land Reclamation and Development Corporation

1.3 Background information

Sri Lanka Land Reclamation and Development Corporation (SLLRDC) originally reserved a borrow area of 100 km2 in 1994 with a view to supply sand for the reclamation of 400 acres of Muthurajawela wetland to create urban development area. In between 1994 and 1995 SLLRDC mined 4.8 millionm3 of offshore sand for this reclamation work. Environment clearance was obtained from CEA after going through EIA process.

SLLRDC continued offshore sand extraction from the same site to supply for the construction industry as follows:

Between 2007‐2008, SLLRDC mined 3million m3 of offshore sand to supply the construction industry. EIA clearance was obtained from CEA.

Between 2011‐2012, SLLRDC mined 2.0million m3 of offshore sand to supply the construction industry. Environmental clearance was obtained from CEA.

Between 2012‐2013, SLLRDC mined 0.8 million m3 of offshore sand to supply the construction industry. Environmental clearance was obtained from CEA.

In September 2012, SLLRDC released 56km2 of borrow area from the original 100 km2 and reserved an additional 12km2 towards the North East of their original site prior to mining the 0.8 miln m3 as the grain size of sand required by the construction industry was scarce in the original area. Later in 2015 SLLRDC reserved another 15km2 adjacent to the 12km2 site. No sand has been mined in this 15km2 area. When sand was requested by the Port City Development Project the SLLRDC reserved another 12km2 of borrow area from within the 56km2 that they released in 2012. Hence SLLRDC now has exploration license for 83km2 of borrow area, out of which 15km2 area has never been mined.

Figure 1.1: Original borrow Area of 100km2 (Reserved from 1994‐2012)


Figure 1.2: Borrow area of 56 km2 (Reserved in 2012)

Figure 1.3: Present borrow area of 83km2 (Reserved in 2015)


Since there is sufficient sand in the area reserved by SLLRDC and there is an additional requirement of sand for the reclamation works of the Colombo Port City Project, due to the conditions stipulated in the Development Permit No PV/16/274 dated March 08, 2016 issued by the Coast Conservation and Coastal Resources Management Department, the Project Proponent; Ministry of Megapolis and Western Development requested SLLRDC to supply sand for the proposed Port City Development Project.

1.4 Objectives and Justification of the project

Under the EIA of November 2007, approval was granted to extract offshore sand from a borrow area of 100 km2at the rate of 4 million cubic meters per annum every 3 years for a period of 15 years to mitigate the impact of over‐exploitation of Sri Lanka’s rivers for sand to meet the needs of the construction industry. Therefore, under the approved EIA, a total of 20 million m3 of sand could be extracted over the 15 year period.

Under this Supplementary EIA to the above, a quantum of 70 million m3of sand is to be extracted from the same sand borrow area on the following basis:

(a) Approximately 40 million m3of sand to be extracted over a maximum 3 year period to meet a portion of the total requirement of 65 million m3needed to complete the Colombo Port City project, which is now under construction, on the basis of an approved SEIA of December 2015 and a Development Permit issued by the Department of Coast Conservation and Coastal Resources Management on 8th March 2016.

(b) Approximately 30 million m3to be extracted over a period of 10‐15 years for the purpose of meeting the increasing demand for sand for the construction industry and to mitigate the adverse environmental impacts of river sand mining

1.5 Objectives of the SEIA study

The objective of the environmental study is to ensure that any environmental consequences due to sand extraction from the proposed project are recognized early in the project cycle and taken into account in project design and implementation.

Relevant conditions of Development Permit of Colombo Port City Development Project:

2.1.1. Sand extraction should be carried out in the proposed sand extraction Site No 02 allocated to Sri Lanka Ports Authority and sand extraction should not be carried out in proposed sand extraction Site No 01 allocated to Sri Lanka Ports Authority as recommended by the Technical Evaluation Committee (TEC).

2.1.2 Any additional amount of sand for reclamation should be obtained from the proposed sand extraction site allocated to the Sri Lanka Land Reclamation and Development Corporation (SLLRDC) as proposed and identified by the Project Proponent. Separate approval should be obtained from the Central Environmental Authority for dredging sand from the site allocated to the Sri Lanka Land Reclamation and Development Corporation (SLLRDC).


1.6 Brief outline of the methodologies adopted in SEIA preparation A number of methods have been adopted to assess the environmental impacts of the proposed sand extraction site. The assessment methodologies described below have been used to evaluate impacts arising from the development at the study area; the surrounding areas and the sand borrow areas.

1.6.1 Geotechnical and Geophysical investigation

1.6.1.1 Geotechnical investigation

The geotechnical investigation was carried out to identify the distribution of sand layers, investigate the physical and mechanical properties of sand and determination of the particle size distribution of sand layers

The field investigation was carried out according to BS5930 (1999) “Code of practice for site investigation” and BS1377‐1~9 (1990) “Methods of test for soils for civil engineering purposes”.

The geotechnical investigation include borehole drilling, soil sampling, in‐situ standard penetration test (SPT), laboratory testing and bottom sampling by diving.

Borehole drilling

A total of thirty three (No.33) boreholes were drilled. The Trimble SPS351 DGPS/Beacon receiver was used to positioning. Firstly, the borehole location was marked by a buoy. Then the drilling vessel was moved to the location and fixed by 4 anchors. Finally the coordinates were checked and recorded. The seawater level at benchmark BQW and seawater depth at the borehole location were measured simultaneously. The seabed level of boreholes was obtained by calculating their difference.

XY‐100 Rotary Rig was used for drilling. The length of each drill run was between 1.0m and 1.5m. Casing or little slurry was adopted for borehole protection. Water or little slurry was used as a flushing medium. The water level in the borehole was kept above the seawater level while drilling.

Soil Sampling

Undisturbed Samples

The undisturbed samples were taken using Piston sampler with steel pipe of 0.2m length and 90mm diameter. Hammering method was used to take undisturbed samples in fine grained soils.

The samples were stored according to BS5930:1999. The undisturbed soil samples retained in steel tubes were sealed with wax, filled with inert materials and closed with plastic caps, which were taped again after closing at both ends. All soil samples were labelled with indelible ink, showing the project name, borehole number, date, sample number, depths below seabed level, sampler depth, sampling person and sample recovery and put in the sample box. All samples were labelled to present the sample position and direction.

All undisturbed samples were placed vertically in special wooden boxes. And the samples were protected with wood flour around from shaking.

Disturbed Samples

The disturbed samples were taken in representative sand layers from core barrel. All disturbed samples were placed into plastic bags.

All soil samples were labelled with indelible ink, showing the project name, borehole number, date, sample number, sampler depth and sample recovery.


In‐situ Tests

Standard Penetration Test (SPT)

The SPT test was performed with an interval of around 1.5m according to BS5930:1999. The 63.5 kg hammer is lifted to free fall at a distance of 760mm; and the blows of 6 successive 75mm penetration are recorded. The field N‐value can be corrected for energy ratio and overburden pressure and then used for soil evaluation.

Laboratory Tests

Laboratory tests were carried out in accordance with contract and BS standards. A total of twenty (No.20) sets of undisturbed soil samples and a total of one hundred and sixteen (No.116) sets of disturbed soil samples were recovered and sent to the site laboratory in Colombo.

The following soil tests were carried out:

(1) Fine‐grained soils: Moisture content, density, specific gravity, liquid limit and plastic limit and unconfined compression strength

(2) Coarse‐grained soils: Particle size analysis, specific gravity

1.6.1.2 Geophysical Investigation

During this survey, bathymetric survey, sub‐bottom profiling survey, side‐scan sonar survey and surface sampling by diving were performed. Bathymetric survey and sub‐bottom profiling survey were performed synchronously. When performing sub‐bottom profiling survey, boomer seismic source and hydrophone were towed behind the vessel. When performing side‐scan sonar survey, sonar tow fish was towed behind the vessel.

Seabed Topography

Original water depth data involve coordinate data (Sri Lanka Grid 1999 coordinate system) and water depth data collected every second. The mapping data is from original data after chosen, tide corrected, edited and sorted according to the interval of points required by mapping scale. The bathymetric map was drawn. The tide correction was conducted by time difference correction method. LWOST base was used in this survey. Water depth (m) =Real survey water depth (m)‐tide (m).

Odom CV100 echo sounder made in USA was made for this bathymetric survey, with the maximum range of 200m, digital display, single beam record and high frequency transducer of 200kHz. The precision of measuring is 0.01%of measuring range. Haida 6.21 was used for navigation and positioning of bathymetric survey.

Sub‐bottom Data Processing

CSP‐D sub‐bottom profiler made in England was made available to detect the distribution and thickness of strata, and analyze the soil based on the borehole data, and determine the buried dangerous source along survey lines. CSP‐D sub‐bottom profiler includes Capacitor Charging Unit Seismic Source andAA251 Boomer Plate. Coda survey engine seismic v2.6.3 was used for positioning and acquired data of sub‐bottom profiling survey.

The data of sub‐bottom profiling survey was used to distinguish various strata. The identification of sand layer is mainly based on the characters of profiles. The reflection signal of seabed surface present as dark parallel thick stripped characteristic which suggests the sediments is dense and hard, possibly is coarse sand or sandy clay, which is consistent with the data of boreholes.

Compressional velocity of various media was used to identify the different soil strata.


Side‐scan Sonar Data Processing

The signal collected by side‐scan sonar survey was analyzed and distinguished to obtain useful information of seabed. Side‐scan sonar data were processed by SonarWiz5, from Chesapeake Tech Company, USA. After original data was inputted into this software, clear image can be obtained after seabed tracking, transducer depth correction and gain adjustment. Then clear images were converted into vectorization data after tracking reflecting boundary and objective borderline which was outputted in AutoCAD format.

SonarPro was used for positioning and acquired data of side‐scan sonar survey.

Precision Analysis of Survey Data

The survey error caused by DGPS positioning error, relative position error of towing point to GPS position, position error of towfish or seismic source to survey vessel and distinguishing objectives error.

(1) Sub‐bottom Profiler survey: Precision of DGPS positioning is better than 2.0m, the error of towing point to GPS is less than 0.10m. Boomer seismic source and hydrophones were towed 25 m behind the vessel. The relative position error of boomer seismic source to vessel is 5.0m, so the error of Sub‐bottom Profiler survey system is as follows:

(2) Side‐scan sonar survey: Precision of DGPS positioning is 2.0m, the error of towing point to GPS is less than 0.05m. During this survey, towfish of sonar and GPS lied at the same point; the relative position error is 0. The range of sonar scanning is 150m, the vertical resolution is 0.07m. The analysis error from two pixels is 0.28m. So the error of side‐scan sonar survey system is as follows:

Based on above analysis, all errors less than 10m meet the requirements of standards.

1.6.2 Coastal Engineering aspects

Hydrodynamic, wave disturbance and sediment dispersion modelling studies have been carried out to investigate the impact of the dredging activities on the coastal regime.

1.6.3 Biological studies

1.6.3.1 Desk Studies

The approach in the preparation of this EIA report was to draw on and build upon the previous EIA study reports, specific technical studies carried out for the proposed SLLRDC site, and information available from the EIAs and EMPs of Colombo South Port Development Project and the SEIA of Colombo Port City Project. Relevant documents have been reviewed and additional studies carried out to validate, where necessary, supplement the existing information to take into account the development of the design under this EIA study.

1.6.3.2 Marine Biological Studies

Description and assessment of present distribution, biodiversity and health of coral reefs

Several methods were adapted to gather relevant information on distribution of different types of reefs and associated fauna.


i. Literature survey

Available bathymetry maps and existing literature were used to extract relevant information on physical features such as nature and distribution of reefs (hard coral, limestone or rocky reef), depth ranges and distance from the shore etc. Using the data provided by the Geotechnical Investigation report, a bathymetry map was prepared to show the distribution of different reefs in the sand mining area.

ii. Indirect sources

The faunal and floral parts which were entangled with the fishing gears (bottom set gillnet and bottom trawling) were observed at the landing sites and identified.

iii. Benthic grab sampling

Benthic grab samples which were collected for macro benthos analysis also provided some information relating to faunal and floral species present in the sand extracting area and they were also used for the identification of hard and soft corals, sea grasses, and sea weeds up to species / genera where available.

iv. Underwater visual survey

An underwater visual survey to assess the reef status, distribution, biodiversity and health of the reefs was unable to conduct during the study period due to unfavourable sea condition. This survey will be carried out once sea gets calm (prior to commencement of dredging activities).

However, the published data were made use in this SEIA report to assess the status and the potential impacts on the reefs habitats and under water ecology.

v. Description and assessment of present distribution and living state of sea grass beds/ seaweeds

Distribution of sea grass/sea weeds based on the specimen gathered through monitoring the possible entanglement with fishing gears (bottom set gillnets and trawl nets) and recording the species.

vi. Description and assessment of present distribution, species composition and richness of sea bottom macro‐benthos

Benthic samples were collected at different sampling locations based on the reference map of the dredging site (CCCC‐FHDI, 2016 – Annex V) using Van Veen Grab Sampler so that representing muddy, sandy, muddy‐sandy and limestone areas. Samples were stored in 10% formalin and Rose Bengal solution. At the laboratory, samples were sieved with 1 mm‐4 mmmesh aperture sizes for the identification and enumeration of sediment‐dwelling macro organisms of different size categories residing in the sediment.

vii. Description and assessment of occurrence of endangered, threatened and protected (ETP)fauna including marine mammals

The information on the occurrence of marine mammals (whales, dolphins etc.) and sea turtles were obtained from the literature. In addition, direct observations were made for marine mammals by NARA study team during the survey period. Furthermore, information on turtles nesting sites and nesting seasons was gathered. The coloured species identification cards of marine turtles, marine mammals and sharks were also used wherever necessary.

viii. Description and assessment of nursery /spawning /breeding grounds for commercial and ecologically important marine organisms

An ichthyoplankton survey was carried out within the proposed sand dredging area in order to find the possible spawning grounds. Fish larvae and eggs were collected by a plankton net of


50cm mouth diameter and mesh size of 200µm in the month of September. The net was towed horizontally within a distance of 150 m with a towing speed of 0.75 ms‐1. Four Samples were taken representing each transects in the early morning just before sunrise. Duplicate samples were taken at the each occasion. The samples were preserved in buffered 5% formalin solution in seawater on board. At the laboratory, fish larvae and eggs were sorted, measured and identified using standard keys. Icthyoplankton densities were calculated in terms of individuals per cubic meter.

1.6.4 Description of the present condition of the water quality concerning nutrient dynamic, algae blooms and water turbidity

The study area consists of 16sampling stations covering dredging site. Samples were collected at two transects parallel to the coast 8 sites on 19th and 20th September 2016. Surface water samples are collected by Rutner sampler for estimation of physico‐chemical parameters such as turbidity, TSS and nutrients (nitrate, phosphate and silicate).At the same time, samples were collected for chlorophyll analysis. Nutrients and chlorophyll‐a are measured using UV‐Spectrophotometer (Optizen 3220 UV).Samples were collected vertically from a known depth(4 m) using plankton net with 10µm mesh size and opening diameter of 35 cm for the qualitative and quantitative analysis of the phytoplankton. Then they were preserved with Lugol’s iodine solution. The samples collected for chlorophyll analysis were immediately filtered. The water samples collected for nutrients are preserved in deep‐freezer until the analysis is done.

1.6.4.1 Phytoplankton analysis

Samples preserved with Lugol’s solution, which were analyzed for phytoplankton cell density and taxonomic identification to determine composition of phytoplankton taxa. After settling of phytoplankton (nearly after 72 hours) the supernatant was siphoned out to concentrate to the known volume (about 50‐75ml). After homogenizing the concentrated aliquot, one ml of sample isolated to a sedge‐wick rafter cell for analysis under light microscope (Olympus Bx41) under the 10x10 magnification. Samples were analyzed for determination of phytoplankton abundance, composition and diversity (Newell and Newell, 1963; Verlencar and Somshekar, 2004). Phytoplanktons were identified up to species or genera using the available identification guides (Newell and Newell, 1963, Verlencar. and Somshekar, 2004, Todd, et al., 1991, Jayasiri, 2009).

1.6.4.2 Determination of Chlorophyll‐a content in waters

Chlorophyll‐a is determined by filtering 1L of water samples using GF/C filters under low vacuum. The pigment is extracted with 10ml of 90% acetone. The optical density (absorbance) of the extract was determined with a UV Visible spectrophotometer. Chlorophyll‐a concentrations were calculated using the equations of Parsons, et al., (1984).

1.6.4.3 Analysis of physico‐chemical parameters

Turbidity and total suspended solids (TSS)

Turbidity is measured directly using the turbidity meter (TN‐100). The filter papers were kept in an oven at 105 ⁰C for overnight. Then the filter papers were weighted (W1) after keeping in desiccators for few minutes. Then the one liter of water sample (V) was filtered using GF/C filter paper and the filter paper was kept in an oven again for overnight in 105 ⁰C. Then the dry weight measured (W2). Using the weight difference (W2‐W1) the TSS was calculated using the following equation.

The total suspended solid (TSS) (mg/l) = (W2 – W1)*1000/V

Where; W1 is dry weight of initial filter paper (g), W2 dry weight of filter paper after filtered (g) and V filtered sample volume (l).


1.6.4.4 Nutrient analysis

Nitrite (NO2‐)

The NO2‐is measured by following colorimetric method. The 25ml of water sample is taken in to glass tubeand 0.5ml of Sulphanilamide solution is added in to each tube and mixed well. Then 0.5ml of N‐(1‐Napthyle) ethylene solution is added to each sample and mixed well. The sample was kept 10 minutes for colour development and then the absorbance was measured in (Optizen 3220 UV) UV‐ VIS spectrophotometer at wavelength of 543 nm with 1 cm cuvette.

Phosphate analysis (PO43‐)

The 25ml of sample was transferred to glass tube and 0.5ml of Ascorbic acid is added to each tube and mixed well for the phosphate analysis, then 0.5ml of mix regent is added to the sample. Then the sample was allowed 10‐30minutes for colour development and the absorbance is measured using (Optizen 3220 UV) UV‐ VIS spectrophotometer at 880 nm wavelength.

Silicate analysis

The 10ml of molybdate solution is transferred to 50 ml plastic bottles and then 25ml of sample was added to each bottle and mixed inverting and allowed 10minutes for colour development and then the reducing regent added rapidly. Then mixture was mixed well and after two to three hours the absorbance was measured Using (Optizen 3220 UV) UV‐ VIS spectrophotometer at 810 nm wavelength in a 1 cm cuvette.

1.6.5 Assessment of the socio‐economic environment

The socio‐economic assessment of the surrounding area of sand dredging site was carried out using both published and unpublished data. Statistical data by the Department of Fisheries and Aquatic Resources (DFAR) was collected on fish production, fishing population and types of fishing crafts operated in the 13 Fisheries Inspections Divisions at Negombo Fisheries District. A structured questioner survey was conducted in order to identify the living status of fishing communities, fishery related activities, income and expenditure patterns and seasonal migrations. The sample was composed of 150 fishing households and 141 fishery related households. Structured interviews with fishers and semi structured interviews with key informants of the fishing community were held in the immediate vicinity of the project area. In addition the participatory rapid appraisal (PRA) held for fishery officials of the district in order to verify the extracted qualitative data and information during the survey.

Description of fishing ground and fishing routes

Tracking of fishing grounds and fishing routes at the sea was done by direct observations made by NARA study team. Only the spacial variability of fishing activities was monitored. The information related to the types of fishing boats operated, fishing gear used and target fish species etc. were collected during the on board survey. The collected information was used for mapping of respective fishing grounds (see Figure No. 3.32).

Species diversity and quantity of fish captures (food fish)

The species diversity was determined through on board observations and fish landing site surveys. The quantity of fish captures was obtained from the fish production statistics of the Department of Fisheries and Aquatic Resources Development.

Value of fisheries (food fish)

The value of fisheries was estimated based on the fish production statistics published by the Ministry of Fisheries and Aquatic Resources Development for the District of Gampaha – Negamboand “farmgate” fish price.


Ornamental fish catches (quantity and diversity)

Information related to ornamental fish collection within and marginal areas of the proposed site was obtained from the fisherman catch records.

1.7 Government policy regarding the project

1.7.1 National Policy on “Sand as a Resource for the Construction Industry”‐ 2006

This policy was introduced by the Government in 2006, after recognizing “sand” as a scarce resource and to ensure sustainable utilization of sand (Annex X). According to this policy, the following activities are prohibited due to the potential damage caused to the environment:

Mining of shore sand Mechanized mining of river sand Export sand for construction industry.

However, the non‐mechanized mining in rivers is allowed as a source of income and livelihood to the communities. The licenses are given to the CBOs (Community Based Organizations) for a period of 5 years, which is renewable.

Offshore sand extraction is encouraged in the policy, as it is a renewable resource. It is considered as the best long‐term solution to meet the national demand for construction industry. In view of the large investment capital involved and the significant national benefits that would accrue as a result, the establishment of an offshore‐sand industry is encouraged by suggesting appropriate incentive in the Policy.

Providing sand for proposed Port City Project must be read in the light of this Policy, where offshore sand is identified and promoted as a sustainable and renewable source of supply for large scale industrial purposes.

1.8 Applicable laws and regulations

1.8.1 National Environmental Act No. 47 as amended by Act No. 56 of 1988 and Act No 53 of 2000 (NEA)

National Environmental (Amendment) Act No. 56 of 1988 of Sri Lanka stipulates EIA as a mandatory requirement for establishment of various large scale developmental projects in Sri Lanka and assigns regulatory functions to the Central Environmental Authority (CEA).

According to Part IV C of the above mentioned amendment act, all "prescribed" development projects and undertakings included in a Schedule in an Order published by the Minister of Environment in terms of section 23 Z of the act in the Gazette Extra Ordinary No. 772/22 dated 24th June 1993 and subsequent amendments are required to be subjected to Environmental Impact Assessment. “Off shore mining and mineral extraction” is a prescribed undertaking in accordance with the above Gazette Notification and hence it is required to go through the EIA procedure and approvals obtain for the implementation.

The National Environmental Act further stipulates that approval for all prescribed projects shall have to be obtained from the appropriate project approving agencies concerned or connected with such prescribed project. Central Environmental Authority (CEA) is the PAA in present case.


1.8.2 Coast Conservation Act No. 57 of 1981

The Coast Conservation Act No. 57 of 1981 together with the Coast Conservation (Amendment) Act, No. 64 of 1988 and Coast Conservation (Amendment) Act, No. 49 of 2011 governs the Coastal Zone. This Zone comprises mainly “the area lying within a limit of three hundred meters landwards of the Mean High Water line and a limit of two kilometres seawards of the Mean Low Water line”. Any person desiring to engage in a development activity within the Coastal Zone will be required to obtain a permit issued by the Department prior to commencing the activity.

The EIA process is part of the permit procedure mandated in Part II of the Coast Conservation Act (CCA). Section 16 of the Coast Conservation Act (CCA) confers on the Director General of Coast Conservation and Coastal Recourse Management Department (CC&CRM), the discretion to request a developer applying for a permit (to engage in a development activity within the Coastal Zone) to furnish an Initial Environmental Examination or Environmental Impact Assessment relating to the proposed development activity. The CCA does not however specify how and when this discretion should be exercised. The Coast Conservation and Coastal Recourse Management Department (CC&CRM) interprets this provision as requiring an EIA when the impacts of the project are likely to be significant.

However, the list of “prescribed projects” published in the Gazette Notification No. 772/22 dated 24.06.1993 under the National Environmental Act states that the CCA applies to those prescribed projects only if they are located wholly within the Coastal Zone.

Nevertheless, as the Coast Conservation Act states that it is established to regulate and control development activities within the Coastal Zone, the Coast Conservation and Coastal Recourse Management Department is responsible to ensure development activities taking place in or in the vicinity of the coastal zone will not negatively impact the coastal environs. Even though the proposed sand extraction is beyond the coastal zone, and the CC& CRM Dept. is not the project approving agency, their active participation in the EIA evaluation process is vital.

1.8.3 Mines and Mineral Act No.33 of 1992 (MMA)

According to Section 12 of MMA, Geological Survey and Mines Bureau (GSMB) is responsible to regulate the mining activities in Sri Lanka. No person can explore for any minerals or mine, transport, process, trade in and export any minerals except under the authority of, or otherwise than in accordance with, a license issued on that behalf under the provisions of this Act and the regulations made there under.

SLLRDC obtained the exploration licence for the proposed sand mining area (Annex VI).

1.8.4 Marine Pollution Prevention Act No. 59 of 1981

As per requirements of the Marine Pollution Prevention Act No. 59 of 1981, all ships that enter the territorial waters of Sri Lanka should comply with appropriate measures for preventing and controlling pollution of the sea from a wide range of sources ranging from sewage to harmful chemicals. This act enables carrying out the requirements and conditions stipulated in the international convention for prevention of pollution from ships (MARPOL Convention) to which Sri Lanka is a signatory.

Coastal Zones of Sri Lanka


Therefore, ships and barges which supply equipment and machinery for the proposed development should comply with the provisions of the Marine Pollution Prevention Act 59 of 1981. The executing agency of the act is the Marine Pollution Prevention Authority of Sri Lanka. The said Act requires that major development projects should include sufficient facilities for pollution abatement of marine waters as well as contingency measures in place to cope with the failure of such systems. The contingency measures are also helpful to prevent pollution of the coastal zone from oil spills.

Waste management plan and oil spill contingency plan are attached as Annex VII and VIII respectively.

1.8.5 The Antiquities Ordinance No. 9 of 1940 (now Act) and the subsequent amendments, in particular Antiquities (Amendment) Act No 24 of 1998

Under the requirements of Sections 43A and 43B of the Antiquities (Amendment) Act No. 24 of 1998, separate approval is required from the Director General, Department of Archaeology, for the satisfactory completion of an Archaeological Impact Assessment. This is implemented through the 'Project Procedure Regulation No.1 of 2000 (published in Gazette Extraordinary No. 1152/14, October 2000).

1.8.6 Colombo District (Low‐Lying areas) Reclamation and Development Board Act No 15 of 1968 and Law No. 27 of 1976, Act No. 52 of 1982 and Act No. 35 of 2006

SLLRDC, the Project Proponent, was established by Act No. 15 of 1968 with the intention of undertaking, preparing and executing development schemes in the reclamation and development areas declared under the same Act.

Subsequently there were several amendments to the Act by Low No. 27 of 1976, Act No. 52 of 1982 and Act No. 35 of 2006, giving more powers to the Corporation.

1.9 Preliminary approvals needed for the proposed project

Central Environmental Authority

As part of the environmental screening process, project proponent (PP), SLLRDC, submitted preliminary information to Project Approving Agency (PAA); the Central Environmental Authority (CEA).

After completing the scoping process the CEA issued the Terms of Reference (ToR); Annex I, for the Supplementary Environmental Impact Assessment (SEIA).

Geological Survey and Mines Bureau

GS&MB has issued exploration licenses for the proposed offshore sand extraction area. Copies of the same are attached (Annex VI). This SEIA is carried out for the area identified by these licenses for extraction of sand.

Marine Environment Protection Authority

Waste Management Plan and the Oil Spill Contingency Plan prepared by the Project received the approval of the MEPA. (Annex VII and Annex VIII)

Dept. of Fisheries and Aquatic Resources

The project proponent has allocated Rs.500M for the fisherman’s livelihood support and benefits programme. The Ministry of Mega Polis and Western Development and the Dept. of Fisheries and Aquatic Resources together with Fisherman’s livelihood support society will implement the proposed programmes and manage the funds allocated for the task.

The objectives of the Fishermen's Livelihood Support Program are as follows:


To implement the programs required for the fulfilment of needs of the fishers and their families.

Increase the living standards and socio economic status of the fisher community through improvement of civic amenities and infrastructure.

Enhance access to credit by introducing soft credit schemes. A grant of Rs.2 million per Village Level Fishery Organizations has been planned.

Compensation for accidental death at sea or land. This scheme is non contributory and provides a compensation of Rs.1 million in case of death following an accident at sea or land. Many more benefits will also be provided under this insurance scheme.

Financial support and enhancing the knowledge and understanding to engage in crab farming and "moda" farming in the lagoon.

Lectures and workshops for fishers and families on sustainable fishing, habitat protection, saving and funds management, alternate livelihood etc...

Dept. of Coast Conservation and Coastal Resources Management

The borrow area lies 6‐7.4 km away from the shore line. Hence it is beyond the coastal zone. In compliance with the Coast Conservation Act No. 57 of 1981, CCD has the responsibility to ensure that activities do not cause adverse impacts to the coastal zone and it will not prevent existing fishing activities.

1.10 Any conditions laid down by state agencies in granting preliminary clearance for the project

Required approvals have been dealt with in 1.8 above.

1.11 Compliance with the existing conservation and development plans of the area

There are no conservation and development plans for the borrow area. With regard to the reclamation area, the major development plan of the area is the proposed Western Region Mega Polis Plan. This has been dealt with in the SEIA of Proposed Colombo Port City Development Project. Dec.2015


CHAPTER 2 : DESCRIPTION OF THE PROJECT AND REASONABLE ALTERNATIVES

2.1 Description of the Project

2.1.1. Proposed Mining Site

2.1.1.1 Location of the Borrow Area (with grid co‐ordinates) in relation to the surrounding sea areas and adjacent coastlines

Proposed extraction site (referred as Site 3) is located at about 6km ‐ 7.4km away from the existing coastline between Hendala to Kepungoda.

Figure 2.1: Present borrow area of 83km2 (Reserved in 2015)

The mining site falls within the following metric grid coordinates approved by the GSMB.

N


Table 2.1: Metric Grid Coordinates of Mining Site

82210 84203 85203 86203 87203 88203 89203 90203 91203

82211 84204 85204 86204 87204 88204 89204 90204 91204

82212 84205 85205 86205 87205 88205 89205 90205 91205

83210 84206 85206 86206 87206 88206 89206 90206 91206

83211 84207 85207 86207 87207 88207 89207 90207 91207

83212 84208 85208 86208 87208 88208 89208 90208 91208

84209 85209 86209 87209 88209 89209 90209 91209

84210 85210 86210 87210 88210 89210 90210

84211 85211 86211 87211 88211 89211 90211

84212 85212 86212 87212 88212 89212 90212

2.1.1.2 Extent of the site

The total extent of the proposed site is about 83km2

2.1.1.3 Water depth to the sand deposit

The average water depth to the sand deposit is about 30m. The maximum water depth is about 35m and the minimum water depth is about 20m. Depth variation along the dredging area is shown in Figure 2.2 below.


(a). Survey Contours (Source: Geophysical Survey Report _Annex V) (b). Bathymetry (Source: Modelling Report _ LHI)

Figure 2.2: Depth Variation within Sand Extraction Area


2.1.1.4 Estimated reserves

The exploration done by the dredging contractor indicates 187 mln m3 of sand availability. However, the estimated reserve, after keeping a safety margin of 0.5m thickness is 144 million m3.

2.1.1.5 Amount of sand to be extracted: 70 million m3

2.1.1.6 Proposed mining depth from the surface of the deposit

Possible mining depths were estimated based on the sub bottom data considering a safety margin of 0.5m thickness of sand layer. Estimated mining depths (average) of each transects is given in Table 2.2 and Figure 2.2.

Table 2.2: Sand reserves calculation

Line No. Geophysical

survey point

Area

(km2)

after calibration

Area (km2)

Average water depth (m)

Average thickness

(m)

Average thickness after

reserving 0.5m (m)

Estimated reserve

volume after reserving 0.5m (m3

)

L1 1‐173 2.00 1.95 28.2 1.99 1.49 2,905,500

L2 174‐339 6.00 5.79 27.7 2.39 1.89 10,943,100

L3 340‐506 8.00 7.05 26.8 2.33 1.83 12,901,500

L4 507‐677 8.00 6.78 25.9 2.45 1.95 13,221,000

L5 678‐839 8.00 6.82 25.5 2.45 1.95 13,299,000

L6 840‐1002 8.00 7.72 25.1 2.3 1.8 13,896,000

L7 1003‐1167 8.00 7.65 25.2 2.26 1.76 13,464,000

L8 1168‐1331 8.00 7.78 25.3 2.24 1.74 13,537,200

L9 1332‐1522 9.00 8.85 26.4 2.36 1.86 16,461,000

L10 1523‐1707 9.00 8.75 26.2 2.4 1.9 16,625,000

L11 1708‐1889 6.75 6.63 25.5 2.44 1.94 12,862,200

L12 1890‐2069 2.25 2.18 25.6 2.4 1.9 4,142,000

Total Sand Volume (m3) 144,257,500

Source: Geophysical Survey Report (Annex V)

2.1.1.7 Dredging plan

Proposed detailed sand dredging plan is as follows;


Proposed Sand Dredging Plan

Working Month 16‐Aug 16‐Sep 16‐Oct 16‐Nov 16‐Dec 17‐Jan 17‐Feb 17‐Mar 17‐Apr 17‐May 17‐Jun 17‐Jul 17‐Aug 17‐Sep 17‐Oct 17‐Nov 17‐Dec 18‐Jan 18‐Feb 18‐Mar 18‐Apr 18‐May 18‐Jun 18‐Jul

Sand Mining Zone Site 2 Site 3

Dredging Volume（1000m³） 1,000 1,000 1,000 2,500 3,300 3,500 3,500 3,600 3,600 3,200 3,200 3,200 3,200 3,200 2,800 3,000 3,000 3,600 3,600 3,600 3,400 1,000 1,000 1,000

Accumulated Volume（1000m³） 1,000 2,000 3,000 5,500 8,800 12,300 15,800 19,400 23,000 26,200 29,400 32,600 35,800 39,000 41,800 44,800 47,800 51,400 55,000 58,600 62,000 63,000 64,000 65,000

Percentage 1.50% 1.50% 1.50% 3.80% 5.10% 5.40% 5.40% 5.50% 5.50% 4.90% 4.90% 4.90% 4.90% 4.90% 4.30% 4.60% 4.60% 5.50% 5.50% 5.50% 5.20% 1.50% 1.50% 1.50%

Accumulated Percentage 1.50% 3.10% 4.60% 8.50% 13.50% 18.90% 24.30% 29.80% 35.40% 40.30% 45.20% 50.20% 55.10% 60.00% 64.30% 68.90% 73.50% 79.10% 84.60% 90.20% 95.40% 96.90% 98.50% 100.00%

No. of Dredger 1 1 1 2 3 3 3 3 3 3 3 3 3 3 2 2 2 3 3 3 3 1 1 1

No. of Trips 165 165 165 330 495 495 495 495 495 495 495 495 495 495 330 330 330 495 495 495 495 165 165 165

Accumulated Trips 165 330 495 825 1320 1815 2310 2805 3300 3795 4290 4785 5280 5775 6105 6435 6765 7260 7755 8250 8745 8910 9075 9240 Remarks: 1. The Plan is proposed as per current situation which may be adjusted in the execution of project.

2. As per current plan, two nos of 10000m3 TSHDs and one 21000m3 TSHD are proposed to be deployed in the project.

3. The dredging volume indicated here is the designed one and the actual sand volume for reclamation shall be more than this designed quantity.

1. First Inter monsoon Season ‐ March ‐ April 2. Southwest monsoon season ‐ May ‐ September 3. Second Inter monsoon season ‐ October ‐ November 4. Northeast Monsoon season ‐ December ‐ February

1,000

1,000

2,500

3,300

3,500

3,500

3,600

3,600

3,200

3,200

3,200

3,200

3,200

2,800

3,000

3,000

3,600

3,600

3,600

3,400

1,000

1,000

1,000

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000 Jul-18


2.1.1.8 Method of dredging and time schedule

Trailer Suction Hopper Dredger (TSHD) will be the most efficient dredger for sand extraction work. The dredger will be equipped with a Global Positioning system (GPS) to ensure accurate position fixing to restrict the dredging within the destination area. The TSHD is a self‐propelled seagoing vessel fitted with a suction pipe dragged across the bottom which moves slowly through the water and scrape sand off the sea bed using a drag head connected to a suction tube and in to the hopper.

Figure 2.3: Schematic diagram of dredging operation

Dredging will be carried out only within the identified locations. When dredging, the dredger will lower its two drag heads to the sea floor, each removing a layer of sand, approximately 300 to 400 mm thick. The dredger would move in linear channels along the borrow pit. This will prevent the formation of isolated pits when dredging the sand. The drag head is connected to the vessel with a suction tube that transports the sand from the sea floor and into the vessel’s hopper. The sand/water mixture is captured in the hopper of the dredger, where the sand component will rapidly settle, forming two distinct layers in the hopper, one is sand and the other is salt water.

2.1.1.9 Safe extraction / acceptable level of extraction

Based on the borehole investigations, minimum and maximum sand thickness within the extraction site is found as 0.4m and 4.9m respectively (refer Fig 2.4 for Borehole locations and Annex V for further details). Further it is proposed to extract maximum of 3m at a location and leave a safety margin of 0.5m thickness from the bed. Therefore, dredgable sand thickness is varies from 0m to 3m (ref. Table 2.3 below).

2.1.1.10 Mining history of the site and its environs

ref. section 1.3


Figure 2.4: Borehole Locations


Table 2.3: Sand thickness (based on Borehole investigation)

Borehole No Top Elevation (m) Base Elevation (m) Thickness (m)

Dredgable Thickness after leaving 0.5m

margin (m)

AH01 ‐21.56 ‐24.86 3.3 2.8 AH02 ‐25.21 ‐26.81 1.6 1.1 AH03 ‐29.81 ‐30.31 0.5 0 AH04 ‐22.46 ‐25.66 3.2 2.7 AH05 ‐18.96 ‐20.76 1.8 1.3 AH06 ‐21.96 ‐23.06 1.1 0.6 AH07 ‐29.06 ‐33.96 4.9 3* AH08 ‐30.56 ‐33.76 3.2 2.7 AH09 ‐19.31 ‐24.01 4.7 3* AH10 ‐29.96 ‐31.56 1.6 1.1 AH11 ‐30.06 ‐32.36 2.3 1.8 AH12 ‐19.61 ‐20.61 1 0.5 AH13 ‐21.31 ‐21.71 0.4 0 AH14 ‐25.41 ‐28.31 2.9 2.4 AH15 ‐20.41 ‐23.91 3.5 3 AH16 ‐28.75 ‐31.85 3.1 2.6 AH17 ‐20.36 ‐20.76 0.4 0 AH18 ‐22.01 ‐22.41 0.4 0 AH19 ‐28.26 ‐28.86 0.6 0.1 AH20 ‐19.86 ‐23.56 3.7 3.2 AH21 ‐22.31 ‐25.81 3.5 3 AH22 ‐29.06 ‐30.56 1.5 1 AH23 ‐28.36 ‐31.96 3.6 3.1 AH24 ‐30.61 ‐32.41 1.8 1.3 AH25 ‐20.56 ‐22.36 1.8 1.3 AH26 ‐26.91 ‐28.11 1.2 0.7 AH27 ‐27.81 ‐28.41 0.6 0.1 AH28 ‐28.96 ‐32.16 3.2 2.7 AH29 ‐19.51 ‐22.61 3.1 2.6 AH30 ‐22.41 ‐23.51 1.1 0.6 AH31 ‐28.09 ‐29.99 1.9 1.4 AH32 ‐26.26 ‐29.56 3.3 2.8 AH33 ‐26.16 ‐27.06 0.9 0.4 Count 33 33 33 33 Max. ‐18.96 ‐20.61 4.9 3 Min. ‐30.61 ‐33.96 0.4 0

Average ‐24.91 ‐27.08 2.17 1.51


2.2 Methodology of operation

2.2.1 Type of dredger/s to be used

Trailer Suction Hopper Dredger (TSHD) will be used for sand extraction work.

2.2.2 Number of vessels to be used

Maximum of four numbers of trailer suction hopper dredgers shall be used at site 3.

2.2.3 Frequency of vessel movements, estimated time frame for mining

The estimated time cycle for dredging, transporting and unloading will be approximately 5 to 6 movements per day per dredger.

The estimated time frame shall be maximum of 36 months from the date contractor gets approval for the mining at site 3.

2.2.4 Route of dredger/ barge operation during the project period

During the working cycle, the TSHD will sail between the sand borrow area and the reclamation area. The contractor will plan their transport route to minimize any disruption to the marine traffic of the approach channel area. Proposed navigation plan is as follows;

Figure 2.5: Proposed Navigation Plan


2.2.5 Unloading of sand at the Port City Development site

When the hopper is full from sand the dredger sails to the reclamation site and places material by bottom dumping or rainbowing. Material would be bottom dumped up to a level of 7m to 9m and then trimmed to profile by the TSHD.

Bottom Dumping: This is done by simply opening the bottom doors (hatches) of the hopper. Once opened bottom doors the substance will simply drop to the seabed because of gravity.). Discharging through bottom doors allows quick, direct and total offloading of dredged material at a selected location.

Rainbowing: TSHD pumps the sand that has been dredged from the seabed in a high arc placing it at the reclamation site. Initially the high pressure pumps will pump water inside the hopper to loosen the substance, which will then be blown away to create land.

2.3 Evaluation of Alternatives

2.3.1 No action alternative

The extraction of sand is for the creation of land for the proposed Port City Development Project and to use in the construction industry. If there is no offshore sand extraction, other sources of sand will have to be explored to make these activities a reality.

Alternatives to offshore sand

Dune sand Land based sand River sand

2.3.1.1 Dune sand

Windblown accumulations of sand heaped into dunes over hundreds of years occur along about a fifth of the coastline in Sri Lanka.

Locations of sand dunes

East coast near Batticaloa North East coast between Pulmoddai and Pt.Pedro West coast intermittently between Ambakandawila and Kalpitiya Peninsula North West coast between Mannar and Pooneryn Peninsula South East coast between Ambalantota and Timitar

Excessive Mining of dune sand in the Kalpitiya Peninsula and the sea belt from Udappuwato Palavi is already causing serious damage to the eco‐system as well as to the livelihood of the villagers, who mainly depend on agriculture.

It is not a renewable supply and it will not be possible to supply such a large quantity as 70 million m3. Furthermore, transporting dune sand from train to Fort Railway station and from there to project site by tippers would mean aggravating an already congested transport network. Hence dune sand cannot be considered as a viable option to meet the sand requirement of proposed Port City Project.

2.3.1.2 Land based sand

Sand and clay could be extracted from the soils available on the banks of upstream of rivers such as Kelani, Maha Oya etc. Here again if will not be possible to supply such a large quantity. Furthermore,


the environmental consequences of large lagoons created by mined out pits will be rather high. Hence this option cannot be considered any further.

2.3.1.3 River sand

This option will not be pursued any further since mining of river sand has already created detrimental effects on the environment including coastal erosion, particularly due to mining for sand in Kelani river and Maha Oya.

2.3.2 Alternative sites

Although Sri Lanka is an island, exploitable sand deposits are not found along the continental shelf of entire periphery of the country. They are found to occur in the continental shelf to the North of Colombo and from Kumbukkan Oya towards Batticoloa. (ref. 26) However extraction of sand from South East (Kumbukkan Oya towards Batticaloa segment) and transporting to Colombo by land (in tippers) or by sea (in barges) would not be economically feasible.

Hence alternative sites from the deposits to the North of Colombo shall be studied.

Three options could be considered.

Extraction of sand from near shore. Extraction of sand in deeper areas beyond the proposed borrow area. Extraction of sand from the navigational channel.

2.3.2.1 Extraction of sand from near shore

In accordance with the regulations of the Coast Conservation Department sand mining is not permitted within 3 km seawards from the shore. Sand mining in the near shore regions very close to the shore line would have a severe impact on increasing erosion and hence cannot be considered as a viable alternative.

2.3.2.2 Extraction of sand in deeper areas beyond the proposed borrow area

Extraction of sand from very deep areas beyond the proposed borrow area will increase the travel time of dredger. As such the operational cost will be extremely high and it will not be economically or technically feasible.

2.3.2.3 Extraction from the navigation channel

The navigation channel is considered a restricted area and hence dredging cannot be carried out in the channel.

For offshore sand mining to be a viable option from both an economical and engineering point of view dredging should be carried out at a sufficient distance off shore from the shoreline such that it does not have an impact on the long shore drift and the onshore – offshore drift components of the coastal sediment budget for the given region. Coastal engineering indicates that extraction of sand well beyond the wave breaking zone has no impact upon coastal erosion or accretion. Dredging experience has established that extraction of sand beyond the MSL –15 m is safe from a coastal engineering point of view in that it would have no impact on near shore processes constituting to coastal erosion or accretion. Hence the site chosen for borrowing of sand is acceptable.


2.3.3 Alternative operational mechanism (quantities, mining depth, transportation routes etc.)

2.3.3.1 Quantity

A quantum of 70 million m3 of sand is proposed to be extracted following:

(a) Approximately 40 million m3of sand to be extracted over a maximum 3 year period to meet a portion of the total requirement of 65 million m3needed to complete the Colombo Port City project.

(b) Approximately 30 million m3 to be extracted over a period of 10‐15 years for the purpose of meeting the increasing demand for sand for the construction industry

If the quantity of sand extraction is to be reduced without compromising on the extent to be filled, then an alternative material (rock or dune sand) would have to be used. It has already been stated previously that dune sand is not a viable option. Supplementing the balance requirement by rock would also neither be economically feasible nor technically viable.

National Policy on “Sand as a Resource for the Construction Industry – 2006”, has recognized the use of Off‐shore sand for construction industry in order to mitigate the adverse environmental impacts of river sand mining.


CHAPTER 3 : DESCRIPTION OF THE EXISTING ENVIRONMENT

3.1 Physical Environment

Physical parameters of the area are assessed initially since it plays a vital role in formulation of impacts. The existing environmental with respect to physical environment, was established through the primary data generated during previous EIA studies and data collected from recent surveys. Since the present study is mainly focused on extraction of sand from SLLRDC Site (mentioned as Site 3 in Figure 3.1 below), physical characteristic related to site 3 is discussed in detail.

Proposed extraction site (mentioned as Site 3) is located at about 6km ‐ 7.4km from the existing coastline between Hendala to Kepungoda. Area of the proposed site 3 is about 83km2 and the average depth is about 25m.

Figure 3.1: Location of the Proposed Site 3

3.1.1 Bathymetric data

Bathymetric survey of the proposed dredging area was done by CCCC‐FHDI Engineering Co. Ltd during April 2016. Based on the findings of the bathymetric survey depth contours was developed in the proposed extraction area and is given in Figure 3.2 below.


Figure 3.2: Bathymetry of the Proposed Site 3

The water depth within sand borrow area is about 18.6‐35.9m, which declines from east to west. The contour of water depth is parallel with shoreline. The depth at eastern side of the extraction area is around 19‐20m while the west side it deepens upto 30‐35m. Contours of eastern side of the reef are almost parallel to the beach. Further, contour distribution of the area indicates few peaks along the 23m contour which reveals a ridge formation (discontinuous reef) in the middle of the area. The discontinuous reef is running parallel to the beach in south‐north direction. Few peaks are extending upto a depth of 19m and between these high peaks contours are gradually decline from east to west. Cross section of the study area across one of the peaks is shown in Figure 3.3 below.

Figure 3.3: Cross Section across the Extraction Site

Further bathymetry of the area entire area was developed based on the previous survey data and admiralty maps of the area in order to assess the hydrodynamic nature of the study area and to assess the impacts due to dredging and dumping operations. Bathymetry map of the area between Negombo to Mount Lavinia is given in Figure 3.4 below.


Figure 3.4: Model Bathymetry from Negombo to Mt. Lavinia

3.1.2 Isopach map (Sand thickness map)

Borehole investigation was done by CCCC‐FHDI Engineering Co. Ltd during April 2016 and a total of 33 bore holes were tested to assess the sub bottom strata of the area. Thickness of the sand layer in the area is found as minimum of 0.4m to maximum of 4.9m. Sand thickness is found as minimum in the area of reef belt which lies in the middle of the extraction area where as the other areas having an average thickness of more than 2m. The estimated quantity of sand reserve in the proposed site 3 is found as 187.2 million m3. According to the environmental concerns it was proposed to preserve at least 0.5m of thick sand layer during exploration and with this limitation available sand quantity at site is found as 144.2 million m3. Contour map of surface sand thickness is shown Figure 3.5.


Figure 3.5: Isopach Map of the Sand Extraction Area

According to borehole data, surface sand layer is mainly composed of medium sand, coarse sand, medium‐coarse sand and gravelly sand with less than 10% fine grain and clayey grain, locally possible silty sand, fine sand, silty fine sand, and medium sand, coarse sand, medium‐coarse sand and gravelly sand with more than 10% fine grain and clayey grain.

3.1.3 Description and assessment of hydrography of the area including tidal regime, wave conditions and directions.

3.1.3.1 Tidal Data

Tide data is important information in any costal development project as it determines the elevation of the structures relative to a datum. The tidal regime in Sri Lanka is semi‐diurnal with diurnal inequalities which mean two high tides (spring tide) and two low tides (neap tide) per day with different heights. The tidal range almost constant from north to south of Sri Lanka and is about 0.6m (during spring tide).

Water level measurement was carried out during August 2013 and January 2014 in order to examine the water levels during SW monsoon and NE monsoon respectively. The measured water levels (m, MSL) are represented in graphical format with their locations in Figure 3.6 below.


(a) NE Monsoon _ T1

(b) SW Monsoon _ T1

(c) NE Monsoon _ T2

(d) SW Monsoon _ T2

Figure 3.6: Measured Water Level Data with Locations

Based on the measured water levels at the project area highest water level during the spring tide is observed as 0.35m MSL and the lowest is ‐0.39m MSL.

3.1.3.2 Current Data

Both ocean currents and tidal currents affect the Sri Lanka coast. The ocean currents including wind driven currents are stronger than the tidal currents. Episodic high current speed events were observed on a few occasions during the month of November 2003 and it was reached upto 0.4‐0.5m/s (from the field measurements programme for the design of the Colombo Port Expansion Project). A desk study showed similar occurrences during November in previous years.

The measurement of current is taken at current stations C1 and C2 and the recordings of the direction and velocity of the current is summarized in Table 3.1. Maximum and minimum current speed was observed as 0.25m/s and 0.06m/s respectively. The velocity profiles indicated that these currents flow northwards in the flood tide condition and flow southwards in ebb tide conditions.

‐0.3

‐0.2

‐0.1

0.0

0.1

0.2

0.3

Water Level (m)

Date & Time

Water Level Variation during NE Monsoon at T1

‐0.5

‐0.4

‐0.3

‐0.2

‐0.1

0.0

0.1

0.2

0.3

Water Level (m)

Date & Time

Water Level Variation during SW Monsoon at T1

‐0.5

‐0.4

‐0.3

‐0.2

‐0.1

0.0

0.1

0.2

0.3

0.4

0.5

Water Level (m)

Date & Time

Water Level Variation during NE Monsoon at T2

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

Water Level (m)

Date & Time

Water Level Variation during SW Monsoon at T2


Table 3.1: Measured Current Velocity and Direction

SW Monsoon

Main direction

Spring tide Neap tide

velocity direction velocity direction

C1 SE 0.11 151 0.08 144

NW 0.17 338 — —

C2 SE 0.15 172 0.06 139

NW — — — —

NE Monsoon

Main direction

Spring tide Neap tide

velocity direction velocity direction

C1 N 0.07 334 0.19 342

S 0.06 170 — —

C2 N 0.06 1 0.25 354

S 0.10 154 — —

The graphic presentation of the current velocity and direction is presented in the Figure 3.7 and Figure 3.8.

Figure 3.7: Current Velocity and Current Direction in SW Monsoon


Figure 3.8: Current Velocity and Current Direction in NE Monsoon

Based on the result of the site measurements, a numerical model was built and calibrated in accordance with the current and tide measurement. The numerical model was then used to simulate the current field of the extraction site and its adjacent water area. The details of the hydraulic circulation and current field are shown in the Figure 3.9 and Figure 3.10 below.

Figure 3.9: Current Field around study area (towards North Direction)


Figure 3.10: Current Field around study area (towards South Direction)

3.1.3.3 Wave Climate

The wave climate is characterized by two simultaneous wave systems. Long periods swell with a southerly direction in deep water that becomes more westerly as it approaches the coast. This exhibits only small differences of height during the year. The other system is the shorter period sea waves which are generated by the local (monsoon) winds but are influenced to a certain degree by local sea breezes.

There are two distinct climatological periods; the southwest (SW) monsoon from May to September and the northeast (NE) monsoon from November to January. Waves from the southwest are predominant during the southwest monsoon, although wav the northwest occur occasionally. Winds from the SW are considerably stronger than from the NE and the wave conditions on the west coast during the SW monsoon are more severe than on the east coast during the NE monsoon.

For the Colombo Port Expansion Project, LHI has undertaken directional wave measurements in the vicinity of Colombo Port from 1998 at a depth around 16m with 3hr intervals. Wave climate in the proposed study area is assessed based on this extensive wave data set.

When considering the overall waves, SW monsoon is more dominant and more than 75% of the high waves can be seen from the directional sector of 210‐280. During the NE monsoon low magnitude waves are observed in the directions of 210‐330. As far as the overall wave condition is concerned, south west sector of 210‐280 could be considered as the dominant directional sector (see Figure 3.11 below)


(a). South West Monsoon (b) North East Monsoon

Figure 3.11: Wave Roses of Measured Wave Data (1998 – 2014) _ Seasonal Overall Waves

The swell wave is an underlying wave, which comes from the SW (210‐240) throughout the year. The sea wave is created by local winds and is superimposed on the swell and forms overall waves. Direction of the sea waves has wider spread than the swell waves but limited to directions 210‐330.

(a). Annual Swell Waves (b) Annual Sea Waves (c) Annual Overall Waves

Figure 3.12: Wave Roses of Measured Wave Data (1998 – 2014) _Annual Swell, Sea and Overall Waves


Wave Histogram for Annual Swell Waves

Wave Histogram for Annual Sea Waves

Wave Histogram for Annual Overall Waves

Figure 3.13: Histogram Plots of Percentage of Occurrence for Hs of Measured Wave Data (1998 – 2014) _ Annual Swell, Sea and Overall Waves

3.1.3.4 Coastal Morphology

Coastal morphology is the study of natural processes ongoing at the shoreline and of the impact due to human interventions within the coastal zone. In Sri Lanka coastal zone is defined as the area lying within a limit of 300m landward of the Mean High Water Line (MHWL) and a limit of 2km seaward of

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

190 ‐‐200

200 ‐‐210

210 ‐‐220

220 ‐‐230

230 ‐‐240

240 ‐‐250

250 ‐‐260

260 ‐‐270

270 ‐‐280

280 ‐‐290

290 ‐‐300

300 ‐‐310

310 ‐‐320

320 ‐‐330

% of O

ccurrence

Wave Direction (Deg)

PERCENTAGE OF OCCURRENCE FOR Hs OF ANNUAL SWELL WAVES (1998 ‐ 2014)

0 ‐‐ 0.1 0.1 ‐‐ 0.2 0.2 ‐‐ 0.3 0.3 ‐‐ 0.4 0.4 ‐‐ 0.5 0.5 ‐‐ 0.6 0.6 ‐‐ 0.7

0.7 ‐‐ 0.8 0.8 ‐‐ 0.9 0.9 ‐‐ 1.0 1.0 ‐‐ 1.1 1.1 ‐‐ 1.2 1.2 ‐‐ 1.3 1.3 ‐‐ 1.4

1.4 ‐‐ 1.5 1.5 ‐‐ 1.6 1.6 ‐‐ 1.7 1.7 ‐‐ 1.8 1.8 ‐‐ 1.9 1.9 ‐‐ 2.0 2.0 ‐‐ 2.1

2.1 ‐‐ 2.2 2.2 ‐‐ 2.3 2.3 ‐‐ 2.4 2.4 ‐‐ 2.5 2.5 ‐‐ 2.6 2.6 ‐‐ 2.7

Wave Heights (m)

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

< 180

180 ‐‐190

190 ‐‐200

200 ‐‐210

210 ‐‐220

220 ‐‐230

230 ‐‐240

240 ‐‐250

250 ‐‐260

260 ‐‐270

270 ‐‐280

280 ‐‐290

290 ‐‐300

300 ‐‐310

310 ‐‐320

320 ‐‐330

330 ‐‐340

340 ‐‐350

% of O

ccurrence


PERCENTAGE OF OCCURRENCE FOR HsOF ANNUAL SEA WAVES (1998‐2014)

0 ‐‐ 0.1 0.1 ‐‐ 0.2 0.2 ‐‐ 0.3 0.3 ‐‐ 0.4 0.4 ‐‐ 0.5 0.5 ‐‐ 0.60.6 ‐‐ 0.7 0.7 ‐‐ 0.8 0.8 ‐‐ 0.9 0.9 ‐‐ 1.0 1.0 ‐‐ 1.1 1.1 ‐‐ 1.21.2 ‐‐ 1.3 1.3 ‐‐ 1.4 1.4 ‐‐ 1.5 1.5 ‐‐ 1.6 1.6 ‐‐ 1.7 1.7 ‐‐ 1.81.8 ‐‐ 1.9 1.9 ‐‐ 2.0 2.0 ‐‐ 2.1 2.1 ‐‐ 2.2 2.2 ‐‐ 2.3 2.3 ‐‐ 2.42.4 ‐‐ 2.5 2.5 ‐‐ 2.6 2.6 ‐‐ 2.7 2.7 ‐‐ 2.8 2.8 ‐‐ 2.9 2.9 ‐‐ 3.03.0 ‐‐ 3.1 3.1 ‐‐ 3.2 3.2 ‐‐ 3.3

Wave Heights (m)

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

<181

180 ‐‐190

190 ‐‐200

200 ‐‐210

210 ‐‐220

220 ‐‐230

230 ‐‐240

240 ‐‐250

250 ‐‐260

260 ‐‐270

270 ‐‐280

280 ‐‐290

290 ‐‐300

300 ‐‐310

310 ‐‐320

320 ‐‐330

330 ‐‐340

% of O

ccurrence


PERCENTAGE OF OCCURRENCE FOR HsOF ANNUAL OVERALL WAVES (1998‐2014)

0 ‐‐ 0.1 0.1 ‐‐ 0.2 0.2 ‐‐ 0.3 0.3 ‐‐ 0.4 0.4 ‐‐ 0.5 0.5 ‐‐ 0.60.6 ‐‐ 0.7 0.7 ‐‐ 0.8 0.8 ‐‐ 0.9 0.9 ‐‐ 1 1 ‐‐ 1.1 1.1 ‐‐ 1.21.2 ‐‐ 1.3 1.3 ‐‐ 1.4 1.4 ‐‐ 1.5 1.5 ‐‐ 1.6 1.6 ‐‐ 1.7 1.7 ‐‐ 1.81.8 ‐‐ 1.9 1.9 ‐‐ 2 2.1 ‐‐ 2.2 2.2 ‐‐ 2.3 2.3 ‐‐ 2.4 2.4 ‐‐ 2.52.5 ‐‐ 2.6 2.6 ‐‐ 2.7 2.7 ‐‐ 2.8 2.8 ‐‐ 2.9 2.9 ‐‐ 3 3 ‐‐ 3.13.1 ‐‐ 3.2 3.2 ‐‐ 3.3 3.3 ‐‐ 3.4 3.4 ‐‐ 3.5

Wave Heights (m)


the Mean Low Water Line (MLWL). Most of the coastal processes which will leads to coastal stability are happening within the coastal zone and it is very dynamic in nature.

Proposed extraction site (Site 3) is located at about 6km ‐7.4km away from the existing coastline between Hendala to Kepungoda which is beyond the periphery of this dynamic zone. Therefore influence of current flow and morphological changes are minimal within this area.

Figure 3.14: Depth Variation across the Extraction Site

In general, sea bed profile declines from east to west with a minimum depth of 18.6m to a maximum depth of 35.9m. Discontinuous reef is visible in the middle of the area which running parallel to the beach in south‐north direction. The depth at eastern side of the reef is around 19‐20m while the west side of it deepens upto 30‐35m.

Based on the findings of sub bottom profile survey, three distinct layers are present below the sea bed as surface sand layer, other soil layer and bed rock. Features of the each layer are as follows;

Surface sand layer is mainly composed of medium sand, coarse sand, medium‐coarse sand and gravelly sand with less than 10% fine grain and clayey grain.

Other soil is mainly composed of clay with sand, sand with clayey soil, clay, silty clay, limestone reef, calcareous cement sand, residual soil and medium sand, coarse sand, medium‐coarse sand and gravelly sand with more than 10% fine grain and clayey grain, locally possible medium sand, coarse sand, medium‐coarse sand and gravelly sand with less than 10% fine grain and clayey grain, and weathered gneiss etc. Overburden involves surface sand and other soil.

Bedrock in this area is mainly gneiss, locally with dense medium‐coarse sand, gravelly sand, soil etc. The sub‐bottom profiler penetration was up to ‐50m. The elevation of bedrock is between ‐25m and ‐50m, locally possible more than ‐50m deep. The bedrock varies deep from east to west.

Reef formation


Figure 3.15: Different Strata below the Sea Bed

Limestone reef is formed in the other soil strata which are not link to the surface sand layer. Therefore extraction of sand from the surface sand layer will not affect the existing limestone reef. Further sand is only available either side of the reef and along the reef sand deposition is zero. Therefore sand extraction will not take place closer to the reef and thereby no impact to the existing reef.

Figure 3.16: Contour Map of Surface Sand Thickness

Shoreline stability is determined by the sediment budget of the coastal area which is the balanced with sediment supplies and losses in natural means. Rivers are major point sources of sediment contribution to the coastal sedimentary budget and any reduction of sediment supply will be adversely impact to the shoreline stability.

Proposed extraction site is located 5.8km away from the coast and hence it is far away from the dynamic coastal zone. Further depth of the extraction site is between 20m to 35m which belongs to


the deep sea region where the morphological changes are minimal. It is proposed to scrape maximum of 3m from the sea bed and the bed variation is not much critical while compared to the actual depth of 25m or more.

3.1.3.5 Coastal Stability

The net longshore sediment transport along the west coast of Sri Lanka is predominantly directed towards the north as a result of the wave climate (mainly dominated by swell waves). Most of the net transport occurs during the southwest monsoon season. However during the NE monsoon the sediment transport (as a result of waves from North West) is usually directed towards south for a limited period.

The stretch is prone to erosion during the high energetic wave condition along the southwest monsoon. The extent of erosion at a given location varies during the year depending on the time period. Decrease in sand supply from the river is considered to be the main reason for erosion north of the river mouth. In the Master Plan for Coast Erosion Management Summary, the erosion rate was identified as 2.5 m/year for 70% of the coastline from Palliyawatte to Uswetikeiyawa. Several stabilization schemes were implemented from 1987 to date targeting the coastal erosion at west coast. The first stabilization scheme was implement in 1987 (DANIDA stage I) to stabilize the 7km of coastal stretch in Negombo. About 400,000 m3 of sand from offshore borrow pits were used to nourished the proposed area with several herd structures to support the infill and minimise loss of sand.

Under DANIDA stage II (1990‐1992), several breakwater and groyne structures were introduce in North of Colombo as a beach stabilization scheme. Further sand nourishment was done in Thoduwawa‐Wellamankara coastal stretch.

Under the Coast Resources Management Project (CRMP‐Coastal Stabilisation Component) during 2001 to 2008 coastal stretches of Colombo North (Modara to Uswatakeiyawa) and Maha oya – Lansigama stretch was developed to prevent coastal erosion.

Coastal stretch between Modara to Uswatakeiyawa was stabilized under this scheme by introducing several hard structural solutions. Stabilization of 400m of coastal stretch of the urban area at Modara (new sea wall, rehabilitation of groyne and extention it by 50m), Crow Island beach (two offshore breakwaters of 125m long and about 100m away from the shore), northern bank of the Kelani river mouth (few number of small groynes, 4 large groynes between river mouth and Palliyawatta, additional groynes further north upto exposed beach rock) and Dikkowita area (stabilization by separating the long bay into several smaller compartments was done under this scheme.

All of these major stabilization projects were implement prior to the Colombo South Port Development and Port City Development. This means erosion in west coast of Sri Lanka is not related to the current developments in the area. The principal causes of erosion in west coast includes; natural process due to monsoon generated wave attacks, man‐induced changes occur due to extraction of sand and corals from the coastal zone and reducing the sand supply by river sand mining.

Proposed port city development it taking place in the shadow of the Colombo south port breakwater and therefore it will not create significant difference to the existing hydrodynamic pattern of the area. This was proved through comprehensive modelling studies during the SEIA of Proposed Colombo Port City Development Project, Dec. 2015.


3.1.4 Description of the present condition of the water quality concerning nutrient dynamic, algae blooms and water turbidity.

Plankton is tiny organisms that drift through the layers of the ocean and productive base of both marine and freshwater ecosystems. Phytoplankton are a key component of marine ecosystems and act as a potential bio‐indicator of water quality alterations in response to local and global impacts viz. urban and industrial inputs, nutrients,, micro‐toxic pollution, temperature and species invasion. The growth and proliferation of phytoplankton in marine environment is affected by nutrient enrichment processes like coastal upwelling, anthropogenic activities and riverine inputs (Berdalt et al. 1996). Prosperous and Nitrogen are more often considered as the principal limiting nutrients for the growth of marine phytoplankton. Eutrophication of coastal ecosystems is caused by excessive nutrients such as phosphate and nitrate. The increase input of nutrient from riverine outflow and domestic sewage effluent into coastal waters has several ecological consequences viz. algal blooms, formation of hypoxia, oranoxia in the bottom water due to the sedimentation of unused organic matter as stratification develops and a change in the phytoplankton species composition due to alteration in ambient nutrient ratios and quantities (Jickells 1988). Coastal nutrients may supply nitrogen, silicon and prosperous for phytoplankton growth at proportions very different Redfield Ratio (16:16:1) (Berdalet et al. 1996). However, sometimes nutrient enrichment may cause a significant role on phytoplankton community composition and diversity (Justic et al. 1995). Chlorophyll‐a concentration is a good indicator of phytoplankton biomass, which reflects the primary productivity. Phytoplankton is the base of the marine food chain thus affects higher trophic levels such as shellfish and fin fish population.

Totally 16 samples collected (figure 3.17) and analyzed for the Phytoplankton abundance, Chlorophyll‐a, TSS and Nutrients.


Figure 3.17: Map of the study area showing sampling sites

3.1.4.1 Phytoplankton abundance

Phytoplankton abundance at four sites (1, 2, 7, 15) ranged from 245‐2099 cells/l is given in figure 3.18.


.

Figure 3.18: Phytoplankton density in the area

Phytoplankton diversity and composition

The most common eukaryotic planktonic flora are the diatoms, the dinoflagellates and the cocolithophorides. Cyanobacteria which are prokaryotic organisms are usually associated with eutrophic waters (Jayasiri, 2009). The diatoms can be categorized into two groups such as centric diatoms and pennate diatoms. All the identified phytoplankton species are categorized into two groups (diatoms and dinoflagellates). Total of 61 phytoplankton species belonging to two taxonomic groups (43 species of diatoms and 18 species of dinoflagellates) are recorded in the area (Table 3.2).

The diatoms are dominated in all the area with a percentage of 87% (Figure. 3.19). The composition of phytoplankton species in the area is shown in Table 3.2. Rhizosolenia sp. is the most dominant species in the region (23.34%) followed by Chaetoceros sp. (15.64%) and Coscinodiscussp. (13.55%). Some other dominant species with higher than 5% in the region are Stellarima stellaris and Ceratium fusus. Thirty‐eight (47) species were identified as rare species and 9 species had moderate composition. Species richness varied from 15 to 37 in the area (Figure 3.20).

Figure 3.19: Relative composition of diatoms and dinoflagellates in the area

0

500

1000

1500

2000

2500

1 2 7 15

Phytoplankton abundance

(cells/l)

Site location

Diatoms

87%

Dinoflagel

lates

13%


Table 3.2: Relative composition of phytoplankton species (dominant;>4.99%, moderate;1.00‐4.99%, rare, <1.00%)

Group Genus /Species Relative Composition (%)

Bassilariophyceae (Diatoms)

Biddulphiasp. 0.004

Cerataulinasp. 0.652

Chaetoceros sp. 15.374

Chaetoceros borealis 0.042

Chaetoceroscontortus 0.111

Chaetocerosanastomosans 0.134

Chaetocerosdensus 0.081

Chaetocerosdanicus 0.395

Chaetocerospseudocurvisetus 0.058

Chaetocerosdecipines 0.290

Chaetocerosrostratus 0.014

Chaetocerossimilis 0.014

Coscinodiscus sp. 17.672

Coscinodiscusgranii 1.255

Coscinodiscus concinnus 1.983

Coscinodiscusstellaris 0.279

Eucampiazodiacus 0.526

Guinardiastriata 3.458

Lauderiaannulata 0.513

Leptocylindricussp. 0.067

Llithodesmiumsp. 0.359

Melosirasp. 4.801

Meunieramembranacea 1.729

Naviculasp. 2.209

Neocalyptrellarobusta 1.281

Nitzschiasp. 0.826

pseudo‐Nitzschiasp. 4.528

Odontellasp. 0.405

Odontellaregia 0.007

Pleurosigmasp. 1.737

Pleurosigmacapense 0.230


Pleurosigmadirectum 2.425

Proboscicasp. 1.654

Rhizosoleniasp. 13.508

Rhizosoleniaimbricata 0.058

Stellarimastellaris 4.874

Thalassionemasp. 0.394

Thalassiosirasp. 0.396

Dynophyceae (Dinoflagellates)

Akashiwosanguinea 0.012

Alexandriumcatenella 0.243

Ceratiumfurca 1.939

Ceratiumtripos 1.191

Ceratiummacroceros 0.007

Ceratiumhorridum 0.409

Ceratiumfusus 10.294

Ceratiumlineatum 0.045

Dinophysiscaudata 0.013

Diplopeltabomba 0.007

Gymnodiniumsp 0.022

Noctiluasp. 0.667

Noctiluascintillans 0.234

Peridiniumsp. 0.020

Preperidiniummeunieri 0.333

Protoperidiniumsp. 0.222

Prorocentrummicans 0.730

Prorocentrumredfeildil 0.344


Figure 3.20: Variation of species richness

3.1.4.2 Chlorophyll‐a

Chlorophyll‐a concentrations in study area are given in figure 3.21. The chlorophyll‐a concentration is very high and varied from 6.98 to 13.49 µg/l. Highest and lowest concentrations are reported at stations 1 and 2 respectively. In all the studied sites, chlorophyll‐a concentration exceed the 1 µg/l which is the trigger value for Australian coastal waters and the level reported in the area indicate the algal blooms (Table 3.3).

Figure 3.21: Chlorophyll‐a contents in the area

0

5

10

15

20

25

30

35

40

1 2 7 8 9 10 15 16

Species richness

0

2

4

6

8

10

12

14

16

1 2 7 8 9 10 15 16

Chlorophyll a (µ

g/l)

Site Location


Table 3.3: Default trigger values of chemical and biological stressors for Australian marine waters.

Parameter

Trigger values

South east Australia

South central Australia

South‐west Australia

Tropical Australia

Chlorophyll‐a (µg/l) 1 1 0.3 offshore

0.7 inshore

0.5‐0.9 Offshore

0.7‐1.4 inshore

NOx ‐ oxides of nitrogen (mg/l)

0.015 0.050 0.005 ‐

Turbidity (NTU) 0.5–10 ‐ 1‐2 1‐20

TSS (mg/l) 10 ‐ ‐ ‐

(Source: National water quality management strategy; no.4 (2000), Australian and New Zealand Environment and Conservation Council, GPO Box 787 CANBERRA)

3.1.4.2 TSS

TSS variation at locations area is given in Figure 3.22. The TSS level varied from 2.8 to 5.5 mg/l. The highest and lowest TSS levels are reported in site 1 and 7 respectively. TSS values are less than the trigger value of South east Australia (refer Table 3.3 above).

Figure 3.22: TSS variation in the area

3.1.4.2 Nutrients

No2‐‐N concentration varied from 0.009 to 0.013 mg/l. The highest NO2

‐‐N concentration of 0.013 mg/l was reported at location 1 while lowest was in location 2 (0.009 mg/l) (Figure 3.23).No3‐‐N concentration varied from 0.025 to 0.080 mg/l. The highest NO3

‐‐N concentration of 0.08 mg/l was reported at location 1 while lowest was in location 16 (Figure 3.24). Nitrate‐N level is higher in all the locations in area than the trigger values of Australian waters (Table 3.3). PO4

3‐P concentration varied from 0.005 to 0.013mg/l showing highest concentration at location 2 while lowest value is at site 1

0.00

1.00

2.00

3.00

4.00

5.00

6.00

1 2 7 8 9 10 15 16

TSS (m

g/l)

Site Location


(Figure 3.25). SiO44‐‐Si concentration varies from 0.007 to 0.025 mg/l showing highest concentration

at site 6 while lowest was at site 1 (Figure 3.26).

Figure 3.23: Variation of nitrite concentration in the area

Figure 3.24: Variation of nitrate concentration in the area

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

1 2 7 8 9 10 15 16

NO2‐ ‐N

(mg/l)

Site Location

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

1 2 7 8 9 10 15 16

NO3‐ ‐N

(mg/l)

Site Location


Figure 3.25: Variation phosphate concentration in the area

Figure 3.26: Variation of silicate concentration in the area

3.2 Biological Environment

3.2.1 Description and assessment of present distribution, biodiversity and health of reef ecosystems

Distribution of reefs

A continuous thin reef could be observed within the proposed sand extraction area running towards South – North direction (Figure 3.27 and Figure 3.2). This reef is situated at the depth around 25m. In addition, patchy distributed limestone reef flats could be observed towards the South‐East area at around less than 25m depth, towards the coast.

Coral species diversity

The distribution of species along the reef through visual inspection could not be surveyed due to unfavorable localized sea conditions. However, the species identification (based on the specimens

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

1 2 7 8 9 10 15 16

PO43‐ ‐P

(mg/l)

0.000

0.005

0.010

0.015

0.020

0.025

0.030

1 2 7 8 9 10 15 16

SiO

44‐ ‐Si (mg/l)


found entangle with fishing nets) showed reefs consisted with scattered coral colonies, soft corals and seaweed etc., and their frequency of occurrence is low.

Corals particles collected (entangled with fishing gears) belong to 12 families. Fourteen coral parts were identified up to the genus: 10 species of hard corals (Table 3.4) and 4 species of soft corals (Table 3.5).

Table 3.4: Hard coral species identified (up to the genus) within the sand mining site or adjacent areas during the survey

Phylum Class Order Family Genus

Cnidaria

Anthozoa Scleractinia Poritidae Porites

Cnidaria

Anthozoa Scleractinia Mussidae Symphyllia

Cnidaria

Anthozoa Scleractinia Pocilloporidae Pocillopora

Cnidaria

Anthozoa Scleractinia Acroporidae Montipora

Cnidaria

Anthozoa Scleractinia Pectinidae Echinophyllia

Cnidaria

Anthozoa Scleractinia Mussidae Acanthastrea

Cnidaria

Anthozoa Scleractinia Acroporidae Acropora

Cnidaria

Anthozoa Scleractinia Agariciidae Pavonas

Cnidaria

Anthozoa Scleractinia Merulinidae Favites

Cnidaria Hydrozoa Anthomedusa Milleporidae Millepora


Figure 3.27: Distribution of reefs within the proposed sand extraction area

Table 3.5: Soft coral species identified within the sand mining site during the survey

Phylum Class Order Family Genus

Cnidaria

Anthozoa Alcyonacea Nephtheidae Dendronephthya

Cnidaria

Anthozoa Alcyonacea Alcyoniidae Lobophytum

Cnidaria

Anthozoa Alcyonacea Gorgoniidae Gorgonia

Cnidaria

Anthozoa Alcyonacea Gorgoniidae Leptogorgia

3.2.2 Description and assessment of present distribution and living state of sea grasses /sea weeds

Sea grasses were not found during this study and this observation is confirmed the previous observation made in previous EIA report. (EIA SLLARDC, 2007). Based on the sea weed specimens found with fishing net entanglement, the following species were identified (Table 3.6). However, the distribution and abundance of sea weeds have to be confirmed with an underwater visual survey.

List of sea weed species possibly available within the proposed sand mining area or surrounding areas are as follows:


Table 3.6: Sea weed species possibly available within the sand mining area or surrounding areas

Scientific name of the species

Ulva fasciata

Ulva reticulata

Chaetomorpha antennina

Chaetomorpha crassa

Cladophora herpestica

Boergesenia forbesii

Stoechospermum polypodioides

Chnoospora minima

Sargassum crassifolium

Sargassumsp.

Actinotrichia fragilis

Galaxaura rugose

Gelidiumsp.

Gracilaria corticata

Portieria hornemannii

Sarcodia montagneana

Grateloupia lithophila

Halymenia durvillei

Chondrophycus ceylanicus

3.2.3 Description and assessment of present distribution, species composition and richness of sea bottom macrobenthos

The community of organisms that live on, or in the bottom (seafloor) of a water body are visible to naked eye (>1.0 or 0.5 mm) are known as “macrobenthos”. The benthic community is complex and plays a vital role in the aquatic ecosystems as primary or secondary consumers representing diversified feeding habits such as grazers, omnivores, carnivores and bacteriovores. Well‐known groups of benthic animals are worms such as polychaetes and oligochaetes, molluscs such as bivalves and gastropods, and crustaceans such as amphipods and decapods. They are a food resource for a large number of predators; benthic fish.

Totally 12 samples were collected from the proposed dredging site for macrobenthos analysis and results of the analysis is shown in Figure 3.28 with respective of abundance (individuals/ per square meter). A total of 53 macro zoobenthos organisms were identified among the analyzed benthic samples (Table 3.7). This mainly represents eight major phyla of Mollusca, Annelida, Arthropoda, Echinodermata, Retaria, Rhodophyta, Cnidaria and Chordate (lower chordata). The sandy substrate was mainly characterized with distribution of bivalves belonging to 11 families of Arcidae, Cardiidae, Carditidae, Donacidae, Glycymerididae, Mactridae, Pectinidae, Pharidae, Tellinidae, Solenidae and Veneridae. Apart from bivalves, sandy and mud bottoms mainly consisted of Foraminifera shells,


polychaets (Nereis sp.) and tube worm of single tubes (Table 3.7 and Figure 3.28). However, more than 95% of the bivalves and gastropod shells observed were dead and degraded. Occurrence and accumulation of these dead shells can be due to washed off from the near shore areas influenced by seasonal current patterns (Figure 3.29).

Other species found in the sample locations are belonging to lower chordate (Amphioxus sp.), scaphopods (Dentalium sp.), malacostracans (Gamarus sp., Penaeus sp., mantis shrimp larvae, crustacean sp. and barnacle), echinodermata (Brittle star and elongate heart urchin (Lovenia elongate), Rhodophyta (Gracilaria sp. and coralline algae) and cnidarians (calcified coral polyps).

Figure 3.28: Macrobenthos found at the sand extracting site with their abundance (individuals/

per square meter).


Table 3.7: Relative abundance of macro‐benthic organisms found in different sampling locations/ substrates in the proposed sand dredging area (individuals/ m2)

Phylum Class Family Species Sampling location and substrate

S7 S3 S6 S4 S5 S9 S11 S10 S12 S8 S2 S1

S/L S S M/S S/G M/S S S M M S S

Mollusca Bivalvia Arcidae Arcasp. 0 0 0 0 380 152 0 0 0 0 0 0

Cardiidae Acrosterigma(Vasticardium) sp.

0 0 0 0 76 0 0 190 0 114 0 0

Cardiidae Acrosterigma (Vasticardium) arenicola

0 0 0 0 0 0 0 0 0 38 0 0

Cardiidae Fulviasp. 0 0 0 0 0 0 0 0 190 0 532 76

Cardiidae Lunulicardia sp. 0 0 0 0 0 0 0 0 0 0 114 0

Cardiidae Trachycardiumsp. 0 0 0 0 0 0 38 0 0 0 0 0

Carditidae Carditasp. 0 0 0 0 0 0 0 0 0 38 0 0

Donacidae Donaxsp. 0 0 0 0 0 608 76 190 0 114 304 0

Glycymerididae Glycymerissp. 0 0 0 76 0 0 76 38 38 0 0 0

Mactridae Oxyperassp. 0 38 0 0 228 152 38 0 0 76 0 0

Mactridae Mactrasp. 0 0 0 0 0 0 0 38 38 0 228 0

Pectinidae Chlamys sp. 0 0 0 0 0 0 0 0 0 0 38 0

Pectinidae Pecten sp. 0 0 0 0 0 304 190 0 0 0 38 38

Pharidae Siliquaradiata 0 0 0 0 0 0 0 0 114 38 0 0

Tellinidae Macomasp. 0 0 0 0 0 608 0 0 0 0 0 0

Tellinidae Tellinasp. 0 0 0 0 0 0 0 152 0 0 0 0

Solenidae Solenroseomaculatus 0 0 0 0 0 0 0 0 0 38 0 0

Veneridae Antigonasp. 0 0 0 0 76 114 38 0 0 152 38 0

Veneridae Dosiniasp. 0 0 0 0 0 152 0 38 0 988 0 0


Veneridae Gafrariumsp. 0 0 0 0 0 304 0 0 0 1292 0 0

Veneridae Lioconchasp. 0 0 0 0 76 38 38 0 152 0 0 0

Veneridae Meretrixcasta 0 0 0 0 0 0 0 0 0 76 0 0

Veneridae Paphiasp. 0 0 0 0 0 0 0 190 0 0 0 0

Veneridae Sunettasp. 0 0 0 0 0 0 38 0 0 228 0 0

Unidentified 0 76 114 0 0 0 0 0 0 304 0 0

Gastropoda Architectonicidae Architectonicasp. 0 0 0 0 0 0 0 0 0 304 0 0

Calyptraeidae Calyptraea (Crucibulum) extinctorium

0 0 0 0 0 152 0 0 0 0 0 38

Cerithiidae Cerithiumsp. 0 0 0 0 76 0 0 0 0 0 0 0

Haminoeidae Haminoeasp. 0 0 0 0 0 0 0 0 0 76 0 0

Muricidae Morula sp. 0 0 0 0 0 0 38 0 0 0 0 0

Muricidae Purpura(Thais) bufo 0 0 0 0 0 0 0 0 0 0 0 38

Naticidae Naticasp. 0 0 0 0 0 0 38 0 0 0 0 0

Olivoidae Olivasp. 0 0 0 0 38 0 38 0 0 152 76 38

Terebridae Duplicaria sp. 0 0 0 38 38 0 0 0 38 0 0 0

Terebridae Oxymeris sp. 0 0 0 0 0 0 0 0 0 0 0 38

Trochidae Monileasp. 0 0 0 0 0 0 152 38 0 76 0 0

Trochidae Trochussp. 0 0 0 0 38 0 0 0 0 0 0 0

Trochidae Umboniumsp. 0 0 0 0 0 0 0 0 0 152 0 0

Scaphopoda Dentallidae Dentaliumsp. 0 0 0 0 76 190 76 0 0 152 190 0

Annelida Polychaeta


Nereidae Nereissp.1 0 0 0 38 228 456 38 0 38 304 0 266

Capitellidae Heteromastussp. 0 0 0 0 0 0 0 0 0 0 38 0

Arthropoda Malacostraca Penaeidae Penaeussp. 0 0 0 0 0 0 0 0 0 0 152 0

Mantis shrimp larvae 0 0 0 0 304 0 0 0 0 0 0 0

Crustacean sp.1 0 0 0 0 152 0 0 0 0 0 0 0

Crustacean sp.2 0 0 0 0 0 0 38 0 0 0 0 0

Barnacle 0 0 0 0 0 0 114 0 0 0 0 0

Echinodermata Ophiuroidea Amphuridae Brittle star 0 0 0 0 0 38 0 76 0 0 0 0

Echinoidea Loveniidae Loveniaelongata 0 0 0 0 0 38 0 0 0 0 0 0

Retaria Foraminifera shells 76 0 0 532 12806 1026 228 0 0 0 1216 1064

Chordata Leptocardii Amphioxus sp. 0 0 0 0 114 76 38 0 0 0 0 0

Rhodophyta Gracilariaceae Gracilariasp. 0 0 0 0 0 0 0 0 0 0 0 228

Florideophyceae Corallinaceae Coraline algae 38 0 0 0 0 0 0 0 0 380 0 0

Cnidaria Anthozoa Calcified single coral polyp 38 0 0 0 380 38 0 0 38 0 76 38

Tube worm tubes

0 0 0 0 38 38 38 0 76 4104 0 684

Total individuals/sq.m 152 114 114 684 15124 4484 1368 950 722 9196 3040 2546


Total Sp./sq.m 3 2 1 4 17 18 19 9 9 22 13 11

Species Richness ‐ Menhinick's index 0.243 0.187 0.094 0.153 0.138 0.269 0.514 0.292 0.335 0.229 0.236 0.218

Species Diversity ‐ Shannon index, H 1.040 0.637 0.000 0.761 0.807 2.434 2.556 1.976 1.983 2.066 1.946 1.651

*Note that: S‐ Sandy substrate M‐ Muddy substrate M/S‐ Muddy Sandy substrate S/G‐ Sandy substrate with small gravel L‐limestone

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Table 3.8: Turtle nesting beaches around proposed sand extracting area

Beach Nature of the beach Species recorded Occurrence

Poruthota Sandy Green turtle, Olive ridley Rare

Eththukala sandy Green turtle, Olive ridley, Logger head Rare

Thalahena Rocky and sandy No information Very rare

Dungalpitiya Rocky and sandy No information Very rare

Seththappaduwa Rocky and sandy No information Very rare

Uswatakeyyawa Rocky and sandy No information Very rare

Dikkowita Rocky and sandy Olive ridley, Letherback Rare

Source: Amarasooriya 1997 and results of the survey

Most of the species are highly migratory, moving between nesting and feeding grounds, which can be thousands of kilometres apart. Further several scientific studies have been proven the existence of this protected species in and around the site of interest (Hewavisenthi, 1990; Wickramasinghhe, 1991; Ekanayake, et al., 2002; Jayawardene, 2006).Three species of marine turtles are recorded around the sand mining site: Green turtle (Cheloniamydas), Olive ridley turtle (Lepidochelysolivacea), and Loggerhead turtle (Carettacaretta). Either foraging or migrating sea turtles could be located within this area.

During the survey period, two species of dolphins (Common dolphin (Delphinus delphinus) and Spinner dolphin (Stenellalongirostris)) were observed in this area. The distribution of the whales in this particular region is not known well but, there are some records (Carcase) of stranded whales washed off to the Negambo coast (Ilangakoon, 2002; NARA, 2016).

3.2.5 Description and assessment of hatchery/breeding grounds for commercial and

ecologically important marine organisms.

The diversity of natural populations of aquatic organisms as well as other living organisms is partially dependent on the environmental variables which always affect the competing populations. Fisheries population is very much dynamic in both temporal and spatial spectrum. Different types of information were gathered on early stages of fish; eggs, larvae and juvenile stages in order to determine the possible spawning seasons, spawning grounds and nursery areas of fishes in the proposed sand mining site.

3.2.5.1 Spawning grounds

The presence of eggs and larvae of pelagic broadcast spawners in the water column can be indicative of spawning grounds, although it should be noted that later larval stages may have been advocated away from the spawning site via water currents. Mature fish with running eggs or sperm can also be indicative of spawning grounds. Determination of spawning and nursery grounds depends mainly on the stage of larvae and where it was collected.

The eggs and larval stages of some pelagic fish have been reported from the western coastal waters of Sri Lanka. Many fish species breed twice a year and the main spawning season has been observed with the beginning of the southwest monsoon i.e. from April to June, and another spawning season has been indicated with the beginning with northeast monsoon, i.e.


November‐December. However, it is possible to observe the spawning throughout the year for some species. The reproductive cycle of different species has developed in respective to the natural range and habitat of the fish. The timing of spawning fish has developed as a response to “ultimate” factors that will maximize the survival of the eggs and fry. Some of these ultimate factors include the water supply and water quality, availability of food and reduced number of predators. Fish are ready to spawn when the ultimate factors are proper. The fish needs to respond to "proximate" factors or cues to adjust the reproductive cycle to match the changing environment (Sumpter, 1990). From April to July, many small pelagics respond to the ultimate factors well when having the appropriate conditions during the southwest monsoon. Therefore, this season can be considered as the main spawning season of many small pelagics even though spawning sometimes takes place throughout the year. Athukorala et al. (2015)concluded the spawning season of A. sirm in the Westcoast belongs to the period from May to July.

Even though the spawning seasons of some pelagic fish are reasonably known, little is known on spawning grounds and migratory routes. The reefs located within this sand mining site could probably be considered as a breeding and hiding places for reef associated demersal species. A possible offshore spawning migration for sardines has been suggested by Dayaratne and Gjsaeter (1986). The majority of penaeid shrimps possess both estuarine and the marine phases in their complex life cycles. Once the nursery life is completed in low saline lagoons, estuaries etc. they migrate to coastal waters for reproduction (De Bruin, 1971). It is highly probable that the resultant osmotic stress due to low saline waters in the Negombo lagoon with the onset of inter‐monsoon rains in April‐May, induces the migration of pre‐adults towards coastal areas for spawning. From the trawl fishery in this region, the high catch rates during the Southwest monsoon could presumably be due to the increased stock density in the trawling grounds owing to migration of shrimps to coastal areas for subsequent maturation and reproduction (Jayawardana, 2004).

During the ichthyoplankton (eggs and larvae of fish) survey, number of pelagic fish larvae (Figure 3.31)and eggs and the larval stages of shrimp varieties were recorded within the sand mining area. This gives some evidence of presence of spawning/ breeding grounds of fish and shrimps most probably in and around the study area, more in shallow depths (Table 3.9).

Table 3.9: The presence of ichthyoplankton (fish eggs/ larvae) at the sand mining site

Transect Ichthyoplankton density/ m3

Fish eggs Fish larvae

T1 9 4

T2 61 15

T3 23 4

T4 33 12


Figure 3.30: Ichthyoplankton (fish eggs/ larvae) density distribution

Figure 3.31: Fish larvae and different developing stages of eggs found at sand mining site

during the ichthyoplankton survey


3.2.5.2 Nursery grounds

The grounds where juveniles are found are termed nursery grounds. It has been suggested that nursery grounds are those sites where juveniles occur at higher densities, have reduced rates of predation and have faster growth rates than in other habitats, which should result in nursery grounds providing a greater relative contribution to adult recruitment in comparison to non‐nursery ground habitats.

Areas where larvae of some species are settled could not be precisely detected within a short study period. Due to lack of relevant information collected over the relevant area during a short period of time, the present work is not sufficient to conclude the occurrence of nursery grounds of fish. However, several observations were made on catching of juvenile fish by different fishing activities (bottom trawling and gillnet fishery etc.) during the fish landing site survey. Further, Jayasooriya (1989) has observed that maturing and mature fish are higher in April/May with the onset of southwest monsoon and again increase in maturing fish in August/September at the latter part of the monsoon in the respective area.

3.2.6 Species diversity and quantity of fish captures (food fish) within the study area

A diversified fish species which are commercially important are captured within the sand extraction area and surrounding areas. Both pelagic and demersal species are available within this area. The major clupeid fish species found during the survey included Amblygaster sirm , Sardinella longiceps, Sardinella gibbosa, Sardinella albella and Hilsa kelee etc, Pony fishes such as Gazza spp. and Leiognathus spp. were also found among the gillnet catches. The demersal fish catches mainly consisted of lutjanidae (snappers), serranidae (groupers), lethrinidae (emperors), carangidae (jacks, trevallies, and scads), leiognathidae (ponyfishes) and some species from the family Dasyatidae. Details of the fish species observed are given in Table 3.10.


Table 3.10: List of food fish species recorded within sand mining area and surrounding areas

Family Scientific Name Common name Local name Commercial Importance

Aridae Arius sp. Sea catfishes Anguluva Moderate Balistidae Abalistes stellatus Starry triggerfish Pothuphora Moderate Pseudobalistes fuscus Rippled triggerfish Low

Belonidae Strongylura leiura Banded needlefish Habaraliya Moderate

Strongylura l

Spottail needlefish Dhiyamoralla Low

Carangidae Carangoides fulvoguttatus

Yellowspotted trevally Thuba parawa Moderate

Carangoides gymnostethus Bludger Vattiya Moderate

Carangoides Malabar trevally Labu Parawa Moderate Caranx heberi Blacktip trevally Guru parawa High Caarnx ignobilis Giant trevally Atanagul High Alectis ciliaris African pompano Kannadiparava Low Atule mate Yellowtail scad Ginnati parava Moderate

Decapterus russelli Indian scad Linna Moderate

Selar crumenophthalmus Bigeyescad Asgedibolla Moderate

Scomberoides commersonianus Talangqueen fish Kattawa Moderate

Parastromateus niger Black pompfret KaluVavvalaya Low Gnathanodon Golden trevally Kabaraparava Low Caesionidae Caesio sp. Fusilier Moderate

Gymnocaesio sp. Moderate

Pterocaesio sp. Moderate Clupeidae Amblygaster sirm Spotted sardinella Hurulla High

Amlygaster clupeoides

Bleeker’s smooth belly sardinella

Galhurulla Moderate

Nematalos anasus Bloch’s gizzard shad Koiyya Moderate Hilsa kelee Kelee shad Katugoi Moderate Sardinella gibbosa Gold strip sardinella Mattasalaya High

Sardinella longiceps Indian oil sardine Pesalaya, yaksalaya High

Sardinella albella White sardinella Sudaya Moderate Chirocentridae Chirocentrus dorab Dorab wolf ‐herring Katuwalla Moderate Coryphaenidae Coryphaena hippurus Dolphinfishes Vannava Low Cynoglossidae Cynoglossus sp. Tongue soles Pathamadiya Low Symphurus sp. Carcharhinidae


Carcharhinus melanopterus Blacktip reef shark Low

Carcharhinus Silky shark Honda mora Moderate Dasitidae Dasyatis kuhlii Sting ray Low Himantura sp. Exocoetidae Cheilopogon sp. Flyingfish Piyamassa Low Exocoetus sp. Engraulididae Stolephorus indicus Indian Anchovy Handalla Moderate

Encrasicholoina heteroloba Shorthead Anchovy Rahuhalmassa Low

Thryssa sp. Lagga Moderate Haemulidae

Plectorhinchus ceylonensis Sweetlips Boraluwa

Plectorhinchus l

Low Pomadasys sp. Grunts Low Leiognathidae Gaza mniuta Toothpony Mas karalla Moderate Leiognathus fasciatus Striped ponyfish Moderate Leiognathu sequulus Common ponyfish Moderate

Leiognathus daura Gold stripe ponyfish Low

Leiognathus splendens Splendid ponyfish Low

Lethrinidae Lethrinus harak Thumbprint Meevatiya Moderate Lethrinus nebulosus Spangled emperor Pullimeevatiya Moderate Lethrinus ornatus Ornate emperor Moderate Lethrinuslentjan Pinkear Emperor High Lutjanidae Lutjanus fulviflamma Blackspot snapper Ranna Moderate Lutjanus decussatus Cheekred snapper Low

Lutjanus kasmira Common bluestripe snapper Irriranna Moderate

Lutjanus madras Indian snapper Low

Lutjanus quinquelineatus Fivelined snapper Moderate

Lutjanus rufolineatus Yellow‐lined seaperch Low

Lutjanus malabaricus Malabar blood snapper Gola Low

Lutjanus monostigma Onespot snapper Low


Lutjanus russelli Russell’s snapper Moderate Lutjanus vitta Brownstripe

snapper Low

Lutjanus argentimaculatus

Mangrove red snapper Thambalaya Moderate

Lutjanus fulvus Black tail snapper Padalla Low

Sphyraenidae Sphyraena barracuda Great barracuda Seelawa Moderate

Sphyraena jello Pickhandle barracuda jeelawa Moderate

Scaridae

Scarusr ubroviolaceus Ember parrot fish Gireva Low Scarus sordidus Daisy parrotfish Gireva Low Scaru sghobban Yelloscale parrotfish Labugireva Moderate Serranidae Cephalopholis argus Peacock hind Kossa Moderate Cephalopolis formosa Blue lined grouper Kangankossa Moderate

Epinephelus l i i i

Longspine grouper Moderate

Epinephalus malabaricus Malabar grouper Galkossa Moderate

Cephalopholis ti

Tomato hind Ranthambuva Low

Epinephelus merra Honeycomb Pullikossa Low

Epinephelus faveatus Barredchest Pullikossa Low Scombridae

Rastrelliger kanagurta Indian mackerel Kumbalawa Moderate

Katsuwonus pelamis Skipjack tuna Balaya High Sarda orientalis Striped bonito Thorabalaya Low Auxis thazard Frigate tuna Alagoduwa Moderate Auxis rochei Bullet tuna Baita Moderate Euthynnus affinis Kawakawa Atawalla Moderate Thunnus albacares Yellowfin tuna Kelawlla High Thunnus obesus Bigeye tuna Asgedikelawalla Low

Acanthocybium solandri Wahoo Sawara, Hera

maha Moderate

Scomberomoru scommerson

Narrowbarred Spanish mackerel AhinThora High

Scomberomorus lineolatus Streaked seerfish Anjilawa Moderate

Scomberomorus guttatus

Indo‐ Pacific king mackerel Moderate

Other non fin fish species

Penaidae Penaeus indicus Indian white KiriIssa High


Penaeus merguiensis Banana prawn Low

Penaeus monodon Giant tiger prawn KarawnduIssa High

Penaeus semisulcatus Green tiger prawn KurutuIssa High

Metapenaeus affinis Jinga shrimps Moderate

Metapenaeus elegance Fine shrimps Moderate

Metapenaeus dobsoni

Kadal shrimps Mal issa High

Metapenaeus moyebi Moyebi shrimps Moderate Portunidae Portunus pelagicus Blue swimming crab Nil Kakuluwa Moderate

Portunus sanguinolentus Blood spotted crab Kakuluwa Low

Scylla serrata Indo‐pacific swamp crab Madakakuluwa Moderate

Sepidae Sepia acculeata Needle Cuttlefish Dalla Moderate Sepia pharaonis Pharaoh cuttlefish Loliginidae Loligo sp. Moderate Octopodidae Octopus sp. Octopus Buwalla Low

3.2.7 Ornamental fish catches (quantity and diversity)

The ornamental fish in this area is normally collected during the calm season from October to March. The species are collected within the shallow inshore reefs as well as the offshore reefs. The important ornamental species included angelfish (pomacanthidae), butterfly fish (chaetodontidae), groupers (serranidae), wrasses (labridae), surgeonfish (acanthuridae) and some species of invertebrates including the fire shrimps (Lysmata debelius) and cleaner shrimps (L. amboinensis). They are mainly harvested from coastal reefs for exports. The recorded species are given in Table 3.11.


Table 3.11: List of ornamental fish species collected by the divers engaged in ornamental fish collection at the sand mining site and surrounding areas

Family Scientific name Common name Occurrence Acanthuridae Acanthurus leucosternon Blue surgeonfish Average

Acanthurus lineatus Lined surgeonfish Average Acanthurus spp Surgeonfish Average Blennidae Ecsenius Rare Chaetodontidae Chaetodon collare Redtail butterflyfish High

Chaetodon falcula Blackwedged butterflyfish High Chaetodon octofasciatus Eightband butterflyfish High Chaetodon decussates Vagabond butterflyfish Average Heniochus acuminatus Pennant coralfish High Haemulidae Plectorhinchus ceylonensis Sri Lanka sweetlips High

Plectorhinchus vittatus IndianOceanoriental sweetlips High

Plectorhinchus schotaf Minstrel sweetlips High

Labridae Cirrhilabrus rubrisquamis Wrasse High

Halichoeres argus Argus wrasse Average Halichoeres sp Average Pomacanthidae Apolemichthys xanthurus Cream angel High Centropyge flavipectoralis Yellowfin angelfish Average Centropyge multispinis Dusky angelfish Average Pomacanthus annularis Blue ring angelfish High Pomacanthus imperator Emperor angelfish High Pomacanthus semicirculatus Koran angelfish High

Scaridae Scarus ghobban Blue‐barred parrotfish High

Scarus rubroviolaceus Ember parrotfish High Serranidae Cephalopholis sonnerati Tomato hind High Cephalopholis argus Peacock hind High Cephalopholis miniata Coral hind High Cephalopholis spp. Average Epinephelus faveatus Barred‐chest grouper Average

Epinephelus merra Honeycomb grouper Average

Epinephelus spp. Average Variola louti Yellow‐edged lyretail High Zanclidae Zanclus cornutus Moorish idol High Hippolytidae Lysmata debelius Fire shrimps Average Lysmata amboinensis Cleaner shrimp Average


3.3 Social Environment

3.3.1 Description and assessment of fisheries and aquaculture resources in the study area including type, catch and production, value etc.

The proposed sand extraction area falls within the Negombo Fisheries District, which is comprised with 13 coastal fisheries inspector divisions (FI Divisions) from Wattala to Kammalthurai. The assessment of fishery in the area is described below.

3.3.1.1 Number of fishers (Fishing population)

The demographic distribution of the fishing population in the Negombo FD is illustrated by table 3.12. The total fishing population in the project area is about 37,372 and 9,692 of them are active fishers those who are directly involved in marine fisheries in year around are to be directly affected due to the sand dredging activities. However, fishermen from Ja‐ela FI division are engaging in only lagoon fishing according to the official data of DFAR. Therefore, it has not been included.

Table 3.12: Distribution of coastal fishing population in the Negombo Fisheries District, 2015

FI Division No. of GN Divisions

No. of fishing families

Fishing Population

Active fishermen

1 Wattala 6 609 2773 591

2 Uswetakeiyawa 8 451 1410 590

3 Kapungoda 3 742 2775 700

4 Aluthkuruwa 2 575 2400 470

5 Pitipana 4 596 4516 1624

6 Duwa 1 460 4810 610

7 City 3 3 1045 4150 1210

8 City 2 4 592 2253 706

9 City 1 4 915 3975 1156

10 Kudapaduwa 3 750 4500 850

11 Eththukala 4 398 1690 460

12 Kammalthurai 5 610 2120 725

Total 47 7,743 37,372 9,692

Source: District Fisheries Office, Negombo, 2015

In accordance with the age wise distribution of the active fishers, majority of the active fishers fall under the age group 50‐59, this is about 36.9%. The age group of above 65 also represents considerable proportion of active fishers. Elderly people are engaging in fishing activities due to the unavailability of any other livelihood opportunities and lack of social security system for them. The age group 40‐59 is the most affected age category by the project as shown in table 3.13.


Table 3.13: Age structure of active fishers

Age group Percent (%) Valid Percent (%) Cumulative Percent (%)

Valid 20 ‐ 29 1.5 1.5 1.5

30 ‐ 39 18.5 18.5 20.0

40 ‐ 49 29.2 29.2 49.2

50 ‐ 59 36.9 36.9 86.2

60+ 13.8 13.8 100.0

Total 100.0 100.0

Source: Socio‐economic Survey‐2014/SED, NARA

Table 3.14 depicts the educational level of the active fishers in the project area. It is observed that 86.2% of the fishermen had attended to grade 6‐11 level education. Almost 3% of the fisherman had obtained secondary education.

Table 3.14: Educational level of active fishers

Percent (%) Valid Percent (%) Cumulative Percent (%)

Valid

grade 1‐5 10.8 10.8 10.8

grade 6‐11 86.2 86.2 96.9

A/L 3.1 3.1 100.0


3.3.1.2 Number and types of fishing crafts and gears operated

A different type of fishing crafts and gears from traditional to modern are in operation as shown in table 3.15. Mainly, three types of fishing crafts are in operation in the area as, Fiber Reinforced Plastic Boats (OFRP), Non ‐Mechanized Traditional Boat (NTRB) and Beach Seine Boat (NBSB). The approximate lengths of these crafts are 19, 12 and 18 feet for OFRP, NTRB and NBSB respectively. The prominent craft operated in the area is OFRP.


Table 3.15: Types and number of craft operated in the proposed project area

FI Division OFRP NTRB NBSB Total Landing sites

1 Wattala 175 169 ‐ 344

2 Uswetakeiyawa 95 110 2 207

3 Kepungoda 38 456 28 522 2

4 Aluthkuruwa 35 285 ‐ 320 5

5 Pitipana 179 80 ‐ 259 7

6 Duwa 118 67 ‐ 185 3

7 City 111 40 50 ‐ 90 3

8 City 11 66 162 ‐ 228 4

9 City 1 370 41 ‐ 411 2

10 Kudapaduwa 150 ‐ ‐ 150 2

11 Eththukala 175 12 ‐ 187 3

12 Kammalthurai 216 58 2 276 9

Total 1,657 1,490 32 3,179 40


Fiber reinforced plastic boats (OFRP)

OFRP is powered by out‐board engine and operates in and outside the project area. The total number of OFRP boats operated in the NFD is about 1,657. The craft generally use a wide array of fishing gears such as small meshed gill nets, medium meshed gill nets, bottom set nets, hand lines, bottom long lines etc,. Generally from 2 to 3 number of crew members including skipper are on board in the OFRP.

Fiber reinforced plastic boat (OFRP)


Non ‐mechanized traditional boat (NTRB)

The NTRB (log raft/teppama) has a traditional design with three logs or fiberglass and paddled by oars. About 1,490 numbers of NTRB are operated inside the project area. Mainly used for small meshed gill netting and hand line fishing. Generally one crew member or most of the time craft owner engaged in fishing operation.

Teppama (Log/Fiber raft) (NTRB)

Beach seine boat (NBSB)

Generally a non‐mechanized craft used for beach seine fishery. This fishery has been existed for centuries and operators having customary property rights. However, traditional beach seine craft and coir made net were replaced by OFRP boat and nylon net in the study area. There were about 32 beach seine boats in the project area and they operate very close proximity from the beach. Generally about 55 members crew including skipper work in a beach seine fishing unit.

Hauling of a Beach seine OFRP boat used for Beach seine operation

Different fishing gears are used by OFRP and NTRB craft depending on the fishing season and availability of fish varieties. In the beach seine fishery a mix of shore seine varieties are caught. Table 3.16 describes the fishing gear used in the project area.


Table 3.16: Fishing gears according craft category

Fishing gear Craft (%)

Total (%) OFRP NTRB NBSB

Indian mackerel net (kumbala del) 33.3 66.7 0 100

Anchovy net (halmessa del) 38.5 61.5 0 100

Lobster net (pokirissa del) 16.7 83.3 0 100

Sea bass net (Moda del) 75 25 0 100

Small pelagic net (suda/sala/hurulla del) 35.7 64.3 0 100

Seer net (thora del) 75 25 0 100

Bottom long line (batalone) 100 0 0 100

Beach seine (madel) 0 0 100 100

Other net 100 0 0 100


Totally 32 registered beach seine are in operate along the shoreline from Wattala to Kammalthurai.

3.3.1.3 No. of dependents

Information about the number of family members according to craft category is given in the table 3.17. The number of family members in a family varies from 2 to 7, 2 to 9 and 3 to 6 for OFRP, NTRB and NBSB craft categories respectively. This is indicated that NTRB fishers show more number of dependents in the area.

Table 3.17: Number of family members according to craft category

Number of family members

OFRP (%) NTRB(%) NBSB(%)

2 15.8 5.3 0

3 26.3 15.8 12.5

4 21.1 34.2 25.0

5 15.8 31.6 37.5

6 15.8 7.9 25.0

7 5.3 0 0

8 0 2.6 0

9 0 2.6 0

Total 100 100 100



3.3.2 Identification of fishing grounds and fishing routes (a map to be provided indicating such areas within the mining area and vessel / barge operational area)

Hendala shrimp trawl ground

There is a shrimp trawl ground in the west coast of Sri Lanka off Hendala (Figure 3.5). The shrimp trawl activities take place in the shallow coastal waters, exploiting the parent stock of shrimps, which utilize the Negombo lagoon for completion of the early phase of their complex life cycle. All shrimp trawls operating off Hendala are mechanized. The crafts are of the 3.5 t type, 10.4 m in length, and of modern design and they are powered by inboard diesel engines of 25 – 40 HP. According to the observations made on shrimp trawls operations, there is no any overlapping area between this trawl ground and sand mining site as trawling is conduct in very shallow depths close to the shore.

Other fishing grounds

Based on the direct observations of the fishing activities, the prepared map of the fishing grounds is shown in Figure 3.32.Some fishing grounds are located inside the proposed sand extraction area whereas the most fishing grounds are located outside.

According to the survey done at the sea, three types of boats were basically operated either within or outer to sand dredging site: outboard engine Fiber Reinforced Plastic (OFRP) boats, non‐motorized traditional log rafts (Theppam) and 3.5t mechanized shrimp trawlers (IDAY) (Figure 3.33). All Theppams were operatingoutside the proposed sand dredging site, more in shallow up to 3km away from the shore.

All shrimp trawlers were operating (even though bottom trawling is a banned fishing method) away from the proposed sand dredging area. OFRPs were operating in a wider area targeting a wide range of species. The wide range of gear usage having different mesh sizes and hook sizes is an evidence for the species diversity (Table 3.18 and Figure 3.32). The Figure 3.34 illustrates the distribution of the fishing fleet with respect to different target species. However maps shown in Figures 3.32,3.33 and 3.34 could not be considered as a comprehensive picture in the distribution of the fishing fleet. The special and temporal distribution of the fishing fleet should be monitored probably for a period of minimum one year in order to understand the behavior of the fishing fleet. During the survey, it was verified some fishing boats which were operating at the areas shown in the maps leave from Negombo main port. During the anchovy fishing season (July – November), a number of fishing boats come from distance areas to the anchovy fishing ground for fishing, which line more in shallow depths (see Figure 3.34).


Figure 3.32: A map of the fishing grounds plotted based on the information and GPS

positions provided by fishermen and through direct observations


Figure 3.33: The map of the operated fishing gears inside and around the proposed sand

dredging site


Figure 3.34: The map of the fishing operations directed to respective target species present

inside or around the proposed dredging site


Table 3.18: Gears operate mostly at sand dredging site, their seasonality and target species

Gear Fishing season Target Group

J F M A M J J A S O N D

Bottom set gillnets X X X X rock fish, carangids

Gill net 2 1/4" X X X Indian mackerel, queen fish

Gill net 2 1/4",Gill net 2 1/2"

X X X X X X X X X X X X Indian mackerel, carangids

Gill net 1 "‐1 1/2" X X X X X X X spotted sardinella, other sardines

Bottom Set Gill Net 2 1/4"

X X X X X X X X X X X X emperrors, groupers, etc

Gill net 1 1/16", 1 3/16", 1 1/2",Gill net 2 1/2"

X X X X X X X X X X X X spotted sardinella, other sardines, Indian mackerel

Gillnets 3 1/2", 4 1/2" X X X X X X X X X X X X Baracuda, seerfish

Gill net 12'' X X X Koorala

Gill net 5/8'' X X X X X Halmessa

Gill net 18'' X X X X X Skates, rays

Gill net 3 1/2",2 1/4'' X X X X X pullunna, ponyfish, carangids

Shark nets 6", 7" X X X X shark, skates and rays

Crab Fishery 4 1/2" X X X X X X X X X X X X Blue swimming crab, mud crab

Bottom Long line, hook size 7,8

X X X X X X X X X X X X rockfish, skates

Scuba diving X X X X X colour fish, groupers

Trolline X X X X X X X X X X X X Seerfish, carangids, yellowfin

3.3.3. Description and assessment of present fishery and fishery related activities

3.3.3.1 Fish production of the area

The annual fish production of Negombo Fisheries District by FI Divisions is given in table 3.19. The total fish production of the NFD in 2015 was about 33,705 mt according to the statistical information of DFAR. The highest contribution to fish production is by Duwa FI Division. Contribution to the fish production from Watttala, Kudapaduwa and City 1 FI divisions is also considerable. Further fish production by craft wise in 2015 is given in table 3.20.


Table 3.19: Annual fish production of Negombo Fisheries District by FI Division

No FI Division Annual Fish production (mt)

2008 2009 2010 2011 2012 2013 2014 2015 1 Kammalthurai 538 704 739 905 2107 1761 1655 1639

2 Eththukala 631 664 822 866 915 883 1871 1281

3 Kudapaduwa 244 1011 3515 6364 6604 5722 6403 5515

4 City‐1 67 981 2129 2732 3787 4917 5417 4820

5 City‐2 921 838 463 356 2012 1407 2335 1331

6 City‐3 332 926 509 737 2614 1510 1482 1010

7 Duwa 543 653 703 775 827 1080 3359 8351

8 Pitipana 1186 6112 11913 11573 14480 8927 7119 1229

9 Aluthkuruwa 215 303 215 237 453 549 1052 404

10 Kapungoda 408 535 320 633 893 793 1056 777

11 Ja‐Ela 152 492 165 94 196 146 157 208

12 Uswetakeiyawa 657 748 609 568 774 884 892 849

13 Wattala 75 81 722 928 976 2770 2453 6291

Total 5,969 14,047 22,826 26,768 36,638 31,349 35,251 33,705


Table 3.20: Annual fish production of Negombo fisheries district by type of fishing crafts in Mt

FI Division OFRP NTRB NBSB Total

1 Wattala 2,003 450 ‐ 2453

2 Uswetakeiyawa 646 161 ‐ 807

3 Kapungoda 112 107 442 661

4 Aluthkuruwa 216 144 ‐ 360

5 Pitipana 448 356 ‐ 804

6 Duwa 1,210 73 ‐ 1283

7 City 111 392 307 ‐ 699

8 City 11 1,233 218 ‐ 1451

9 City 1 5,298 175 ‐ 5473

10 Kudapaduwa 900 ‐ ‐ 900

11 Eththukala 875 130 ‐ 1005

12 Kammalthurai 1,300 120 40 1460

Total 14,631 2,240 482 17,353



Out of the total fish production (2015) of proposed project area 84% is from OFRP boats while 13% from NTRB and the rest from catch of NBSB. The highest catch is reported in OFRP boats of City 1 FID, which is about 36% of the total OFRP fish catch of the project area. NBSB are in operation only in two fisheries inspector divisions; Kammalthurai and Kepungoda.

OFRP boats are operated throughout the year whereas both NTRB and NBSB are operated 6‐8 months per year. The cost involvement for one fishing round is highest in NSBS over other two boat types since the labour intensive nature. OFRP and NTRB boats need only two people for fishing while NBSB required 50‐60 persons at once. OFRP, NTRB and NBSB boats are operated averagely 20, 18‐20 and 15‐18 days per month respectively (Table 3.21).

Table 3.21: Fishing trip details by boat type


3.3.3.2 Value of fisheries (food fish)

The annual production of each fish group and average farm rate price were incorporated in order to estimate the value of fisheries in Negombo Fisheries District for 2014 (Table 3.22). Accordingly, the value of the fisheries in the Negombo Fisheries District in 2014 was estimated at 15864.8 Million LKR.

Table 3.22: Fish catch, average farm rate value and fish value in Negombo fisheries district in 2014 by major commercial groups

Source: MFARD, 2015

Boat Type Fishing duration per year

No. of Fishing days per month

No. of crew members

Cost/fishing per trip

OFRP Throughout the year 20 2 Rs.4000.00

NTRB 6‐8 Month 18‐20 2 Rs.400.00

NBSB 6‐8 Month 15‐18 (rotational basis) 50‐60 Rs.12500.00

Fish Group Quantity in Mt Avg. Farm Rate Price (Rs/kg) Fish Value (Million.LKR)

Seer 2,560 896 2,292.5

Carangids 1,760 392 689.9

Skipjack tuna 4,910 303 1,485.6

Yellowfin tuna 4,370 633 2,766.2

Tuna like fishes 5,310 220 1,169.5

Sharks and skates 820 414 339.3

Mullets 4,120 317 1,306.0

Small pelagic fishes 8,320 226 1,877.9

Prawns 3,220 826 2,658.6

Lobsters 90 2733 246.0

Crabs 310 188 58.4

Others 2,240 435 974.9


3.3.3.3 Income of the fishing community

Monthly gross and net incomes of fishers who engaged in fishing operations according to different the craft categories are shown in Table 3.23.

Table 3.23: Net income calculation for OFRP boats


The daily average fish catch of OFRP boats is higher than the NTRB. The daily expenditure for OFRP boat operation is significantly higher than the NTRB due to cost of fuel. The daily net income of an OFRP is about Rs. 6,800 higher than the daily net income of NTRB boat.

Table 3.24: Net income calculation for NTRB boats


The highest monthly net income is earned by OFRP. The present prevailing income distribution ratio among owner and crew member is 3:1. Accordingly the lowest share of net income is earned by NBSB fishers due to nature of large number of crewmembers in a unit.

3.3.3.4 Fishery related activities

Fishery related or allied activities are provided supporting services to the smooth function of the fishing industry. The fishing community cannot be sustained without continues support of fishery related community. The fishery related economic activities comprised of input supply (fuel, ice, bait), services supply (net mending/making, net clearing) and processing (dried fish making). The table 3.25 is illustrated the fishery related activities in the project area.

Daily average catch 31Kg

Total daily average expenditure Rs. 2500

Average fish price (per Kg) Rs. 300

Average net income/day RS. 6,800

No. of fishing days/ month 20

Monthly average net income Rs. 136, 000

Daily average catch 14Kg

Total daily average expenditure Rs. 100

Average fish price (per Kg) Rs. 300

Average net income/day RS. 4,100

No. of fishing days/ month 20

Monthly average net income Rs. 82,000


Table 3.25: Fishery related activities of Negombo fisheries district by FI divisions

No FI Division Fish vendors

Ice suppliers

Net menders

Dried fish makers

Fuel suppliers

Beach /Dried fish labours

Total

1 Kammalthurai 75 10 25 50 4 275 439

2 Eththukaala 85 1 2 2 2 30 122

3 Kudapaduwa 100 8 0 10 0 70 188

4 City‐1 700 8 100 750 8 1600 3166

5 City‐2 2 0 50 0 0 20 72

6 City‐3 150 4 40 30 8 150 382

7 Duwa 1303 5 100 50 5 450 1913

8 Pitipana 71 2 5 20 3 225 326

9 Aluthkuruwa 25 8 30 20 2 65 150

10 Kapungoda 32 0 0 10 0 60 102

11 Ja‐ela 100 12 30 30 5 60 209

12 Uswetakeiyawa 36 4 4 2 3 36 85

13 Wattala 25 9 20 21 3 37 115

14 Total 2,704 71 406 995 43 3,078 7,269

15 Percentage (%) 37 0.9 6 14 0.1 42 100


According to the PRA conducted, there were 7,269 persons engaged in fishery related activities in the Negombo FD. Their livelihood is indirectly depended from fishing. Any impact on fishery may affect to the socio‐economic well being of them. Beach/Dried fish labours, fish vendors, dried fish makers, and net menders were among the leading fishery related economic activities comprising of 42%, 37%, 14% and 6% respectively.


Table 3.26: Ice plants and production capacities in the Negombo fisheries district

Year No. of Ice plants Capacity (Mt/day) 2004 6 105

2005 10 329

2008 13 555

2010 6 245

2011 12 553

2012 12 623

2013 12 657

2014 12 657

Source: Statistics Unit, MFARD, 2015

As illustrated in table 3.26, there are 12 ice plants in operation in the Negombo fisheries district with a daily capacity of 657 Mt/day. The demand for ice produced is necessarily depend of fish production of the area. The impact on fish production (if any) will negatively affect on the operation of ice plants and the direct employment in this industry.

3.3.3.5 Demographic characteristics of fishery related community

Totally 79% of fishery related people are male and 21% of them are female according to the collected statistics. The average age of them is about 49 years. The average number of members in a household is about 4. The table 3.27 is shown the percentage distribution of number of family members in a households.

Table 3.27: Total number of members in a household of fishery related family

Frequency Percent Valid Percent Cumulative Percent

Valid

1 8 5.7 5.8 5.8

2 18 12.8 12.9 18.7

3 29 20.6 20.9 39.6

4 34 24.1 24.5 64.0

5 27 19.1 19.4 83.5

6 15 10.6 10.8 94.2

7 6 4.3 4.3 98.6

8 2 1.4 1.4 100.0

Total 139 98.6 100.0

Missing 2 1.4

Total 141 100.0

Source: Socio‐economic Survey‐2016/SED,NARA


The marital status shows that 93% is married and the average number of dependents of a family is 4. Therefore, it assumed that, 30,000 people in the area are supported by fishery related activities.

3.3.3.6 Education level of fishery related people

Among those who engaged in fishery related activities 32% had education up to primary level and 62% up to secondary level education while 1% obtained secondary education as shown in table 3.28.

Table 3.28: Education level of fishery related persons

Frequency Percent Valid Percent Cumulative Percent

Valid Grade1‐5 45 31.9 32.1 32.1

Grade 6‐11 85 60.3 60.7 92.9

GCE A/L 2 1.4 1.4 94.3

No formal Education 8 5.7 5.7 100.0

Total 140 99.3 100.0

Missing 1 0.7

Total 141 100.0

Source: Socio‐economic Survey‐2016/SED,NARA

3.3.3.7 Age structure of fishery related persons

The highest percentage of fishery related persons are from 40‐49 age groups which is about 30%. Age groups 50‐59 and 60‐69 comprised of 25% and 19.3% respectively. It is important that approximately 91% of fishery related persons are between the age ranges of 30‐69 as shown in table 3.29.

Table 3.29: Age Structure of fishery related persons

Frequency Percent Valid Percent

Cumulative Percent

Valid <= 19.00 1 .7 .7 .7

20.00 ‐ 29.00 5 3.5 3.6 4.3

30.00 ‐ 39.00 25 17.7 17.9 22.1

40.00 ‐ 49.00 42 29.8 30.0 52.1

50.00 ‐ 59.00 35 24.8 25.0 77.1

60.00 ‐ 69.00 27 19.1 19.3 96.4

70.00+ 5 3.5 3.6 100.0

Total 140 99.3 100.0

Missing 1 0.7

Total 141 100.0


3.3.3.8 Income from fishery related activities

The average monthly income in a family varies from Rs. 15,000‐54,000 depending on their activity. The highest monthly family income is about Rs. 54,000from fish buying and selling. The daily net return of the same is about Rs.2,388. Table 3.30 is provided details of mean income by fishery related activity. The lowest income recorded in food and beverage selling for fishers at the landing centres. Beach labours daily income is Rs. 1,000 while fuel suppliers and Ice suppliers are earned Rs.1500 and 3075 per day respectively. Hence fishing industry generates an array of allied employment opportunities for thousands of coastal population.

Table 3.30: Mean Income by fishery related activity

Service provided to fishing community/industry

Average monthly family income (Rs)

Daily turnover (Rs)

Daily cost (Rs)

Daily return (Rs)

Fish buying and selling

Mean 53,479 18,723 17,504 2,388

N 49 39 43 48

Fuel supply Mean 35,000 NA NA 1,500

N 2 1

Ice supply Mean 29,333 24,033 20,066 3,075

N 3 3 3 4

Net making/ mending

Mean 25,125 1,200 54 978

N 20 10 11 19

Dry fish making Mean 42,545 1,800 7,720 1,523

N 22 1 5 12

Net clearing/ sorting fish

Mean 25,445 2,350 20 1,034

N 20 8 10 22

Cutting fish Mean 27,400 1,475 290 2,128

N 5 4 4 5

Food and beverage selling

Mean 15,000 NA NA 600

N 1 1

Repairing boats and engines

Mean 25,000 NA

N 1 NA NA Beach seine/beach labour

Mean 25,000 NA NA 1000

N 4 2

Other Mean 41,333 10,750 9,750 2,166

Total Mean 39,480 12,870 11,191 1,785

N 133 67 78 120


The table 3.31depicts factors affecting fishery related economic activity. These factors are given considering the current situation and not indicated any concern of sand dredging. Decreasing fish landings, weather changes, low income, decrease of customers were among the main factors affecting fishery related livelihoods. Though, 27% stated that they have not any factor affecting their income. Selling fish by fishermen is affecting for 2.7% of them.


However, 69% of them stated that if sand dreading started that may affect to livelihoods of fishery related community. Of them 30% opined no affect and 1% said they are unaware of the effects.

Table 3.31: Factors affecting fishery related activity

Factor Frequency Rank of importance

Percent Valid Percent

Cumulative Percent

Decreasing fish landings 25 2 17.7 18.9 18.9

Highly competition among fish sellers

2 8 1.4 1.5 20.5

High fish price 3 7 2.1 2.3 22.7

Beach erosion 2 8 1.4 1.5 24.2

High price of fishing gears 1 9 .7 .8 25.0

Weather problems 9 4 6.4 6.8 31.8

Selling fish by fishermen 3 7 2.1 2.3 34.1

Uncleaned beach 1 9 .7 .8 34.8

Decreasing customer demand 3 7 2.1 2.3 37.1

Unsold fish 2 8 1.4 1.5 38.6

Decrease of customers due to decrease fish landings of decrease of fish

6 5 4.3 4.5 43.2

Fishermen go to other areas for fishing

1 9 .7 .8 43.9

Indebtedness 3 7 2.1 2.3 46.2

Low income 6 5 4.3 4.5 50.8

Other 16 3 11.3 12.1 62.9

No issues 36 1 25.5 27.3 90.2

Lack of places to net clearing 1 9 .7 .8 90.9

Insufficient fish storage facilities. 1 9 .7 .8 91.7

Decrease fish price in glut periods 1 9 .7 .8 92.4

Compensation are provided only to fishermen

1 9 .7 .8 93.2

Decrease of net usage due to long line usage

1 9 .7 .8 93.9

Lack of places to sell fish 2 8 1.4 1.5 95.5

Lack of space to dry fish 2 8 1.4 1.5 97.0

No fulltime occupation 4 6 2.8 3.0 100.0

Missing 9 6.4

Total 132 93.6 100.0



3.3.4 Seasonal migration /movement of fishermen

The seasonal calendar of fishing operations according to the craft category is illustrated in tables 3.32, 3.33 and 3.34. The OFRP boats operate annually and NTRB craft operate only 08 months in a year. The beach seine (NBSB) operates for 09 months only. However, the seasonality of fishing operation also determines by the type of fishing gear used and favorable weather conditions.

Table 3.32: Seasonal calendar of fishing operations for OFRP craft

Fishing gear

Seasonality pattern of fishing gear usage in OFRP


Lobster 67 0 83 67 17 17 17 17 17 0 100 83

Small pelagic 60 60 60 40 20 0 0 0 0 0 60 60

Medium pelagic 91 91 100 75 27 18 9 0 18 27 55 55

Rock fish/Galmalu 50 50 50 50 50 100 100 100 100 100 100 100

Anchovy/Halmasso 67 17 17 0 0 0 0 17 17 17 83 100

Baracuda/Ulawa 20 20 60 60 80 80 40 40 20 40 20 0

Carangids/Parawa 0 100 100 100 100 0 0 0 0 0 0 0


Table 3.33: Seasonal calendar of fishing operations for NTRB crafts

Fishing gear

Seasonality pattern of fishing gear usage in NTRB


Lobster 75 0 88 75 25 25 19 13 0 0 100 69

Small pelagic 91 100 91 55 18 18 9 0 0 9 91 91

Medium pelagic 89 89 78 33 11 11 11 22 22 33 89 89

Anchovy/Halmassa 83 50 33 17 0 0 0 0 0 17 83 100

Half beek/Murali 100 100 100 100 0 0 0 0 0 0 100 100


Table 3.34: Seasonal calendar of fishing operations for NBSB crafts

Fishing gear

Seasonality pattern of fishing gear usage in NBSB craft


Beach seine net 100 100 100 75 63 0 0 0 38 38 88 100


Legend

>75% 75%‐50% <25%


Beach seine operates migrate to Northern and Eastern provinces during the period of May to September. It could be observed that the Teppam (NTRB) fishers move from sea to Negombo lagoon in the south west monsoon period from May to September. Further fishermen from Kudapaduwa FI division migrate in May to September to Mannar and Trincomalee (Kokilai) areas for fishing. However, fishermen from Wattala, Uswetakeiyawa, Kepungoda or Aluthkuruwathose are in closer proximity of proposed sand dredging sites are not migrating outside the Negombo fisheries district during the off season.


CHAPTER 4 : ANTICIPATED ENVIRONMENTAL IMPACTS

4.1 Physical Environment

4.1.1 Coastal morphology

General statements about the impact of maintenance dredging on the hydrodynamics and geomorphology of a site cannot be made as the effects are site specific, very difficult to isolate from other 'forcing effects', such as sea level rise or reclamation, and are often little understood. Although all dredging activities can cause some change to the hydrodynamic flow, the magnitude and type of effect will be related to the overall size of the excavation compared to the overall size of the system.

The proposed extraction site is located minimum of 6.4km away from the south west coast and a minimum depth of 15m which is far away from the dynamic coastal zone. Therefore any activities at the prescribed site will not alter the coastal hydrodynamics of the area. Further offshore sand is not the sediment feeder to the dynamic coastal sedimentary budget and hence extraction from offshore locations does not affect any sediment unbalance in the system. Therefore offshore sand extraction does not cause any coastal erosion in adjacent areas.

Dredging is proposed to carry out using trailer suction hopper dredgers (TSHD). Since the suction method is used to extract the sand from the specified locations where the surface sand is present, there will be no damage to the secondary strata or existing reefs in the area.

Further sand extraction is limited to maximum of 3m at a location to avoid scattered deep holes in the area. The depth at the extraction site is between 20m to 35m and it belongs to the deep water area. Maximum of 3m of morphological changes in deep water does not create significant difference in coastal hydrodynamic pattern of the area. If the extraction of sand is limited to maximum of 3m, the mining would not have significant impact on the coastal stability of this particular stretch.

4.1.2 Water quality impacts due to sediments

4.1.2.1 Possible Impacts

Present study mainly focused on the dredging activities which are proposed in the extraction site 3. Due to the fine sediment content of the seabed material, the dredging process has the potential to mobilise fine seabed sediments into suspension and hence increase the turbidity level. High levels of fine suspended sediment over long periods may have an adverse environmental impact therefore a comprehensive sediment dispersion study was commissioned to investigate these potential impacts in detail.

The effect of turbidity induced dredging on the environment is not always unfavorable. The impact due to turbidity is mainly depend on the ambient turbidity levels of the area therefore turbidity generated by the dredger must be seen in relation to the turbidity, which results from natural causes including extreme events.

Dredging activities often generate no more increased suspended sediments than commercial shipping operations, bottom fishing or generated during severe storms (Parr et al 1998). Furthermore, natural events such as storms, floods and large tides can increase suspended sediments over much larger areas, for longer periods than dredging operations (Environment Canada 1994). It is therefore often very difficult to distinguish the environmental effects of


dredging from those resulting from natural processes or normal navigation activities (Pennekamp et al 1996).

Increases in suspended sediments and turbidity levels from dredging and disposal operations may under certain conditions have adverse effects (short term) on marine animals and plants by reducing light penetration into the water column and by physical disturbance.

The degree of resuspension of sediments and turbidity from dredging and disposal depends on four main variables (Pennekamp and Quaak 1990):

the sediments being dredged (size, density and quality of the material), method of dredging (and disposal), hydrodynamic regime in the dredging and disposal area (current direction and speed,

mixing rate, tidal state), and existing water quality and characteristics (background suspended sediment and

turbidity levels).

All methods of dredging release suspended sediments into the water column, during the excavation itself and during the flow of sediments from hoppers and barges. Turbidity resulting from hopper loading and transport to site can be due to the following:

Overflowing of the hopper: here fines are discharged with the overflow through the keel. When the flow reaches the propeller stream of the vessel, suspended sediment may be further distributed;

Lean mixture overboard: if the suction flow is of a very low density, it may be pumped overboard in order not to dilute the load. This will increase turbidity in the top water layer; and

During the excavation: While suction there can be a possibility of releasing fine sediments

Turbidity resulting from placement depends upon the method adopted. Load discharge through dredger bottom doors or by split hull vessels will increase turbidity in the water column due to mixing of the falling mass and the resulting impact on the seabed. This operation releases some fines, but the material descends quickly and most is trapped within the mass and does not escape.

Placement by rainbowing involves the pumping of a soil/water mixture at high velocity out of a discharge pipe in the bow of the vessel. The mixture is directed upwards at an angle. During this process some fines escape. If the discharge is pumped ashore via a pipeline, fines can be contained within settling basins so that the runoff water has a low fine content. It is expected that most of the sand material will be placed by bottom dumping method and very little fine material will escape.

A detailed study on dispersal of dredged sediment movement was undertaken through LHI in 2016 to explore the transport and dispersion of suspended sediments release from the borrow area and reclamation area due to dredging and reclamation processes.

The Particle Tracking module of MIKE 21 Flow Model FM (MIKE 21 HD/PT1) is used to simulate the transport and track of the suspended substances discharged during dredging and dumping process for the proposed port city development.

1MIKE 21 PT is a Particle Tracking module which simulates the transport and fate of dissolved and suspended

substances discharged or accidentally spilled in lakes, estuaries, coastal areas or in the open sea. The pollutant is

considered as particles being advected with the surrounding water body and dispersed as a result of random processes

in two dimensions. Each particle is assigned a corresponding mass, which can change during the simulation due to

decay or deposition. The particles may settle with a constant settling velocity and settled particles may be re-


Hydrodynamic model (MIKE 21 HD) was used to provide a description of tidal current flows and water level variations based upon an unstructured triangular mesh. This model was combined with particle tracking model (MIKE 21 PT) which extends the model capabilities to consider the transport, deposition, erosion and re‐suspension of fine sediments and used to simulate the operational cycle of the dredger based on the dredging work plan and sediment release rates.

Figure 4.1: Bathymetry of the Study Area with Computational Mesh

Trailer suction hopper dredger (TSHD) with hopper capacity 21000m3 is proposed to be deployed for dredging and dumping operations in a continuous manner. A TSHD trails its suction pipe when working, and loads the dredged spoil into hoppers in the vessel. When the hoppers are full, the TSHD sails to a disposal area and pumps the material out of the hoppers.

It is likely that during operations, most sediment will be released into the marine environment due to overspill at the dredge location and pumping of dredged slurry in to reclamation area. When dredge material is pumped onto the vessel the fines are partially separated from sand sized sediments. A proportion of the fines are return to the water column due to over‐spilling, and the sand sized sediments are retained. This technique allows the most efficient use of

suspended. A corresponding mass is attached to each particle which may be reduced during the simulation due to

decay..

(Particle Tracking) PT models such processes as settling, deposition, re-suspension and particle bed interactions to

simulate the transport of both fine and coarse sediment. PT requires the input of hydrodynamics (i.e. water surface

elevation and velocity), mesh and bathymetry information, and sediment characterization of both the native or bed

sediment and the sediment sources. These sources may initiate from sediment re-suspended during dredging and/or

placement. Instead of undertaking the impossible task of modeling every grain of sand, PT instead discretizes the

sediment into “parcels”. Each parcel is representative of a specific mass of sediment. These parcels preserve the overall

size distribution of the sediment source. The model then steps through time tracking the position of each parcel. PT

outputs time accurate horizontal and vertical positions of sediment parcels.


dredging operations and results in a higher quality material for fill and reclamation. Therefore it is proposed to utilized 15000m3 of sand through the overflowing process.

Each dredge produces specific types of losses during dredging and placement that result in suspended sediment entering the water column. To simulate the sources of a dredging operation, PT model requires the following data;

Positions of sediment introduced into the water column Rate of sediment introduction (sediment loss) Size distribution of suspended sediment

Native sediment data was provided in the form of grain size distribution for surface sediment samples at the site. The dispersion of suspended particles during dredging and dumping operations was specified as moving point sources. The mass flux of each source was specified in kg/s with horizontal and vertical position. With specifying source, it is possible to specify the number of particles released per time step to make the concentration fields more "smooth".

Model simulations were done considering several dredging cycles in continuous operation (including both dredging and bottom dumping) using two dredgers in simultaneous operation to observe the impact if any. Rainbow dumping simulations were done considering 10 complete cycles including the offshore breakwater construction at different stages while bottom dumping and dredging were done for 25 cycles. The total duration of each cycle is 305min for bottom dumping and 355min for rainbow dumping.

Several locations in dredging site as well as reclamation site were selected to represent the different stages of dredging and dumping operations and different combinations of those were considered during simulations.

Process of reclamation is proposed through bottom dumping as well as rainbow dumping. Initial filling is going to be done using bottom dumping up to 11m depth and once the area filled up to 11m level rainbow dumping started. Therefore separate model bathymetries were used during modelling process to incorporate the different stages of the rainbow dumping operations.

An assessment of the potential for dispersion of dredged fine sediments in proposed Port City development is carried out using MIKE 21 PT model with the combination of selected dredging locations, dumping locations and different stages of dredging process. Total dredging and reclamation process is scheduled to be carried out continuously throughout the year and hence all possible seasons were considered during the modelling simulations. Months of July 2013 and Jan 2014 were selected to represent the wind and wave conditions in SW and NE respectively while Nov 2013 and April 2014 were selected to represent inter monsoon periods.

Model simulation was carried out for the period of two weeks in each selected month by allowing extra time for complete sedimentation of dispersion material and also to incorporate the effect of both spring and neap tide.

Available water quality data was collected over recent years (1995‐2014) in the study area from different studies was used to assess the reasonable suspended sediment concentration in the ambient condition to use as a guideline for the results comparison. Following studies were considered to obtain representative value of total suspended sediment (TSS) concentration in the study area.

Colombo Port Expansion Project (JICA, 1995 – 1999): Colombo Port Expansion Project (ADB, 2003 – 2005): Scott Wilson (UK) and LHI Assessing Colombo Municipality Wastewater System (ADB, 2009)


Baseline Water Quality Survey under Greater Colombo Wastewater Management Project (ADB, 2013‐2014)

Based on the results of those previous investigations, ambient suspended sediment concentration is ranging from 5mg/l to 20mg/l.

4.1.2.2 Dredging Process

Under dredging operations releasing of fine sediments at the suction head are considered at corresponding dredge levels and the releasing of the sediment through overflow is considered at the water surface. 25 continuous dredging cycles were considered in one model simulation with use of two dredgers simultaneously in selected dredging locations (D2, D3, D4, D5 and D6) to represent entire dredging activity of the proposed development.

Figure 4.2: Selected Areas in Dredging Site for Modelling

Sediment loss rate during overflow is taken as 1% and then total sediments in overflow are estimated as 390m3. Percentage of very fine particles in the overflow is considered as 8% and those are mentioned as “Floaters” in the simulations. The rest of the overflow sediment is considered as coarse particles, and these coarse particles will settle down on the seabed within relatively short distance from the point of discharge. As such, they are not counted as suspended sediment. Overflow starts after 55 min of dredging operation and the total overflow volume is 39000m3 of mixture. Further 0.2% of sediment loss rate is taken into account at the suction head while dredging.

Total dredging time is estimated as 170min and approximately 24.5km is assumed as travelling distance to the dumping site. Travelling time is estimated as 65 minutes. The total duration of each dredging cycle with bottom dumping is 305 min (approximately 5 hrs) while that for rainbow dumping is 355min (approximately 6hrs).

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fishing activities. If fishing gears are operated in such areas, the gear and the fish caught will be contaminated with oil. If oil spillage extends to the coast, the near‐shore sandstone reef and sandy beach will be polluted causing the adverse impacts already discussed.

Any waste generated by the dredger should be removed from the dredger under the permit from the Marine Pollution Prevention Authority. [Annex VIII]

Hazards such as pollution due to oil could be expected during navigation. Precautions should be taken to avoid oil leakage. Disposal of solid waste should carry out in accidence with the approved Waste Management Plan (Annex VII).

4.2 Biological Impacts

4.2.1 Impact on coral reefs and sea grass beds

A continuous thin reef is running towards South – North direction and patchy limestone reefs are available within the proposed sand dredging area.

The organisums associated within the reef habitat could get physically damaged if cutting machines and equipment are used for sand mining directly contact with them. The primary effect of the sand dredging with respect to reefs is the re‐suspension and transport of particulates by currents to reef areas if proper mining methods and preventing measures are not applied. From the results of comprehensive modelling studies based on the operations of modern trailer suction hopper dredgers proved that the spreading of sediment plume is limited to 100m radius from the dredging location (please refer section 4.1.2).

.Since the absence of sea grass beds and coral reefs in proposed sand extraction area or close vicinity, no direct impact on the ecological stability of these habitats are envisaged. However, ecosystem in the area is somewhat naturally conditioned to tolerate variation in sedimentation from natural process especially of river plumes.

Based on the results of sea water and sea sediment analysis it was proved that heavy metal levels in the proposed sand mining area are insignificant (Annex IX).

4.2.2 Impact on Soft Bottom Macrobenthos

The benthic community will be affected in the dredge location as a result of dredging. Most studies have shown that dredging itself is usually accompanied by a significant fall in species numbers, population density and biomass of benthic organisms. The loss of the local benthic fauna can have effects further down food chains. However, the extraction activity could inadvertently create an abundance of food in the form of damaged animals like bivalves or crustaceans. This can temporally enhance number of fish present in the area. All these negative and positive impacts are temporal and localized.

Indirect impacts

Re‐colonization of extraction sites upon cessation of dredging depends on the various factors and their rates i.e. nature of the habitat, the scale and duration of disturbance, the intensity of dredging, hydrodynamics and associated bed‐load transport processes, the topography of the area, and the degree of similarity of the habitat to that which existed prior to dredging (Newell et al., 1998).Since dredging is confined only to a limited depth or the upper most layers of the sand deposit, it would facilitate early recovery.


4.2.3 Impact on Endangered species

The mathematical modelling studies shows that the turbidity levels (in worst case scenario) will not go beyond the background level 100m away from the dredging site and thus it is likely that marine mammals would not be negatively impacted of sand dredging .

4.2.4 Impact on breeding and spawning ground

Potential effects to breeding and spawning grounds of both finfish and non‐finfish could occur through entrainment, smothering and turbidity. Considering vast sea area compared to the limited dredging area, spawning impact on broadcast spawners would be insignificant since the sediment particles will not travel more than 100m from the dredging site.

There is no well‐defined spawning or breeding area identified on the seabed of the proposed dredging site potential effects to breeding and spawning grounds of both finfish and non‐finfish would be minimum.

4.2.5 Impact on fishing ground and route

The impacts of offshore sand dredging on fisheries will be that fishing could not be made in the immediate dredging area. Loss of fishing due to habitat destruction and increase level of maritime traffic may reduce access to their conventional fishing areas. Therefore, fishermen have to travel somewhat long distance in search of new fishing grounds spending more time and fuel. Delay in fish landing would affect the quality of fish and thereby may decline value.

Sand dredging may not affect fisheries in sand/mud bottom areas in the shallow sea because dredging will take place some distance (2‐3 km) away from these areas. Modelling of sediment dispersion proved that sediment particles will not travel more than 100m from the dredging site. This manifests the recruitment of fish may not change as the spawning grounds will not be destroyed or affected due to sand dredging activities which is taken place far away from these areas.

However shrimp fishing conducted in sand/mud area by bottom trawl is currently designated as a destructive method and is not permitted.

4.2.6. Impact on phytoplankton and other aquatic plants

Generation of suspended sediment plumes in the dredging areas may reduce the productivity of phytoplankton and other aquatic plants. The potential effects are expected to extend over the duration of the dredging activity. Due to concentration of organic matter and nutrient in the sediments in the waters are likely to be moderate to low the risks of eutrophication due to introductions of nutrients to the water column is considered to be low/moderate.

4.3 Social Impacts

Direct employment loss is not anticipated; however net income of fishers could be reduced, due to the increased fishing and travel time. Aquaculture is not practiced at the site or associated waters.

4.3.1 Curtailment of fisheries industry

Disturbances to the routes travelled by fishing vessels due to sand mining can be expected for very short periods of time. It may possible to entangle of fishing gears with dredging equipment. However, the anticipated impacts due to sand extraction will be minimal to the fisheries conducted in shallow depths using OFRP and NTRB, where they conduct fishing far away from proposed sand dredging site.


Since dredging would be carried out more than 6 km from the shoreline where the fishing activities are minimum, above impacts are expected to be minimal.

4.3.2 Perceptions of fishery related persons on impact of sand dredging

Out of 141 persons, 134 responded to the question of negative impacts of sand dredging. Of which 69% responded ‘yes” and 30% answer was ‘no’. Therefore, fishermen would have to be educated on technologies and equipment used during dredging activities and on mitigation measures to correct such misconceptions.

4.3.3. Impacts on food‐fish and ornamental fish catches (quantity and diversity), fishing seasons, economic gains to fisher communities

Impact for the food fish varieties would be minimum, due to the fishermen are allowed to engaging fishing in dredging area. However, quantity of the fish catch may reduce temporarily. Marine ornamental fish collection exists in the area outside the dredging sites in associate with reefs in Thalhena, Basiyawatta, Morawala area. Short term impact can be expected for them also.

4.3.4 Value of fishery and aquaculture impact by the project

Since a temporal declining in the ocean productivity around the dredging area could be anticipated, it may cause minor effect on the fish catch and also catch composition. Fast moving fish could be temporary low down Due to move out avoiding the dredging site. Since mariculture sites are not located around the sand mining area, other aquaculture related impacts by the project are minimal.

4.3.5 Impacts on food fish and ornamental fish catch (Quantity and diversity)

Some food fish and ornamental fish species which are more sensitive with environment changes (Example: Butterfly fish) could be reduced their populations if dredging take place within the reef area. Hence, it is proposed to avoid dredging in the reef area (Ref figure 5.1).

4.3.6 Navigational hazards

4.3.6.1 Marine Pollution and Oil Spillage arising from accidents

The Marine Pollution Prevention Authority Act requires that harbour and marine developments should include sufficient facilities for pollution abatement of marine waters as well as contingency measures in the event of the failure of such systems. The contingency measures are also useful to prevent pollution of the coastline from oil spills originating from accidents. In order to minimize the risks posed by operational oil spillages, the contractor should adopt good operating practice, ensure the adoption of principles of safety for the operation of the barges between loading out point and the South Harbour site and operate an Oil Spill Contingency Management Plan (OSCMP). It is recommended that Client/Contractor prepare an Oil Spill Contingency Management Plan in accordance to the guidelines provided by Marine Environmental Protection Authority (MEPA). The prior approval for the said plan has to be obtained from MEPA.

As part of assessing the risk of oil spills along the Sri Lankan coastline impacts of potential oils spills which may take place along the international shipping lanes outside have been modelled previously based on historical data. The relevant pre computed databases for the areas of concern provides valuable information on the order of the magnitude of the problem, its spread with time and the potential areas subjected to impact. This enables the identification and selection of suitable mitigation systems to control potential impacts of oils spills. The


system at hand should be able to control potential oils spills, which are most likely to take place. This aspect has also been considered in detail for the Colombo Port Expansion Project site and it seems logical that the contractor makes use of this approach and information.

With the adoption of the measures described in the above two paragraphs of this sub section, the potential for impacts related to oil spills can be effectively managed to a suitable level of safety. In connection with dredging process, equipment and dredging material transportation, potential impacts would be addressed through the following measures:

(a) Only equipment specially designed and manufactured by reputed companies with built‐in environmental protection mechanisms will for marine construction works. All equipment will be periodically checked and maintained by the contractor as per the safety and quality procedures stipulated in the contract documents. This will also minimize the risk of silt and other contaminants being released into the water column or deposited in locations other than designated location

(b) Although 21,000 cum capacity trailer suction hopper dredgers are used, only 15,000 cum of dredged material is transported to the site during each trip. Since loading and offloading barges are not used, this will ensure elimination of splashing of dredged material to the surrounding water

(c) The dredgers used will not dredge marine mud. Also the out‐dated Lean Mixture Overboard System technology will not be used for the Port City reclamation works. Overflow from the dredgers will be disposed from pipes located at the bottom of the dredger. The analysis of sediment spreading plume concentration conservatively assumes that the overflow is discharged at the water surface. Even with this conservative assumption, as shown in the numerical modelling carried out for this study, the suspended sediment concentration beyond the 100m radius of dredging location is less than 4mg/l for almost all cases. at extraction site. Although spreading is occurring up to certain extent, concentration of the suspended sediment is less than 4mg/l, which is almost equal to ambient concentration. Therefore dispersion of fine sediment due to dredging operations doesn’t show any impact to the surrounding environment.

(d) Material overflow during dredging will help to increase the efficiency of the dredging process and improve the quality of the dredged material. Overflowing method is used in dredging operations throughout the world for improving the sand quality and efficiency of dredging.

(e) Before moving dredgers, excess material from the decks and exposed fittings of vessels shall not be dumped to sea except at approved locations. Note that according to the Project Agreement, it is the responsibility of the SLPA to provide an “at‐sea” area for dumping unsatisfactory material.

(f) Adequate freeboard shall be maintained on dredgers to ensure that decks are not washed by wave action

(g) All bottom dumping vessels shall be fitted with tight‐fitting seals to their bottom openings to prevent leakages of material and periodically checked.

(h) Dredgers that will be used in Sri Lankan waters shall obtain the necessary certification from country of origin and will be free of hull‐fouling contaminated ballast water. A certificate from the Director General of Merchant Shipping of Sri Lanka will be obtained to make sure the Barge/ Vessel is free of any impurities. (This condition was fulfilled during the dredging period of the project)


(i) Dredgers should dispose of all ship‐generated waste in accordance with MEPA guidelines.

(j) Refuelling will occur within reclamation area only using fuel suppliers with required permits and licenses for bunkering in Sri Lanka.

4.3.6.2 Collisions of vessels

Collision of the dredger and fishing vessels is a potential problem. It is extremely important that the fishermen are duly educated on the route, frequency of operation of the dredgers. Health and safety measures have to adopt at the highest level. Warning lights have to be used in the dredgers and floating markers to be utilized to clearly demarcate the rout of the dredgers. Special care should be undertaken when the dredgers are manoeuvring where fishermen operate. There may be periods of high traffic in the operation of the dredgers during which the risk is high in view of increased hazards. The contractor should focus special attention during periods of high frequency of dredger movement, which increases potential hazards. By adopting measures described above and being alert by monitoring

The fishermen have to be well educated on the said route to be used by the dredgers. This should be done with the assistance of the Fisheries Department covering the area of dredging to the Port City site. The dredgers should be well lit in the night so as to be observed by fishermen. Where necessary, closer to the shoreline marker buoys have to be used to indicate the path used by the dredgers.


CHAPTER 5 : PROPOSED MITIGATORY MEASURES

5.1 Mitigation Measures _ Physical Resources

5.1.1 Near Shore Coastal Processes

General statements about the impact of dredging on the hydrodynamics and geomorphology of a site cannot be made as the effects are site specific, very difficult to isolate from other 'forcing effects', such as sea level rise or reclamation, and are often little understood. Although all dredging activities can cause some change to the hydrodynamic flow, the magnitude and type of effect will be related to the overall size of the excavation compared to the overall size of the system. Most reported adverse effects of dredging on hydrodynamics and geomorphology of coastal and estuarine areas are associated with dredging activities related to nearshore dynamic areas.

Proposed extraction site (mentioned as Site 3) is located at about 6km ‐7.4km from the existing coastline which means far away from the dynamic coastal zone. Further site is located in deep water where the depth is beyond 20m. Almost all the coastal processes including se bed sediment movement are happening within the nearshore area. Sand extraction within the specified area will not affect the nearshore coastal processes and sediment movement and hence coastal erosion will not occurs due to extraction. It is important to limit the sand extraction in deep sea specified area only in order to minimize or avoid coastal impacts to the adjacent coastlines.

Extraction should be limited to maximum of 3m at a location and reserve at least 0.5m of surface sand layer without disturbing the sea bed would prevent the creation of scattered deep holes on the sea bed which will leads to geotechnical problems in the sea bed. These conservative limits will ensure safety with respects to the minimum influence the dredging would have on the dynamic coastal zone and the seabed stability against sliding and collapse of near shore profiles.

In most cases, existing regulations and careful dredging practice are sufficient to avoid the potential effects discussed above and there is no need for further steps to be taken.

It is strongly recommended to commence beach monitoring as soon as the commencement of dredging to assess whether there will be a significant change occurring (even though it is very unlikely) due to the dredging activities. It is recommended that baseline measurements of beach profiles be undertaken prior to project commencement (this has been done) and thereafter monitoring be carried out at prescribed time intervals.

5.1.2 Turbidity

Turbidity resulting from dredging and placement depends upon the method adopted, properties of the sediment, location of the extraction site etc. Impact due to turbidity could be minimized by selecting a proper site with less percentage of fine particles within it. From the field investigations it was found that the proposed site consists of very low percentage of fine sediments. Therefore the amount of fine particles which release to the water body during dredging is limited. Further it is proposed to use trailer suction hopper dredgers for dredging operations where the suction method is used to extract the material which will generate less fine sediments than the cutting method. This way, emission of fine sediments to the surrounding environment would be minimized.


From the modelling it was proved that suspended sediment concentration due to dredging activities will not cause significant impact to the marine environment. For the worst case scenario it was found that 10mg/l of suspended sediment concentration closer to the dredging location and 4mg/l concentration beyond the 100m radius of dredging location. Therefore it can be concluded that the impact zone is less than 100m radius from the dredging location and the turbidity level (TSS) is less than the recorded maximum ambient concentration during the flood events of Kelani river.

It is recommended to monitor the turbidity levels during the dredging and dumping process and maintain turbidity levels at the boundary of the study area below the standard level. Since the permissible turbidity levels for dredging activities are not available in CEA standards it is recommended to maintain the turbidity levels below the maximum observed ambient turbidity levels during the flood events of Kelani river. It is necessary to minimize overflow losses as much as possible. Further as a mitigatory measure it is recommend to use silt curtains where required, if the turbidity levels at the boundary of the study area exceed the standard level. Therefore, silt curtains should be readily available at the project area in sufficient quantity and it should be mobilize/installed within 24 hour if an unforeseen plume of sediments develop.

5.2 Mitigation Measures _ Biological Resources

Following mitigation measures are suggested with the method of monitoring in order to minimize the impacts and after‐effects to the biological environment,

5.2.1 Impact for the sensitive habitats (Reefs and Seagrass bed)

i. Sand extraction activities should be avoided around the reefs as marked in following figure during spawning periods (April, May and June)

Figure 5.1: Recommended Dredging Area

This area should be avoided during spawning period (April, May and June)


ii. Modern dredging methods should be applied to minimize amount of suspended sediment release to the environment especially where the reefs or hard bottom areas, located in the vicinity of the dredging sites.

iii. Dredging activities should be completed within a shorter time of period

iv. Employ marine biology expert as an observer onboard around the sand extracting areas.

5.2.2 Impact of breading grounds / spawning grounds

i. Confining the sand extraction activities to the areas where it has not been marked or identified as either important sensitive habitats /fish breeding / spawning grounds or somewhere close to such areas.

ii. If possible confining sand extraction activities to non‐spawning peaks (Peak spawning season for most species in the west coast is during April‐ June)

iii. Dredging should be confined to maximum of 2meters from the surface of the sediment iv. Dredging activities should be completed within a shorter time period v. Employ marine biology expert as an observer onboard around the sand extracting

areas

5.2.3 Impact to the soft bottom macrozoobenthos and endangered species.

i. Avoiding sites having unique habitat or other value, including habitats of threatened or endangered species.

ii. The dredging can be limited to short term as much as possible to avoid spawning or migratory seasons and other biologically critical time periods.

iii. Maintain proper extraction methods and technology to prevent or minimize any potential damage.

iv. Encourage and support to carry out research in relation to fishing impacts/ biological impacts etc. due to sand extraction ( ex: impacts to benthic communities and demersal fish production and recovery time etc.)

v. Contractor should strictly adhere to sand dredging guidelines and strictly follow mitigatory measures put forward to minimize sedimentation

vi. Actions need be taken to control the population increases of harmful optimistic species (ex: introduction of a new fishing gear to catch the species like Blood spotted crab while ensuring minimum damage to fishing nets)

5.2.4 Impact of fishing grounds

Disturbances can be occurred to the fishing ground due to the vessel movements. Therefore extra fishing cost may have to be incurred to the fisherman.

i. Allow fishermen to engaging in fishing within the dredging site by giving proper signals about the vessel movement and transportation routes

ii. Fishermen should be empowered to access alternative fishing grounds iii. Fishermen will also be encouraged and fund should be allocated to explore alternative

sources of livelihood during the operation phase of the project. iv. Continuous monitoring of the both impacts to biological environment and fishing

during the sand extracting period and after the extraction is required.


Accidents and vessel traffic can be occurred within the fishing ground, therefore it is suggesting to;

i. Employment of only trained and authorized persons to operate machinery. ii. Use appropriate signals to indicate vessel movements and dredging activity both

day and night iii. Deploy minimum number of vessels during dredging period iv. Enforcement and adherence to safety procedures and preparation of contingency

plan for accident response

5.2.5 Suspended sediment (turbidity) effect on phytoplankton and other aquatic plants

i. Use of silt screens wherever possible or maintain turbidity level of the dredging site (500 m around the dredging site) to the standard level

ii. Loading process should be made precautionary by reducing the pumping flow during the final stages of the loading process or by reducing the total loading time

v. Applied modern technology and make use improved machinery

5.3 Impact for Water quality

i. Avoid overflow and other contaminants from machinery and vessels ii. Minimize overflow losses vi. Use of silt screens or maintains turbidity level of the dredging site (500 m around

the dredging site) to the standard level.

5.4 Mitigation Measures _ Social Resources

Curtailment of fisheries industry

Proper warning signal system must be established to inform locations of the vessels operation. Locate signal buoys in the vessel operation track and the area. Awareness must be done for fishers on vessel operation before commence the work and during the work.

Conduct awareness for all stakeholders prior to project commencement and keep transparency in project operation.

Fisheries is one of the major income source and livelihood support of the community. Sand extraction activities may affect to the fishers’ incomes and livelihoods. Thus, it is recommended to establish a social beneficiary system for the impact community.

During the socio‐economic survey, perspective of fishing community and stakeholders on sand dredging in the proposed area obtained, as follows;

Establish a better management of Negombo lagoon as an alternative for mitigation of negative impacts (if any) of sand dredging. Fish and shellfish resources in the lagoon and adjacent coastal water would be sustained for the benefit of coastal fishing communities by lagoon development and management. The following measures were suggested;

Clean the landing sites by removing un‐decomposed and durable wastes. remove deposited silt from the bottom of the lagoon build‐up strong waste management system increase depth of water cannels to carry large volume of water to the lagoon Empowering fishing community to organize fishing cooperatives to face adverse effect

of port city


CHAPTER 6 : ENVIRONMENTAL MANAGEMENT PROGRAMME

7.1 Purpose of an Environmental Management Plan

The Environmental Management Plan (EMP) is prepared as part of the wider Environmental Impact Assessment Process. The EMP is used as a tool for the management of the environmental performance of the project and it is developed and implemented as an important component of project activity. The EMP guides the implementation of Mitigatory Measures and Monitoring throughout the implementation of the project and contributes to the overall process of Project Monitoring and Auditing. The EMP therefore presents a consolidation of the recommendations given in the EIA Report, including specific recommendations for environmental mitigation, monitoring and management. In particular it specifies the mechanisms for the implementation of the mitigatory measures and for monitoring.

The EMP is developed as a part of project preparation activity. However, prior to construction it has to be updated in full consultation with the Environmental Monitoring Committee (EMC) and the Contractor. Discussions with the Contractor are critical because the EMP is part of the relevant contract.

7.2 Implementation of Mitigatory Measures

With respect to Mitigatory Measures (as described in Chapter 5), the EMP sets out the mechanisms for the implementation of such measures for which prior agreement has to be reached between the Contractor and the EMC. The agreement is required in view of the EMP being part of the contract. Therefore the EMP will be used as means by which the Contractor (and any Sub Contractors) will implement the recommended mitigation measures and achieve the environmental performance standards defined and recommended in Sri Lankan environmental legislation, in the EIA and in the Contract. The primary reason for adopting the EMP approach is to make all parties including the Contractor aware of environmental responsibilities and to be proactive in his commitment to achieve the standards specified. The EMP not only facilitates environmental audit of the works but is also a useful tool by which the construction works can be readily audited by the project proponent.

6.3 Implementation of Mitigatory Procedures

With respect to Monitoring Procedures, the EMP will set out the relevant mechanisms and institutional arrangements to achieve the objectives of Compliance and Impact Confirmation Monitoring through the Environmental Monitoring Program. As the EMP will form part of the contract there will be provisions to ensure that the Contractor fulfils his obligations regarding the implementation mitigation measures. It is recommended that the Coast Conservation Department appoints specialist(s) from the EMC to independently verify that the measures are implemented correctly and efficiently as part of third party verification. This arrangement will fully satisfy the requirement of Compliance Monitoring.

6.4 Institutional Arrangements for Compliance Monitoring and Impact Confirmation Monitoring

It is recommended that an Environmental Monitoring Committee (EMC) be appointed to oversee the implementation of the Monitoring Plan. A well‐structured programme will ensure both Compliance and Impact Confirmation Monitoring to high degree of efficiency.


The EMC should be chaired by the Central Environmental Authority. Appointees to the EMC should be approved by the Central Environmental Authority, and should include representatives from key stakeholders. The following membership is recommended:

Central Environmental Authority Coast Conservation Department National Aquatic Resources Research and Development Agency Marine Environment Protection Authority Sri Lanka Ports Authority Department of Fisheries Sri Lanka Navy Office of the District Secretary Department of Archaeology Ministry of Megapolis and Western Development Contractor(s); and EIA Consultants

The EMC should also include representatives from the SLLRDC, Ministry of Megapolis and Western Development and Colombo Port City Development Project. This is required in view of the close physical interaction between the two projects.

The EMC will work in close consultation with the CEA, Contractor, EIA Consultants on all matters relating to monitoring. The EMC will have regular meetings in order to review the monitoring. In areas of potential conflict, the EMC will have responsibility to resolve such issues.

It is recognized that Compliance Monitoring and Impact Confirmation Monitoring are required to ensure that the project includes the satisfactory implementation of the EIA recommendations and to confirm that no potential adverse impacts have been excluded from the assessment process. The EIA team believes that the wider participation of all stakeholders is important to achieve this objective. For this purpose it is important to develop and implement a formal mechanism for such participation and dissemination of information to the general public. If necessary, technical assistance should be provided for adequate understanding of project interactions with the environmental components and mitigatory actions.

Arising from such activity, the EMC in consultation with the Contractor(s) should develop a mechanism to manage, investigate, respond and act upon, any issues raised by the public during construction.

6.5 Environmental Monitoring Programme (EMoP)

Table 6.1 shows the summery of the Environmental Monitoring Plan adopted during the sand dredging period by SLLRDC.


Table 6.1: Environmental Monitoring Programme adopted during sand dredging period by SLLRDC

No Parameter To Be Monitored Monitoring Locations Frequency of Monitoring

Party to undertake Monitoring Work

Party Supervising Monitoring Work

Party Who Has to Receive the Report

1. Dredging Dredging location, depth, and dates of dredging.

Sand dredging area Fortnight during dredging SLLRDC CHEC CEA,CCD

2. Dredging Visual inspection Status of anchorage & pipelines.

Anchorage &along the pipeline Fortnight during dredging SLLRDC CHEC CEA,CCD

3.Dredging

Visual inspection status of cleanliness of dredging and sand pumping area

Sand dredging area & along the pumping line

During dredging period. SLLRDC CHEC CEA,CCD

4.Water Quality (WQ)

Water Quality– Surface & ground water salinity

Reclamation site (stock piling area)

Monthly sampling during dredging operation.

SLLRDC MEPA CEA,CCD

5.Pollution

Monitor oil spill or waste oil contamination of marine environment

Sand dredging area

Monthly during dredging SLLRDC MEPA CEA,CCD

6.Drainage management plan

Status of drains specified by the said plan Sand stocking area Before and during dredging SLLRDC NWSDE CEA,CCD


The EMP and the EMoP is presented in Table 6.2 and 6.3 respectively.

Table 6.2: Environmental Management Plan

Potential Environmental Impact

Mitigation Action Monitoring Scope Standards Responsibility Implementation Schedule

Remarks

Project Activity: Dredging of seabed for extraction of sand Impact on sensitive habitats, Reefs and seagrass beds

Minimize the suspended sediment release through use of modern dredging methods.

Species diversity by underwater visual survey Thambagala

PP/Contractor with assistance from NARA

Operational Post‐operational (Annual)

Dredging activities to be completed in the shortest period possible.

Soft bottom macrozoobenthos and endangered species

Minimize suspended solids release through use of modern dredging methods.

Species sampling through grab sampling in sand dredging area



Avoid sites with unique habitats.

The dredging should be limited to short term

Supporting research activities related to sand extraction.

Impact of breeding grounds/spawning grounds

Avoid intensive sand extraction during spawning period.

Species diversity and density of mature /running fish Ichthyoplankton analysis‐ Plankton survey Spawning biomass –Shrimp, squid



Dredging to be confined to maximum of 2 metres from surface of sediment Mining site.

Dredging activities to be completed in the shortest period possible.


Table 6.2 Contd..



Remarks

Increase in the suspended solid and turbidity impacting phytoplankton and other aquatic plants and animals

Restrict overflow Water quality analysis of NO3‐N, NO2‐N, PO4

3‐‐P, SiO4

4‐Si, TSS, Turbidity, Chlorophyll‐a 500m around dredging area

Proposed (CEA) ambient Water Quality standards


Operational (Quarterly)

Monitoring water quality Use of silt screens where required

Impacts on fishing grounds and fishing routes

Dredging to be carried out area‐wise and in phases.

Physical inspection and details of fish catch

PP/Contractor and DFAR

Operational (Monthly)

Facilitate access to fishing grounds Empower fishermen to access alternative fishing grounds

Warning signal system to be established to inform other vessels of dredger operation.

Impacts on the fishing community

Implementation of Income Support and Benefits Programme for Potential Income Lost.

Statistics from Fisheries Department on fish catch and income

PP/Contractor and DFAR

Operational


Table 6.2 Contd..



Remarks

Impacts on the fishing community

Social responsibility and awareness programs

Community needs assessment

DFAR, Operational, post operational

Alternative sources of livelihoodduring dredging phase.

Number of programs conducted and number of people attended

DFAR Before the commence, During the operation

Project Activity: Reclamation

Sediment plumes Silt curtains (if need arises). Activity area PP/Contractor Construction

Oil Spills Oil Spill Contingency Management Plan.

Immediate application of contingency plan.

Inaccordance to guidelines of Marine Environment Protection Agency.

PP/Contractor CHEC

Immediately on event of oil spill


Table 6.3: EnvironmentalMonitoringPlan (EMoP)

Category Mitigation Activities Parameters to be monitored and method of monitoring the environmental changes

Location/timing of sampling Frequency of Monitoring

Institution/ Agency responsible for Monitoring

Institution/ Agency responsible for supervision

1.Marine Environment and Ecology

Minimize the release of suspended solids using modern dredging technologies.

Species diversity and species density

Construction/ Post‐Construction Underwater visual survey at Thambagala.

Annually PP (MoM&WD) /NARA

EMC and MoM&WD

Reduce impact on Soft bottom macro zoo benthos and endangered species by minimizing suspended solids and limiting dredging to the shortest time period possible.

Species diversity by Grab sampling Species density in sand dredging area

Construction/Post‐Construction Annually PP (MoM&WD)

EMC and MoM&WD

Reducing impact on breeding grounds/spawning grounds by minimizing suspended solids and avoiding spawning grounds during dredging

Species diversity‐Ichthyoplankton analysis Species density‐Plankton survey

Construction/Post‐Construction Quarterly /NARA EMC and MoM&WD

Density of mature/running fish‐Spawning biomass–

Shrimp, squid

Reducing suspended solids and turbidity through restriction of overflow.

Water quality analysis NO3‐N, NO2‐N, PO4

‐3 ‐P, SiO4

‐4‐Si, TSS, Turbidity, Chlorophyll‐a

Construction/ Post‐Construction

Bi annually PP(MoM&WD) EMC and MoM&WD

Monitoring water quality


Table 6.3 Contd..

Category Mitigation Activities Parameters to be monitored and method of monitoring the environmental changes

Location/timing of sampling

Frequency of Monitoring

Institution/ Agency responsible for Monitoring

Institution/ Agency responsible for supervision

2. Social Reducing impacts on fishing grounds and fishing routes by:

Physical inspection of Fish Catch and Fishing location

Construction Monthly PP (MoM&WD)/ DFAR

EMC and MoM&WD

facilitating access to fishing grounds

Empowering fishermen to access alternative fishing grounds

Reducing impacts to the fishing community by:

Fish Catch and income‐Statistics from Fisheries Department

Construction/ Post‐Construction

Once a month PP/ (MoM&WD) DFAR

EMC and MoM&WD

Implement the Income Support and Benefits Programme for Potential Income Lost.

Community needsassessment: DFAR,

Number of programs conducted

Conduct social responsibility and awareness programs.

Number of people attended

SEIA Report– Proposed Sand Extraction Site 3 – December 201 Chapter 7- Page | 1

CHAPTER 7 : CONCLUSION AND RECOMMENDATION

The manner in which impacts may arise from the physical aspects of dredging activities are discussed in detail. Most of the impacts arising from dredging are anticipated to be temporal and confined to the areas of work.

Comprehensive modelling studies were carried out using state of art modelling software in order to assess the excess turbidity levels which could happen due to dredging activities. Existing physical environment and the hydrodynamic nature of the study area is regenerated through the model based on the actual measurements of wave, current, water level and bathymetry. Morphological changes were assessed based on the findings of geotechnical and geophysical investigations in the proposed sand extraction site. Hydrodynamic nature of the sand dredging area will not vary with the proposed sand extraction process since it is located away from the dynamic coastal zone. Further, sand extraction is proposed to limit maximum of 3m at a location to avoid scattered deep holes in the area. Maximum of 3m of morphological changes in deep water (depth beyond 20m) would not create significant difference in nearshore wave climate or current pattern and hence no influence to the coastal stability of the area.

Proposed extraction site is located at about 6km ‐7.4km away from the existing coastline between Hendala to Kepungoda which is beyond the periphery of this dynamic zone. Therefore maximum of 3m of morphological changes in the deep water (beyond 20m depth) does not influence of current regime of the area and hence no impact to the coastal hydrodynamics in the neighbouring area. Hence sand extraction at the proposed site does not create significant impact on the coastal stability of this particular stretch.

From the comprehensive modelling investigations it was proved that the sediment dispersion due to dredging is localized and it will limited to a maximum of 100m from the dredging location. Further recorded maximum concentration is 4mg/l at the dredging site which is far below the recorded maximum ambient TSS levels during flood event of Kelani river. Therefore, increase in suspended sediment level during dredging operations is negligible and therefore no significant impact occurs during dredging operations. The proposed sand dredging area, experiences high turbidity conditions due to the discharges from Kelani River and hence the existing organisms have higher tolerance level to high turbidity levels.

Discontinuous reef is visible in the middle of the area which running parallel to the beach in south‐north direction. Based on the findings of sub‐bottom profile survey, three distinct layers are present below the sea bed as surface sand layer, other soil layer and bed rock. Limestone reef is formed in the other soil strata which are not link to the surface sand layer. Therefore, extraction of sand from the surface sand layer will not affect the existing limestone reef.

In order to minimise the impacts (if any) on the environment, it is recommended to avoid reef areas and confined the dredging activities more towards the western side of the reef. Based on the study results the proposed site has subdivided to three zones (see figure bellow); zone A is recommended to dredge sand for reclamation purpose; Zone B for construction industry and the rest of the area shall not be used for sand extraction. Thereby any anticipated impact of dredging could be further minimize and also protect from damaging to the available limestone reefs in the area. The use of modern dredging methods and proper loading mechanisms along with silt screens in the dredging area should be applied to minimize the levels of suspended sediments. The risks of eutrophication due to release of nutrients from the bottom sediments to the water column is considered low, particularly because the proposed excavation site is located in the open sea. The strong long shore current in the open sea would facilitate high exchange of water mass. It is recommended that the

SEIA Report– Proposed Sand Extraction Site 3 – December 201 Chapter 7- Page | 2

dredging vessels and machinery shall be maintained in good conditions that would ensure no contaminants are released from the vessels.

The dominant fish resources in the area are small pelagic and demersal finfish species. The pelagic transient species that are likely to avoid unsuitable environmental conditions and return once normal conditions are established in the long term. The area selected for dredging has previously been dredged in number of occasions and as such is not a pristine habitat. Moreover, it is recommended that Environmental Monitoring System should be established to assess short term and long term impacts of dredging that would be useful to monitor future dredging activities.

Fisheries are expected to be disturbed due to dredging activities and movement of dredging vessels. It is recommended to adopt appropriate dredging plan, which limits dredging to smaller areas at a given time with a proper signal (marker) buoys to minimize restrictions on fishing. A transparent process where fishermen are informed of dredging areas will reduce inconvenience to fishermen. As a remedial measure for any potential disturbance and nuisance to fishers, it is proposed to implement the Fishermen’s Livelihood Support and Benefits Programme as planned.

Based on the findings, two separate areas were selected to extract sand for the following purposes as given below.

Zone A : recommended for reclamation works or construction industry

Zone B : recommended for extract sand for construction industry

Rest of the area : not recommended for sand dredging

Figure 7.1: Proposed Areas for Sand Extraction

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